514
FXUS21 KWNC 091819
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 09 2025
SYNOPSIS: AT THE BEGINNING OF THE FORECAST PERIOD A SURFACE LOW PRESSURE SYSTEM
OVER QUEBEC BRINGS THE POTENTIAL FOR HIGH WINDS TO MUCH OF THE GREAT LAKES AND
NORTHEAST U.S. AND UNSEASONABLY COLD TEMPERATURES TO THESE REGIONS AND AS FAR
SOUTH AS THE MID-ATLANTIC AND TENNESSEE VALLEY. SURFACE LOW PRESSURE IS FAVORED
TO DEVELOP OVER THE GREAT PLAINS DURING WEEK-2, BRINGING THE POTENTIAL FOR HIGH
WINDS TO PORTIONS OF THE SOUTHERN AND CENTRAL PLAINS AS WELL AS THE CENTRAL AND
SOUTHERN ROCKIES. POTENTIALLY HEAVY PRECIPITATION IS DEPICTED BY MULTIPLE MODEL
ENSEMBLES EAST OF THIS SURFACE LOW PRESSURE, POSSIBLY PROLONGING FLOODING
CONCERNS IN THE OHIO AND MISSISSIPPI WATERSHEDS. SURFACE LOW PRESSURE OVER THE
GULF OF ALASKA BRINGS THE POTENTIAL FOR HIGH WINDS TO PORTIONS OF THE ALASKAN
COAST.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE OHIO, TENNESSEE, LOWER
AND MIDDLE MISSISSIPPI VALLEYS, AND SOUTHERN AND CENTRAL PLAINS, THU-SAT, APR
17-19.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE MID-ATLANTIC AND
APPALACHIANS, AS WELL AS THE OHIO AND TENNESSEE VALLEYS AND PORTIONS OF THE
GREAT LAKES AND SOUTHEAST U.S., THU-FRI, APR 17-18.
SLIGHT RISK OF HIGH WINDS FOR THE SOUTHERN PLAINS AND SOUTHERN ROCKIES, AS WELL
AS PORTIONS OF THE DESERT SOUTHWEST, CENTRAL ROCKIES, CENTRAL PLAINS, AND LOWER
AND MIDDLE MISSISSIPPI VALLEY, THU-FRI, APR 17-18.
SLIGHT RISK OF HIGH WINDS FOR THE GREAT LAKES, CENTRAL APPALACHIANS, AND
NORTHEAST U.S., AS WELL AS PORTIONS OF THE OHIO VALLEY AND MID-ATLANTIC, THU,
APR 17.
SLIGHT RISK OF HIGH WINDS FOR COASTAL PORTIONS OF ALASKA FROM PRINCE WILLIAM
SOUND EASTWARD, THU-SAT, APR 17-19.
FLOODING POSSIBLE FOR PORTIONS OF THE OHIO, TENNESSEE, AND MIDDLE AND LOWER
MISSISSIPPI VALLEYS.
DETAILED SUMMARY
FOR SATURDAY APRIL 12 - WEDNESDAY APRIL 16:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY APRIL 17 - WEDNESDAY APRIL 23: MODEL ENSEMBLES DEPICT A VERY
TRANSIENT SYNOPTIC PICTURE DURING THE WEEK-2 PERIOD CHARACTERIZED BY MULTIPLE
WEAK SHORTWAVE TROUGHS MOVING ACROSS THE CONTIGUOUS U.S. (CONUS). AT THE OUTSET
OF WEEK-2 LOW PRESSURE AT THE SURFACE AND ALOFT IS FAVORED OVER QUEBEC, SETTING
UP A TIGHT PRESSURE GRADIENT AND THE POTENTIAL FOR HIGH WINDS OVER THE
NORTHEASTERN CONUS DURING THE EARLY PORTION OF THE FORECAST PERIOD. THIS IS
SUPPORTED BY THE ECMWF PROBABILISTIC EXTREMES TOOL (PET), WHICH INDICATES AT
LEAST A 20% CHANCE OF 3-DAY MAXIMUM WIND SPEED EXCEEDING THE 85TH
CLIMATOLOGICAL PERCENTILE AND AT LEAST 20MPH OVER MUCH OF THE GREAT LAKES,
NORTHEAST U.S., AND CENTRAL APPALACHIANS AS WELL AS PORTIONS OF THE
MID-ATLANTIC AND OHIO VALLEY EARLY IN THE FORECAST PERIOD. THIS LOW PRESSURE IS
FAVORED TO EXIT THE REGION QUICKLY, WITH MODELS INDICATING THE STRONGEST SIGNAL
FOR HIGH WINDS DURING APR 17, WARRANTING THE CONTINUATION OF A SLIGHT RISK OF
HIGH WINDS FOR THE REGIONS LISTED. ADDITIONALLY, TODAY’S MODEL SOLUTIONS DEPICT
STRONGER COLD AIR ADVECTION ASSOCIATED WITH THIS LOW PRESSURE SYSTEM AND THE
POTENTIAL FOR UNSEASONABLY COLD TEMPERATURES. BOTH THE ECMWF AND GEFS PETS FOR
MINIMUM TEMPERATURE INDICATE AT LEAST A 20% PROBABILITY OF MINIMUM TEMPERATURES
FALLING BELOW THE 15TH PERCENTILE FOR MUCH OF THE EASTERN CONUS FOR APR 17-18,
WITH POTENTIAL FROST CONDITIONS EXTENDING AS FAR SOUTH AS ATLANTA. THEREFORE A
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES IS POSTED FOR THE MID-ATLANTIC
AND APPALACHIANS, AS WELL AS MUCH OF THE OHIO AND TENNESSEE VALLEYS, AND
PORTIONS OF THE SOUTHEAST U.S. AND GREAT LAKES FOR APR 17-18.
MULTIPLE MODELS ALSO FAVOR THE DEVELOPMENT OF SURFACE LOW PRESSURE IN THE LEE
OF THE ROCKIES EARLY IN WEEK-2. THIS FEATURE IS NOT VERY STRONG IN ENSEMBLE
MEANS BUT IS FAIRLY PERSISTENT AND MODEL SOLUTIONS FORM AN EXPANSIVE RAIN
SHIELD EAST OF THE LOW PRESSURE CENTER, BRINGING THE POTENTIAL FOR HEAVY
PRECIPITATION OVER SOME REGIONS RECENTLY AFFECTED BY EXCESSIVE RAIN.
UNCALIBRATED PROBABILITIES FROM THE ECMWF INDICATE AT LEAST A 20% CHANCE OF
3-DAY PRECIPITATION TOTALS TO EXCEED 1 INCH EARLY IN WEEK-2. THIS IS ALSO WELL
INDICATED IN THE ECMWF AND GEFS PETS. TODAY’S SOLUTIONS DEPICT CONTINUING
PRECIPITATION IN THE REGION THROUGHOUT WEEK-2 BUT ACCUMULATION TOTALS TAIL OFF
AFTER THE 19TH, SO THE SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE
OHIO, TENNESSEE, LOWER AND MIDDLE MISSISSIPPI VALLEYS, AND SOUTHERN AND CENTRAL
PLAINS IS NOW POSTED ONLY FOR APR 17-19. AT THE OUTSET OF WEEK-2 SURFACE HIGH
PRESSURE OVER THE SOUTHEASTERN CONUS TEAMS UP WITH THIS SURFACE LOW TO FORM A
TIGHT PRESSURE GRADIENT OVER THE SOUTHERN AND CENTRAL PLAINS. 10M WIND
FORECASTS FROM THE ECMWF AND GEFS INDICATE PERIODIC HIGH WINDS OVER MUCH OF
TEXAS AND EXTENDING WESTWARD INTO NEW MEXICO AND NORTHWARD WELL INTO THE
CENTRAL PLAINS. THIS IS ALSO INDICATED BY THE ECMWF PET, WHICH SHOWS AT LEAST A
20% CHANCE OF 3-DAY MAXIMUM WIND SPEED EXCEEDING THE 85TH PERCENTILE AND 20MPH
EARLY IN THE FORECAST PERIOD. THE LOW PRESSURE CENTER IS FAVORED TO MOVE
QUICKLY EASTWARD, ALONG WITH WEAKENING SURFACE PRESSURE GRADIENTS, THEREFORE A
SLIGHT RISK OF HIGH WINDS IS POSTED FOR THE SOUTHERN PLAINS AND SOUTHERN
ROCKIES, AS WELL AS PORTIONS OF THE DESERT SOUTHWEST, CENTRAL ROCKIES, CENTRAL
PLAINS, AND LOWER AND MIDDLE MISSISSIPPI VALLEY FOR APR 17-18, AFTER WHICH
CHANCE OF HIGH WINDS DIMINISH. FINALLY, GIVEN THE COPIOUS ANTECEDENT RAINFALL
AND RECURRING FLOODING CONCERNS IN THIS REGION, A FLOODING POSSIBLE HAZARD IS
POSTED FOR PORTIONS OF THE OHIO AND MIDDLE MISSISSIPPI VALLEYS DUE TO THE
POTENTIAL FOR NEW AND RENEWED RISES IN RIVER LEVELS. WHILE MAIN CHANNELS ARE
ALREADY VERY HIGH, AND THUS LIKELY WON’T RESPOND TOO MUCH TO ADDITIONAL
PRECIPITATION, TRIBUTARIES AND STREAMS WILL BE MORE SUSCEPTIBLE TO RENEWED
FLOODING OR FLASH FLOODING.
IN ALASKA, MULTIPLE MODELS DEPICT A SURFACE LOW PRESSURE SYSTEM TRACKING ACROSS
THE GULF OF ALASKA DURING WEEK-2. THIS SYSTEM IS DEPICTED WITH STRONG PRESSURE
GRADIENTS AND DEVELOPING STRONG WINDS THAT MAY POTENTIALLY AFFECT COASTAL AREAS
OF SOUTHEAST ALASKA. THE ECMWF AND GEFS PETS FOR MAXIMUM WIND SPEED INDICATE AT
LEAST A 20% CHANCE OF 3-DAY WIND SPEEDS EXCEEDING THE 85TH PERCENTILE AND AT
LEAST 40MPH, SO A SLIGHT RISK OF HIGH WINDS IS POSTED FOR COASTAL ALASKA FROM
PRINCE WILLIAM SOUND EASTWARD THROUGH SOUTHEAST ALASKA FOR APR 17-19. IN
ADDITION, AS SPRING CONTINUES AND DAILY INCOMING SOLAR RADIATION FLUX TOTALS
INCREASE, ICE-BOUND RIVERS WILL BEGIN TO BREAK UP. THERE IS NO ASSOCIATED
HAZARD POSTED AT THIS TIME BUT THIS SITUATION WILL BE CLOSELY MONITORED IN THE
COMING DAYS AND WEEKS AS CONDITIONS CAN QUICKLY CHANGE, LEADING TO THE
POTENTIAL FOR ICE JAMS AND ASSOCIATED FLOODING.
FORECASTER: DANNY BARANDIARAN
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