008
FXUS21 KWNC 041911
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 04 2024
SYNOPSIS: PERSISTENT, 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 AND CENTRAL 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 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, THU, SEP 12.
SLIGHT RISK OF EXCESSIVE HEAT FOR THE DESERT SOUTHWEST, THU-FRI, SEP 12-13.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE GULF COAST AND THE
SOUTHEAST, THU-MON, SEP 12-16.
SLIGHT RISK OF HIGH WINDS OVER THE NORTHERN AND CENTRAL HIGH PLAINS, FRI-SUN,
SEP 13-15.
FLOODING POSSIBLE ALONG MUCH OF THE GULF COAST AND NORTHERN AND CENTRAL
FLORIDA.
RISK FOR RAPID ONSET DROUGHT FOR PORTIONS OF THE OHIO AND MIDDLE MISSISSIPPI
VALLEYS.
DETAILED SUMMARY
FOR SATURDAY SEPTEMBER 07 - WEDNESDAY SEPTEMBER 11:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY SEPTEMBER 12 - WEDNESDAY SEPTEMBER 18: 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 SOUTHEAST.
A SLIGHT RISK (20-40% CHANCE) OF EXCESSIVE HEAT IS DEPICTED OVER THE NORTHERN
PLAINS, SEP 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 12-13, 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 105-110 DEGREES F.
A SLIGHT RISK OF HEAVY PRECIPITATION HAS BEEN POSTED ACROSS THE GULF COAST AND
PORTIONS OF THE SOUTHEAST FROM SEP 12-16, 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 EXCEED 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 MOST OF THE GULF COASTAL AREA, AND NORTHERN AND
CENTRAL FLORIDA. THE PRIMARY REASON FOR THIS POTENTIAL FLOOD RISK DURING WEEKS
1 AND 2 IS THE NEARLY STATIONARY MEAN FRONTAL BOUNDARY ANTICIPATED IN THIS PART
OF THE COUNTRY. OVER THE MAIN DEVELOPMENT REGION (MDR) OF THE TROPICAL ATLANTIC
BASIN, THREE TROPICAL WAVES ARE CURRENTLY (2PM EDT TODAY) BEING MONITORED BY
THE NATIONAL HURRICANE CENTER (NHC) FOR POSSIBLE DEVELOPMENT. AT THIS TIME,
THERE IS LITTLE CONFIDENCE REGARDING THE FUTURE TRACK OR INTENSITY OF ANY OF
THESE SYSTEMS.
DETERMINISTIC GFS AND ECMWF MODEL RUNS HAVE INDICATED THE POSSIBILITY OF A
TROPICAL CYCLONE OVER THE EASTERN PACIFIC MOVING PAST 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.
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
13-15. THESE HIGH WINDS COULD BE CAUSED BY DOWNSLOPE FLOW AND POSSIBLE LEE
CYCLOGENESIS. RECENT PRECIPITATION THAT HAS FALLEN ACROSS THE PACIFIC NORTHWEST
HAS PROVIDED SOME RELIEF FROM THE ONGOING WILDFIRES IN THAT AREA.
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.
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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