FXUS21 KWNC 191831 PMDTHR US Hazards Outlook NWS Climate Prediction Center College Park MD 300 PM EDT May 19 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 mainly over the Southern Plains and Lower Mississippi Valley. The duration of above-normal precipitation coupled with the multiple rounds of potentially heavy rainfall may lead to flooding over portions of eastern Texas. 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 Moderate risk of heavy precipitation for the Southern Plains and Lower Mississippi Valley, Wed, May 27. Slight risk of heavy precipitation for portions of the Central and Southern Plains, Lower and Middle Mississippi, Tennessee, and Ohio Valleys, Southeast, Southern Appalachians, and lower Mid-Atlantic, Wed-Fri, May 27-29. Flooding possible for much of eastern Texas, portions of Arkansas and Louisiana. DETAILED SUMMARY FOR FRIDAY MAY 22 - TUESDAY MAY 26: https://www.wpc.ncep.noaa.gov/threats/threats.php FOR WEDNESDAY MAY 27 - TUESDAY JUNE 02: Consistent with previous ensemble mean guidance, 500-hPa height anomaly forecasts from the GEFS and ECMWF continue to show discrepancies in regards to the shape and strength of the mid-level pattern towards the middle of next week. While both models favor amplified ridging over eastern Canada, the respective mean ridge centers are displaced from one another in the anomaly fields, with the ECMWF favoring a more westerly and much stronger mean solution of this feature over the Hudson Bay. More critically, mid-level height anomalies continue to be of opposite sign upstream, where the ECMWF ensemble is resolute in favoring anomalous troughing digging southward into the Interior West, whereas the GEFS maintains a broad distribution of positive height departures over much of the western CONUS extending westward into the northeastern Pacific. Across the lower latitudes, better agreement exists between the GEFS and ECMWF where there continues to be weaknesses in the height anomalies characterized by broad cyclonic flow from the Desert Southwest to the Southern Plains. Accompanied by enhanced low-level southerly flow from the Gulf, the pattern looks to be conducive for above-normal, and possibly heavy precipitation across the southern tier of the U.S. early in week-2, however significant uncertainty remains in the outlook as a result of these variations in predicted height pattern elsewhere throughout the U.S. Based on the latest precipitation tools, a moderate risk of heavy precipitation continues to be designated for the Southern Plains and Lower Mississippi Valley, and remains valid through May 27. Within this highlighted area, the uncalibrated GEFS and ECMWF tools feature at 30-50% chances for 3-day amounts exceeding one inch, with the calibrated Probabilistic Extreme Tools (PETs) also indicating 20-30% chances for amounts exceeding the 85th percentile early in the period. Surrounding this moderate risk area, a slight risk of heavy precipitation remains posted from the Southern and Central Plains eastward to portions of the Ohio and Tennessee Valleys and Southeast, where both GEFS and ECMWF PETs show at least 20% chances for amounts exceeding the 85th percentile and 1 inch through day 10 (May 29). Relative to yesterday, the slight risk area is expanded eastward to cover more of the Southeast and lower Mid-Atlantic based on wetter signals in the GEFS PET. The ECMWF has become more bullish in placing elevated chances (30-40%) for 3-day amounts exceeding an inch over the lower eastern Seaboard, however GEFS and Canadian favors more mid-level ridging aloft, suppressing this higher precipitation potential. 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 alleviating antecedent dryness and bring 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 remains posted and is expanded in the updated outlook, highlighting the highest potential for river and stream flooding. However, urban and flash flooding is possible outside this area, and caution should always be exercised when approaching floodwater. Tied to the amplified ridge center over Canada, ensembles maintain a broad coverage of positive height departures supportive of above-normal temperatures over much of north-central and northeastern CONUS throughout the period. Based on raw tools, the strongest positive temperature departures are favored in proximity to the anomalous ridge center over the upper Midwest. PETs continue to highlight increased chances for daytime temperatures exceeding the 85th percentile, with the ECMWF PET remaining more bullish, depicting 30-40% chances for exceeding this climatological threshold focused over the Northern Plains, Upper Mississippi Valley, and northern Great Lakes for most of the week-2 period. These stronger warm signals in the ECMWF PETs are likely due to the stronger ridging favored over the Hudson Bay. But regardless of these differences in the PETS, there is little to no signal in the tools for actual temperatures reaching above 90 deg F to drive higher heat index values over this part of the country, precluding any corresponding heat hazards. Even with the low risk for heat, the Northern Plains is being monitored for a potential Rapid Onset Drought (ROD) given the prevailing warmth expected combined with antecedent dryness. Soil moisture percentiles are running quite low from eastern Montana to North Dakota, where any continued dearth of rainfall could worsen dryness, abetted by the above-normal temperatures to elevate evapotranspiration rates. However, there continues to be a number of precipitation tools that favor a tilt towards above-normal precipitation during week-2 to allay any ROD risk at this time. The stronger mean mid-level trough that is favored to shift eastward from the northeastern Pacific in the ECMWF ensemble supports the potential for high winds across portions of the West Coast, as well as across parts of the Interior West and High Plains associated with additional shortwave energy. While this potential is reflected in both raw and calibrated wind tools from the ECMWF, the ridging favored in the GEFS results in lowered wind risk, and no corresponding wind hazards are issued for week-2. 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 $$