133
FXUS02 KWBC 260659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT WED MAR 26 2025
VALID 12Z SAT MAR 29 2025 - 12Z WED APR 02 2025
..OVERVIEW
CONTINUE TO EXPECT A MODERATELY PROGRESSIVE PATTERN WITH ACTIVE
WEATHER ACROSS PORTIONS OF THE LOWER 48. A SOUTHERN STREAM
SHORTWAVE SHOULD BRING A THREAT OF LOCALLY HEAVY RAIN INTO THE
EAST-CENTRAL GULF COAST EARLY THIS WEEKEND, BUT WITH LESS EXTREME
TOTALS THAN EXPECTED FARTHER WEST IN THE SHORT RANGE TIME FRAME.
MEANWHILE EMERGING WESTERN DYNAMICS WILL HELP TO DEVELOP A WAVY
FRONTAL SYSTEM PUSHING EASTWARD FROM THE PLAINS THROUGH THE EAST
THIS WEEKEND INTO NEXT MONDAY. THIS SYSTEM SHOULD PRODUCE SOME
WINTRY WEATHER OVER NORTHERN LATITUDES WITH AREAS OF ENHANCED
RAINFALL FARTHER SOUTH. A SYSTEM MOST LIKELY TO TRACK NORTHWARD
OFFSHORE THE WEST COAST SHOULD SPREAD PRECIPITATION INTO THE WEST
FROM LATE WEEKEND INTO EARLY NEXT WEEK. ADDITIONAL PRECIPITATION
MAY REACH THE WEST INTO MIDWEEK, WHILE LEADING MOISTURE REACHES THE
EAST-CENTRAL STATES, BUT GUIDANCE SHOWS A LOT OF SPREAD FOR FLOW
DETAILS BY THEN SO FORECAST CONFIDENCE TRENDS WELL BELOW AVERAGE.
VERY WARM TEMPERATURES WILL PREVAIL AHEAD OF THE PLAINS/EASTERN
U.S. SYSTEM WHILE TRAILING COOLER AIR WILL BRING READINGS BACK DOWN
TO NEAR OR BELOW NORMAL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS ARE STILL WORKING ON RESOLVING IMPORTANT FINER DETAILS OF
SHORTWAVE ENERGY EMERGING FROM THE WEST DURING THE WEEKEND AND
CONTINUING EASTWARD THEREAFTER. SHORTWAVE DIFFERENCES HAVE A
MEANINGFUL IMPACT ON SURFACE WAVE SPECIFICS, WITH DYNAMICAL AND
MACHINE LEARNING (ML) MODELS STILL EXHIBITING A FAIRLY WIDE
ENVELOPE BY THE TIME THE SYSTEM REACHES THE EAST. AMONG THE 12Z/18Z
GUIDANCE, GFS RUNS AND THE UKMET WERE ON THE SHARP/STRONG SIDE
WITH THE SHORTWAVE AND THE CMC ON THE WEAK/BROAD SIDE. ULTIMATELY
PREFERRED A BLEND OF THE 18Z GFS/12Z ECMWF AND THEIR ENSEMBLE MEANS
EARLY IN THE PERIOD, TRENDING TO JUST 30 PERCENT ECMWF AND THE
REST MEANS BY DAY 5/MONDAY.
FARTHER WEST, GUIDANCE HAS ALSO BEEN QUITE DIVERSE FOR LOW
PRESSURE THAT MAY DEVELOP CLOSE TO THE WEST COAST AROUND SUNDAY-
MONDAY. SOME SOLUTIONS LIKE THE 12Z CMC/UKMET MERELY BROUGHT A WEAK
WAVE INTO CALIFORNIA WHILE OTHER SOLUTIONS WRAP IT NORTHWARD INTO
THE MEAN LOW OFF THE PACIFIC NORTHWEST. ML MODELS VARIED A LOT AS
WELL, THUS PROVIDING LITTLE ADDITIONAL INSIGHT. THE AFOREMENTIONED
PREFERENCE MAINTAINED GOOD CONTINUITY WITH OFFSHORE DEVELOPMENT
LIFTING INTO THE NORTHERN MEAN LOW.
BEHIND THIS SYSTEM THERE IS STILL REMARKABLY WIDE DIVERGENCE FOR
ASPECTS OF THE BLOCKY PATTERN OVER THE PACIFIC AND EXTENDING INTO
THE LOWER 48, WITH AREAS OVER THE EASTERN PACIFIC AND WESTERN U.S.
IN PARTICULAR SHOWING ENSEMBLE MEMBERS RANGING BETWEEN A RIDGE AND
A TROUGH--THE GFS/GEFS TENDING TO HAVE MORE TROUGHING OVER THE
EASTERN PACIFIC AND THE ECMWF/CMC FAVORING A DEEPER TROUGH OVER THE
WEST. ADDING TO THE CONFUSION, SOME ML MODELS ACTUALLY DEVELOP A
DECENT RIDGE OVER THE WEST WHILE THE AIFS TILTS IN THE OPERATIONAL
ECMWF DIRECTION. EVEN WITH THE DIFFERENCES ALOFT, BY WEDNESDAY
THERE IS AT LEAST A COMMON SURFACE THEME OF HIGH PRESSURE OVER THE
EAST AND AN AXIS OF LOWER PRESSURES OVER THE PLAINS. AT THAT TIME
FAVOR A CONSERVATIVE FORECAST COMBINING THE GEFS/ECENS MEANS TO
YIELD FLAT TO BROADLY CYCLONIC FLOW ALOFT WHILE WAITING BETTER
AGREEMENT IN THE DYNAMICAL AND ML MODELS.
..WEATHER/HAZARDS HIGHLIGHTS
THE DAY 4/SATURDAY EXCESSIVE RAINFALL OUTLOOK MAINTAINS A MARGINAL
RISK AREA ALONG AND SOMEWHAT NORTH OF THE CENTRAL/EAST-CENTRAL
GULF COAST REGION, WITH ONLY MINOR ADJUSTMENTS FROM CONTINUITY.
GUIDANCE IS CONSISTENT WITH THE SETUP FOR LOCALLY HEAVY RAINFALL
(BUT TRENDING SOMEWHAT LIGHTER THAN ACROSS AREAS FARTHER TO THE
WEST), AS THE SUPPORTING SOUTHERN TIER UPPER SHORTWAVE PUSHES
EASTWARD. THE DISTRIBUTION OF SOLUTIONS HAS REMAINED SIMILAR AS
WELL, WITH THE ECMWF/UKMET AND MACHINE LEARNING MODELS CLUSTERED IN
SHOWING MEANINGFUL RAINFALL POTENTIAL GIVEN SUFFICIENT MOISTURE
AND INSTABILITY VERSUS A MORE DIFFUSE SIGNAL IN OTHER GUIDANCE. BY
DAY 5/SUNDAY EXPECT A BROAD AREA OF CONVECTION TO DEVELOP OVER THE
EAST-CENTRAL U.S. AHEAD OF THE WAVY FRONT PUSHING EASTWARD FROM THE
PLAINS. CURRENT GUIDANCE RECOMMENDS A BROAD MARGINAL RISK AREA
FROM THE OHIO VALLEY SOUTHWEST INTO PARTS OF THE LOWER MISSISSIPPI
VALLEY. IMPROVED GUIDANCE CLUSTERING ESPECIALLY FROM THE OHIO
VALLEY SOUTHWARD WHERE SOILS ARE ON THE DAMP SIDE COULD EVENTUALLY
LEAD TO AN EMBEDDED UPGRADE IN RISK LEVEL.
MORE BROADLY, THE WAVY FRONTAL SYSTEM AFFECTING THE CENTRAL AND
EASTERN U.S. WILL PRODUCE MEANINGFUL PRECIPITATION FROM THE
NORTHERN ROCKIES/HIGH PLAINS INTO THE NORTHEAST AS WELL FARTHER
SOUTH OVER THE EAST, THOUGH THE LATTER SHOULD BE WITH LIGHTER
TOTALS THAN FORECAST OVER THE AREA COVERED BY THE AFOREMENTIONED
DAY 5 MARGINAL RISK. IN ADDITION, THE STORM PREDICTION CENTER IS
MONITORING THE POTENTIAL FOR SEVERE WEATHER FROM THE EAST-CENTRAL
U.S. TO THE MID-ATLANTIC/SOUTHEAST DURING SUNDAY-MONDAY. CHECK
LATEST SPC OUTLOOKS FOR THE LATEST INFO ON SEVERE THREATS. SOME
SNOW WILL BE POSSIBLE ACROSS NORTHERN LATITUDES, WITH ROCKIES AND
PLAINS TOTALS DEPENDENT ON ELEVATION AND/OR TIME OF DAY. THERE MAY
BE A BAND OF WINTRY MIX SEPARATING THE SNOW FROM RAIN FROM THE
UPPER MIDWEST INTO NEW ENGLAND.
AFTER A BRIEF BREAK, AN AREA OF RAIN AND HIGH ELEVATION SNOW
SHOULD REACH INTO THE WEST BY SUNDAY-MONDAY, MOST LIKELY FROM
NORTHERN CALIFORNIA INTO THE PACIFIC NORTHWEST AND PERHAPS
EXTENDING INTO THE NORTHERN ROCKIES BY EARLY NEXT WEEK. THERE IS
STILL SPREAD IN THE GUIDANCE FOR SUPPORTING LOW PRESSURE BUT NEW
SOLUTIONS ARE STARTING TO CLUSTER SOMEWHAT BETTER FOR LOW PRESSURE
WRAPPING UP OFFSHORE THE PACIFIC NORTHWEST. INCREASINGLY DRAMATIC
GUIDANCE DIFFERENCES FOR THE EASTERN PACIFIC/WESTERN U.S. PATTERN
EARLY-MID WEEK LEAD TO LOW CONFIDENCE FOR HOW MUCH ADDITIONAL
PRECIPITATION MAY REACH THE WEST COAST. INITIALLY PREFERRED
ENSEMBLE-BASED GUIDANCE SUGGESTS A WETTER TREND FOCUSED ALONG THE
CENTRAL WEST COAST INTO MIDWEEK, BUT THERE IS A MINORITY OF
SOLUTIONS WITH A DRIER FORECAST.
VERY WARM TEMPERATURES WILL PREVAIL IN THE WARM SECTOR AHEAD OF
THE WAVY FRONTAL SYSTEM EVOLVING OVER THE PLAINS AND THEN PUSHING
EASTWARD. DURING THE WEEKEND EXPECT THE WARMEST ANOMALIES TO EXTEND
FROM THE SOUTHERN HALF OF THE PLAINS THROUGH THE MIDWEST, OHIO
VALLEY, AND MID-ATLANTIC WITH READINGS 10-25F ABOVE NORMAL (WITH
MORNING LOWS TENDING TO BE SOMEWHAT MORE ANOMALOUS THAN DAYTIME
HIGHS). FRONTAL PROGRESSION WILL CONFINE THE WARMTH MORE TOWARD THE
EAST COAST BY NEXT MONDAY. NORTHERN NEW ENGLAND SHOULD REMAIN A
LOT COLDER THOUGH, AS A SHARP FRONT STAYS JUST TO THE SOUTH. NEAR
TO BELOW NORMAL READINGS WILL PROGRESS EASTWARD BEHIND THE
PLAINS/EASTERN U.S. FRONT, WITH PRECIPITATION KEEPING SOME
NORTHERN-CENTRAL HIGH PLAINS LOCATIONS 10-15F BELOW NORMAL FOR
HIGHS DURING THE WEEKEND. PERIODS OF UNSETTLED WEATHER WILL KEEP
THE DIURNAL SPREAD OVER THE WEST COAST STATES MORE NARROW THAN
USUAL.
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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