663
FXUS02 KWBC 181900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT TUE MAR 18 2025
VALID 12Z FRI MAR 21 2025 - 12Z TUE MAR 25 2025
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
PROGRESSIVE UPPER FLOW WITH MULTIPLE EMBEDDED SYSTEMS THIS WEEK IN
TWO MAIN STREAMS WILL AMPLIFY INTO NEXT WEEK WITH THE DEVELOPMENT
OF A WARMING/BUILDING WEST COAST RIDGE AND A COOLING/DEEPENING AND
UNSETTLING EAST-CENTRAL U.S. TROUGH.
MODELS AND ENSEMBLES SHOW GOOD AGREEMENT ON THE GENERAL EVOLUTION
OF THE ABOVE-MENTIONED WEATHER PATTERN THROUGH THE MEDIUM RANGE
PERIOD, BUT WITH NOTABLE DISAGREEMENT ON A COUPLE OF FEATURES. THE
FIRST FEATURE OF CONCERN IS A COASTAL CYCLONE THAT IS FORECAST TO
FORM BY ALL OF THE GUIDANCE NEAR COASTAL NEW ENGLAND ON FRIDAY.
RECENT GFS AND CMC RUNS HAVE SHOWN A DEEPER AND SLOWER MOTION FOR
THIS CYCLONE COMPARED WITH THE ECMWF RUNS. THE EC-AIFS HAS TRENDED
TOWARD THE FASTER ECMWF SOLUTIONS LATELY. WITH THESE IN MIND,
PREFERENCE HAS BEEN GIVEN TO THE FASTER SOLUTIONS DUE TO ECMWF'S
BETTER CONSISTENCY FORECASTING THIS SYSTEM WITH THE SUPPORT OF
RECENT EC-AIFS.
THE NEXT SYSTEM OF CONCERN WILL BE FROM THIS WEEKEND INTO EARLY
NEXT WEEK ACROSS THE EASTERN HALF OF THE COUNTRY. BOTH THE GFS AND
CMC AS WELL AS THEIR ENSEMBLE MEANS HAVE RECENTLY TRENDED FARTHER
NORTH REGARDING THE CYCLONE TRACK IN THE GENERAL DIRECTION OF THE
GREAT LAKES IN BETTER AGREEMENT WITH THE ECMWF SOLUTIONS.
THEREFORE, THE WPC MEDIUM-RANGE FORECAST PACKAGE THIS MORNING WAS
BASED ON A HIGHER PERCENTAGES (55%) FROM THE 00Z ECMWF SOLUTIONS,
TOGETHER WITH 30% FROM THE 06Z GFS/GEFS, AND 15% FROM THE CMC/CMC
MEAN. THIS BLEND MAINTAINED REASONABLY GOOD AGREEMENT WITH THE
NATIONAL BLEND OF MODELS AND WPC PRODUCT CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
CYCLOGENESIS NEAR NEW ENGLAND COAST ON FRIDAY WOULD INCREASE THE
HIGH WIND THREAT FOR COASTAL SECTIONS. A DEEPER STORM WOULD
INCREASE THE HEAVY SNOW THREAT FOR NORTHERN/INTERIOR NORTHEAST AS
WELL. HOWEVER, ONLY A SMALL HIGH WIND AREA IS DEPICTED ACROSS THE
HIGHER ELEVATIONS OF INTERIOR NEW ENGLAND IN FAVOR OF THE FASTER
AND WEAKER ECMWF SOLUTIONS. THE CYCLONE IS FORECAST TO DEPART NEW
ENGLAND AS A MARITIMES HAZARD HEADING INTO THE WEEKEND.
WELL UPSTREAM, A SERIES OF PACIFIC SYSTEMS AND MOISTURE FEEDS WILL
FUEL PERIODS OF UNSETTLED WET WEATHER TO THE WEST/NORTHWEST, WITH
AN ENHANCED MOISTURE/RAIN FOCUS FOR THE PACIFIC NORTHWEST AND
TERRAIN ENHANCED HEAVY SNOWS INLAND TO THE ROCKIES. THE WPC DAY
4/FRIDAY EXCESSIVE RAINFALL OUTLOOK MAINTAINS A MARGINAL RISK AREA
FOR COASTAL NORTHWEST OREGON AND WASHINGTON, WITH RENEWED FOCUS TO
MONITOR LATER WEEKEND INTO EARLY NEXT WEEK. COMPOUNDING EFFECTS OF
MULTIPLE DAYS OF PRECIPITATION MAY LEAD TO LOCAL RUNOFF ISSUES.
WELL DOWNSTREAM, LESS DEFINED RAINY PERIODS OVER THE CENTRAL TO
EASTERN U.S. LATE THIS WEEK ARE EXPECTED TO BECOME MUCH BETTER
ORGANIZED BY SUNDAY OVER THE MID-MISSISSIPPI VALLEY AS A MODESTLY
DEEP CYCLONE IS FORECAST TO TRACK GENERALLY ACROSS THE GREAT LAKES
TO THE NORTHEAST EARLY NEXT WEEK. INFLUX OF MOISTURE FROM THE GULF
APPEARS TO SUPPORT A HEAVY RAIN THREAT FOR THE DEEP SOUTH FROM
LATE SUNDAY INTO EARLY MONDAY. IN ADDITION, COLD AIR WRAPPING
AROUND THE MAIN LOW CENTER APPEARS TO SUPPORT A HEAVY SNOW THREAT
TOWARD THE UPPER GREAT LAKES SUNDAY INTO MONDAY, THEN POSSIBLY
SPREADING INTO INTERIOR NEW ENGLAND MONDAY AND TUESDAY WHEN A
TRIPLE-POINT LOW DEVELOPMENT IS POSSIBLE NEAR THE COAST OF NEW
ENGLAND.
KONG/SCHICHTEL
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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