943
FXUS21 KWNC 071858
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 07 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 LAKERS AND
NORTHEAST U.S. 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.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE OHIO, TENNESSEE, LOWER
AND MIDDLE MISSISSIPPI VALLEYS, AND SOUTHERN AND CENTRAL PLAINS, THU-MON, APR
17-21.
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, TUE-THU, APR 15-17.
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,
TUE-THU, APR 15-17.
FLOODING POSSIBLE FOR PORTIONS OF THE OHIO, TENNESSEE, AND MIDDLE AND LOWER
MISSISSIPPI VALLEYS.
DETAILED SUMMARY
FOR THURSDAY APRIL 10 - MONDAY APRIL 14:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY APRIL 15 - MONDAY APRIL 21: 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 FOR APR 15-17.
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 FOR MOST OF WEEK-2, PARTICULARLY
FROM THE 17TH ONWARD. THIS IS ALSO WELL INDICATED IN THE ECMWF PET. CURIOUSLY,
THE GEFS PET DOES NOT SHOW MUCH SIGNAL FOR EXCESSIVE PRECIPITATION, BUT THE
GEFS ENSEMBLE MEAN SHOWS SIMILAR TOTAL ACCUMULATIONS TO THE ECMWF. DESPITE SOME
UNCERTAINTY DUE TO THESE DIFFERENCES IN THE FORECAST TOOLS, THERE IS SUFFICIENT
EVIDENCE TO WARRANT A SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE
OHIO, TENNESSEE, LOWER AND MIDDLE MISSISSIPPI VALLEYS, AND SOUTHERN AND CENTRAL
PLAINS FOR APR 17-21. 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 FOR APR 15-17,
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. 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 STREAMFLOW, TRIBUTARIES AND STREAMS WILL BE MORE
SUSCEPTIBLE TO FLOODING OR FLASH FLOODING.
IN ALASKA, 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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