277
FXUS21 KWNC 281825
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MARCH 28 2025
SYNOPSIS: POTENTIALLY STRONG MID-LEVEL LOW PRESSURE IS FAVORED OVER THE FOUR
CORNERS, WITH SURFACE LOW FORMATION IN THE LEE OF THE ROCKIES. THIS FAVORS
ELEVATED CHANCES FOR HEAVY PRECIPITATION ACROSS MANY PARTS OF THE SOUTH-CENTRAL
AND SOUTHEASTERN CONTIGUOUS U.S. (CONUS), WHERE LOCALIZED FLOODING IS POSSIBLE
EXTENDING FROM THE SOUTHERN PLAINS NORTHWARD TO THE LOWER GREAT LAKES REGION.
THIS PATTERN WOULD BRING INCREASED CHANCES FOR HIGH WINDS AND HEAVY SNOW OVER
MUCH OF THE INTERIOR WEST, WITH HEAVY SNOWFALL ALSO POSSIBLE IN THE HIGH PLAINS.
HAZARDS
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHERN PLAINS, LOWER
AND MIDDLE MISSISSIPPI AND TENNESSEE VALLEYS, AND SOUTHEAST, SAT-SUN, APR 5-6.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE OHIO, TENNESSEE, AND
MISSISSIPPI VALLEYS, CENTRAL AND SOUTHERN PLAINS, SOUTHEAST, LOWER GREAT LAKES,
AND THE APPALACHIANS, SAT-TUE, APR 5-8.
SLIGHT RISK OF HIGH WINDS FOR MANY PARTS OF THE INTERIOR WEST AND GREAT PLAINS,
SAT-MON, APR 5-7.
SLIGHT RISK OF PERIODS OF HEAVY SNOW FOR HIGHER ELEVATIONS OF THE CENTRAL AND
SOUTHERN ROCKIES, GREAT BASIN, AND WESTERN PARTS OF THE GREAT PLAINS, SAT-SUN,
APR 5-6.
FLOODING POSSIBLE FOR PORTIONS OF THE SOUTHERN PLAINS, LOWER AND MIDDLE
MISSISSIPPI, TENNESSEE AND OHIO VALLEYS, APPALACHIANS, AND THE SOUTHEAST.
DETAILED SUMMARY
FOR MONDAY MARCH 31 - FRIDAY APRIL 04:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY APRIL 05 - FRIDAY APRIL 11: DYNAMICAL MODELS ARE IN FAIRLY POOR
AGREEMENT IN REGARDS TO THE 500-HPA HEIGHT ANOMALY PATTERN AND ITS EVOLUTION
THROUGHOUT THE WEEK-2 PERIOD. IN RECENT MODEL RUNS, A KEY DEVELOPMENT IS
DEPICTED IN THE 0Z ECWMF ENSEMBLE, WHICH NOW FAVORS AMPLIFIED RIDGING OVER THE
GULF OF ALASKA AND SOUTHWESTERN CANADA BY THE OUTSET OF THE PERIOD. THIS
MID-LEVEL FEATURE IS NOT ONLY EXPECTED TO ENHANCE THE SHORTWARE TROUGHING
DOWNSTREAM OVER THE FOUR CORNERS, BUT ALSO INTRODUCE INCREASED CHANCES FOR
ANOMALOUSLY COLD TEMPERATURES FOR MANY AREAS WEST OF THE MISSISSIPPI. BY
CONTRAST, THE 0Z GEFS AND CANADIAN CONTINUE TO FAVOR WEAKER SHORTWAVE ENERGY
EJECTING FROM THE ROCKIES, AND PLACES THE AMPLIFYING RIDGE AXIS FURTHER EAST
OVER THE WEST COAST AND INTERIOR WEST, RESULTING IN A VASTLY DIFFERENT SURFACE
TEMPERATURE RESPONSE EARLY IN WEEK-2. HOWEVER, THE ONE CONSTANT EVIDENT IN THE
ENSEMBLE GUIDANCE REMAINS THE ANOMALOUS 500-HPA RIDGING OVER THE SOUTHEASTERN
CONUS, WHERE THERE IS BETTER FORECAST CONFIDENCE FOR ABOVE-NORMAL TEMPERATURES
FOR THIS PART OF THE COUNTRY. THIS ALSO SETS THE STAGE FOR ENHANCED GULF RETURN
FLOW TO BRING PERIODS OF INCREASED, AND POSSIBLY HEAVY PRECIPITATION THROUGHOUT
THE PLAINS, MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS TIED TO ANY SURFACE LOW
DEVELOPMENT IN THE LEE OF THE ROCKIES.
WITH SHORTWAVE TROUGHING AND MEAN SURFACE LOW FORMATION FAVORED IN THE LEE OF
THE ROCKIES EARLY IN WEEK-2, A MODERATE RISK OF HEAVY PRECIPITATION REMAINS
POSTED FOR PARTS OF THE SOUTHERN PLAINS, MISSISSIPPI, TENNESSEE AND OHIO
VALLEYS FOR APR 5-6 BASED ON RAW AND CALIBRATED PRECIPITATION TOOLS. A HIGH
RISK DESIGNATION WAS CONSIDERED BASED ON THE UNCALIBRATED ECMWF WHICH FEATURES
>60% CHANCES FOR 3-DAY AMOUNTS EXCEEDING 2 INCHES, HOWEVER, THERE IS LITTLE TO
NO SUPPORT FOR THIS POTENTIAL ASSOCIATED WITH THE WEAKER TROUGHING IN THE GEFS
AND CANADIAN. A SLIGHT RISK AREA FOR HEAVY PRECIPITATION ALSO REMAINS ISSUED,
BUT IS BROADENED IN COVERAGE, AND EXTENDED THROUGH APR 8 TO CAPTURE THE MORE
EXPANSIVE AND PERSISTENT HEAVY PRECIPITATION SIGNALS IN THE ECMWF GUIDANCE,
RELATIVE TO YESTERDAY. DUE TO ANTECEDENT WETNESS FROM THE OHIO VALLEY SOUTHWARD
TO THE LOWER MISSISSIPPI VALLEY, WITH ABOVE-NORMAL PRECIPITATION FAVORED DURING
WEEK-1 (WPC QPF SHOWS 7-DAY AMOUNTS EXCEEDING 3 INCHES), A FLOODING POSSIBLE
HAZARD IS CONSIDERABLY EXPANDED IN THE UPDATED OUTLOOK WHERE WATER MODELS ALSO
HIGHLIGHT THE STRONGEST CHANCES WHERE FLOODING MAY OCCUR. WITHIN THESE
HIGHLIGHTED AREAS, THUNDERSTORM ACTIVITY IS POSSIBLE GIVEN THE ADDED
BAROCLINICITY WITH STRONGER COLD AIR ADVECTION IN THE ECMWF, CLIMATOLOGY, AND
WITH DETERMINISTIC AND ENSEMBLE MEMBER SOLUTIONS INDICATING DEWPOINT
TEMPERATURES EXCEEDING 60 DEGREES IN THE WARM SECTOR OF THE MEAN SURFACE LOW.
ALONG THE AXIS OF THE MEAN SHORTWAVE TROUGHING UPSTREAM, A SLIGHT RISK OF HIGH
WINDS REMAINS ISSUED (APR 5-7) AND IS EXPANDED IN COVERAGE OVER THE INTERIOR
WEST AND GREAT PLAINS BASED ON THE STRONGER MEAN SURFACE HIGH PRESSURE
DESCENDING FROM SOUTHERN CANADA IN THE ECMWF. SIMILARLY, A SLIGHT RISK OF HEAVY
SNOW IS CONTINUED AND ALSO EXPANDED IN COVERAGE TO INCLUDE THE WESTERN PARTS OF
THE HIGH PLAINS, VALID THROUGH APR 6, WHERE THE ECMWF SHOWS INCREASED MEAN
SNOWFALL TOTALS OVER EASTERN COLORADO, AND NEIGHBORING PARTS OF WESTERN SOUTH
DAKOTA, NEBRASKA AND KANSAS. CONSISTENT WITH PRECIPITATION RISK DOWNSTREAM, A
MODERATE RISK FOR HEAVY SNOWFALL OVER THE FRONT RANGE WAS CONSIDERED, HOWEVER
THE GEFS AND CANADIAN ARE UNSUPPORTIVE OF THIS DESIGNATION.
DUE TO THE AFOREMENTIONED DEVELOPMENT OF STRONG MID-LEVEL RIDGING IN THE ECMWF
THAT IS ABSENT IN THE GEFS AND CANADIAN OVER THE GULF OF ALASKA, THERE IS
INCREASED FORECAST UNCERTAINTY OVER ALASKA RESULTING IN NO HAZARDS BEING ISSUED
OVER THE STATE.
FORECASTER: NICK NOVELLA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page