094
FXUS02 KWBC 020648
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 AM EDT TUE APR 2 2024
VALID 12Z FRI APR 05 2024 - 12Z TUE APR 09 2024
...MAJOR NEW ENGLAND COASTAL STORM WITH MARITIME HAZARDS AND HIGH
WIND/COASTAL FLOODING ALONG WITH HEAVY SNOW TO LINGER INTO FRIDAY...
...WIDESPREAD PRECIPITATION/COOLING PATTERN FOR THE WEST INTO LATE
WEEK TO WORK OVER THE CENTRAL U.S. THIS WEEKEND/EARLY NEXT WEEK...
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE SEEMS REASONABLY AGREEABLE WITH THE OVERALL PATTERN
THROUGH THIS FORECAST PERIOD AS HIGHLIGHTED BY FORMATION AND
SUBSEQUENT SLOW TRANSITION OF A MASSIVE OMEGA STYLE BLOCKING
PATTERN OVER THE LOWER 48 AND VICINITY STARTING BY LATER THIS
WEEK. THE LARGE SCALE FEATURES CONSIST OF AN UPPER TROUGH/CLOSED
LOW OVER THE NORTHEAST FINALLY EJECTING INTO THE ATLANTIC EARLY
NEXT WEEK, ANOTHER UPPER LOW TRACKING FROM THE EASTERN PACIFIC INTO
THE WEST LATER THIS WEEK PIVOTING INTO THE NORTH-CENTRAL PLAINS
EARLY NEXT WEEK WITH RIDGING AHEAD OF IT, AND ADDITIONAL ENERGY
DIGGING INTO THE WEST BY NEXT SUNDAY-TUESDAY.
FORECAST SPREAD AND UNCERTAINTY ARE GENERALLY BELOW NORMAL OVERALL,
BUT DOES INCREASE INTO EARLY NEXT WEEK WITH THE EJECTION OF SYSTEM
ENERGIES FROM THE WEST TO THE PLAINS ALONG WITH COMPLEX ASSOCIATED
CYCLO/FRONTO GENESIS TRANSITIONS. FORECAST SPREAD IS CERTAINLY
WITHIN TYPICAL LEVELS FOR THE DAYS 6-7 PERIOD, BUT HAS IMPLICATIONS
FOR FRONTAL POSITIONS (AND CLOUD COVER FOR THE ECLIPSE IN THE
CENTRAL TO EAST- CENTRAL U.S.).
THE WPC FORECAST WAS MAINLY DERIVED FROM A MULTI-MODEL BLEND OF
THE 18 UTC GFS AND 12 UTC ECMWF/CANADIAN/UKMET FOR MAXIMUM SYSTEM
DETAIL CONSISTENT WITH ABOVE NORMAL PREDICTABILITY FRIDAY INTO
SUNDAY. OPTED TO USE A COMPOSITE OF THE 18 UTC GEFS AND 12 UTC ECMWF
ENSEMBLE MEANS LATER SUNDAY INTO NEXT TUESDAY ALONG WITH BEST
CLUSTERED MODEL GUIDANCE OF THE 12 UTC ECMWF/CANADIAN TO BOTH REDUCE
INDIVIDUAL MODEL DIFFERENCES, BUT MAINTAIN SOME DEPTH OF SYSTEMS.
THE LATEST 00 UTC MODEL AND ENSEMBLE SUITE REMAINS MAINLY IN LINE.
..WEATHER/HAZARDS HIGHLIGHTS
POTENT CLOSED UPPER LOW ROTATION WILL SUPPORT A MAJOR NOR'EASTER
OFFSHORE NEW ENGLAND, LINGERING INTO FRIDAY. THIS SYSTEM WILL
SUPORT SIGNIFICANT WRAP-BACK EARLY SPRING HEAVY SNOWS OVER
THE NORTHEAST AS DEPICTED IN THE WPC WINTER WEATHER OUTLOOK. WHILE
SNOW WILL BE THE PRIMARY PRECIPITATION TYPE INLAND, PROTRACTED
FETCH OFF THE ATLANTIC WITH THIS DEEP LOW MAY KEEP NEAR COASTAL
AREAS WARM ENOUGH NEAR THE GROUND FOR SLEET AND RAIN LEADING INTO
THIS FORECAST PERIOD. THE HEAVIEST OF THE WET SNOW IS EXPECTED TO
FALL ACROSS THE HIGHER ELEVATIONS OF THE INTERIOR NORTHEAST.
ADDITIONALLY, THE DEEP SURFACE LOW SHOULD PRODUCE HIGH WINDS, THAT
FOR A TIME SHOULD BE ONSHORE AND COULD LEAD TO COASTAL FLOODING.
LIGHTER SNOW LIKELY LINGERS INTO FRIDAY, WHILE WESTERLY FLOW COULD
CREATE UPSLOPE FLOW ACROSS THE APPALACHIANS THURSDAY-FRIDAY FOR
SNOW THERE AND ALSO ACROSS THE LOWER GREAT LAKES FOR SOME
ENHANCEMENT THERE. TEMPERATURES ARE FORECAST TO BE COOLER THAN
AVERAGE FOR THE EASTERN SEABOARD BEHIND THIS SYSTEM, GRADUALLY
WARMING UP INTO EARLY NEXT WEEK.
MODELS AND ENSEMBLES MEANWHILE SHOW A HIGHLY AMPLIFIED UPPER
PATTERN ALSO UPSTREAM ACROSS THE U.S. LATER WEEK, WITH A RIDGE OVER
THE CENTRAL U.S. AND POTENT UPPER TROUGHING DIGGING DOWN THE WEST
COAST. THIS STRONGLY AMPLIFYING UPPER TROUGH/CLOSED LOW AND LEADING
AND WAVY COLD FRONT/SECONDARY CANADIAN COLD SURGE DIGGING INTO THE
WEST WILL ACT TO COOL TEMPERATURES. THIS MAY RISK RECORD COLD
MAXIMUM TEMPERATURES THROUGH SOUTHERN CALIFORNIA. THE SPREAD OF
ENHANCED PRECIPITATION AND WINDY/UNSETTLED FLOW WILL INCLUDE
PACIFIC NORTHWEST THROUGH CALIFORNIA RAINS CLOSER TO COASTAL AREAS,
ALONG WITH A PROLONGED PERIOD FAVORABLE FOR TERRAIN/MOUNTAIN SNOWS
INCREASINGLY INLAND ACROSS MUCH OF THE WEST LATER WEEK INTO THE
WEEKEND AS MAIN UPPER TROUGH ENERGY AND HEIGHT FALLS SHIFT ROBUSTLY
INLAND. NO EXCESSIVE RAINFALL RISKS ARE IN PLACE, THOUGH THE RISK
MAY BE NONZERO IN SOUTHERN CALIFORNIA WHICH HAS SEEN A WET PATTERN
LATELY. THE ENERGY WILL EJECT NORTHEASTWARD OVER THE CENTRAL U.S.
SUNDAY INTO MONDAY ALONG WITH AN ASSOCIATED LEAD RETURN CONDUIT OF
MOISTURE AND CLOUDS. THIS WILL INITIATE AND SPREAD ORGANIZED
PRECIPITATION ACROSS THE BROAD REGION WITH CYCLOGENESIS/FRONTOGENESIS.
A WPC MARGINAL RISK EXCESSIVE RAINFALL AREA HAS BEEN INTRODUCED
FOR DAY 5/SATURDAY FOR LOCALLY FOCUSING RAINFALL UP ACROSS THE
NORTHERN HIGH PLAINS GIVEN AN ANOMALOUS MOISTURE PLUME FEED AND
UPSLOPE/TERRAIN LIFT AND SUSCEPTABILITY. SNOW MAY BE POSSIBLE IN
THE NORTHERN ROCKIES AND VICINITY WITH RAIN AND THUNDERSTORMS
FARTHER SOUTH AND EAST. THEN BEHIND THE SYSTEM IN THE
SOUTHERN/CENTRAL HIGH PLAINS, HIGH WINDS AND CRITICAL FIRE DANGER
ARE POSSIBLE. RENEWED LIGHT TO MODERATE PRECIPITATION IS POSSIBLE
ALONG THE WEST COAST EARLY NEXT WEEK AS NEW NEW PACIFIC UPPER
TROUGH SYSTEM ENERGIES AGAIN DIG BACK DOWN THERE.
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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