446
FXUS21 KWNC 141824
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 14 2025
SYNOPSIS: ONE OR MORE SURFACE LOW PRESSURE SYSTEMS FAVORED IN THE LEE OF THE
ROCKIES SUPPORTS INCREASED CHANCES FOR LOCALLY HEAVY PRECIPITATION FOR MUCH OF
THE SOUTH-CENTRAL AND SOUTH-EASTERN CONTIGUOUS U.S (CONUS) DURING THE PERIOD.
DUE TO EXCESSIVE PRECIPITATION OBSERVED IN THE MISSISSIPPI AND OHIO RIVER
VALLEYS DURING THE PAST FEW WEEKS, ANY ABOVE-NORMAL PRECIPITATION RECEIVED
DURING WEEK-2 MAY TRIGGER ADDITIONAL FLOODING IN THIS PART OF THE COUNTRY.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS AND MIDDLE AND LOWER MISSISSIPPI, TENNESSEE AND OHIO VALLEYS, SOUTHERN
APPALACHIANS, AND SOUTHEAST, WED-FRI, APR 23-25.
SLIGHT RISK OF HIGH WINDS OVER PARTS OF CALIFORNIA AND THE PACIFIC NORTHWEST,
TUE-FRI, APR 22-25.
FLOODING POSSIBLE FOR THE MIDDLE AND LOWER MISSISSIPPI, AND LOWER OHIO RIVERS.
DETAILED SUMMARY
FOR THURSDAY APRIL 17 - MONDAY APRIL 21:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY APRIL 22 - MONDAY APRIL 28: DYNAMICAL MODEL GUIDANCE CONTINUES TO
FAVOR A FULL LATITUDE LONGWAVE RIDGE OVER EASTERN NORTH AMERICA, WITH NEAR TO
BELOW-NORMAL MEAN 500-HPA HEIGHTS UPSTREAM OVER THE WESTERN CONUS IN THE MEAN
WEEK-2 PATTERN. THIS LATTER MID-LEVEL FEATURE FAVORED WOULD SET THE STAGE FOR A
SERIES OF SHORTWAVE DISTURBANCES AND SURFACE LOW DEVELOPMENT IN THE LEE OF THE
ROCKIES, WITH PLENTY OF GULF MOISTURE ADVECTION CONDUCIVE FOR ENHANCED AND
POSSIBLY HAZARDOUS PRECIPITATION FOR PORTIONS OF THE CENTRAL AND EASTERN CONUS
DURING WEEK-2. EARLY NEXT WEEK, THE GEFS AND ECMWF FEATURE A SHORTWAVE TROUGH
WITH AN ACCOMPANYING SURFACE LOW TRACKING OVER THE GREAT LAKES. WHILE BOTH
PRECIPITATION TOOLS SHOW INCREASED PRECIPITATION AMOUNTS TIED TO THIS LOW, THE
STRONGEST SYNOPTIC FORCING AND HEAVIEST PRECIPITATION APPEARS MOST LIKELY LATE
IN WEEK-1 RESULTING IN NO CORRESPONDING HAZARDS BEING POSTED. HOWEVER, A
SECONDARY SHORTWAVE TROUGH IS FAVORED TO DEVELOP UPSTREAM OVER THE INTERIOR
WEST, WITH SURFACE LOW FORMATION AGAIN FAVORED IN THE LEE OF ROCKIES
IMMEDIATELY IN THE WAKE OF THE FIRST SYSTEM. COMPARED TO THE GEFS, THE ECMWF IS
DEEPER AND SLIGHTLY STRONGER WITH THE ANOMALOUS MID-LEVEL TROUGHING, BUT THERE
IS GOOD MULTI-MODEL AGREEMENT IN BOTH THE RAW AND CALIBRATED PROBABILISTIC
EXTREMES TOOLS (PETS) DEPICTING 20-30% CHANCES FOR 3-DAY PRECIPITATION AMOUNTS
EXCEEDING THE 85TH PERCENTILE AND 1 INCH EXTENDING FROM THE PLAINS EASTWARD TO
THE OHIO AND TENNESSEE VALLEYS. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION
IS POSTED, AND VALID FOR DAYS 9-11 (APR 23-25) BASED ON THE TIMING OF
PRECIPITATION INCREASES IN THE RAW TOOLS. WITHIN THE HIGHLIGHTED AREA,
THUNDERSTORM ACTIVITY AND CONVECTIVE PRECIPITATION IS QUITE POSSIBLE BASED ON
DETERMINISTIC SOLUTIONS, AND ALSO COINCIDES WITH AN UPTICK IN CLIMATOLOGY FOR
SUCH CONDITIONS DURING MID TO LATE APRIL OVER PARTS OF THE SOUTHERN PLAINS AND
ADJACENT MISSISSIPPI VALLEY. EPISODES OF HIGH WINDS ARE ALSO POSSIBLE OVER
PORTIONS OF THE PLAINS, THOUGH RAW ENSEMBLES AND PETS REMAIN UNSUPPORTIVE OF A
WIND HAZARD AT THIS TIME. LATER IN WEEK-2, ADDITIONAL LEE CYCLOGENESIS IS NOT
BEING RULED OUT BASED ON THE MID-LEVEL PATTERN, BUT ANY RENEWED HEAVY
PRECIPITATION RISKS WILL BE REASSESSED AS IT COMES INTO BETTER FOCUS LATER THIS
WEEK.
WITH COPIOUS ANTECEDENT RAINFALL AND RECURRING FLOODING CONCERNS FOR PORTIONS
OF THE LOWER OHIO, MIDDLE AND LOWER MISSISSIPPI VALLEYS, A FLOODING POSSIBLE
HAZARD REMAINS POSTED FOR THIS PART OF THE COUNTRY GIVEN THE POTENTIAL FOR NEW
AND RENEWED RISES IN RIVER LEVELS DURING WEEK-2. 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 IF ADDITIONAL RAINFALL OCCURS. WITH POTENTIALLY
HEAVY RAINFALL FAVORED TO THE WEST OVER THE EASTERN PLAINS AND WESTERN
MISSISSIPPI VALLEY LATE IN WEEK-1, LOCALIZED FLOODING AND STREAMFLOW RISES ARE
ALSO POSSIBLE NEAR THE ARKLATEX REGION DURING WEEK-2, BUT CONFIDENCE IS
SOMEWHAT LOW TO ISSUE ADDITIONAL FLOODING HAZARDS AT THIS TIME.
OVER THE WESTERN U.S., SPRING SNOWFALL IS FAVORED OVER THE HIGHER ELEVATIONS OF
THE NORTHERN INTERMOUNTAIN, CENTRAL AND NORTHERN ROCKIES TIED TO THE WEAK MEAN
TROUGHING ALOFT. THE HIGHEST ACCUMULATIONS ARE FAVORED EARLY IN THE PERIOD,
THOUGH NO HEAVY SNOW HAZARDS ARE POSTED DUE TO THE RAW ENSEMBLES AND THE GEFS
SNOW WATER EQUIVALENT (SWE) PET REMAINING UNSUPPORTIVE OF AMOUNTS EXCEEDING
HAZARD THRESHOLDS. OVER THE WEST COAST, A SLIGHT RISK OF HIGH WINDS IS POSTED
FOR APR 22-25 FOR PARTS OF CALIFORNIA AND THE PACIFIC NORTHWEST. ALTHOUGH PETS
ARE RATHER WEAK WITH WIND POTENTIAL IN GENERAL, AN EASTWARD ADVANCING AREA OF
STRONG SURFACE HIGH PRESSURE OVER THE EASTERN PACIFIC, WITH MEAN LOW PRESSURE
ESTABLISHED OVER THE GREAT BASIN MAY INDUCE EPISODES OF ELEVATED WINDS IN THE
HIGHLIGHTED REGION.
OVER ALASKA, ABOVE NORMAL PRECIPITATION IS PREDOMINATELY FAVORED OVER THE
MAINLAND ASSOCIATED WITH WEAK TROUGHING NORTH OF THE ALEUTIANS. NO HAZARDS ARE
ISSUED, BUT AS SPRING CONTINUES AND INCOMING SOLAR RADIATION FLUX TOTALS
INCREASE, ICE-BOUND RIVERS WILL BEGIN TO BREAK UP WHICH MAY LEAD TO ICE JAMS
AND ASSOCIATED FLOODING IN THE COMING WEEKS. OVER THE CENTRAL PACIFIC,
PERSISTENT TROUGHING IS FAVORED UPSTREAM OF AN AMPLIFIED EAST PACIFIC RIDGE
DURING WEEK-2. AN ACCOMPANYING AREA OF SURFACE LOW PRESSURE IS FAVORED TO
DEVELOP TO THE NORTH OF THE HAWAIIAN ISLAND CHAIN, WHICH COULD BRING LOCALLY
HEAVY PRECIPITATION TO THE NORTHERN WINDWARD ISLANDS.
FORECASTER: NICK NOVELLA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page