707
FXUS21 KWNC 261938
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 26 2024
SYNOPSIS: HEAVY RAINFALL IS FORECAST ACROSS MUCH OF THE SOUTHEAST, EXTENDING
THROUGH THE MIDDLE MISSISSIPPI VALLEY TO THE SOUTHERN MID-ATLANTIC DURING
WEEK-1 RELATED TO THE REMNANTS OF HURRICANE HELENE. WHILE THE SYSTEM IS
FORECAST TO DISSIPATE WELL BEFORE THE START OF WEEK-2, FLOODING IMPACTS ARE
LIKELY TO 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 WIND AND RAIN IMPACTS TO PARTS
OF SOUTHERN ALASKA DURING THE OUTLOOK PERIOD.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT OVER THE DESERT SOUTHWEST, FRI, OCT 4.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE SOUTHEAST, FRI-MON,
OCT 4-7.
SLIGHT RISK OF HIGH WINDS OVER THE NORTHERN PLAINS, FRI, OCT 4.
FLOODING POSSIBLE ACROSS PORTIONS OF THE SOUTHEAST, APPALACHIANS, AND SOUTHERN
MID-ATLANTIC.
RISK OF RAPID ONSET DROUGHT (ROD) ACROSS PORTIONS OF EASTERN OKLAHOMA AND
NORTHEASTERN TEXAS.
DETAILED SUMMARY
FOR SUNDAY SEPTEMBER 29 - THURSDAY OCTOBER 03:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY OCTOBER 04 - THURSDAY OCTOBER 10: AS OF 1PM CDT TODAY, THE NATIONAL
HURRICANE CENTER (NHC) FORECASTS HURRICANE HELENE (CURRENTLY OVER THE EASTERN
GULF OF MEXICO) TO MAKE LANDFALL THIS EVENING OVER THE BIG BEND AREA OF
NORTHERN FLORIDA. THE REMNANTS OF THIS SYSTEM ARE FORECAST TO TRACK INLAND AND
CURVE NORTHWESTWARD RESULTING IN HEAVY RAINFALL EXTENDING NORTHWARD INTO THE
SOUTHERN MID-ATLANTIC AND APPALACHIANS, AND WESTWARD INTO THE TENNESSEE AND
MIDDLE MISSISSIPPI VALLEYS. THE HEAVIEST RAINFALL IS FORECAST TO OCCUR WELL
BEFORE THE START OF WEEK-2, ALTHOUGH CONTINUED FLOODING REMAINS POSSIBLE OVER
THESE AREAS. LINGERING CYCLONIC FLOW ALOFT MAY RESULT IN SOME AREAS OF
PRECIPITATION OVER THE EASTERN CONTIGUOUS U.S. (CONUS), BUT COVERAGE IS FAVORED
TO BE MORE SPORADIC AND LOWER TOTALS ARE FORECAST COMPARED TO WEEK-1. BY THE
START OF WEEK-2, THERE IS THE 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 MEANS OVER THE EASTERN CONUS, WHICH IS
EXPECTED TO IMPEDE THE NORTHERN ADVANCE OF THE PRECIPITATION NOTED OVER
FLORIDA. THIS FAR IN ADVANCE, THERE IS TOO MUCH UNCERTAINTY 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) FOR PRECIPITATION DEPICTS A 20-30 PERCENT CHANCE 3-DAY RAINFALL
TOTALS EXCEED 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. THEREFORE,
A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR THE MOST LIKELY STRETCH OF
THE GULF COAST WHICH EXTENDS FROM CENTRAL LOUISIANA EASTWARD THROUGH FLORIDA
AND AS FAR NORTH AS SOUTH CAROLINA, OCT 4-7.
ANOMALOUSLY WARM TEMPERATURES ARE FORECAST ACROSS MUCH OF THE CONUS DURING
WEEK-2, WITH A SLIGHT RISK OF EXCESSIVE HEAT FAVORED OVER THE DESERT SOUTHWEST
ON OCT 4. THIS IS BASED LARGELY ON ECENS PET TEMPERATURE GUIDANCE, WHICH FAVORS
MAXIMUM TEMPERATURES ABOVE THE 85TH PERCENTILE AND RANGING FROM ABOUT 100 TO
105 DEG F, WITH THE POSSIBILITY OF SLIGHTLY HIGHER TEMPERATURES LOCALLY. THIS
IS RELATED TO A MID-LEVEL RIDGE FORECAST OVER THE REGION. IN ADDITION TO THE
EXCESSIVE HEAT RISK THAT IS POSTED, THERE IS AN ELEVATED RISK OF WILDFIRES.
ANTECEDENT HEAVY RAINFALL ACROSS WESTERN AND CENTRAL PORTIONS OF OKLAHOMA FAVOR
DECREASED CHANCES OF DROUGHT DEVELOPMENT, WITH PORTIONS OF EASTERN OKLAHOMA AND
NORTHEASTERN TEXAS REMAINING AT ELEVATED RISK FOR RAPID ONSET DROUGHT
DEVELOPMENT. THE ROD AREA HAS BEEN EXTENDED SLIGHTLY SOUTHWARD TODAY 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 WITH FUTURE TROPICAL STORM DEVELOPMENT AND TRACKS, THE
EXTENDED ROD REGION WAS KEPT WELL AWAY FROM THE TEXAS COAST.
A SLIGHT RISK OF HIGH WINDS (GREATER THAN THE 85TH CLIMATOLOGICAL PERCENTILE
AND AT LEAST 20 MPH) IS DEPICTED OVER THE NORTHERN PLAINS, OCT 4, WITH VERY
GOOD AGREEMENT AMONG THE ECENS, GEFS, AND CMCE PETS. THIS MAY BE ASSOCIATED
WITH ENHANCED DOWNSLOPE FLOW RESULTING FROM INCREASED MID-LEVEL WESTERLIES.
SURFACE LOW PRESSURE IS FORECAST ACROSS THE GULF OF ALASKA DURING WEEK-2, WITH
INDIVIDUAL CYCLONIC SYSTEMS BRINGING THE 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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