783
FXUS21 KWNC 201800
PMDTHR
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:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
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
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