684
FXUS21 KWNC 181827
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 18 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 SOUTHERN
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, TUE-WED, MAY 26-27.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS, LOWER AND MIDDLE MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS, AND
SOUTHEAST., TUE-FRI, MAY 26-29.
FLOODING POSSIBLE FOR MUCH OF EASTERN AND CENTRAL TEXAS, AND WESTERN LOUISIANA.
DETAILED SUMMARY
FOR THURSDAY MAY 21 - MONDAY MAY 25:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY MAY 26 - MONDAY JUNE 01: DYNAMICAL MODEL 500-HPA HEIGHT FORECASTS
FROM THE GEFS AND ECMWF ENSEMBLES CONTINUE TO FEATURE ANOMALOUS RIDGING OVER
THE NORTHERN PACIFIC AND SOUTHEASTERN CANADA, WITH A BROAD COVERAGE OF POSITIVE
HEIGHT ANOMALIES FAVORED MAINLY EAST OF THE ROCKIES. WHILE BOTH MODELS SHOW
WEAKNESSES IN THE HEIGHT PATTERN WITH BROAD CYCLONIC FLOW FROM THE DESERT
SOUTHWEST INTO THE SOUTHERN PLAINS, THE GEFS AND ECMWF REMAIN AT ODDS WITH
EVOLUTION OF TROUGHING OVER THE GULF OF ALASKA BY EARLY NEXT WEEK. THE GEFS
FAVORS MORE ANOMALOUS RIDGING OVER THE NORTHWESTERN CONUS, WHEREAS THE ECMWF
FEATURES MORE AMPLIFIED TROUGHING ENCROACHING THE PACIFIC NORTHWEST TO BRING
MORE UNSETTLED WEATHER ACROSS PORTIONS OF THE WESTERN CONUS. AS A RESULT,
THERE ARE DISPARITIES IN THE ENSEMBLE GUIDANCE IN REGARDS TO ENHANCED MOISTURE
FROM THE PACIFIC AS WELL AS ANY ADDITIONAL SHORTWAVE ENERGY EJECTING FROM THE
WEST LATER NEXT WEEK. REGARDLESS OF THESE DIFFERENCES, THE PATTERN CONTINUES TO
SUPPORT THE POTENTIAL FOR A LINGERING HEAVY PRECIPITATION RISK ASSOCIATED WITH
CONTINUED ENHANCED RETURN FLOW FROM THE GULF, AS WELL AS UNSEASONABLY WARM LATE
SPRING TEMPERATURES OVER PARTS OF THE MIDWEST UNDERNEATH THE ANOMALOUS RIDGING
FAVORED ALOFT.
WITH THE CONTINUED MOIST, SOUTHERLY FLOW FROM THE GULF FAVORED TO PERSIST FROM
WEEK-1 AND INTO EARLY WEEK-2, ALONG WITH LINGERING FRONTAL ACTIVITY, A MODERATE
RISK OF HEAVY PRECIPITATION REMAINS POSTED FOR PORTIONS OF THE SOUTHERN PLAINS
AND LOWER MISSISSIPPI VALLEY. WITHIN THE HIGHLIGHTED AREA, THE UNCALIBRATED
GEFS AND ECMWF TOOLS FEATURE AT LEAST 40% (20%) CHANCES FOR 3-DAY AMOUNTS
EXCEEDING ONE (TWO) INCH(ES), WITH THE CALIBRATED PROBABILISTIC EXTREME TOOLS
(PETS) ALSO INDICATING AT LEAST 30% CHANCES FOR AMOUNTS EXCEEDING THE 85TH
PERCENTILE. THE MODERATE RISK AREA IS ADJUSTED TO COVER MORE AREAS OF CENTRAL
TEXAS IN THE UPDATED OUTLOOK BASED ON INCREASED PRECIPITATION SIGNALS IN THE
TOOLS OVER THIS PART OF THE STATE COMPARED TO YESTERDAY. 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 THE MIDDLE OF
WEEK-2 (MAY 29). THE ECMWF FAVORS A WETTER SOLUTION FOR THE LOWER EASTERN
SEABOARD, HOWEVER THIS IS LESS SUPPORTED BY THE GEFS AND IS NOT INCLUDED IN THE
SLIGHT RISK AREA AT THIS TIME.
GIVEN THE PREVAILING DROUGHT CONDITIONS FOR MANY AREAS ACROSS THE SOUTH, THE
FAVORED ENHANCED RAINFALL MAY PROVE TO BE BENEFICIAL. HOWEVER, THE LENGTHENING
DURATION OF ABOVE-NORMAL PRECIPITATION COUPLED WITH THE MULTIPLE ROUNDS OF
POTENTIALLY HEAVY RAINFALL MAY TRIGGER FLOODING OVER EASTERN TEXAS AND WESTERN
LOUISIANA, AS SOME WATERSHEDS ARE ALREADY BEGINNING TO RISE IN RESPONSE TO THE
LARGE INFLUX OF SURFACE WATER. DAYS 6 AND 7 QPF FORECASTS FROM THE WEATHER
PREDICTION CENTER DEPICT PRECIPITATION TOTALS EXCEEDING 1-2 INCHES ACROSS
SOUTHEASTERN TEXAS, AND ANY CONTINUED HEAVY PRECIPITATION INTO WEEK-2 SUPPORTS
THE POTENTIAL OF RIVER FLOODING. A FLOODING POSSIBLE HAZARD IS POSTED,
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 FLOODWATERS.
TIED TO THE AMPLIFIED RIDGING OVER SOUTHERN CANADA, EXPERIMENTAL HEAT RISK
TOOLS FAVOR THE GREATEST CHANCES FOR TEMPERATURES EXCEEDING RED LEVEL CRITERIA
OVER THE OHIO VALLEY AND GREAT LAKES EARLY IN WEEK-2. HOWEVER, BOTH RAW AND
CALIBRATED TEMPERATURE TOOLS ARE LESS SUPPORTIVE OF THIS RISK OVER THIS PART OF
THE COUNTRY, AND INSTEAD FAVOR A LARGER AND STRONGER COVERAGE OF POSITIVE
TEMPERATURE DEPARTURES FOCUSED OVER THE NORTH-CENTRAL CONUS IN PROXIMITY TO THE
RIDGE CENTER ALOFT DURING THE PERIOD. A SLIGHT RISK OF EXCESSIVE HEAT WAS
CONSIDERED FOR ADDITION OVER PARTS OF THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY, THOUGH ACTUAL TEMPERATURES LOOK TO STRUGGLE TO REACH INTO THE 90S (DEG
F), PRECLUDING ANY EXTREME HEAT HAZARDS AT THIS TIME. IN ADDITION, THE
COMBINATION OF ABOVE-NORMAL TEMPERATURES, ALONG WITH ANTECEDENT DRYNESS MAY
SUPPORT THE POTENTIAL FOR RAPID ONSET DROUGHT (ROD) OVER THE NORTHERN PLAINS.
BASED ON A NUMBER OF PRECIPITATION FORECASTS WHICH TILT SLIGHTLY ABOVE-NORMAL
DURING WEEK-2, THERE IS NOT ENOUGH CONFIDENCE TO POST ANY ROD HAZARDS AT THIS
TIME, BUT PORTIONS OF EASTERN MONTANA, NORTH DAKOTA AND ADJACENT MINNESOTA WILL
BE CLOSELY MONITORED MANY OF THESE AREAS HAVE RECEIVED LESS THAN AN INCH OF
PRECIPITATION OVER THE PAST 30 DAYS.
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 AND
SURFACE LOW DEVELOPMENT IN THE LEE OF THE ROCKIES. 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
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