232
FXUS02 KWBC 230659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT SUN MAR 23 2025
VALID 12Z WED MAR 26 2025 - 12Z SUN MAR 30 2025
..OVERVIEW
EXPECT THE AMPLIFIED WESTERN RIDGE/EASTERN TROUGH UPPER PATTERN
LINGERING INTO WEDNESDAY TO MOVE STEADILY EASTWARD WHILE TRENDING A
LITTLE FLATTER, AS DYNAMICS FROM A STRONG EAST PACIFIC UPPER
TROUGH WEDNESDAY-THURSDAY (SUPPORTING A STORM SYSTEM OFF THE
PACIFIC NORTHWEST COAST) PUSH INTO THE WESTERN AND CENTRAL U.S.
WITH A SLIGHTLY SLOWER TREND NOTED IN THE GUIDANCE, THE MEAN RIDGE
SHOULD REACH THE EAST BY NEXT WEEKEND. EXPECT VERY WARM
TEMPERATURES UNDER THE WESTERN UPPER RIDGE THROUGH MIDWEEK OR SO
WITH SOME DAILY RECORDS POSSIBLE. ANOMALOUS WARMTH WILL THEN MOVE
INTO THE PLAINS, FOLLOWED BY MODERATION FARTHER EAST. UPPER
DYNAMICS AND THE LEADING FRONT ARRIVING FROM THE PACIFIC WILL BRING
RAIN AND HIGH ELEVATION SNOW TO THE NORTHWEST MID-LATE WEEK, WITH
ANOTHER SYSTEM POSSIBLY APPROACHING BY NEXT SUNDAY. A SOUTHERN TIER
SHORTWAVE WILL SUPPORT THE THREAT OF LOCALLY HEAVY RAINFALL OVER
PARTS OF TEXAS LATE IN THE WEEK. THIS MOISTURE AND ADDITIONAL GULF
INFLOW MAY COMBINE TO SPREAD A BROADER AREA OF PRECIPITATION OVER
PARTS OF THE PLAINS AND EAST-CENTRAL U.S. LATE WEEK INTO THE
WEEKEND, IN ASSOCIATION WITH PLAINS THROUGH UPPER MIDWEST LOW
PRESSURE.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE WEDNESDAY-THURSDAY FORECAST OF THE STORM OFF THE PACIFIC
NORTHWEST COAST HAS IMPROVED CONSIDERABLY OVER THE PAST DAY, WITH
TRENDS AMONG DYNAMICAL/MACHINE LEARNING (ML) MODELS LEANING DEEPER.
MEANWHILE SOLUTIONS HAVE RECENTLY BEEN TRENDING TOWARD AN
INTERMEDIATE IDEA FOR THE UPPER TROUGH REACHING THE WEST COAST
(ECMWF CLUSTER TRENDING WEAKER AND/OR SLOWER, GFS TRENDING A LITTLE
DEEPER). HOWEVER MODEL/ENSEMBLE SOLUTIONS STILL DIVERGE
CONSIDERABLY FROM FRIDAY THROUGH THE WEEKEND AS THE UPPER TROUGH
ENERGY FROM THIS SYSTEM CONTINUES THROUGH THE WESTERN/CENTRAL U.S.
POTENTIAL ARRIVAL OF UPSTREAM SHORTWAVE ENERGY FURTHER COMPLICATES
THE FORECAST. OVERALL, ML MODELS DO NOT SUPPORT A PRONOUNCED CLOSED
UPPER LOW LATE IN THE PERIOD, WHICH ESPECIALLY QUESTIONS THE 00Z
CMC RUN, WHILE THE SUGGEST THE PRIMARY SURFACE WAVE REACHING A
POSITION BETWEEN THE UPPER MIDWEST AND GREAT LAKES BY NEXT SUNDAY.
THIS IS SIMILAR TO THE DYNAMICAL ENSEMBLE MEANS. THERE ARE A LOT OF
DIFFERENT IDEAS FOR HOW LOW PRESSURE COULD EVOLVE OFFSHORE THE
WEST COAST BY NEXT SUNDAY, WITH NO DISCERNIBLE CLUSTERING IN
DYNAMICAL OR ML GUIDANCE, THUS FAVORING A CONSERVATIVE DEPICTION
FOR NOW. OVER THE EAST, PREFERENCE REMAINS WITH THE MAJORITY ECMWF
CLUSTER FOR THE WEAK WAVE DEPARTING FROM THE MID-ATLANTIC COAST ON
WEDNESDAY. THE PREVIOUSLY SLOW CMC HAS JOINED THIS GROUP WHILE THE
GFS IS ON THE FAST SIDE. THEN BY NEXT WEEKEND GUIDANCE SHOWS SPREAD
WITH A FRONT THAT REACHES INTO THE MID-ATLANTIC, LIKELY WITH A
PRONOUNCED TEMPERATURE GRADIENT. AT THE VERY LEAST, ML MODELS OFFER
LESS SUPPORT FOR THE NORTHERN SIDE OF THE SPREAD.
THE UPDATED FORECAST CONTINUED TO EMPLOY A MODEL COMPOSITE EARLY
WITH 40 PERCENT 12Z ECMWF AND THE REST SPLIT AMONG THE
GFS/UKMET/CMC, FOLLOWED BY A RAPID INCREASE OF 18Z GEFS AND 12Z
ECENS/CMCENS INPUT WHILE PHASING OUT THE GFS/CMC, YIELDING 75
PERCENT MEANS AND 25 PERCENT ECMWF BY NEXT SUNDAY.
..WEATHER/HAZARDS HIGHLIGHTS
FROM WEDNESDAY INTO THURSDAY NIGHT THE MOST PROMINENT HEAVY
RAINFALL FOCUS SHOULD BE OVER PORTIONS OF TEXAS BY THURSDAY AS
MOIST SOUTHEASTERLY LOW LEVEL FLOW FROM THE GULF INTERACTS WITH AN
UPPER SHORTWAVE CROSSING NORTHERN MEXICO. SOME ACTIVITY MAY
INITIATE IN THE DAY 4 PERIOD NEAR THE RIO GRANDE VALLEY BUT THE
SIGNAL IS DIFFUSE ENOUGH NOT TO MERIT ANY RISK AREA IN THE
EXCESSIVE RAINFALL OUTLOOK. BY DAY 5 THERE IS A MUCH STRONGER
SIGNAL, THOUGH WITH TYPICAL SPREAD FOR WHERE THE BEST FOCUS WILL
BE. OVERALL THE BEST OVERLAP OF DYNAMICAL AND ML GUIDANCE EXISTS
OVER SOUTHERN TEXAS. THE DAY 5 ERO STARTS OUT WITH A BROADER
MARGINAL RISK AREA, WITH NO EMBEDDED SLIGHT RISK DEPICTED YET DUE
TO INITIALLY DRY GROUND CONDITIONS AND EXISTING GUIDANCE SPREAD.
IMPROVED CLUSTERING FOR LOCATION AND AMOUNTS IN THE HEAVIER PART OF
THE ENVELOPE COULD EVENTUALLY MERIT AN UPGRADE. ELSEWHERE,
CONSENSUS AMOUNTS ALONG THE PACIFIC NORTHWEST COAST IN ASSOCIATION
WITH THE WEDNESDAY-THURSDAY SYSTEM HAVE GENERALLY DECREASED
SOMEWHAT FROM 24 HOURS AGO, WHILE THE SIGNAL FOR A POTENTIAL BAND
OF ENHANCED RAINFALL OVER THE MID MISSISSIPPI VALLEY AHEAD OF A
WARM FRONT IS TOO DIFFUSE TO WARRANT A RISK AREA YET ON DAY 5.
PRECIPITATION WILL SPREAD ACROSS NORTHERN AND CENTRAL PARTS OF THE
WEST LATE THIS WEEK, WITH PLAINS LOW PRESSURE AND ITS TRAILING
FRONT EVENTUALLY PUSHING THE TEXAS RAINFALL EASTWARD WHILE
SPREADING A BROADER SHIELD OF MOISTURE ACROSS THE CENTRAL AND EAST-
CENTRAL U.S. SOME WINTRY WEATHER WILL BE POSSIBLE OVER FAR
NORTHERN LATITUDES BUT OTHERWISE MOST PRECIPITATION SHOULD BE IN
THE FORM OF RAIN. HOW MUCH SNOW FALLS OVER THE NORTHERN PLAINS NEXT
WEEKEND WILL DEPEND ON HOW STRONGLY THE PLAINS/UPPER MIDWEST
SYSTEM DEVELOPS, WITH LOW CONFIDENCE IN SPECIFICS AT THIS TIME. THE
NEXT PACIFIC SYSTEM MAY INCREASE PRECIPITATION ALONG THE WEST
COAST BY NEXT SUNDAY.
THE WEAK WAVE FORECAST TO TRACK OFF THE MID-ATLANTIC/NEW ENGLAND
COAST ON WEDNESDAY MAY PRODUCE SOME LIGHT PRECIPITATION EARLY BUT
MOST LIKELY JUST NEAR THE COAST.
THE STRONG UPPER RIDGE OVER THE WEST INTO WEDNESDAY WILL BRING
WELL ABOVE NORMAL TEMPERATURES TO THE REGION, WITH A BROAD AREA OF
HIGHS 10-20F ABOVE NORMAL WITH LOCALLY HIGHER ANOMALIES. THERE WILL
ALSO BE POTENTIAL FOR NUMEROUS DAILY RECORDS FOR HIGHS/WARM LOWS,
ESPECIALLY DURING WEDNESDAY. AS THE UPPER RIDGE SHIFTS EASTWARD
WITH TIME, THE WEST WILL COOL DOWN WHILE ALREADY ABOVE NORMAL
ANOMALIES OVER THE CENTRAL U.S. WILL INCREASE. LOCATIONS FROM THE
NORTHERN-CENTRAL PLAINS INTO MIDWEST SHOULD SEE ONE OR TWO DAYS OF
HIGHS REACHING 20-25F OR SO ABOVE NORMAL BY THURSDAY-FRIDAY, WITH
BEST POTENTIAL FOR SOME DAILY RECORDS OVER THE CENTRAL HIGH PLAINS
ON THURSDAY. THE EAST WILL SEE NEAR TO SLIGHTLY BELOW NORMAL
TEMPERATURES WEDNESDAY-THURSDAY AND THEN INCREASING COVERAGE OF
HIGHS 10-20F ABOVE NORMAL FRIDAY INTO THE WEEKEND. HOWEVER A FRONT
REACHING THE NORTHEAST/MID-ATLANTIC MAY DEFINE A SHARP GRADIENT
BETWEEN THIS WARMTH AND COOLER READINGS JUST TO THE NORTH.
RAUSCH
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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