522
FXUS21 KWNC 211809
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 21 2026
SYNOPSIS: A SLOW-MOVING FRONTAL BOUNDARY IS FORECAST TO INTERACT WITH MOIST
SOUTHERLY FLOW EARLY WEEK-2, INCREASING THE POTENTIAL OF HEAVY PRECIPITATION
FOR PORTIONS OF THE SOUTHERN PLAINS, THE TENNESSEE AND LOWER MISSISSIPPI
VALLEYS, AND THE SOUTHEAST. SURFACE LOW PRESSURE DEVELOPMENT IS POSSIBLE OVER
OR NEAR THE EASTERN CONTIGUOUS UNITED STATES (CONUS) TOWARD THE MIDDLE OF THE
PERIOD WITH ANOTHER FRONTAL BOUNDARY POSSIBLY AFFECTING PARTS OF THE SOUTH LATE
WEEK-2, BUT THERE IS TOO MUCH UNCERTAINTY TO POST ANY ASSOCIATED HAZARDS AT
THIS TIME.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHERN PLAINS; THE
TENNESSEE, LOWER MISSISSIPPI, AND SOUTHERN OHIO VALLEYS; AND ADJACENT AREAS OF
THE SOUTHEAST AND SOUTHERN APPALACHIANS, WED-THU, APR 29-30.
DETAILED SUMMARY
FOR FRIDAY APRIL 24 - TUESDAY APRIL 28:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY APRIL 29 - TUESDAY MAY 05: ENSEMBLE SOLUTIONS FROM THE ECENS AND
GEFS FOR 500-HPA HEIGHT ANOMALIES DEPICT A SHORTWAVE TROUGH MOVING FROM THE
WESTERN CONTIGUOUS U.S. (CONUS) TO THE GREAT LAKES BY THE OUTSET OF THE WEEK-2
PERIOD, WITH AN ACCOMPANYING SURFACE LOW PRESSURE AND A TRAILING COLD FRONT
AHEAD OF THE TROUGH. MODELS FAVOR THIS FRONTAL BOUNDARY TO MOVE SLOWLY THROUGH
THE SOUTH FROM THE SOUTHEASTERN GREAT PLAINS THROUGH THE LOWER MISSISSIPPI AND
TENNESSEE VALLEYS, INTO THE SOUTHEAST. THESE FEATURES ARE NOT PARTICULARLY
AMPLIFIED BUT FORM WHILE MODERATE SOUTHERLY FLOW IS ESTABLISHED TO THE WEST OF
A SURFACE HIGH PRESSURE SYSTEM OVER THE WESTERN NORTH ATLANTIC. THIS RETURN
FLOW IS ANTICIPATED TO INCREASE MOISTURE AVAILABLE TO THE DEVELOPING SYSTEM,
ENHANCING PRECIPITATION ACCUMULATIONS. THE PROBABILISTIC EXTREMES TOOL (PET)
FROM THE EUROPEAN ENSEMBLE (ECENS) SHOWS 30 TO 40 PERCENT PROBABILITIES OF
3-DAY PRECIPITATION ACCUMULATIONS EXCEEDING 1” EARLY WEEK-2 OVER MUCH OF THE
LOWER MISSISSIPPI VALLEY AND SOME ADJACENT AREAS. PETS FROM THE GEFS AND THE
CANADIAN ENSEMBLE (CMCE) ARE LESS ROBUST, SHOWING 20 TO 30 PERCENT CHANCES FOR
3-DAY TOTALS OVER AN INCH. THE ECENS MEAN DEPICTS 1 TO 2 INCHES OF RAIN FROM
CENTRAL MISSISSIPPI EASTWARD INTO GEORGIA AND NORTHEASTWARD INTO KENTUCKY WHILE
THE DYNAMICAL EUROPEAN MODEL (ECMWF) SHOWS A LESS WIDESPREAD PATTERN OF HEAVY
RAIN, BUT WITH LOCALIZED AREAS APPROACHING 3 INCHES. THESE FACTORS SUPPORT A
SLIGHT RISK OF HEAVY PRECIPITATION FROM PORTIONS OF THE SOUTHERN PLAINS THROUGH
THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS AND INTO ADJACENT SECTIONS OF THE
OHIO VALLEY, SOUTHEAST, AND SOUTHERN APPALACHIANS APR 29-30. BY MAY 1, THE COLD
FRONT IS EXPECTED TO HAVE CLEARED THE GULF AND SOUTH ATLANTIC COASTS, ENDING
THE HEAVY RAIN THREAT. ISOLATED, BRIEF HIGH WIND GUSTS ARE POSSIBLE ASSOCIATED
WITH POTENTIALLY STRONG THUNDERSTORMS, BUT GUIDANCE DOES NOT SUPPORT
WIDESPREAD STRONG WINDS, SO NO HIGH WIND THREAT IS POSTED.
AS THE COLD FRONT CLEARS THE SOUTHERN AND EASTERN CONUS, SOME MODELS SHOW A
SURFACE LOW PRESSURE SYSTEM FORMING SOMEWHERE OVER OR NEAR THE EASTERN CONUS
THAT GETS PICKED UP BY THE NEGATIVELY-TILTED MID-LEVEL TROUGH MOVING TOWARD THE
GREAT LAKES AND NEW ENGLAND. THE DYNAMICAL ECMWF ARTIFICIAL INTELLIGENCE MODEL
(ECMWF-AI) IS MOST ROBUST WITH SUCH A SYSTEM, SHOWING LOW PRESSURE FORMING OVER
THE SOUTH ATLANTIC REGION AND MOVING UP THE EASTERN SEABOARD. IF A SIGNIFICANT
SURFACE STORM SYSTEM DEVELOPS, HEAVY PRECIPITATION COULD AFFECT ALL OR PART OF
THE GREAT LAKES AND ATLANTIC SEABOARD, PARTICULARLY IN THE NORTHEASTERN CONUS
WHICH WILL BE DOWNSTREAM FROM A MID-LEVEL TROUGH. AT THIS TIME, THERE IS TOO
MUCH UNCERTAINTY TO JUSTIFY POSTING ANY HAZARDS, BUT THE SITUATION WILL
CONTINUE TO BE MONITORED.
BREEZY CONDITIONS ARE LIKELY IN THE WAKE OF THE COLD FRONT AS COOL AND DRY HIGH
PRESSURE SETTLES INTO THE CENTRAL AND EASTERN CONUS. WINDS ARE NOT EXPECTED TO
REACH HAZARDS THRESHOLDS, BUT LARGE PORTIONS OF THIS REGION ARE CURRENTLY
ENTRENCHED IN SOME DEGREE OF DROUGHT. THE COMBINATION OF DRY AND BREEZY
CONDITIONS OVER PARTS OF THE CENTRAL AND EASTERN CONUS WHERE THERE IS
ANTECEDENT DRYNESS SIGNIFICANTLY INCREASES THE RISK OF WILDFIRE ACTIVITY, WHICH
COULD SPREAD RAPIDLY. CARE SHOULD BE TAKEN TO MINIMIZE THE CHANCES OF WILDFIRE
INITIATION.
LATER IN WEEK-2, SOME TOOLS, INCLUDING THE ECMWF, SHOW ANOTHER COLD FRONT
MOVING INTO THE SOUTH, POTENTIALLY TRIGGERING ANOTHER ROUND OF HEAVY
PRECIPITATION THERE. AT THIS TIME, MOST TOOLS FAVOR SUB-HAZARDOUS PRECIPITATION
TOTALS WITH THIS SYSTEM, AND SOME MODELS DO NOT SHOW ANY LATE-WEEK FRONTAL
SYSTEM AFFECTING THIS REGION. THIS, ALONG WITH RUN-TO-RUN INCONSISTENCY AMONG
THE MODELS, PRECLUDES POSTING ANY RELATED HAZARDS AT THIS TIME.
NO HAZARDS ARE ISSUED OVER ALASKA, WITH NONDESCRIPT WEATHER EXPECTED UNDER
SLOWLY-BUILDING MID-LEVEL HEIGHTS. HOWEVER, THE TYPICAL PEAK OF THE RIVER ICE
BREAKUP SEASON IS APPROACHING, AND ICE JAM FLOODING CAN OCCUR THIS TIME OF YEAR
WITH LITTLE OR NO NOTICE AS CONDITIONS ON FROZEN RIVERS CAN CHANGE QUICKLY.
CHECK WITH THE ALASKA PACIFIC RIVER FORECAST CENTER FOR THE LATEST CONDITIONS
AND ADVISORIES.
FORECASTER: RICH TINKER
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