134  
FXUS21 KWNC 271943  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT SEPTEMBER 27 2024  
 
SYNOPSIS: HEAVY RAINFALL IS FORECAST ACROSS MUCH OF THE SOUTHEAST, EXTENDING  
THROUGH PORTIONS OF THE MIDDLE MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS TO THE  
MID-ATLANTIC DURING WEEK-1 RELATED TO THE REMNANTS OF HELENE. WHILE THE SYSTEM  
IS FORECAST TO DISSIPATE WELL BEFORE THE START OF WEEK-2, FLOODING IMPACTS MAY  
CONTINUE OVER THESE AREAS. ANY ADDITIONAL RAINFALL OVER PARTS OF FLORIDA AND  
THE SOUTHEAST DURING WEEK-2 COULD FURTHER EXACERBATE FLOODING CONCERNS.  
LATE-SEASON EXCESSIVE HEAT IS FAVORED ACROSS THE DESERT SOUTHWEST EARLY IN  
WEEK-2. SURFACE LOW PRESSURE MAY BRING ENHANCED WIND AND RAINFALL TO PARTS OF  
SOUTHERN ALASKA DURING THE OUTLOOK PERIOD BUT ARE NOT ANTICIPATED TO REACH  
HAZARDOUS CRITERIA AT THIS TIME.  
 
HAZARDS  
 
SLIGHT RISK OF EXCESSIVE HEAT OVER THE DESERT SOUTHWEST, SAT, OCT 5.  
 
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE SOUTHEAST AND GULF  
COASTS, SAT-TUE, OCT 5-8.  
 
FLOODING POSSIBLE ACROSS PORTIONS OF THE SOUTHEAST, SOUTHERN APPALACHIANS, AND  
UPPER TENNESSEE VALLEY.  
 
RISK OF RAPID ONSET DROUGHT (ROD) ACROSS PORTIONS OF EASTERN OKLAHOMA AND  
NORTHEASTERN TEXAS.  
 
DETAILED SUMMARY  
 
FOR MONDAY SEPTEMBER 30 - FRIDAY OCTOBER 04:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
FOR SATURDAY OCTOBER 05 - FRIDAY OCTOBER 11: THE REMNANTS OF HELENE ARE  
EXPECTED TO RESULT IN AN EXTENDED PERIOD OF VERY HEAVY RAIN AND FLASH FLOODING  
DURING WEEK-1 ACROSS PARTS OF THE SOUTHEAST, SOUTHERN APPALACHIANS, AND UPPER  
TENNESSEE VALLEY. SOME FLOODING MAY PERSIST INTO THE WEEK-2 PERIOD. BY THE  
OUTSET OF WEEK-2, THERE IS INCREASED POTENTIAL FOR TROPICAL CYCLONE DEVELOPMENT  
OVER THE VICINITY OF THE BAY OF CAMPECHE. TROPICAL MOISTURE ASSOCIATED WITH  
THIS SYSTEM IS FORECAST TO STREAM NORTHEASTWARD ACROSS FLORIDA DURING WEEK-2,  
BRINGING ADDITIONAL RAINFALL TO THE STATE. SURFACE HIGH PRESSURE IS FORECAST BY  
THE GEFS, ECENS, AND CMCE ENSEMBLE MEAN MODELS TO BE CENTERED NEAR THE SOUTHERN  
APPALACHIANS AND IS EXPECTED TO IMPEDE THE NORTHERN ADVANCE OF THE  
PRECIPITATION NOTED OVER FLORIDA. THERE IS TOO MUCH UNCERTAINTY THIS FAR IN  
ADVANCE REGARDING THE POTENTIAL TRACK AND INTENSITY OF ANY TROPICAL CYCLONE  
THAT MIGHT FORM. WHILE THE GEFS AND CMCE FAVOR HEAVIER PRECIPITATION MOVING  
ACROSS THE CENTRAL AND EASTERN GULF COAST, THE ECENS FAVORS A MUCH BROADER  
PRECIPITATION SWATH THAT ALSO INCLUDES THE WESTERN GULF COAST REGION. THE ECENS  
PROBABILISTIC EXTREMES TOOL (PET) DEPICTS AT LEAST A 20 PERCENT CHANCE OF 3-DAY  
RAINFALL TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 1-INCH OVER  
MOST OF THE GULF COAST, ESPECIALLY DURING THE FIRST HALF OF WEEK-2. THE GEFS  
AND CMCE PETS ARE NOT AS WIDESPREAD IN COVERAGE NOR AS CONFIDENT AS THE ECENS  
IS. GIVEN THE UNCERTAINTY, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR  
MOST OF THE GULF AND SOUTHEAST COASTS (INCLUDING ALL OF FLORIDA), OCT 5-8.  
 
ANOMALOUSLY WARM TEMPERATURES ARE FORECAST ACROSS MUCH OF THE CONTIGUOUS U.S.  
(CONUS) DURING WEEK-2, WITH A SLIGHT RISK OF EXCESSIVE HEAT FAVORED FOR THE  
DESERT SOUTHWEST ON OCT 5. THIS IS BASED ON PET TEMPERATURE GUIDANCE FROM THE  
GEFS, ECENS, AND CMCE, WHICH FAVOR MAXIMUM TEMPERATURES ABOVE THE 90TH  
PERCENTILE AND SLIGHTLY EXCEEDING 105 DEG F. OVERNIGHT LOW TEMPERATURES ARE  
FORECAST TO FALL ONLY TO THE MID-UPPER 70’S. THIS HEAT POTENTIAL IS ATTRIBUTED  
TO A MID-LEVEL RIDGE FORECAST OVER THE REGION. INCREASED CHANCES FOR EXCESSIVE  
HEAT RISK SUPPORTS ELEVATED RISK OF WILDFIRES.  
 
THE MID-LEVEL CIRCULATION PATTERN DURING WEEK-2 FAVORS A MODERATE RIDGE OVER  
THE WESTERN CONUS AND A TROUGH OVER THE EASTERN CONUS. THE GEFS AND ECENS  
PREDICT AT LEAST A 20 PERCENT CHANCE OF MINIMUM TEMPERATURES FALLING BELOW THE  
15TH HISTORICAL PERCENTILE AND OVERNIGHT LOWS FALLING BELOW 40 DEG F ASSOCIATED  
WITH THIS TROUGH OVER MUCH OF THE EAST EARLY IN WEEK-2. THE ECENS PREDICTS THIS  
ANOMALOUSLY COLD AIR WILL REACH AS FAR SOUTH AS THE MIDDLE MISSISSIPPI AND  
TENNESSEE VALLEYS, WHILE THE GEFS ADVANCES THE ANOMALOUSLY COLD AIR EASTWARD  
ACROSS THE NORTHEAST WITH TIME. THE POSSIBILITY OF THIS RELATIVELY COLD AIR  
SWEEPING ACROSS MUCH OF THE EASTERN CONUS WILL BE REASSESSED MORE CLOSELY EARLY  
NEXT WEEK. FOR NOW, SOME AGRICULTURAL INTERESTS FROM THE UPPER MISSISSIPPI  
VALLEY EASTWARD ACROSS THE NORTHERN GREAT LAKES AND NORTHEAST MAY EXPERIENCE  
THEIR FIRST FREEZE OF THE SEASON.  
 
THE RAPID ONSET DROUGHT (ROD) AREA WAS RECENTLY EXTENDED SLIGHTLY SOUTHWARD TO  
INCLUDE MORE OF EAST-CENTRAL TEXAS, AND IS BASED ON 30-DAY PRECIPITATION  
DEFICITS, LOW SOIL MOISTURE, AND LITTLE PREDICTED RAINFALL DURING THE NEXT TWO  
WEEKS. WITH ALL THE UNCERTAINTY REGARDING FUTURE TROPICAL STORM DEVELOPMENT AND  
TRACKS, THE EXTENDED ROD REGION WAS KEPT WELL AWAY FROM THE TEXAS COAST.  
 
SURFACE LOW PRESSURE IS FORECAST ACROSS THE GULF OF ALASKA DURING WEEK-2, WITH  
INDIVIDUAL CYCLONIC SYSTEMS BRINGING THE INCREASED POTENTIAL FOR HIGH WINDS AND  
HEAVY RAIN TO THE SOUTHERN COAST, PRIMARILY EAST OF THE KENAI PENINSULA. AT  
THIS TIME, PRECIPITATION AND WINDS ARE EXPECTED TO REMAIN BELOW HAZARDOUS  
THRESHOLDS.  
 
FORECASTER: ANTHONY ARTUSA  
 
 
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