166
FXUS21 KWNC 211950
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT OCTOBER 21 2024
SYNOPSIS: MID-LEVEL LOW (HIGH) PRESSURE OVER THE WESTERN (EASTERN) HALF OF THE
CONTIGUOUS U.S. (CONUS) IS PREDICTED FOR THE WEEK-2 PERIOD. THIS PATTERN FAVORS
A SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE MISSISSIPPI VALLEY AND
CENTRAL AND SOUTHERN PLAINS AND HIGH WINDS ACROSS THE CENTRAL CONUS AT THE
BEGINNING OF THE PERIOD. LOCALIZED THUNDERSTORMS ARE POSSIBLE IN THE
HIGHLIGHTED HEAVY PRECIPITATION RISK AREA.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE MISSISSIPPI VALLEY AND
CENTRAL AND SOUTHERN PLAINS, TUE-THU, OCT 29-31.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF THE CENTRAL CONUS, TUE-THU, OCT
29-31.
DETAILED SUMMARY
FOR THURSDAY OCTOBER 24 - MONDAY OCTOBER 28:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY OCTOBER 29 - MONDAY NOVEMBER 04: THERE IS GOOD AGREEMENT AMONG
MULTIPLE MODEL ENSEMBLE MEANS INDICATING MID-LEVEL TROUGHING (RIDGING) OVER THE
WESTERN (EASTERN) HALF OF THE CONUS DURING WEEK-2, ALTHOUGH WITH VARYING
DETAILS REGARDING THE PLACEMENT AND EVOLUTION OF THESE FEATURES. THIS PATTERN
IS CONDUCIVE TO LEE CYCLOGENESIS AND FRONTAL ACTIVITY OVER THE CENTRAL CONUS
WHICH COULD SUPPORT ENHANCED WIND SPEEDS AND PRECIPITATION AT THE BEGINNING OF
WEEK-2. A SLIGHT RISK OF HEAVY PRECIPITATION IS HIGHLIGHTED ACROSS PARTS OF THE
MISSISSIPPI VALLEY AND CENTRAL AND SOUTHERN PLAINS, OCT 29-31, ASSOCIATED WITH
THE INCREASED POTENTIAL FOR THUNDERSTORMS WHICH MAY PRODUCE LOCALIZED HEAVY
PRECIPITATION. THE RISK AREA HIGHLIGHTED IS PRIMARILY BASED ON THE ECENS WHICH
IS MORE SUPPORTIVE OF THIS HEAVY PRECIPITATION SIGNAL, WITH THE ASSOCIATED
PROBABILISTIC EXTREMES TOOL (PET) INDICATING AT LEAST A 50% CHANCE OF 3-DAY
RAINFALL TOTALS EXCEEDING THE 85TH PERCENTILE CLIMATOLOGICALLY. TOTALS MAY
EXCEED ONE INCH IN THE DESIGNATED TIME PERIOD. THE GEFS’ SIGNAL IS MUCH WEAKER,
INDICATING ONLY AT LEAST A 20% CHANCE OF EXCEEDING THE 85TH PERCENTILE, WITH
ONE INCH TOTALS LIMITED TO THE ARK-LA-TEX REGION.
IN ADDITION TO INCREASED POTENTIAL FOR HEAVY PRECIPITATION, THE AFOREMENTIONED
FRONTAL SYSTEM MAY ALSO SUPPORT ENHANCED WIND SPEEDS. THEREFORE A BROAD AREA OF
SLIGHT RISK OF HIGH WINDS IS POSTED ACROSS THE GREAT PLAINS AND MISSISSIPPI
VALLEY, OCT 29-31. THE GEFS, ECENS, AND CANADIAN PETS ARE IN GOOD AGREEMENT
INDICATING AT LEAST A 20% CHANCE OF WIND SPEEDS EXCEEDING THE 85TH PERCENTILE
AND 20 MPH ACROSS THE HIGHLIGHTED RISK AREA.
SURFACE LOW PRESSURE MAY EXTEND FROM THE GULF OF ALASKA SOUTHWARD TO THE
PACIFIC NORTHWEST COAST AT THE BEGINNING OF WEEK-2, WHICH COULD BRING ENHANCED
MOISTURE AND PRECIPITATION TO THE PACIFIC NORTHWEST. THE GEFS AND ECENS
INTEGRATED VAPOR TRANSPORT (IVT) TOOLS SHOW SOME INCREASED CHANCES FOR ENHANCED
IVT (>250 KG/M/S) AT THE BEGINNING AND TOWARDS THE END OF WEEK-2. THE GEFS IS
THE MOST SUPPORTIVE OF IMPACTS ASSOCIATED WITH A SHORTWAVE TROUGH FORMING OVER
THE COASTAL BRITISH COLUMBIA THAT WOULD ENHANCE WESTERLY ONSHORE FLOW INTO THE
PACIFIC NORTHWEST. HOWEVER, THERE IS SIGNIFICANT DISAGREEMENT AMONG MODELS
REGARDING THE INTENSITY AND POSITION OF THIS LOW WHICH PRECLUDES ANY ASSOCIATED
HAZARDS FROM BEING DESIGNATED AT THIS TIME.
THE AREA OF RAPID ONSET DROUGHT RISK PREVIOUSLY DESIGNATED OVER THE ARK-LA-TEX
REGION AND WESTERN MISSISSIPPI IS REMOVED IN TODAY’S OUTLOOK DUE TO ANTICIPATED
RAINFALL DURING THE WEEK-2 PERIOD. OVER FLORIDA, THE POSSIBLE FLOOD RISK HAZARD
IS ALSO REMOVED DUE TO EXPECTED DRIER CONDITIONS DURING WEEKS 1 AND 2.
BROAD MID-LEVEL TROUGHING IS ANTICIPATED OVER ALASKA THROUGHOUT WEEK-2,
SUPPORTING INCREASED CHANCES FOR BELOW NORMAL TEMPERATURES ACROSS MUCH OF THE
STATE EXCLUDING NORTHERN ALASKA, AND ABOVE NORMAL PRECIPITATION. SURFACE LOW
FORMATION IS PREDICTED OVER THE GULF OF ALASKA THAT COULD BRING WET AND WINDY
WEATHER TO SOUTHEASTERN ALASKA, BUT CONDITIONS ARE NOT EXPECTED TO REACH
HAZARDOUS THRESHOLDS.
FORECASTER: MELISSA OU
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