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FXUS21 KWNC 211810
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 21 2025
SYNOPSIS: AT THE OUTSET OF WEEK-2 SURFACE LOW PRESSURE IS FORECAST TO BE
DEPARTING ACROSS THE GREAT LAKES, WITH A TRAILING COLD FRONT EXTENDING ACROSS
THE CENTRAL AND EAST-CENTRAL CONTIGUOUS U.S. (CONUS). THIS FAVORS ENHANCED
CHANCES OF HEAVY PRECIPITATION AND THUNDERSTORMS CONTINUING INTO THE EARLY PART
OF WEEK-2 ACROSS THE CENTRAL AND SOUTHERN PLAINS AND MIDDLE AND LOWER
MISSISSIPPI VALLEY. GUSTY WINDS ARE POSSIBLE BEHIND THE DEPARTING STORM SYSTEM,
INITIALLY ACROSS THE NORTHERN PLAINS, AND THEN SHIFTING EASTWARD TO THE GREAT
LAKES. BROAD MID-LEVEL HIGH PRESSURE IS FORECAST TO REDEVELOP ACROSS THE CONUS
LATER IN WEEK-2, FAVORING INCREASED CHANCES FOR ABOVE-NORMAL TEMPERATURES OVER
MANY AREAS.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS AND THE MIDDLE AND LOWER MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS,
TUE-WED, APR 29-30.
SLIGHT RISK OF HIGH WINDS OVER PORTIONS OF THE NORTHERN PLAINS, UPPER
MISSISSIPPI VALLEY, AND GREAT LAKES, TUE-WED, APR 29-30.
POSSIBLE FLOODING FOR THE LOWER MISSISSIPPI RIVER.
DETAILED SUMMARY
FOR THURSDAY APRIL 24 - MONDAY APRIL 28:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY APRIL 29 - MONDAY MAY 05: LATE IN WEEK-1, SURFACE LOW PRESSURE IS
FORECAST TO TRACK ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST. AS THIS SYSTEM
DEPARTS, A TRAILING COLD FRONT IS PREDICTED TO REMAIN ACROSS PARTS OF THE GREAT
PLAINS AND MISSISSIPPI VALLEY EARLY IN WEEK-2 SERVING AS A FOCUS FOR CONTINUED
INCREASED CHANCES OF HEAVY PRECIPITATION AND THUNDERSTORMS. THE UNCALIBRATED 0Z
ECENS DEPICTS A SWATH OF HEAVY PRECIPITATION STRETCHING FROM NORTHEASTERN TEXAS
INTO THE MIDDLE MISSISSIPPI VALLEY ON DAY-8 (APR 29), FOLLOWED BY A
SOUTHEASTWARD SHIFT INTO THE LOWER MISSISSIPPI VALLEY ON DAY-9 (APR 30). THE
ECENS PROBABILISTIC EXTREMES TOOL (PET) DEPICTS ALL OF THESE AREAS HAVING AT
LEAST A 20 PERCENT CHANCE 3-DAY PRECIPITATION TOTALS EXCEED THE 85TH
CLIMATOLOGICAL PERCENTILE AND 1-INCH. WHILE THE UNCALIBRATED 0Z GEFS IS
CONSIDERABLY DRIER COMPARED TO THE ECENS, THE CORRESPONDING GEFS PET DEPICTS A
REGION OF ELEVATED POTENTIAL FOR PRECIPITATION REACHING HAZARDOUS THRESHOLDS
ACROSS THE MIDDLE MISSISSIPPI VALLEY. AS A RESULT, A SLIGHT RISK OF HEAVY
PRECIPITATION IS POSTED ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS AND
THE MIDDLE AND LOWER MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS, APR 29-30.
THE CONVECTIVE AND SPORADIC NATURE OF THE PRECIPITATION EARLY IN WEEK-2 LEADS
TO LESS CONFIDENCE IN DETERMINING EXACT AREAS MOST AT RISK OF ADDITIONAL
FLOODING. THEREFORE, THE POSSIBLE FLOODING RISK ACROSS THE CENTRAL AND SOUTHERN
PLAINS INTO ADJACENT AREAS OF THE MISSISSIPPI VALLEY HAS BEEN REMOVED, ALTHOUGH
LOCALIZED FLOODING REMAINS A CONCERN OVER AREAS THAT DO RECEIVE HEAVY RAINFALL.
A POSSIBLE FLOODING HAZARD REMAINS POSTED ACROSS THE LOWER MISSISSIPPI RIVER
GIVEN THE POTENTIAL FOR NEW AND RENEWED RISES IN WATER LEVELS DURING WEEK-2
TIED TO ANY ADDITIONAL RAINFALL OVER THE REGION AS WELL AS RUNOFF FROM RAINFALL
UPSTREAM. MAIN CHANNELS ARE ALREADY VERY HIGH, AND THUS ARE UNLIKELY TO HAVE
LARGE RESPONSES TO ADDITIONAL PRECIPITATION. REGARDLESS, TRIBUTARIES AND
STREAMS WILL CONTINUE TO BE SUSCEPTIBLE TO RENEWED FLOODING OR FLASH FLOODING
IF ADDITIONAL RAINFALL OCCURS.
AS THE AFOREMENTIONED SURFACE LOW AND ASSOCIATED MID-LEVEL TROUGH EXIT THE
REGION EARLY IN WEEK-2, THERE IS SOME POTENTIAL FOR ELEVATED WIND SPEEDS ACROSS
THE NORTHERN CONUS. UNCALIBRATED GUIDANCE FROM THE 0Z ECENS AND GEFS DEPICTS AN
AREA OF ELEVATED PROBABILITIES FOR WIND SPEEDS TO EXCEED 20-MPH INITIALLY
ACROSS THE NORTHERN PLAINS ON DAY-8 (APR 29), WITH THE GEFS DEPICTING AN
EASTWARD SHIFT INTO THE GREAT LAKES ON DAY-9 (APR 30). ADDITIONALLY, THE ECENS
AND GEFS PETS DEPICT SOME OF THESE AREAS HAVING AT LEAST A 20 PERCENT CHANCE
WIND SPEEDS EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 20-MPH. GIVEN THESE
SIGNALS, A SLIGHT RISK FOR HIGH WINDS IS POSTED FROM THE NORTHERN PLAINS
EASTWARD TO THE GREAT LAKES, APR 29-30.
ANOMALOUS RIDGING IS FORECAST ACROSS THE EASTERN CONUS AT THE BEGINNING OF THE
PERIOD. THIS FAVORS A PERIOD OF UNSEASONABLY WARM TEMPERATURES OVER MUCH OF THE
EAST DURING THE FIRST HALF OF WEEK-2. WHILE THE CALIBRATED ECENS HEAT RISK TOOL
DEPICTS SOME AREAS HAVING A 30-50 PERCENT CHANCE HEAT INDICES EXCEED THE 90TH
CLIMATOLOGICAL PERCENTILE DURING WEEK-2, ACTUAL TEMPERATURES (70S AND 80S DEG
F) ARE NOT ANTICIPATED TO BE IMPACTFUL DUE TO THE TIME OF YEAR, AND NO RELATED
HEAT HAZARDS ARE POSTED. A GENERAL TREND TOWARD MORE BROAD RIDGING AND A
PATTERN TYPICAL OF LATE-SPRING IS FORECAST TO EMERGE LATER IN WEEK-2.
TROUGHING FORECAST ACROSS ALASKA FAVORS INCREASED CHANCES FOR NEAR- TO
ABOVE-NORMAL PRECIPITATION OVER MOST AREAS OF THE STATE, WITH ACTUAL
PRECIPITATION AMOUNTS NOT EXPECTED TO REACH HAZARDS THRESHOLDS. BELOW-NORMAL
TEMPERATURES FORECAST OVER MANY AREAS FAVOR A DELAY IN SEASONAL RIVER ICE
BREAKUP. HOWEVER, AS TEMPERATURES CONTINUE TO WARM, THE EVENTUAL RIVER ICE
BREAKUP MAY LEAD TO ICE JAMS AND ASSOCIATED FLOODING IN THE COMING WEEKS.
FORECASTER: THOMAS COLLOW
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