002
FXUS21 KWNC 251929
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 25 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 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 AROUND THE MIDDLE OF THE PERIOD.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT OVER THE DESERT SOUTHWEST, THU-SAT, OCT 3-5.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE SOUTHEAST, THU-SUN,
OCT 3-6.
SLIGHT RISK OF HIGH WINDS OVER THE NORTHERN AND CENTRAL PLAINS, THU-SUN, OCT
3-6.
FLOODING POSSIBLE ACROSS PORTIONS OF THE SOUTHEAST, APPALACHIANS, AND SOUTHERN
MID-ATLANTIC.
RISK OF RAPID ONSET DROUGHT ACROSS PORTIONS OF EASTERN OKLAHOMA AND
NORTHEASTERN TEXAS.
DETAILED SUMMARY
FOR SATURDAY SEPTEMBER 28 - WEDNESDAY OCTOBER 02:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY OCTOBER 03 - WEDNESDAY OCTOBER 09: AS OF 1PM CDT TODAY, THE
NATIONAL HURRICANE CENTER (NHC) FORECASTS HURRICANE HELENE (CURRENTLY NEAR THE
YUCATAN CHANNEL) TO INTENSIFY INTO A MAJOR HURRICANE BEFORE STRIKING THE
NORTHEASTERN GULF COAST IN THE NEXT DAY OR TWO. 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 THE SECOND HALF OF WEEK-2, BRINGING ADDITIONAL RAINFALL TO THE
STATE. A SURFACE HIGH PRESSURE CENTER IS FORECAST BY THE THREE ENSEMBLE MEANS
OVER THE SOUTHERN APPALACHIANS DURING MUCH OF THE FORECAST PERIOD, 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. THE
ECENS PROBABILITY EXTREMES TOOL (PET) FOR PRECIPITATION DEPICTS A 20-40
PERCENT CHANCE 3-DAY RAINFALL TOTALS EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE
AND 1-INCH OVER PORTIONS OF FLORIDA AND THE COASTAL SOUTHEAST DURING WEEK-2.
THE UNCALIBRATED ECENS PRECIPITATION TOOL INCREASES THE RISK OF HEAVY
PRECIPITATION ACROSS THIS AREA TO AT LEAST 40%, BUT GEFS AND CMCE PRECIPITATION
GUIDANCE ARE NOT AS ROBUST. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS
POSTED FOR THE VICINITY OF FLORIDA AND THE EASTERN GULF COAST AREA, OCT 3-6.
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
FROM OCT 3-5. THIS IS BASED LARGELY ON ECENS PET TEMPERATURE GUIDANCE, WHICH
FAVORS MAXIMUM TEMPERATURES ABOVE THE 85TH PERCENTILE AND RANGING FROM THE
UPPER 90’S TO SLIGHTLY GREATER THAN 105 DEG F, TIED TO THE ENHANCED 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 WHERE PRECIPITATION DEFICITS OF AROUND 3-INCHES REMAIN AND
BELOW-NORMAL PRECIPITATION IS FORECAST DURING WEEK-2.
A SLIGHT RISK OF HIGH WINDS (GREATER THAN THE 85TH CLIMATOLOGICAL PERCENTILE
AND AT LEAST 20 MPH) IS DEPICTED OVER THE NORTHERN AND CENTRAL PLAINS, OCT 3-6,
WITH VERY GOOD AGREEMENT BETWEEN 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 ALEUTIANS AND GULF OF ALASKA DURING
WEEK-1 BRINGING THE POTENTIAL FOR HIGH WINDS AND HEAVY RAIN ACROSS THE SOUTHERN
COAST OF THE STATE. THIS SYSTEM IS FORECAST TO WEAKEN BY THE OUTSET OF WEEK-2,
WITH ANOTHER AREA OF SURFACE LOW PRESSURE EXPECTED TO BRING MORE PRECIPITATION
TO THE SOUTHERN COAST DURING THE MIDDLE AND LATTER PORTIONS OF THE FORECAST
PERIOD. AT THIS TIME, PRECIPITATION AND WINDS ARE EXPECTED TO REMAIN BELOW
HAZARDOUS THRESHOLDS.
FORECASTER: ANTHONY ARTUSA
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