826
FXUS02 KWBC 220658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 AM EDT SAT MAR 22 2025
VALID 12Z TUE MAR 25 2025 - 12Z SAT MAR 29 2025
..OVERVIEW
AN AMPLIFIED WESTERN RIDGE/EASTERN TROUGH UPPER PATTERN AS OF
TUESDAY WILL GRADUALLY PROGRESS EASTWARD WHILE TRENDING FLATTER, AS
DYNAMICS FROM A STRONG MIDWEEK UPPER TROUGH (SUPPORTING A STORM
SYSTEM OFF THE PACIFIC NORTHWEST COAST) PUSH INTO THE WESTERN HALF
OF THE LOWER 48. THE MEAN RIDGE SHOULD REACH THE EAST BY FRIDAY OR
SATURDAY. EXPECT VERY WARM TEMPERATURES UNDER THE WESTERN UPPER
RIDGE THROUGH MIDWEEK 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. A SOUTHERN TIER SHORTWAVE WILL SUPPORT THE
THREAT OF LOCALLY HEAVY RAINFALL OVER SOUTHERN PARTS OF TEXAS LATE
IN THE WEEK, WITH THIS MOISTURE AND ADDITIONAL GULF INFLOW
POTENTIALLY COMBINING TO SPREAD A BROADER AREA OF MOSTLY RAIN OVER
PARTS OF THE PLAINS AND EAST-CENTRAL U.S. BY THE END OF THE WEEK. A
WEAK MIDWEST WAVE ON TUESDAY MAY PRODUCE A BAND OF MOSTLY LIGHT
PRECIPITATION NEAR ITS TRACK THAT MAY EXTEND OFFSHORE THE MID-
ATLANTIC/NEW ENGLAND COAST BY WEDNESDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MOST GUIDANCE IS FAIRLY AGREEABLE WITH THE FORECAST DURING
TUESDAY- WEDNESDAY. THE PRIMARY EXCEPTION IS THE CMC THAT HAS BEEN
PERSISTENTLY DIGGING EASTERN U.S. SHORTWAVE ENERGY MORE SLOWLY AND
SHARPLY TO PRODUCE A SURFACE WAVE THAT IS WEST OF OTHER GUIDANCE.
THE GFS/ECMWF/UKMET AND THE GEFS/ECENS MEANS OFFER A REASONABLE
CLUSTER FOR THE UPPER DYNAMICS AND WEAK MIDWEST TO WESTERN ATLANTIC
SURFACE WAVE. MACHINE LEARNING (ML) GUIDANCE AGREES WITH THIS
CLUSTER IN PRINCIPLE AS WELL.
BY THURSDAY GUIDANCE CONTINUES TO DIVERGE, FOR THE STORM FORECAST
TO TRACK OFFSHORE THE PACIFIC NORTHWEST AND AMPLITUDE OF THE UPPER
TROUGH NEARING THE WEST COAST. BOTH DYNAMICAL AND ML MODELS SHOW
LATITUDE VARIATION FOR THE EASTERN PACIFIC STORM WITH SHIFTING
TRENDS, IN PARTICULAR THE CMC ADJUSTING NORTHWARD AFTER BEING ON
THE SOUTHERN SIDE EARLIER VERSUS THE NEW 00Z ECMWF TRENDING
SOUTHWARD. IN ADDITION GFS RUNS CONTINUE TO BE FLATTER WITH THE
UPPER TROUGH THAN MOST OTHER GUIDANCE.
THIS DEVELOPING SPREAD NEAR THE WEST COAST EXPANDS INLAND ACROSS
THE WESTERN HALF OF THE COUNTRY DURING FRIDAY-SATURDAY. GFS RUNS
REMAIN ON THE HIGH SIDE OF THE SPREAD FOR HEIGHTS ALOFT. MOST OTHER
GUIDANCE SHOWS BETTER DEFINED SHORTWAVE ENERGY BUT WITH INCREASING
SPREAD FOR DETAILS. THIS SPREAD EXTENDS TO THE ML MODELS AS WELL.
NOT SURPRISINGLY, GEFS ENSEMBLES GENERALLY LEAN TOWARD HIGHER
HEIGHTS THAN CMC/ECMWF MEMBERS, THOUGH AT LEAST THE LATEST GEFS
MEANS TEMPER THE QUESTIONABLE ASPECTS OF THE OPERATIONAL GFS RUNS.
THIS SPREAD TEMPERS CONFIDENCE IN THE EXACT DETAILS OF LOW PRESSURE
THAT SHOULD REACH THE CENTRAL U.S. TOWARD THE END OF THE WEEK.
ALSO OF NOTE, THE DIFFERENCES OVER THE WEST LEAD THE GFS TO LEAN ON
THE SLOWER SIDE OF THE SPREAD FOR THE SOUTHERN STREAM SHORTWAVE
FORECAST TO REACH INTO THE SOUTHERN PLAINS BY FRIDAY.
GUIDANCE COMPARISONS LED TO FAVORING A 12Z/18Z MODEL BLEND OF THE
GFS/ECMWF/UKMET EARLY IN THE PERIOD, FOLLOWED BY PHASING OUT THE
GFS AND STEADILY INCREASING ENSEMBLE MEAN INPUT (18Z GEFS AND 12Z
ECENS/CMCENS). THIS LED TO FORECAST CONSISTING OF 75 PERCENT
ENSEMBLE MEANS AND 25 PERCENT 12Z ECMWF BY DAY 7 SATURDAY.
..WEATHER/HAZARDS HIGHLIGHTS
THE DAYS 4-5 EXCESSIVE RAINFALL OUTLOOKS COVERING THE PERIOD FROM
TUESDAY THROUGH WEDNESDAY NIGHT CURRENTLY DEPICT NO RISK AREAS BUT
THERE ARE A COUPLE REGIONS OF INTEREST FOR CONTINUED MONITORING.
DURING DAY 4 THERE ARE SOME GUIDANCE SIGNALS FOR LOCALIZED HEAVY
RAINFALL POTENTIAL OVER AND WEST/NORTHWEST OF THE ARKLATEX REGION,
FOCUSED BY A COUPLE FRONTAL BOUNDARIES AND WITH INCREASING
AFTERNOON INSTABILITY. DRIER THAN AVERAGE GROUND CONDITIONS AND
SMALL-SCALE NATURE OF THIS ACTIVITY HAVE FAVORED NO RISK ARE THUS
FAR, BUT IMPROVED CLUSTERING ON THE HEAVIER SIDE OF THE RANGE COULD
EVENTUALLY MERIT A RISK AREA. THEN ON DAY 5 THE PACIFIC SYSTEM
AFFECTING THE WEST COAST MAY BRING A BRIEF PERIOD OF ENHANCED
RAINFALL TO THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA COAST.
THERE IS CONTINUED SPREAD WITH MAGNITUDE AND COVERAGE (THOUGH WITH
MOST GUIDANCE SUGGESTING HIGHER AMOUNTS EXTENDING FARTHER SOUTH
THEN GFS RUNS) WHILE FIRST-GUESS GUIDANCE IS FAIRLY MUTED WITH ITS
EXCESSIVE RAINFALL POTENTIAL FOR THE TIME BEING. AGAIN WILL MONITOR
GUIDANCE FOR IMPROVED CLUSTERING HERE.
EXPECT THE SOUTHERN TIER SHORTWAVE NEARING THE SOUTHERN PLAINS
AFTER MIDWEEK TO START GENERATING RAINFALL NEAR THE RIO GRANDE
VALLEY ON WEDNESDAY WITH HEAVIER ACTIVITY LIKELY REACHING EASTWARD
MORE INTO TEXAS BY THURSDAY. PRECIPITATION SHOULD PUSH ACROSS THE
WEST LATE IN THE WEEK, WITH LEADING GULF INFLOW HELPING TO INCREASE
THE COVERAGE AND INTENSITY OF PRECIPITATION OVER THE PLAINS/EAST-
CENTRAL U.S. BY FRIDAY-SATURDAY. MOST OF THIS PRECIPITATION SHOULD
BE RAIN BUT SOME WINTRY WEATHER WILL BE POSSIBLE NEAR THE CANADIAN
BORDER.
EARLIER IN THE PERIOD, A WEAK WAVE THAT SHOULD TRACK FROM THE
MIDWEST TO OFFSHORE THE MID-ATLANTIC/NEW ENGLAND COAST TUESDAY-
WEDNESDAY MAY PRODUCE A BAND OF MOSTLY LIGHT PRECIPITATION ALONG
ITS PATH. THE MAJORITY OF THIS ACTIVITY SHOULD BE RAIN, THOUGH A
LITTLE SNOW IS POSSIBLE ON THE NORTHERN FRINGE OF THE MOISTURE BAND
AND IN THE APPALACHIANS.
THE STRONG UPPER RIDGE OVER THE WEST EARLY-MID WEEK 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 TUESDAY-WEDNESDAY. SOME PLACES OVER THE DESERT
SOUTHWEST COULD GET CLOSE TO 100 DEGREES. 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. THE EAST WILL SEE INCREASING COVERAGE OF HIGHS 10-20F ABOVE
NORMAL BY FRIDAY-SATURDAY AFTER NEAR TO SLIGHTLY BELOW NORMAL
READINGS TUESDAY-THURSDAY.
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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