Composite Map Day 8-14

Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Thursday May 28, 2026 to Wednesday June 03, 2026

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT May 20 2026

Synopsis: A continuation of mid-level cyclonic flow over the southwestern contiguous U.S. (CONUS) as well as enhanced low-level moist, southerly flow from the Gulf of America from week-1 into early week-2, supports a lingering risk for heavy precipitation from the Southern Plains to the Southeast. The duration of above-normal precipitation coupled with the multiple rounds of potentially heavy rainfall may lead to flooding over portions of the Southern Plains and Lower Mississippi Valley. Mid-level low pressure favored over the western CONUS supports an increased risk of episodes of high winds across the Interior West, High Plains, and portions of the West Coast. Mid-level high pressure favored over Canada is expected to bring well above-normal temperatures for the north-central CONUS, though actual temperatures are expected to remain below heat thresholds.

Hazards

• Slight risk of heavy precipitation for portions of the Southern Plains, Lower and Middle Mississippi, Tennessee, and Ohio Valleys, Southeast, Southern Appalachians, and lower Mid-Atlantic, Thu-Sat, May 28-30.
• Flooding possible for much of eastern Texas, portions of Oklahoma, Arkansas, Louisiana, and Mississippi.
• Slight risk of high winds for much of the Interior West and High Plains, Thu-Sat, May 28-30.
• Slight risk of high winds for portions of coastal California and Oregon, Thu-Sat, May 28-30.

Detailed Summary

For Saturday May 23 - Wednesday May 27: WPC Days 3-7 U.S. Hazards

For Thursday May 28 - Wednesday June 03: Dynamical model 500-hPa height forecasts from the GEFS and ECMWF ensembles have come into much better agreement today, following a few days where guidance had been struggling to resolve a number of key mid-level features across North America. Early in week-2, both the GEFS and ECMWF favor an amplifying ridge center over the Hudson Bay, with a broad coverage of positive height departures over the north-central and northeastern CONUS. Weaknesses in the height pattern look to persist across the southern tier of the U.S., characterized by broad cyclonic flow conducive for continued enhanced precipitation across the Gulf states next week. Upstream, the GEFS has become better aligned with the ECMWF and Canadian ensemble, and now features anomalous troughing digging into the Interior West to promote cooler and more unsettled weather later next week. Over time, both the GEFS and ECMWF ensembles are starting to show signs of the ridging over Canada to retrograde, with rising heights favored over the northwestern CONUS. If realized, this pattern transition might promote the expansion of unseasonable warmth out West by the start of June.

Associated with cyclonic mid-level flow across the southern tier and return flow from the Gulf at the surface next week, there is a lingering threat of heavy precipitation heading into the start of the period. The ECMWF continues to remain the most bullish with this risk, with its uncalibrated tool continuing to indicate 30-50% chances for 3-day amounts exceeding an inch, and its Probabilistic Extreme Tool (PET) depicting similar chances for these amounts exceeding the 85th climatological percentile. However, drier conditions are favored in the GEFS, GEFS-AI, and Canadian guidance due to the weakening of the mean surface high over western Atlantic resulting in weaker return flow. Therefore, the moderate risk of heavy precipitation is discontinued, but a corresponding slight risk area remains posted where both the GEFS and ECMWF PETs maintain at least 20% chances of 3-day amounts exceeding the 85th percentile and 1 inch. Relative to yesterday, coverage for the slight risk area has been slightly adjusted and is extended an additional day (now valid through May 30) based on an uptick in wet signals among the tools towards the middle of week-2.

The risk of heavy precipitation highlighted early in week-2 follows an active precipitation regime over the south-central CONUS during week-1. While this pattern may prove to be beneficial in bringing improvement to prevailing drought conditions, the duration of above-normal precipitation coupled with multiple rounds of potentially heavy rainfall may trigger flooding, as some watersheds are already beginning to rise in response to the large influx of surface water. Week-1 QPF forecasts from the Weather Prediction Center depict precipitation totals exceeding 3-5 inches from southeastern Texas northeastward into portions of Arkansas and Louisiana, and any continued heavy precipitation into week-2 supports the potential of river flooding. A flooding possible hazard is expanded in the updated outlook to include portions of Oklahoma, Arkansas, and Mississippi, highlighting the highest potential for river and stream flooding.

Given the better agreement between the ECMWF and GEFS in regards to anomalous troughing over the Interior West, a slight risk of high winds is posted at the base and ahead of the mean mid-level trough favored early in week-2, where the uncalibrated ECMWF shows increased chances for wind gusts exceeding 34kts (~40mph) over many parts of the Rockies and High Plains. The combination of above-normal temperatures, antecedent dryness and periods of high winds is supportive of an elevated wildfire risk within the slight risk area. In addition, a second slight risk area for high winds is also posted over portions of coastal California and southern Oregon, based on strengthening gradients favored in the GEFS and ECMWF surface pressure fields and increased wind speed signals in both the GEFS and ECMWF PETs. Both wind hazards remain valid through May 30 before the troughing aloft deamplifies.

For temperatures, there is better model and tool agreement favoring the strongest positive temperature departures over much of north-central and northeastern CONUS in proximity to the amplified ridge center over the Hudson Bay throughout the period. Compared to the GEFS, there continues to be stronger warm signals in the ECMWF PET due to the stronger ridging, but regardless of these differences in magnitude among the PETS, there is little to no signal in the tools for actual temperatures reaching above 95 deg F to drive higher heat index values over this part of the country, precluding any corresponding heat hazards. This is supported in the NWS probabilistic National Blend of Models (NBM) Heat Risk guidance, which depicts modest chances for temperatures exceeding red level thresholds over the Northern Plains, Upper Mississippi Valley, Great Lakes and Ohio Valley. Even with the low risk for extreme heat conditions, the Northern Plains continues to be monitored for a potential Rapid Onset Drought (ROD) given the prevailing unseasonable late spring warmth expected combined with antecedent dryness. Soil moisture percentiles are running quite low from eastern Montana to North Dakota, as any continued lack of rainfall to worsen dryness, abetted by elevated evapotranspiration rates would support a ROD risk. However, there continues to be a number of precipitation tools that favor a tilt towards above-normal precipitation during week-2 to allay this risk at this time.

In Alaska, river ice breakup season is now well underway. Parts of the middle or lower Yukon are currently partially open, but are expected to be clear by the week-2 period. However, the threat of ice jam flooding would most likely be along rivers north of the Arctic Circle as they are currently mostly ice. River breakup flooding can occur with little or no notice as conditions on frozen rivers can change quickly, so please check with the Alaska Pacific River Forecast Center for the latest conditions and advisories.

Forecaster: Nick Novella

$$ Please consult local NWS Forecast Offices for short range forecasts and region-specific information.

Resources

Week-2 Probabilistic Extremes Tool

GFS Ensemble Forecasts