Click the link to read the article on the NOAA website (Rebecca Lindsey):

June 13, 2024

After a year of dominance, El Niño released its hold on the tropical Pacific in May 2024, according to NOAA’s latest update. El Niño—the warm phase of the El Niño-Southern Oscillation (ENSO), our planet’s single largest natural source of year-to-year variations in seasonal climate—has been disrupting climate in the tropics and beyond since May 2023, likely contributing to many months of record-high global ocean temperatures, extreme heat stress to coral reefs, drought in the Amazon and Central America, opposing wet and dry precipitation extremes in Africa, low ice cover on the Great Lakes, and record-setting atmospheric rivers on the U.S. West Coast. 

(That’s an incomplete list! I’d love to see readers use the comments to identify all the seasonal climate extremes over the past year that are consistent with the typical influence of El Niño.)

That’s a lot of climate upheaval. Is ENSO going to give us some time to idle in neutral (a state in between the warmer and cooler extremes of the El Niño-La Niña cycle) and catch our breaths? Not much, apparently. The tropical Pacific’s climate pendulum appears to be swinging back toward its other extreme: La Niña. In the Pacific, La Niña brings cooler-than-average temperatures in the central-eastern part of the basin, stronger winds both near the surface and at high altitudes, and heavier rain than normal over Indonesia and the rest of the Maritime Continent. The forecasting team thinks there’s a 65 percent chance that La Niña will arrive by July-September. 

That timing means there’s a pretty good chance La Niña will be around to influence the peak of the Atlantic hurricane season. (1) Even if the transition occurs more slowly, the odds of La Niña being in place by Northern Hemisphere winter are still 85 percent, which is similar to the NOAA forecast in previous months. Given those odds, it’s probably a good idea to refresh your memory of the typical impacts of La Niña on U.S. temperature and precipitation. 

The slow pokey ocean

Emily explained in our April update that the atmospheric part of El Niño—weak-to-absent east-to-west trade winds across the tropical Pacific, dryness over Indonesia, strong convection and rainfall east of the International Dateline—had more or less shut down by early April. But surface water temperatures in the central-eastern tropical Pacific were still more than a degree Celsius (nearly 2 degrees Fahrenheit) warmer than the long-term average (long-term = 1991-2020), and some parts of the tropics still appeared to be experiencing El Niño’s typical side effects. Forecasters concluded it was too soon to issue El Niño’s curtain call. 

Without the atmosphere reinforcing those warm anomalies (anomaly means “difference from average”), however, surface temperatures cooled off significantly through April and May. We’re already seeing stronger easterly (from the east) trade winds, which have cooled the overheated surface waters. You can see it happening in the animation below. 

The most recent weekly and monthly observations from the key ENSO-monitoring region (dubbed “Niño 3.4”) show surface temperatures are close to average, and now cooler, deeper waters have begun surfacing. Now that both the atmosphere and the ocean have shifted away from El Niño, the event is truly over. Beneath the surface of the eastern pacific, a pool of cool water has been lurking for several months in standby mode, ready to re-supply the surface and intensify the cool anomaly required to create and maintain La Niña. 

Historically, does big El Niño=big La Niña? 

Of course, one of the most common questions we receive from readers is how strong do we expect the predicted La Niña to be? As far as model forecasts go, it’s too soon to put much stock in the forecasts: we’re just barely out of the notorious spring predictability barrier. The spread of possible outcomes is still pretty wide. 

So, how about historical events? Does coming off a relatively strong El Niño like the recent one mean the developing La Niña will also be strong? That’s the question I posed to the team via email earlier this week. In true scientist fashion, Michelle answered me with a plot (2), which I have translated below.

First things first, let’s acknowledge that there have only been 10 times in the historical record where ENSO flipped from El Niño into La Niña within a year. That’s not enough examples to draw any solid conclusions from. Still, it’s interesting to look at what we have and speculate as to what it might mean, so that’s all I am doing here. 

Each line on the graph above represents a year in which the tropical Pacific shifted from El Niño to La Niña with no neutral winter in between. The lines are colored based on the strength of the El Niño: red for strong events (peak Niño 3.4-region sea surface temperature anomalies above 1.5 ˚C, or 2.7 ˚F), orange for moderate events (peak anomaly between 1 and 1.5 ˚C, or 1.8-2.7 ˚F), and pink for weak events (peak anomaly less than 1 ˚C, or 1.8 ˚F). 

The relationship between the strength of the El Niño and the strength of the subsequent La Niña is kinda messy. It’s unlikely, but not impossible, for weak and moderate El Niños to lead to a strong La Niña (Niño 3.4 temperature anomaly of more than 1.5 ˚C below average). Only one of the pink and orange lines gets below that threshold. Meanwhile, 4 of the 6 strong El Niños do evolve into strong La Niñas. But before we put too much stock in that pattern, we should note that the strongest El Niño of all (top red line at the left hand side of the graph) wound up developing into the weakest La Niña (3). So…yeah. It’s complicated. 

Strong events not required for strong impacts 

The likely strength of the upcoming La Niña will become clearer the closer we get, and you’ll hear more about that in coming posts. Of course, it’s also important to remember that the strength of a given El Niño or La Niña isn’t a good predictor of the strength of the temperature or precipitation impacts in a particular place. Stronger events do make it more likely that places prone to be influenced by El Niño or La Niña will experience some level of their typical impacts, but they don’t necessarily lead to stronger impacts. In other words, even a moderate or weak La Niña can have a strong impact on a given place. So it’s important to pay attention to what we already know, which is that odds are very high (85% chance) that this winter will feature La Niña. If you’d like to know more about what a La Niña winter might mean for your part of the world, here are some great places to start. 

• Global impacts of El Niño and La Niña
• U.S. impacts of El Niño and La Niña
• U.S. winter precipitation for the 20 strongest La Niña events (through 2021-22) 
• U.S. winter temperature for the 20 strongest La Niña events (through 2021-22)

Footnotes

1. Later this month, we’ll have a guest post about how La Niña influenced NOAA’s 2024 seasonal hurricane outlooks from lead forecaster Matt Rosencrans of NOAA’s Climate Prediction Center. In the meantime, you can read a vintage post from our early days and a more recent one with some additional detail.) 
2. Scientists use the word plot to refer to any data visualization, whether map or graph.
3. This analysis defines strength based on how temperatures in the Niño 3.4-region compare to the long-term average in that area. By this definition, that top line is occupied by the 2015-16 El Niño. But as we have blogged about before, when it comes to ENSO impacts, what may matter more is how warm temperatures in that area are relative to the rest of the tropical oceans. Relative to the tropics-wide average, the warm anomaly associated with the 2015-16 event might not have been large enough to really count as record strong, which might explain why the La Niña that followed it was also not very strong. 

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor website.

Click the link to go to the US Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

A highly variable precipitation pattern was noted across the contiguous 48 states this past week, resulting in a significant number of changes in the Drought Monitor depiction. Another week of heavy rain June 4-11 continued to ease drought and abnormal dryness in parts of the central and southern Plains, with excessive amounts resulting in 2-category improvements in portions of central Kansas. Moderate to heavy rainfall also brought improvements to portions of the middle and upper Mississippi Valley, the Northeast, the Washington Cascades, and southernmost Florida. Meanwhile, deficient rainfall caused abnormal dryness and drought to expand or intensify in parts of southern New England, the mid-Atlantic region, the interior Southeast, the central and northern Florida Peninsula, a few scattered areas across Texas, part of the central Rockies, the northern High Plains, some sections of interior Washington and Oregon, and a small region in northeastern Alaska. Other areas were unchanged, including Hawaii and Puerto Rico…

High Plains

Parts of the southern High Plains Region were hit by heavy to excessive rains, bringing widespread improvement to the entrenched dryness and drought affecting much of Kansas and eastern Colorado. The heaviest amounts soaked a swath across central Kansas, with more scattered heavy rains observed farther north in Kansas and across eastern Colorado. Between 5 and 8 inches fell on central Rice, eastern McPherson, central Marion, and much of Chase Counties in central Kansas, prompting some 2-category improvements there. D3 conditions were eliminated from the High Plains Region, and severe drought (D2) is now limited to a few several-county south and west of the band where the heaviest rains fell last week. Moderate rains (over 1.5 inch) reached into southern Nebraska as well, improving conditions in southeastern Nebraska. Farther north and west, conditions were considerably drier, and most sites recorded several tenths of an inch of rain at best. This kept conditions essentially unchanged in most areas, although some D0 expansion was introduced in north-central Colorado, western Nebraska and adjacent South Dakota, and north-central South Dakota. A dry week also allowed conditions to deteriorate in part of southwestern Colorado, with moderate drought (D1) expanding northward into west-central Colorado. There was an additional, small area of improvement in part of Laramie County in southeastern Wyoming, where a mesoscale heavy rain event (2.0 to 4.5 inches) eased D0 to D1 conditions…

West

Similar to western Texas, moderate to heavy precipitation also doused much of eastern New Mexico last week, inducing widespread 1-category improvement. The heaviest amounts (4.5 to locally 8.0 inches) fell on southern and west-central Guadalupe County, but most of the eastern half of the state reported at least 0.5 inch. Another area that experienced some drought relief was the higher elevations of the Cascades in Washington. During the past 30 days, 8 to 15 inches of precipitation has fallen on the peaks, with the largest totals observed in Snohomish County. Another 0.5 to 2.0 inches fell along and just east of the highest elevations last week. As a result, moderate drought was reduced to abnormal dryness there. However, across the northern tier of the region to the south and east of the Washington Cascades, persistently below-normal precipitation in many areas led to the expansion of abnormal dryness (D0) and moderate drought (D1) in a few areas, in particular the north-central Oregon Cascades, part of interior southeastern Oregon, part of the central and eastern Washington plains, and a broad area of northern and central Montana from east of the Rockies to near North Dakota. Soil moisture and some streamflows have begun to reflect the past few weeks of subnormal rainfall across portions of central and eastern Montana…

South

Widespread dryness and drought continued to cover western Oklahoma, the western Texas Panhandle, and most other areas across southern and western Texas. Rainfall totals were generally unremarkable across western Oklahoma, keeping D0 to D2 conditions generally unchanged, save for a couple of small patches near the central part of the state. In contrast, rainfall was highly variable in the areas of Texas that have been affected by dryness and drought (D0 to D3) recently, leading to sizeable areas that felt both deterioration and improvement. Most of the dry areas in the Texas Panhandle received at least moderate rain last week (1.5 inches or more), with several patches soaked by 3 to 5 inches of rain. As a result, improvement was introduced in many locations across this region. Farther south, moderate to locally heavy rains were observed in portions of the southern Edwards Plateau and southward through parts of Bandera, Medina, and Bexar Counties. Totals of 1-2 inches were fairly common in this region, although a few swaths received more, up to 4 inches at a few isolated locations. Improvement was also introduced in significant parts of this region, although less broadly than farther north since heavier totals were not as widespread. In sharp contrast, dry and hot weather across Deep South Texas and western parts of the Edwards Plateau led to broad-scale deterioration in these regions. Agricultural interests in the western Edwards Plateau report slowed planting due to quickly depleting surface moisture, resulting in blowing sand and dirt with little or no soil moisture. Over the past 90 days, a broad area from the southern Big Bend southward along the Rio Grande Valley into Maverick County recorded only 10 to 50 percent of normal rainfall, with similar amounts reported across portions of the western Edwards Plateau. The remainder of the South region is nearly free of notable dryness. Moderate drought is restricted to a couple of patches in northeastern Arkansas, with abnormal dryness covering the remainder of northeastern Arkansas and a large part of northern Mississippi. Moderate rains brought limited improvement to portions of northeastern Arkansas this past week, but only light rains fell across northern Mississippi, increasing short-term moisture deficits and prompting an increase in D0 coverage. Northwestern Mississippi has recorded near or just over one-half of normal rainfall since mid-April…

Looking Ahead

During the next five days (June 13-17, 2024), tropical moisture is expected to interact with mid-level low pressure across southern Florida, resulting in heavy rain. Flood watches are currently in effect, and 3 to 5 inches of rain are expected before precipitation tapers off later in the period. Tropical moisture from the Gulf of Mexico may also push into the central Gulf Coast region, bringing 1.5 to 2.5 inches of rain to the Louisiana Bayou and southern Mississippi. Farther north, thunderstorms along a frontal boundary are expected to drop 1.5 to 3.5 inches of rain on parts of the northeastern Great Plains and Upper Mississippi Valley. Moderate precipitation is expected in other parts of the northern Great Plains, upper and middle Mississippi Valley, western Great Lakes region, eastern New England, northern Florida Peninsula, southern lower Mississippi Valley, and higher elevations of the northern Rockies and Cascades. Meanwhile, the summer’s first extended period of excessive heat is forecast to develop toward the end of the period in the central Great Plains, expanding eastward across the middle and upper Mississippi Valley, the Ohio Valley, the mid-Atlantic region, and the Northeast by the end of the period. Highs well into the 90s should be widespread by the end of the period, and warm nighttime lows are expected, providing little relief. Subnormal temperatures are forecast to be limited to the Pacific Northwest.

The Climate Prediction Center’s 6-10 day outlook (valid June 18-22, 2024) favors above-normal temperatures from the southern Rockies and most of the Plains eastward to the Atlantic Ocean, with the most prohibitive odds (over 80 percent) across the Northeast and New England away from the immediate Atlantic Coast. There is a good chance that excessive heat will continue through at least part of the period across central and northern parts of the U.S. from the Mississippi Valley eastward. Farther west, subnormal temperatures are favored in many areas, but only slightly, with odds remaining below 40 percent (climatological odds are 33 percent). Below-normal precipitation is favored across the mid-Atlantic region, the Carolinas, the upper Southeast, and the Ohio Valley, as well as southeastern Alaska. However, odds tilt toward above-normal precipitation over a larger area encompassing the Gulf Coast region, the northern and southern Great Plains, the High Plains, the Great Lakes Region, the southern Rockies, the northern tier of the contiguous U.S. from the northern Rockies to the Pacific Coast, northeastern Alaska, and Hawaii. The best chances for surplus rainfall (50 to 70 percent) cover southern Texas.

Click the link to read the release on the AGU website (Liza Lester and Maheshwari Neelam):

May 21, 2024

Sudden onset of drying is a rising problem, particularly acute in South America and southern Africa. but in high mountain regions of central asia, climate change has instead brought more moisture

Sudden, severe dry spells known as flash droughts are rising in intensity around the world, with a notable exception in mountainous Central Asia, where flash drought extent is shrinking, according to new research. Heat and changes to precipitation patterns caused by a warming climate are driving these trends, the study found.

Flash droughts arrive suddenly, within weeks, hitting communities that are often not prepared and causing lasting impact. They are an emerging concern for water and food security. The new study is the first to apply a systematic, quantitative approach to the global incidence of flash drought, mapping hotspots and regions of rapid increases in recent decades.

“For many parts of the world, we saw flash droughts extending over larger areas, for longer time, with faster onset speed,” said Maheshwari Neelam, a climate scientist at NASA’s Marshall Space Flight Center and the Universities Space Research Association. She is the lead author of the study, published in Geophysical Research Letters, AGU’s journal for high-impact, short-format reports with immediate implications spanning all Earth and space sciences.

The study defined and tracked three critical measures of drought severity: speed of onset, duration and geographic extent. It analyzed 40 years of NASA’s MERRA-2 climate data, from 1980 to 2019, drawn from weather observations, satellite imagery and modeled root-zone soil moisture, with the aim of improving prediction and disaster preparedness.

“For example, in watersheds in South America, onset is getting faster by about 0.12 days per year, so over a decade they are developing a day earlier. Extent is increasing by 1 to 3% per year,” Neelam said. “The metrics can be used by early warning systems to incorporate rates of change in flash drought characteristics in risk assessment and disaster preparedness.”

South America, particularly southern Brazil and the Amazon, is experiencing strong intensification in all three dimensions of flash drought, aligning with deforestation patterns in the region, high temperatures and less rain. Congo, Angola, Zambia, Zimbabwe, South Africa, Lesotho, and Madagascar are also hotspots. High temperatures were found to be more important than declining precipitation in the African watersheds.

Land cover is also important to flash drought vulnerability. Savanna and grasslands are more susceptible to flash droughts than other ecotypes, particularly in humid and semi-humid climates, the study found.

In Central Asian watersheds, centered on high mountains, including the Himalaya Karakoram, Tianshan and Hindu Kush, flash drought extent shrank over the study period, bucking the worldwide trend. Climate-driven changes in precipitation, melting snowpack and a shift from snow to rain in the mountains have kept soils moist. These changes can cause an increase in flash floods, which have been observed in the region, Neelam said.

Neelam emphasized the importance of understanding landscapes’ response to disasters on a watershed scale for assessing water budgets and water management, transcending geopolitical boundaries.

“Natural hazards have no political values,” Neelam said. “This is why we looked at watersheds and not countries.”

[…]

This study was published in Geophysical Research Letters, an open-access AGU journal. Neither the study nor this press release is under embargo. View and download a pdf of the study here.

17% of the Lower 48 is short/very short; a 2% increase since last week. The East Coast saw a mix of improvement & degradation, with quick drying soils in ME, VT, & MA. In the West, all but CO & CA dried since last week.

Click the link to read the article on the Summit Daily News website (Robert Tann). Here’s an excerpt:

May 28, 2024

Early predictions point towards a dryer, warmer than normal summer. But a lot can still change — and how much of an influence La Nina will be is hard to say.

So what does the transition from an El Nino winter and spring to a La Nina summer mean for Colorado? 

Early predictions show the state could be in for a hot and dry summer. A three-month outlook from the Climate Prediction Center issued on May 16 shows Colorado has a chance of seeing above-normal temperature and below-normal precipitation from June to August.  Specifically, northeast Colorado has a 33% to 50% of higher-than-normal temperatures while southwestern Colorado has as much as a 60% to 70% chance. Northwest and southeast areas, as well as central Colorado, have between a 50% and 60% chance for higher temperatures. Practically all of the state has a 40% to 50% chance of seeing below-normal precipitation, according to the projections…

La Nina tends to have the strongest influence on summer weather in areas east of the Rocky Mountains, particularly the midwest. Any impact in Colorado tends to be concentrated around the eastern plains, with La Nina potentially bringing warmer, dryer weather, Johnson added.

Click the link to read the latest briefing on the Western Water Assessment website:

June 7, 2024 – CO, UT, WY

Cool May temperatures coupled with continued snowpack accumulation in some mountain areas slowed snowmelt, leading to above average seasonal streamflow volume forecasts for many river basins including the Arkansas, Gunnison, North Platte, Powder, Provo, Six Creeks, Weber and Yampa. Regional drought conditions contracted to cover 8% of the region, driven largely by drought removal in northern Wyoming. NOAA seasonal outlooks predict an increased probability of above average temperatures and below average precipitation for June-August.

Regional May precipitation was a mix of above and below average conditions. Average to much-above average (150-200%) precipitation fell in northwestern and central Colorado and northern Wyoming. In Utah, the central Wasatch and western Uinta Mountains received near-average precipitation during May. Locations in western and southern Utah, southwestern and northeastern Colorado and southeastern Wyoming received less than 50% of average May precipitation. Isolated locations in Larimer and La Plata Counties in Colorado and Washington County in Utah received record low May precipitation. In Boulder, CO, total May precipitation was only 0.44”, the driest May in 50 years and the second driest on record.

May temperatures were below average for nearly the entire region. In central Colorado, northern Utah and western Wyoming, temperatures were 2-4ºF below average. Region-wide (CO, UT, WY), May 2024 was the coldest since May 2019.

Despite below average May precipitation across much of the region, cool May temperatures preserved existing snowpack and regional snow water equivalent (SWE) is above-to-much-above average in most river basins. SWE is highest relative to average in Utah where SWE is 585% of average in the Weber River Basin and 225% of average in the Provo-Jordan River Basin. On a statewide basis, SWE is 136% of average in Colorado, 196% of average in Utah and 125% of average in Wyoming. Snow is completely melted in the Rio Grande River Basin and nearly melted in the Dolores and San Juan watersheds. Significant May snow accumulation occurred in Wyoming’s Bighorn Mountains and in parts of the Colorado Rockies.

Seasonal streamflow volume forecasts on June 1 are generally average to slightly above average except for below average streamflow forecasts in the Cheyenne, Upper Green, Rio Grande and San Juan River Basins. Snowpack accumulation continued in some mountain regions during May and cool May temperatures slowed snowmelt for much of the month. Relative to average, the highest streamflow volumes are forecasted in northern Utah, particularly the Provo, Six Creeks and Weber River Basins. Significant increases in streamflow volume forecasts compared to May 1 were observed in the Arkansas, Gunnison, North Platte, Powder and Tongue River Basins. The lowest streamflow volumes relative to average are forecasted for the Dolores (44%) and San Juan Rivers (64%). The inflow volume forecast for Lake Powell is 80% of average (5.1 million acre-feet).

Regional drought conditions improved during May and now cover 8% of the region, compared to 10% at the end of April. Much-above average precipitation in northern Wyoming caused the removal of D1 and D2 drought conditions. Drought was entirely removed from Utah during May and the area of D1 drought contracted in western Colorado. Dry conditions in other parts of the region caused drought emergence in southeastern Wyoming, severe (D2) drought emergence in southeastern Colorado and a slight expansion of D1 drought conditions in southwestern Colorado.

The strong El Niño event of 2023-2024 ended during May and Pacific Ocean temperatures are near average and ENSO-neutral conditions exist. There is at least a 70% probability of ENSO-neutral conditions remaining through summer, but by fall, there is a 50-60% probability of La Niña conditions forming. The NOAA Monthly Precipitation Outlook suggests an increased probability of below average June precipitation in northern Utah and above average June precipitation for southeastern Colorado. The NOAA Seasonal Outlook for June-August forecasts an increased probability of below average precipitation and above average temperatures for the entire region.

May significant weather event: Front Range severe thunderstorms. On May 30, two supercell thunderstorms rapidly formed over the Front Range and caused severe hail damage in the northern Denver metro area. Very large hail fell on the north side of Denver with hail covering roads and reaching up to 2” in diameter. (BoulderCast, Denver Hailstorm Recap, https://bouldercast.com/denver-hailstorm-recap-unexpected-nocturnal-supercells-pummeled-parts-of-the-denver-area-with-up-to-baseball-sized-hail-thursday-night/) Rainfall amounts from these thunderstorms were only a quarter to a half inch in the Denver area, but storms lingered to the northeast of Denver where up to 1.3” of rain fell in Akron on 5/30-5/31.

Hail images from Jayson Luber on X @Denver7Traffic.

Click the link to read the release on the NRCS website:

June 8, 2024

A cooler and wetter May have resulted in all but the Upper Rio Grande and the combined San Miguel-Dolores-Animas-San Juan River basins maintaining an above median snowpack

A cooler and wetter May have resulted in all but the Upper Rio Grande and the combined San Miguel-Dolores-Animas-San Juan River basins maintaining an above median snowpack. With much of the lower elevation snow melted out, only 45 of Colorado’s 124 SNOTEL stations recorded snow on the ground at the end of May. Most of the remaining snowpack is in northern and central basins along the Continental Divide. “During May, much of the central part of the state received above normal precipitation, combined with cooler temperatures, has allowed more snow to persist at higher elevations in some areas. These factors are leading to optimistic late season runoff volume forecasts for many river basins,” notes NRCS Hydrologist Joel Atwood. Runoff volume forecasts for June and July across the state are generally optimistic with the Gunnison, Arkansas and the combined Yampa-White-Little Snake River basins all forecasted to have well above median runoff. In addition, the South Platte and Colorado Headwaters River basins are also expecting slightly above median runoff volumes at 109 and 108 percent of median, respectively. Atwood continues, “In southern Colorado, many SNOTEL stations in the San Juan Mountains melted off around a week earlier than normal despite a near normal peak snowpack. In addition, the northern Sangre de Cristo mountains had a below normal peak snowpack. These conditions contribute to a less optimistic late season water supply in southwest Colorado.” The southwestern river basins of the combined San Miguel-Dolores-Animas-San Juan and Upper Rio Grande are forecasted to have below normal runoff volumes for June and July, at 59 and 74 percent of median, respectively. 

At of the end of May, reservoir storage across Colorado was 94 percent of median. Several basins were reporting above median storage, ranging from 100 percent of median in the Arkansas River basin to 112 percent of median in the Colorado Headwaters River basin. The combined San Miguel-Dolores-Animas-San Juan, Upper Rio Grande and Eastern Arkansas River basins all were reporting below median reservoir storage ranging from 70 percent of median in the Eastern Arkansas River basin to 86 percent of median in the Gunnison River basin.

Most of the state received well above median precipitation with a few exceptions. The combined Laramie-North Platte, South Platte, and San Miguel-Dolores-Animas-San Juan River basins each received 100, 89 and 63 percent of median precipitation, respectively. Other basin across the state received much higher totals compared to normal, ranging from 110 percent of median in the Colorado Headwaters River basin to 153 percent of median in the Arkansas River basin. Statewide precipitation during May was above normal at 107 percent of median.

_{* San Miguel-Dolores-Animas-San Juan River basin}

_{* *For more detailed information about April mountain snowpack refer to the June 1st, 2024 Colorado Water Supply Outlook Report. For the most up to date information about Colorado snowpack and water supply related information, refer to the Colorado Snow Survey website.} 

Click on a thumbnail graphic to view a gallery of data on the US Drought Monitor website.

Click the link to go to the US Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

Following a stormy pattern with frequent periods of heavy precipitation and severe weather outbreaks, major drought improvement occurred this spring across the Great Plains and Mississippi Valley. Recent heavy precipitation from May 28 to June 3 resulted in additional improvements to parts of the central and southern Great Plains. A dry start to the thunderstorm season and above-normal temperatures continued to result in drought expansion and intensification across the southern half of the Florida Peninsula. Anomalously heavy precipitation for late May into the beginning of June led to drought improvement across parts of Washington, northern Idaho, and western Montana. Alaska and Puerto Rico remain drought-free, while drought of varying intensity persists for parts of Maui and the Big Island of Hawaii…

High Plains

Widespread heavy precipitation (1 to 3 inches, locally more) resulted in a 1-category improvement to parts of Kansas, eastern Colorado, and southeastern Nebraska. A small area of long-term D1 was maintained for southeastern Nebraska that received less than 1 inch of precipitation this past week and a long-term drought signal continues. Based on neutral or wet soil moisture percentiles and NDMC drought blends, a 1-category improvement was made to northwestern North Dakota where more than 1 inch of precipitation occurred this past week. 30 to 60-day SPI and soil moisture indicators supported an expansion of abnormal dryness (D0) and moderate drought (D1) for northern Colorado and southeastern Wyoming…

West

The climatology becomes much drier during May through the beginning of June across California, the Great Basin, and Southwest. There was little to no change in Dx coverage throughout these areas. Heavy precipitation (1.5 inches or more) this past week supported a 1-category improvement to parts of northeastern New Mexico. Recent precipitation with a relatively cool late spring and SPIs at multiple time scales resulted in a 1-category improvement to western Montana and adjacent areas of northern Idaho. Unusually heavy precipitation (locally more than 3 inches) for the late spring led to a decrease in abnormal dryness (D0) and moderate drought (D1) coverage across parts of Washington. However, much of the existing moderate drought area of north-central Washington remained unchanged with precipitation averaging less than 50 percent of normal since October 1, 2023…

South

Widespread heavy precipitation (2 to 5 inches, locally more) this past week generally occurred outside of existing Dx areas of the South region. However, the heavy precipitation did overspread a few of the Dx areas. Heavy precipitation along with considerations of NDMC drought blends supported a 1-category improvement to parts of northwestern Oklahoma, Texas Panhandle, and south-central Texas. Also, a slight reduction in abnormal dryness (D0) was warranted for northeastern Arkansas and western Tennessee. 30 to 60-day SPEI and soil moisture indicators led to a 1-category degradation to parts of southern Texas and the middle Rio Grande Valley. Maximum temperatures have averaged 4 to 8 degrees F above normal during the past two weeks across the middle to lower Rio Grande Valley which is likely drying out topsoil and a factor in worsening drought conditions…

Looking Ahead

During the next five days (June 6-10, 2024), multiple cold fronts are forecast to progress across the eastern and central contiguous U.S. The heaviest precipitation (more than 1 inch) is forecast for the Northeast, Tennessee Valley, and Ozarks region. Locally heavy rainfall may accompany thunderstorms across the central to southern Great Plains. Dry weather, typical for this time of year, is forecast for the Southwest, California, and the Pacific Northwest. A heat wave will affect the Southwest and Central Valley of California during early June.

The Climate Prediction Center’s 6-10 day outlook (valid June 11-15, 2024) favors above-normal temperatures across most of the West, Great Plains, New England, and Florida. Below-normal temperatures are most likely for the Ohio and Tennessee Valleys and central to southern Appalachians. Below-normal precipitation probabilities are slightly elevated for much of the Corn Belt, Mississippi Valley, and Pacific Northwest. Above-normal precipitation is favored for the central to southern Rockies and high Plains along with the coastal Southeast and Florida.

Just for grins here’s a slideshow of early June US Drought Monitor maps for the past few years.