468
FXUS21 KWNC 031945
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 03 2024
SYNOPSIS: BROAD MID-LEVEL HIGH PRESSURE IS PREDICTED TO EXTEND FROM THE
NORTH-CENTRAL CONTIGUOUS U.S. (CONUS) TO THE SOUTHWESTERN STATES, CONTRIBUTING
TO INCREASED CHANCES FOR EXCESSIVE HEAT OVER THE NORTHERN GREAT PLAINS AND
THE DESERT SOUTHWEST EARLY IN THE FORECAST PERIOD. HEAVY PRECIPITATION IS
FAVORED FOR PORTIONS OF THE GULF COAST AND COASTAL PORTIONS OF THE SOUTHERN
MID-ATLANTIC DURING MUCH OF WEEK-2, WITH POSSIBLE FLOODING ACROSS MUCH OF THE
GULF COASTAL AREA AND NORTHERN FLORIDA. THERE IS SIGNIFICANT UNCERTAINTY AS TO
THE DEVELOPMENT AND FUTURE TRACKS OF TROPICAL SYSTEMS DURING THIS FORECAST
PERIOD. DESPITE THE UNCERTAINTY, IT WOULD BE PRUDENT FOR INTERESTS ALONG THE
GULF COAST (ESPECIALLY THE TEXAS COAST) TO KEEP UPDATED WITH THE LATEST
TROPICAL WEATHER CONDITIONS AS WE MOVE PAST THE CLIMATOLOGICAL PEAK OF THE
ATLANTIC HURRICANE SEASON.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT FOR THE NORTHERN PLAINS, WED-THU, SEP 11-12.
SLIGHT RISK OF EXCESSIVE HEAT FOR THE DESERT SOUTHWEST, WED-FRI, SEP 11-13.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE GULF COAST AND COASTAL
PORTIONS OF THE SOUTHERN MID-ATLANTIC, WED-SUN, SEP 11-15.
SLIGHT RISK OF HIGH WINDS OVER THE NORTHERN AND CENTRAL HIGH PLAINS, THU-SAT,
SEP 12-14.
FLOODING POSSIBLE ALONG MUCH OF THE GULF COAST AND NORTHERN FLORIDA.
RISK FOR RAPID ONSET DROUGHT FOR PORTIONS OF THE OHIO AND MIDDLE MISSISSIPPI
VALLEYS.
DETAILED SUMMARY
FOR FRIDAY SEPTEMBER 06 - TUESDAY SEPTEMBER 10:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY SEPTEMBER 11 - TUESDAY SEPTEMBER 17: AN ANOMALOUS MID-LEVEL RIDGE
IS PREDICTED TO EXTEND FROM THE HUDSON BAY, CANADA, ACROSS THE NORTH-CENTRAL
CONUS, AND INTO THE SOUTHWEST. MULTIPLE MODELS INDICATE MAXIMUM 500-HPA HEIGHTS
ACROSS THE UNITED STATES RANGING FROM 30-90 METERS ABOVE NORMAL OVER THE
NORTHERN PLAINS, WITH HIGHER HEIGHTS NORTH OF THE CANADIAN BORDER. ANOTHER
ANOMALOUS RIDGE IS FORECAST SOUTH OF THE ALEUTIANS, WITH MAXIMUM HEIGHTS
POSSIBLY BEING GREATER THAN 120 METERS ABOVE NORMAL. WEAK MID-LEVEL TROUGHS ARE
PREDICTED FROM WESTERN ALASKA SOUTHEASTWARD ACROSS THE GULF OF ALASKA TO THE
PACIFIC COAST OF THE LOWER 48 STATES, AND OVER THE EASTERN CONUS.
A SLIGHT RISK (20-40% CHANCE) OF EXCESSIVE HEAT IS DEPICTED OVER THE NORTHERN
PLAINS, SEP 11-12. THIS IS ASSOCIATED WITH THE PROXIMITY OF A MODERATELY STRONG
ANOMALOUS RIDGE AND POSITIVE HEIGHT DEPARTURES IN THAT REGION, AND ANTICIPATED
DOWNSLOPE FLOW. WITHIN THIS SLIGHT RISK AREA, THE ECENS AND GEFS MODELS PREDICT
2-METER TEMPERATURES WILL RANGE FROM 15-20 DEGREES F ABOVE NORMAL, WITH DAYTIME
HIGH TEMPERATURES PRIMARILY IN THE LOW 90S, WITH SOME READINGS IN THE MID 90’S.
THOUGH THIS EVENT IS EXPECTED TO WIND DOWN EARLY IN WEEK-2, HIGH TEMPERATURES
COMBINED WITH LOW DEW POINTS AND GUSTY WINDS OF ABOUT 20 MPH MAY INCREASE THE
RISK OF WILDFIRES ACROSS THE REGION. ANOTHER SLIGHT RISK AREA FAVORING
EXCESSIVE HEAT IS POSTED ACROSS THE DESERT SOUTHWEST, SEP 11-13, ALSO BASED ON
MID-LEVEL RIDGING AND POSITIVE HEIGHT DEPARTURES. TWO-METER TEMPERATURE
ANOMALIES ARE PREDICTED BY THE ENSEMBLE MEANS TO RANGE FROM 5-10 DEGREES ABOVE
NORMAL, WITH A FEW LOCATIONS HAVING SLIGHTLY LARGER ANOMALIES. MAXIMUM DAYTIME
HIGH TEMPERATURES MAY REACH 100-110 DEGREES F.
A SLIGHT RISK OF HEAVY PRECIPITATION HAS BEEN POSTED ACROSS THE GULF COAST AND
COASTAL PORTIONS OF THE SOUTHERN MID-ATLANTIC FROM SEP 11-15, ASSOCIATED WITH A
QUASI-STATIONARY, MEAN FRONTAL ZONE 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
EXCEEDING THE 85TH PERCENTILE OF THE HISTORICAL DISTRIBUTION, AND REACH AT
LEAST 1 INCH. 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 THE WESTERN HALF OF THE GULF COASTAL
AREA, WITH AN EASTWARD EXTENSION INDICATED FOR WEEK-2 TO INCLUDE MOST OF THE
EASTERN HALF OF THE GULF COASTAL AREA. THE PRIMARY REASON FOR THIS POTENTIAL
FLOOD RISK DURING WEEK-1 IS THE NEARLY STATIONARY MEAN FRONTAL BOUNDARY
ANTICIPATED IN THIS PART OF THE COUNTRY. THE SAME HOLDS TRUE FOR WEEK-2, BUT
WITH THE ADDITIONAL POTENTIAL FOR TROPICAL CYCLONE ACTIVITY. ONE SYSTEM BEING
MONITORED BY THE NATIONAL HURRICANE CENTER (NHC) FOR POSSIBLE DEVELOPMENT IS
CURRENTLY OVER THE CENTRAL CARIBBEAN SEA, AND (AS OF 2PM EDT TODAY) HAS A 30%
CHANCE OF DEVELOPING INTO AT LEAST A TROPICAL DEPRESSION DURING THE NEXT 7
DAYS. THIS TROPICAL WAVE IS EXPECTED TO REACH THE BAY OF CAMPECHE IN THE 4-7
DAY PERIOD, AND MAY BRING HEAVY PRECIPITATION TO SOUTHERN PORTIONS OF THE TEXAS
COAST, BUT THIS ALSO MIGHT OCCUR JUST PRIOR TO THE START OF WEEK-2. THERE ARE
TWO OTHER TROPICAL WAVES BEING MONITORED BY NHC OVER THE CENTRAL AND EASTERN
ATLANTIC, BUT IT IS TOO EARLY TO TELL WITH ANY CONFIDENCE WHERE THESE SYSTEMS
WILL EVENTUALLY REACH, OR WITH WHAT INTENSITY.
AS MENTIONED ABOVE, WIND SPEEDS COULD BE AN IMPORTANT FACTOR FOR THE NORTHERN
PLAINS, ESPECIALLY IN REGARD TO INCREASED WILDFIRE RISK. A SLIGHT RISK OF HIGH
WINDS (>85TH PERCENTILE AND >20 MPH) HAS BEEN POSTED ACROSS THIS REGION, SEP
12-14. THESE HIGH WINDS COULD BE CAUSED BY DOWNSLOPE FLOW AND POSSIBLE LEE
CYCLOGENESIS.
THE POTENTIAL FOR RAPID ONSET DROUGHT CONTINUES OVER PARTS OF THE OHIO AND
MIDDLE MISSISSIPPI VALLEYS. 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. THIS AREA IS BEING MONITORED FOR POTENTIAL EXPANSION INTO THE
TENNESSEE VALLEY.
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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