354
FXUS21 KWNC 081751
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 08 2023
SYNOPSIS: MID-LEVEL HIGH (LOW) PRESSURE IS FORECAST OVER THE WEST (EAST) DURING
MID-SEPTEMBER. MAJOR HURRICANE LEE, CURRENTLY LOCATED ACROSS THE CENTRAL
ATLANTIC, IS FORECAST TO TRACK NORTHWESTWARD THROUGH SEPTEMBER 12. LATER NEXT
WEEK, THE MODEL GUIDANCE DEPICTS LEE TAKING A TURN TO THE NORTH ACROSS THE
WESTERN ATLANTIC. BY SEPTEMBER 15, HURRICANE LEE MAY INCREASE THE CHANCES OF
HIGH WINDS AND HEAVY PRECIPITATION ACROSS NEW ENGLAND. A RAPID ONSET DROUGHT
RISK EXISTS FOR THE LOWER MISSISSIPPI VALLEY DUE TO RECENT/ONGOING HEAT AND
INCREASING PRECIPITATION DEFICITS. ENHANCED ONSHORE FLOW RESULTS IN AN ELEVATED
CHANCE OF HEAVY PRECIPITATION ACROSS SOUTHEASTERN ALASKA.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF NEW ENGLAND, SAT-SUN, SEP 16-17.
SLIGHT RISK OF HIGH WINDS FOR LONG ISLAND AND PARTS OF NEW ENGLAND, SAT-SUN,
SEP 16-17.
SLIGHT RISK OF HEAVY PRECIPITATION FOR COASTAL SOUTHERN MAINLAND ALASKA AND
SOUTHEASTERN ALASKA, SAT-MON, SEP 16-18.
RAPID ONSET DROUGHT RISK FOR PARTS OF THE LOWER MISSISSIPPI VALLEY AND
SOUTHEAST.
DETAILED SUMMARY
FOR MONDAY SEPTEMBER 11 - FRIDAY SEPTEMBER 15:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY SEPTEMBER 16 - FRIDAY SEPTEMBER 22: MODEL SOLUTIONS CONTINUE TO
DEPICT MAJOR HURRICANE LEE EVENTUALLY TURNING NORTHWARD OVER THE WESTERN
ATLANTIC. A KEY FACTOR IN ITS FUTURE TRACK WILL BE AN AMPLIFIED 500-HPA TROUGH
OVER THE EASTERN CONTIGUOUS U.S. (CONUS) AND A COLD FRONT FORECAST TO BE
LOCATED NEAR THE EAST COAST. THIS MID-LEVEL AND SURFACE PATTERN WOULD FAVOR A
TRACK OFFSHORE OF THE EAST COAST, BUT LEE’S FUTURE TRACK SHOULD BE CLOSELY
MONITORED ESPECIALLY ACROSS THE NORTHEAST. THE ENSEMBLE SPREAD FROM THE GEFS
AND ECMWF MODELS BECOMES LARGE ON SEPTEMBER 14 AS LEE NEARS THE 70W LONGITUDE.
A MAJORITY OF THE GEFS AND ECMWF ENSEMBLE MEMBERS CONTINUE TO FEATURE AN
OFFSHORE TRACK, BUT SEVERAL OF THE 6Z GEFS AND 0Z ECMWF ENSEMBLE MEMBERS DEPICT
LEE MAKING LANDFALL ACROSS OR NEAR EASTERN NEW ENGLAND FROM SEPTEMBER 15 TO 17.
GIVEN THE CONTINUED LARGE ENSEMBLE SPREAD, UNCERTAINTY INHERENT ON A PREDICTED
TRACK PARALLELING THE COAST, AND POOR CONTINUITY IN RECENT DETERMINISTIC ECMWF
MODEL RUNS, ONLY A SLIGHT RISK OF HIGH WINDS AND HEAVY PRECIPITATION IS POSTED
FOR PARTS OF THE NORTHEAST ON SEPTEMBER 16 AND 17. PLEASE REFER TO THE NATIONAL
HURRICANE CENTER FOR THE LATEST UPDATES/FORECASTS ON HURRICANE LEE.
THE RAPID ONSET OF DROUGHT (2-CATEGORY DEGRADATION IN DX LEVELS WITHIN 4 WEEKS
BASED ON THE U.S. DROUGHT MONITOR) RECENTLY OCCURRED ACROSS SOUTHERN
MISSISSIPPI, LOUISIANA, TEXAS, AND SOUTHERN OKLAHOMA. A RAPID ONSET DROUGHT
RISK CONTINUES FROM THE LOWER MISSISSIPPI VALLEY EAST TO PARTS OF ALABAMA,
BASED ON RECENT/ONGOING HEAT AND HIGH EVAPOTRANSPIRATION RATES, 30-DAY
PRECIPITATION DEFICITS, AND THE LACK OF A WET SIGNAL AMONG THE MODEL SOLUTIONS
DURING THE NEXT TWO WEEKS. ALTHOUGH DROUGHT MAY EXPAND ACROSS PARTS OF THE
MIDWEST DURING THE REMAINDER OF SEPTEMBER, THE TRANSITION TOWARDS COOLER
TEMPERATURES MAKES A RAPID ONSET OF DROUGHT LESS LIKELY.
NO TEMPERATURE HAZARDS ARE POSTED TODAY. ALTHOUGH COOLER-THAN-NORMAL
TEMPERATURES ARE FORECAST ACROSS THE CORN BELT AND OHIO VALLEY ON SEPTEMBER 16
AND 17, THE RISK OF A DAMAGING FROST OR FREEZE IS MINIMAL. THE MOST ANOMALOUS
WARMTH IS LIKELY TO BE OVER THE WESTERN AND NORTH-CENTRAL CONUS, BUT EXCESSIVE
HEAT IS UNLIKELY AS THE TRANSITION FROM SUMMER TO EARLY FALL BEGINS.
MULTIPLE MODEL ENSEMBLE MEANS DEPICT AN AMPLIFIED 500-HPA TROUGH OVER THE
EASTERN BERING SEA WHICH PROMOTES ENHANCED ONSHORE FLOW ACROSS COASTAL SOUTHERN
MAINLAND ALASKA AND SOUTHEASTERN ALASKA. BASED ON THE GEFS AND ECMWF
PROBABILISTIC TOOLS (MORE THAN A 20 PERCENT CHANCE OF 3-DAY PRECIPITATION
TOTALS EXCEEDING THE 85TH PERCENTILE AND 2 INCHES) ALONG WITH THE 24-HOUR
UNCALIBRATED ENSEMBLE MEANS, THE SLIGHT RISK OF HEAVY PRECIPITATION WAS
EXPANDED WEST COMPARED TO YESTERDAY AND IS VALID THROUGH SEPTEMBER 18.
FORECASTER: BRAD PUGH
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