031
FXUS21 KWNC 061906
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 06 2024
SYNOPSIS: PERSISTENT, BROAD MID-LEVEL HIGH PRESSURE IS PREDICTED TO EXTEND FROM
EASTERN CANADA ACROSS THE NORTHEAST QUADRANT OF THE CONTIGUOUS U.S. (CONUS),
CONTRIBUTING TO INCREASED CHANCES FOR EXCESSIVE HEAT OVER PORTIONS OF THIS
REGION IN WEEK-2. THERE IS MUCH UNCERTAINTY IN THE HAZARDOUS PRECIPITATION
OUTLOOK ACROSS THE GULF COAST AND FLORIDA. THIS PRECIPITATION OUTLOOK REMAINS
UNCHANGED FROM YESTERDAY, AS DOES THE POSSIBLE FLOOD RISK AREA OVER THIS
REGION. MUCH OF THE UNCERTAINTY STEMS FROM THE FACT THAT THE PREDICTED TROPICAL
CYCLONE PATTERN OVER THE ATLANTIC BASIN IS FAR FROM CLEAR. AS THIS IS ALSO THE
CLIMATOLOGICAL PEAK OF THE ATLANTIC HURRICANE SEASON, IT WOULD BE PRUDENT FOR
INTERESTS ALONG THE GULF COAST TO KEEP UPDATED WITH THE LATEST TROPICAL WEATHER
CONDITIONS.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT FOR MIDDLE AND LOWER PORTIONS OF THE MISSOURI
RIVER VALLEY, THE MIDDLE MISSISSIPPI VALLEY AND OHIO VALLEY, AND SOUTHERN
PORTIONS OF LOWER MICHIGAN, SAT-SUN, SEP 14-15.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF THE GULF COAST AND FLORIDA,
SAT-SUN, SEP 14-15.
SLIGHT RISK OF HIGH WINDS OVER THE NORTHERN AND CENTRAL HIGH PLAINS, SAT-SUN,
SEP 14-15.
FLOODING POSSIBLE ALONG MUCH OF THE GULF COAST AND NORTHERN AND CENTRAL
FLORIDA.
RISK FOR RAPID ONSET DROUGHT FOR PORTIONS OF THE OHIO, TENNESSEE, AND MIDDLE
MISSISSIPPI VALLEYS.
DETAILED SUMMARY
FOR MONDAY SEPTEMBER 09 - FRIDAY SEPTEMBER 13:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY SEPTEMBER 14 - FRIDAY SEPTEMBER 20: AN ANOMALOUS MID-LEVEL RIDGE
IS PREDICTED TO EXTEND FROM EASTERN CANADA ACROSS THE NORTHEAST QUADRANT OF THE
LOWER 48 STATES. MULTIPLE MODELS INDICATE MAXIMUM 500-HPA HEIGHTS ACROSS THIS
PART OF THE CONUS RANGE FROM ABOUT 30-60 METERS ABOVE NORMAL. ANOTHER ANOMALOUS
RIDGE IS FORECAST SOUTH OF THE ALEUTIANS, WITH MAXIMUM HEIGHTS GREATER THAN 120
METERS ABOVE NORMAL. WEAK MID-LEVEL TROUGHS ARE PREDICTED FOR FAR WESTERN
ALASKA, NEAR OR JUST INLAND OF THE WEST COAST OF THE CONUS, AND THE SOUTHERN
ATLANTIC COAST.
A SLIGHT RISK (20-40% CHANCE) OF EXCESSIVE HEAT IS DEPICTED FOR MIDDLE AND
LOWER PORTIONS OF THE MISSOURI RIVER VALLEY, THE MIDDLE MISSISSIPPI VALLEY AND
OHIO VALLEY, AND SOUTHERN PORTIONS OF LOWER MICHIGAN, SEP 14-15. THIS IS
ASSOCIATED WITH THE PROXIMITY OF A MODERATELY STRONG ANOMALOUS RIDGE AND
POSITIVE HEIGHT DEPARTURES IN THAT REGION. WITHIN THIS SLIGHT RISK AREA, THE 0Z
ECENS AND 12Z GEFS MODELS PREDICT 2-METER TEMPERATURES WILL RANGE FROM ABOUT
6-15 DEGREES F ABOVE NORMAL (GEFS BEING THE SLIGHTLY WARMER SOLUTION), WITH
DAYTIME HIGH TEMPERATURES PEAKING NEAR 90 DEGREES F. GIVEN THE LIKELIHOOD OF
LOW DEW POINT TEMPERATURES DURING THIS SAME PERIOD, AND THEREFORE COOLER
OVERNIGHT TEMPERATURES, THE HIGHLIGHTED EXCESSIVE HEAT RISK IS CONSIDERED
MARGINAL.
ACROSS THE WEST, A SIGNIFICANT MID-LEVEL TROUGH IS PREDICTED TO MOVE INTO THE
INTERMOUNTAIN REGION, WITH ENHANCED WINDS AND POSSIBLE RELATED INCREASE IN
WILDFIRE RISK. AS THIS TROUGH ADVANCES EASTWARD, THERE IS THE INCREASED
POTENTIAL FOR THUNDERSTORM ACTIVITY ACROSS THE GREAT PLAINS, AS THIS TIME OF
YEAR FEATURES A SECONDARY MAXIMUM IN SEVERE WEATHER CLIMATOLOGY.
A SLIGHT RISK OF HEAVY PRECIPITATION REMAINS POSTED ALONG MOST OF THE GULF
COAST AND FLORIDA, SEP 14-15, ASSOCIATED WITH A DECAYING MEAN FRONTAL ZONE
FORECASTED TO BE DRAPED ACROSS THIS REGION. PRECIPITATION GUIDANCE FROM THE
PROBABILISTIC EXTREMES TOOLS (PETS) AND FROM THE UNCALIBRATED ECENS PREDICT
THREE-DAY PRECIPITATION AMOUNTS WITHIN THIS VALID PERIOD TO REACH 1 INCH,
THOUGH THE ECENS PREDICTS THE BEST CHANCE FOR REACHING AND/OR EXCEEDING THIS
1-INCH THRESHOLD TO BE OVER THE FLORIDA PENINSULA, WITH A DRIER PATTERN
DEPICTED FOR THE WESTERN GULF REGION. A POSSIBLE FLOOD RISK AREA IS HIGHLIGHTED
BASED ON THE NATIONAL WATER CENTER’S (NWC) EXPERIMENTAL FLOOD HAZARD OUTLOOK
FOR DAYS 1-7 (WEEK-1), WHICH DEPICTS POSSIBLE FLOODING ALONG/NEAR MOST OF THE
GULF COASTAL AREA, AND NORTHERN FLORIDA. THIS FLOOD RISK IS EXPECTED TO EXTEND
INTO THE EARLY PORTION OF THE WEEK-2 TIME FRAME. THERE IS MAJOR UNCERTAINTY
WITH REGARD TO POTENTIAL TROPICAL CYCLONE ACTIVITY DURING WEEK-2. THIS
SITUATION IS COMPOUNDED BY THE FACT THAT THE CLIMATOLOGICAL PEAK OF THE
ATLANTIC HURRICANE SEASON IS RAPIDLY APPROACHING. IN ADDITION, SEA SURFACE
TEMPERATURES ACROSS THE GULF OF MEXICO ARE MORE THAN ADEQUATE IN INTENSIFYING
ANY SYSTEM THAT MAY FORM DURING THIS PERIOD.
DETERMINISTIC MODEL RUNS HAVE INDICATED THE POSSIBILITY OF A TROPICAL CYCLONE
OVER THE EASTERN PACIFIC MOVING RELATIVELY CLOSE TO THE MOUTH OF THE GULF OF
CALIFORNIA DURING WEEK-2. THESE EVENTS ARE SOMETIMES ACCOMPANIED BY GULF SURGES
OF MOISTURE INTO THE AMERICAN SOUTHWEST, AND THE LIKELIHOOD OF THIS OCCURRING
WILL BE MONITORED WITH FUTURE MODEL RUNS.
A SLIGHT RISK FOR HIGH WINDS HAS BEEN EXTENDED INTO THE FIRST TWO DAYS OF THE
FORECAST PERIOD. SURFACE LOW PRESSURE DEVELOPMENT OVER THE NORTHERN AND CENTRAL
HIGH PLAINS MAY PRODUCE WIND SPEEDS IN EXCESS OF 30 MPH.
THE POTENTIAL FOR RAPID ONSET DROUGHT (ROD) CONTINUES OVER PARTS OF THE OHIO
AND MIDDLE MISSISSIPPI VALLEYS, AND WAS EXPANDED YESTERDAY TO INCLUDE MORE OF
KENTUCKY AND PARTS OF THE TENNESSEE VALLEY. SOIL MOISTURE VALUES IN THIS REGION
ARE WITHIN THE LOWEST QUARTILE (AND IN SOME CASES, DECILE) OF THE HISTORICAL
DISTRIBUTION. PRECIPITATION DEFICITS WITHIN THE LAST 90 DAYS HAVE MOUNTED FROM
ONE TO AS MUCH AS SIX INCHES.
IN ALASKA, THE SOUTHERN COAST IS FAVORED TO GET ABOVE NORMAL PRECIPITATION
DURING THE WEEK-2 PERIOD, WITH UP TO 2 INCHES PREDICTED BY THE ENSEMBLE MEANS.
HOWEVER, THIS FALLS SOMEWHAT SHORT OF THE HAZARDOUS PRECIPITATION CRITERION FOR
THIS AREA (NEAR 3 INCHES), AND THEREFORE NO HAZARD IS POSTED.
FORECASTER: ANTHONY ARTUSA
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