667
FXUS02 KWBC 011901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 PM EDT MON APR 1 2024
VALID 12Z THU APR 04 2024 - 12Z MON APR 08 2024
...MAJOR NEW ENGLAND COASTAL STORM WITH MARITIME HAZARDS AND HIGH
WIND/COASTAL FLOODING ALONG WITH NORTHEAST HEAVY SNOW INTO
THURSDAY...
...WIDESPREAD PRECIPITATION/COOLING PATTERN FOR THE WEST INTO LATE
WEEK TO WORK INTO THE CENTRAL U.S. THROUGH NEXT WEEKEND...
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE SEEMED REASONABLY AGREEABLE WITH THE OVERALL
PATTERN THROUGH THE PERIOD. 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 SUNDAY-MONDAY.
FOR THE LATE WEEK NORTHEAST SYSTEM, THE 00Z AND NOW 12Z CMC RUNS
SPLIT ENERGY BETWEEN TWO CLOSED LOWS AS SOME ENERGY PIVOTS
SOUTHWEST AROUND THE MAIN LOW. OTHER GUIDANCE SHOWS THIS SHORTWAVE
BUT KEEPS IT WITHIN THE MAIN UPPER LOW. UPSTREAM, THE UPPER
LOW/TROUGH SHOWS GOOD AGREEMENT MOVING THROUGH THE WEST, BUT A
LITTLE MORE SPREAD INTO THE WEEKEND/EARLY NEXT WEEK AS IT EJECTS
INTO THE HIGH PLAINS ALONG WITH A SURFACE LOW. GENERALLY THE ECMWF
RUNS ARE ON THE WESTERN SIDE, WITH GFS RUNS ON THE SOUTHEASTERN
SIDE. 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 USED A MULTI-MODEL BLEND OF DETERMINISTIC
GUIDANCE FAVORING THE GFS AND ECMWF THROUGH THE EARLY PART OF THE
PERIOD. INCLUDED AND GRADUALLY INCREASED THE PROPORTION OF THE GEFS
AND EC ENSEMBLE MEANS DAYS 5-7, REACHING 40 PERCENT MEANS TO
REDUCE INDIVIDUAL MODEL DIFFERENCES BUT MAINTAIN SOME DEPTH OF
SYSTEMS. REGARDING QPF, HAD TO INCREASE WRAPAROUND NORTHEASTERN
U.S. PRECIPITATION LATE THIS WEEK BECAUSE MODELS WERE GENERALLY
HIGHER THAN THE DEFAULT NBM.
..WEATHER/HAZARDS HIGHLIGHTS
POTENT CLOSED UPPER LOW ROTATION WILL SUPPORT A MAJOR NOR'EASTER
ACROSS NEW ENGLAND LASTING INTO THURSDAY. THIS SYSTEM WILL LEAD TO
SIGNIFICANT WRAP-BACK EARLY SPRING HEAVY SNOW AS HIGHLIGHTED 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. 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
MODERATE PRECIPITATION ACROSS THE BROAD REGION WITH
CYCLOGENESIS/FRONTOGENESIS. SNOW MAY BE POSSIBLE IN THE NORTHERN
HIGH PLAINS 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.
TATE/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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