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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