866
FXUS21 KWNC 171844
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 17 2024
SYNOPSIS: A STALLED FRONTAL BOUNDARY COUPLED WITH POTENTIALLY INCREASING
TROPICAL ACTIVITY OVER THE WESTERN CARIBBEAN AND GULF OF MEXICO INCREASES THE
POTENTIAL FOR HEAVY PRECIPITATION AND HIGH WINDS FOR PORTIONS OF THE SOUTHEAST
U.S. HIGH WINDS ARE ALSO POSSIBLE OVER THE NORTHERN AND CENTRAL PLAINS IN THE
WAKE OF A COLD FRONT FORECAST TO MOVE THROUGH THE NORTHERN TIER AT THE OUTSET
OF WEEK-2. LOW PRESSURE AT THE SURFACE AND ALOFT OVER THE ALEUTIAN ISLANDS IS
FAVORED TO BRING HEAVY PRECIPITATION TO THE SOUTHEAST COAST OF ALASKA EARLY IN
WEEK-2.
HAZARDS
MODERATE RISK OF HEAVY PRECIPITATION FOR THE FLORIDA PENINSULA, WED-THU, SEP
25-26.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF FLORIDA, AND COASTAL
SOUTHEAST U.S. AND MID-ATLANTIC, WED-SUN, SEP 25-29.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF SOUTHEASTERN ALASKA,
WED-FRI, SEP 25-27.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE FLORIDA PENINSULA, WED-THU, SEP 25-26.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS,
WED-THU, SEP 25-26.
DETAILED SUMMARY
FOR FRIDAY SEPTEMBER 20 - TUESDAY SEPTEMBER 24:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY SEPTEMBER 25 - TUESDAY OCTOBER 01: TODAY’S MODEL SOLUTIONS DEPICT
A STALLED FRONTAL BOUNDARY ALONG THE SOUTHEAST COAST OF THE CONTIGUOUS U.S.
(CONUS) AT THE OUTSET OF WEEK-2. THIS COINCIDES WITH AN INCREASED POTENTIAL FOR
TROPICAL CYCLONE (TC) ACTIVITY OVER THE WESTERN CARIBBEAN AND GULF OF MEXICO.
THERE IS A GREAT DEAL OF UNCERTAINTY REGARDING THE EVOLUTION OF THIS SITUATION,
WITH A LARGE SPREAD REGARDING THE TIMING AND LOCATION OF ANY POTENTIAL TC
FORMATION. REGARDLESS, WITH THESE FACTORS IN PLAY THERE IS ENHANCED POTENTIAL
FOR HEAVY PRECIPITATION AND HIGH WINDS FOR THE SOUTHEAST U.S., PARTICULARLY
EARLY IN WEEK-2 FOR CENTRAL AND SOUTHERN FLORIDA. THIS HEAVY PRECIPITATION RISK
IS WELL-SUPPORTED BY THE GEFS AND ECMWF PROBABILISTIC EXTREMES TOOL (PETS),
WHICH INDICATE AT LEAST A 20% CHANCE OF 3-DAY PRECIPITATION TOTALS EXCEEDING
THE 85TH PERCENTILE AND 1 INCH FOR MUCH OF FLORIDA AND ALONG THE COAST OF THE
SOUTHEAST U.S. EARLY IN WEEK-2. THE ECMWF FAVORS MORE WIDESPREAD COVERAGE
INLAND BUT THIS APPEARS TO BE AN ARTIFACT OF A WET BIAS IN THE ECMWF PET. A
SLIGHT RISK FOR HEAVY PRECIPITATION IS POSTED FOR MUCH OF FLORIDA AND UP THE
SOUTHEAST COAST AS FAR NORTH AS THE OUTER BANKS FOR SEP 25-29. ADDITIONALLY, A
MODERATE RISK OF HEAVY PRECIPITATION IS POSTED FOR THE FLORIDA PENINSULA FOR
SEP 25-26, WHERE MODEL GUIDANCE PLACES THE HIGHEST CHANCE FOR HEAVY
PRECIPITATION. FINALLY, GIVEN THE POTENTIAL FOR INCREASED TC ACTIVITY BEING A
COMPONENT OF THIS WEATHER HAZARD A SLIGHT RISK FOR HIGH WINDS FOR SEP 25-26 IS
ISSUED FOR THE SAME AREA IN FLORIDA WHERE A MODERATE RISK OF HEAVY
PRECIPITATION IS DESIGNATED.
MULTIPLE MODEL SOLUTIONS DEPICT A PAIR OF COLD FRONTS SITUATED ACROSS THE GREAT
PLAINS AT THE OUTSET OF WEEK-2, ALONG WITH THE INCREASED ASSOCIATED POTENTIAL
FOR HIGH WINDS. THE GEFS AND ECWMF PETS INDICATE AT LEAST A 20% PROBABILITY OF
WIND SPEEDS EXCEEDING THE 85TH PERCENTILE AND AT 20 MPH FOR PORTIONS OF THE
NORTHERN AND CENTRAL PLAINS EARLY IN THE FORECAST PERIOD, THEREFORE A SLIGHT
RISK OF HIGH WINDS IS POSTED FOR SEP 25-26. THE PETS ALSO INDICATE THE
POTENTIAL FOR HIGH WINDS ASSOCIATED WITH THE SECOND FRONT FURTHER SOUTH IN
NORTHERN TEXAS, BUT HAZARD THRESHOLDS ARE NOT FORECAST TO BE EXCEEDED SO NO
ASSOCIATED HAZARD IS ISSUED AT THIS TIME.
THERE IS GOOD CONSENSUS AMONG MULTIPLE MODEL ENSEMBLES WITH REGARD TO AN
AMPLIFIED MID-LEVEL TROUGH AND ASSOCIATED SURFACE LOW PRESSURE OVER THE
ALEUTIAN ISLANDS IN PLACE AT THE START OF WEEK-2 AND REMAINING THROUGHOUT THE
WEEK. ADDITIONALLY THERE HAS BEEN INCREASED TC ACTIVITY IN THE WESTERN PACIFIC,
WHICH IS EXPECTED TO CONTINUE FOR THE NEAR FUTURE, WITH THE JOINT TYPHOON
WARNING CENTER CURRENTLY MONITORING MULTIPLE AREAS OF INTEREST IN THE WESTERN
PACIFIC. LIKE THE SOUTHEAST CONUS, THESE CONVERGING FACTORS HAVE THE POTENTIAL
TO BRING HEAVY PRECIPITATION TO THE SOUTHERN AND SOUTHEAST COAST OF ALASKA.
THIS IS SUPPORTED BY THE ECMWF AND GEFS PETS, WHICH INDICATE THE POTENTIAL FOR
3-DAY PRECIPITATION TOTALS TO EXCEED 3 INCHES FOR PORTIONS OF THE PANHANDLE OF
ALASKA FOR MUCH OF WEEK-2. UNCERTAINTY INCREASES LATER IN THE FORECAST PERIOD
SO FOR NOW A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR THE SOUTHERN
COAST AND PANHANDLE OF ALASKA FOR SEP 25-27, AND THIS SITUATION WILL BE CLOSELY
MONITORED IN THE COMING DAYS. WHILE THERE IS THE POSSIBILITY OF INCREASED WINDS
ASSOCIATED WITH THIS SYSTEM, HAZARDOUS CRITERIA ARE NOT ANTICIPATED TO BE MET
SO NO ASSOCIATED HAZARD IS POSTED AT THIS TIME.
FORECASTER: DANNY BARANDIARAN
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