310
FXUS02 KWBC 250700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT TUE MAR 25 2025
VALID 12Z FRI MAR 28 2025 - 12Z TUE APR 01 2025
..OVERVIEW
LATEST GUIDANCE SHOWS A MODERATELY PROGRESSIVE PATTERN THAT WILL
BRING ACTIVE WEATHER TO PORTIONS OF THE LOWER 48. A SOUTHERN STREAM
SHORTWAVE WILL PROMOTE A THREAT OF HEAVY RAIN ALONG THE WESTERN-
CENTRAL GULF COAST LATE THIS WEEK. BEHIND THIS FEATURE, EASTERN
PACIFIC INTO WESTERN U.S. DYNAMICS WILL SPREAD PRECIPITATION ACROSS
NORTHERN PARTS OF THE WEST AND THEN DEVELOP ONE OR MORE
WAVES/FRONTS FROM THE PLAINS EASTWARD WITH ASSOCIATED AREAS OF
ENHANCED RAINFALL AS WELL AS WINTER WEATHER POTENTIAL OVER FAR
NORTHERN LATITUDES. ANOTHER PACIFIC SYSTEM SHOULD SPREAD
PRECIPITATION INTO THE WEST FROM LATE WEEKEND INTO EARLY NEXT WEEK.
VERY WARM TEMPERATURES WILL PREVAIL AHEAD OF THE OVERALL AREA OF
PLAINS LOW PRESSURE, WHILE TRAILING COOLER AIR WILL BRING READINGS
BACK DOWN TO NEAR OR SLIGHTLY BELOW NORMAL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
PRIMARY FORECAST DIFFERENCES AT THE SURFACE AND ALOFT INVOLVE THE
EVOLUTION OF INCOMING WESTERN ENERGY AND EVOLUTION OF LOW PRESSURE
FROM THE PLAINS NORTHEASTWARD, FOLLOWED BY LOW PRESSURE NEAR THE
WEST COAST BY SUNDAY-MONDAY AND THE EASTERN PACIFIC INTO LOWER 48
PATTERN BY EARLY NEXT WEEK.
OVER RECENT DAYS THE GUIDANCE HAS GRADUALLY BEEN SHIFTING EMPHASIS
OF SEPARATE SHORTWAVES COMING INTO THE WEST, WITH TRENDS TOWARD
WEAKENING THE FIRST SHORTWAVE AND EMPHASIZING THE SECOND. THIS
LEADS TO A MORE ELONGATED LOOK FOR LOW PRESSURE BY SUNDAY, WITH
SEPARATE WAVES NEAR THE LOWER GREAT LAKES AND SOUTH-CENTRAL PLAINS.
THE MOST COMMON THEME IN THE GUIDANCE IS FOR A SHORTWAVE REACHING
THE EAST-CENTRAL U.S. TO SUPPORT A CONSOLIDATING SURFACE SYSTEM
(WITH A FAIR AMOUNT OF SPREAD FOR DEPTH) REACHING THE LOWER-EASTERN
GREAT LAKES OR UPPER OHIO VALLEY BY EARLY MONDAY AND THEN NEAR THE
CANADIAN MARITIMES BY TUESDAY. MACHINE LEARNING (ML) MODELS HAVE
OCCASIONALLY SHOWED MORE VARIED SOLUTIONS, TEMPERING CONFIDENCE.
GUIDANCE HAS CONTINUED TO SHOW A SYSTEM AFFECTING THE WEST COAST
SUNDAY INTO MONDAY BUT WITH A VERY WIDE SPREAD FOR STRENGTH/TRACK
AND NO CLEAR CLUSTERING. PREFERENCE INCORPORATES SOME IDEAS OF
ENSEMBLE MEANS THAT HAVE BEEN KEEPING THE OVERALL AREA OF LOW
PRESSURE OFFSHORE, BUT THE NEW 00Z GFS AND ECMWF BRING IT TO THE
PACIFIC NORTHWEST COAST. ML MODELS OFFER LITTLE HELP, ALSO SHOWING
WIDE VARIANCE AND GENERALLY WEAKER SOLUTIONS THAN DYNAMICAL
GUIDANCE.
TOWARD THE END OF THE PERIOD THE SPECIFICS OVER THE LOWER 48
BECOME INFLUENCED BY DEVELOPING DIFFERENCES WITHIN A LARGE SCALE
BLOCKY PACIFIC PATTERN, ULTIMATELY YIELDING MODEL/ENSEMBLE SPREAD
RANGING BETWEEN A TROUGH AND A RIDGE OVER SOME AREAS BETWEEN THE
EASTERN PACIFIC AND CENTRAL U.S. A GENERAL MODEL/ENSEMBLE BLEND
PROVIDES AN INTERMEDIATE SOLUTION THAT REFLECTS AT LEAST A MODEST
PORTION OF WEST COAST SHORTWAVE ENERGY AS OF MONDAY CONTINUING
INLAND THROUGH TUESDAY, WITH LATEST GFS/GEFS RUNS TILTING THIS WAY
VERSUS THE 12Z GFS THAT HAD MORE RIDGING OVER THE WEST-CENTRAL
STATES.
GUIDANCE PREFERENCES AMONG 12Z/18Z RUNS LED TO STARTING WITH
GREATER 18Z GFS/12Z ECMWF EMPHASIS RELATIVE TO THE 12Z CMC/UKMET
FOR THE FIRST HALF OF THE PERIOD, FOLLOWED BY STEADILY INCREASING
18Z GEFS/12Z ECENS INPUT SUCH THAT DAY 7 TUESDAY CONSISTED OF 60
PERCENT MEANS AND 40 PERCENT GFS/ECMWF.
..WEATHER/HAZARDS HIGHLIGHTS
LATEST GUIDANCE IS CONSISTENT WITH THE GENERAL THEME OF HEAVY RAIN
POTENTIAL ALONG AND NEAR THE WEST-CENTRAL INTO CENTRAL GULF COAST,
AS AN UPPER TROUGH INTERACTS WITH LOW LEVEL GULF MOISTURE AND A
WARM FRONT. THE DAY 4/FRIDAY EXCESSIVE RAINFALL OUTLOOK HAS
INTRODUCED A SLIGHT RISK AREA COVERING PARTS OF SOUTHEASTERN TEXAS
AND SOUTHWESTERN LOUISIANA, WITH MODELS/ENSEMBLES NOW CLUSTERING
BETTER FOR THIS REGION SEEING THE BEST FOCUS. BY DAY 5/SATURDAY,
GUIDANCE BECOMES MUCH MORE DIFFUSE WITH THE RAINFALL SIGNAL. RECENT
ECMWF/ECMWF AIFS/UKMET RUNS SHOW THE MOST AGREEABLE THEME OF SOME
ACTIVITY FROM FRIDAY-FRIDAY NIGHT CONTINUING INTO SATURDAY, WITH
SOME INSTABILITY, BEFORE TRENDING LIGHTER. THUS THE DAY 5 ERO
DEPICTS A MARGINAL RISK AREA ALONG AND NORTH OF THE CENTRAL GULF
COAST REGION.
ELSEWHERE, RAIN AND HIGH ELEVATION SNOW WILL CROSS THE NORTHERN
HALF OF THE WEST LATE THIS WEEK, FOLLOWED BY AN INCREASING AREA OF
PRECIPITATION FROM THE NORTH-CENTRAL PLAINS THROUGH NORTHEAST AND
EXTENDING SOUTHWARD THROUGH THE MISSISSIPPI VALLEY AND POINTS EAST
DURING THE WEEKEND INTO EARLY NEXT WEEK AS ONE OR MORE FRONTAL
WAVES EVOLVE AND THE OVERALL FRONTAL SYSTEM EVENTUALLY PUSHES
EASTWARD. IT MAY BE COLD ENOUGH TO SUPPORT WINTRY PRECIPITATION
TYPES FOR A TIME FROM THE NORTHERN PLAINS THROUGH THE UPPER GREAT
LAKES INTO NORTHERN NEW ENGLAND. TO THE SOUTH, SOME RAIN COULD BE
LOCALLY HEAVY OVER THE NORTH CENTRAL PLAINS AS WELL AS FROM THE
MISSISSIPPI VALLEY EASTWARD. IN ADDITION, THE STORM PREDICTION
CENTER IS MONITORING THE POTENTIAL FOR SEVERE WEATHER FROM PARTS OF
THE EASTERN PLAINS INTO A LARGE PART OF THE EAST- CENTRAL U.S.
DURING THE WEEKEND. CHECK LATEST SPC OUTLOOKS FOR THE LATEST INFO
ON SEVERE THREATS.
AFTER A BRIEF BREAK, ANOTHER AREA OF PRECIPITATION SHOULD SPREAD
ACROSS THE WEST FROM SUNDAY INTO EARLY NEXT WEEK. THERE IS STILL A
DECENT AMOUNT OF UNCERTAINTY FOR THE SPECIFICS OF SUPPORTING
EASTERN PACIFIC LOW PRESSURE, BUT CURRENTLY EXPECT HIGHEST TOTALS
TO BE OVER THE CENTRAL WEST COAST/NORTHERN CALIFORNIA.
VERY WARM TEMPERATURES WILL PREVAIL IN THE WARM SECTOR AHEAD OF
THE WAVY FRONTAL SYSTEM EVOLVING OVER THE PLAINS AND THEN PUSHING
EASTWARD. SOME AREAS FROM THE CENTRAL HIGH PLAINS INTO THE MIDWEST
MAY SEE HIGHS 20-30F ABOVE NORMAL ON FRIDAY. THE WARMTH WILL SHIFT
SOUTH AND EAST OVER THE WEEKEND WITH PLUS 20F OR GREATER ANOMALIES
FOR MORNING LOWS REACHING FROM THE MIDWEST INTO THE OHIO VALLEY
WHILE PLUS 10-20F ANOMALIES FOR HIGHS EXTEND FROM THE SOUTHERN HALF
OF THE PLAINS INTO THE MID-ATLANTIC AND SOUTHEAST. CONTINUED
FRONTAL PROGRESSION WILL CONFINE ABOVE NORMAL READINGS TO THE EAST
COAST BY MONDAY. HOWEVER THE NORTHEAST WILL BE ON THE COOL SIDE, TO
THE NORTH OF A FRONT SETTLING OVER OR NEAR THE NORTHERN MID-
ATLANTIC. BEHIND THE MAIN FRONTAL SYSTEM, MODESTLY BELOW NORMAL
HIGHS WILL PROGRESS FROM THE WEST LATE THIS WEEK INTO THE GREAT
LAKES/OHIO VALLEY BY NEXT TUESDAY.
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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