752
FXUS02 KWBC 311948
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
348 PM EDT SUN MAR 31 2024
VALID 12Z WED APR 03 2024 - 12Z SUN APR 07 2024
...MAJOR NEW ENGLAND COASTAL STORM INTO WEDNESDAY/THURSDAY WITH
MARITIME HAZARDS AND HIGH WIND/COASTAL FLOODING/RAINFALL THREATS
ALONG WITH AN INLAND HEAVY SNOW THREAT...
...WIDESPREAD PRECIPITATION/COOLING PATTERN FOR THE WEST MIDWEEK-
LATE WEEK TO EXPAND INTO THE PLAINS NEXT WEEKEND...
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE MEDIUM-RANGE PERIOD WILL BEGIN ON WEDNESDAY LIKELY WITH
CYCLOGENESIS WELL UNDER WAY OVER THE EASTERN U.S. MODELS HAVE
GENERALLY SHOWN A SLIGHT SLOW DOWN OF THE FORWARD SPEED OF A
TRIPLE-POINT LOW THAT IS FORECAST TO DEVELOP RAPIDLY OVER THE MID-
ATLANTIC STATES WEDNESDAY MORNING. SIMILAR SLOW DOWN IS NOTED
REGARDING THE LOW CENTER LINGERING NEAR THE LOWER GREAT LAKES AS IT
WEAKENS AND DISSIPATES WITH TIME. THESE ARE IN RESPONSE TO A TREND
TOWARD MORE AMPLIFIED INTERACTION BETWEEN A COLD UPPER TROUGH
DIGGING DOWN FROM CENTRAL CANADA WITH ANOTHER UPPER TROUGH LIFTING
NORTHEAST TOWARD THE OHIO VALLEY. THURSDAY WILL LIKELY BE THE DAY
WHEN NEW ENGLAND WILL BE IMPACTED BY A SIGNIFICANT NOR'EASTER AT
PEAK INTENSITY. GIVEN THE TREND FOR A MORE AMPLIFIED UPPER LEVEL
PATTERN, MODELS CONTINUE TO INDICATE SOME TENDENCY TO SLOW THE CORE
OF THE LOW PRESSURE SYSTEM NEAR THE NEW ENGLAND COAST, WITH THE
GFS AND ECMWF SHOWING THE POSSIBILITY OF LOOPING/MEANDERING MOTION
OF THE LOW CENTER NEAR THE COAST AS IT INTERACTS WITH THE UPPER
LOW. NEVERTHELESS, THE CANADIAN MODEL (CMC) AS WELL AS THE ENSEMBLE
MEAN SOLUTIONS FROM GFS, EC, AND CMC MEAN ARE MUCH LESS PROMINENT
WITH RESPECT TO THE LOOPING MOTIONS. BY NEXT WEEKEND, MODELS
INDICATE A TENDENCY TO KEEP THE DEEP LOW FROM EXITING TOO QUICKLY
INTO THE ATLANTIC.
IN THE MEANTIME, MODELS CONTINUE TO TREND TOWARD A MORE AMPLIFIED
UPPER TROUGH TO DIG FARTHER SOUTH INTO THE WEST COAST DURING THE
LATTER HALF OF THE WEEK. THE CMC WAS THE LEAST-AMPLIFIED GUIDANCE
REGARDING THIS UPPER TROUGH, WHICH DID NOT AGREE WELL WITH THE GFS,
ECMWF AND THEIR ENSEMBLE MEANS. THEREFORE, ONLY 10% OF THE 00Z
CMC/CMC MEAN WAS INCLUDED IN TODAY'S WPC MEDIUM-RANGE FORECAST
BLEND FROM DAY 4 FORWARD, WITH THE REST BASED ON THE CONSENSUS OF
00Z EC/EC MEAN AND THE 06Z GFS/GEFS. THIS BLEND TENDS TO PROVIDE
DETAIL WHILE REASONABLY MITIGATING THESE DIFFERENCES CONSISTENT
WITH INDIVIDUAL PREDICTABILITY. WPC PRODUCT CONTINUITY IS WELL
MAINTAINED WITH THIS PLAN.
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
A MAJOR NOR'EASTER WILL PRESENT HEIGHTENED THREAT FOR COASTAL
FLOODING/HEAVY RAINS AND INLAND HEAVY SNOWS WEDNESDAY INTO
THURSDAY FOR NEW ENGLAND 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 HEAVY RAIN.
GIVEN WET AMBIENT SOILS, AN AREA OF MARGINAL THREAT OF EXCESSIVE
RAINFALL HAS BEEN KEPT FOR DAY4/WEDNESDAY ACROSS
EASTERN/SOUTHEASTERN NEW ENGLAND. FLOODING CONCERNS IN THIS AREA
ARE EXPECTED TO BE A COMBINATION OF RAIN CHANGING TO SNOW WITH
UNCERTAINTY ON THE TIMINGS OF THEIR DURATIONS, ALONG WITH
STRENGTHENING WINDS AND SEA-WATER FLOODING NEAR THE COAST.
WEDNESDAY INTO THURSDAY MORNING WILL LIKELY BE THE PERIOD WHEN THE
HEAVIEST OF THE WET SNOW IS EXPECTED TO FALL ACROSS THE HIGHER
ELEVATIONS OF INTERIOR NEW ENGLAND. ADDITIONAL HEAVY SNOW IS
POSSIBLE INTO THURSDAY FARTHER NORTHEAST ACROSS INTERIOR MAINE. THE
SNOW COULD LINGER INTO FRIDAY AND EVEN SATURDAY ACROSS NEW ENGLAND
BUT WITH A PROGRESSIVELY LIGHTER AND MORE SCATTERED NATURE.
DEPENDING ON HOW CLOSE THE CENTER LINGERS NEAR THE COAST, THE SNOW
COULD MIX WITH AND/OR CHANGE OVER TO RAIN CLOSER TOWARD THE COAST
IF THE LOW CENTER EDGES CLOSER TO LAND OR MAKES LANDFALL.
TOWARD THE END OF NEXT WEEK, MODELS SHOW GOOD AGREEMENT ON A
HIGHLY-AMPLIFIED UPPER PATTERN ACROSS THE U.S. WITH A RIDGE
BUILDING OVER THE CENTRAL U.S. AS THE DEEP LOW SLOWLY PULLS OUT OF
THE NORTHEAST AND THE NEXT UPPER TROUGH DIGS JUST OFF THE WEST
COAST. THIS STRONGLY AMPLIFYING UPPER TROUGH/CLOSED LOW AND LEADING
AND WAVY COLD FRONT/SECONDARY CANADIAN COLD SURGE DIGGING INTO THE
WEST SHOULD ACT TO COOL TEMPERATURES AND SPREAD ENHANCED
PRECIPITATION AND WINDY/UNSETTLED FLOW TO INCLUDE COASTAL RAINS
DOWN THROUGH CALIFORNIA ALONG WITH A PROLONGED PERIOD WITH INTERIOR
AND TERRAIN/MOUNTAIN SNOWS INCREASINGLY INLAND ACROSS MUCH OF THE
WEST MIDWEEK INTO NEXT WEEKEND. DEPICTED AREAS OF PRECIPITATION ARE
CURRENTLY ON THE MODEST TO MODERATE SIDE GIVEN TRACK/MOISTURE, BUT
AMPLE UPPER SUPPORT AND FAVORED TERRAIN LIFT MAY LEAD TO LOCALLY
HEAVIER FOCUS AND ACTIVITY TO MONITOR. THE WPC WINTER WEATHER
OUTLOOK SHOWS THE GREATEST SNOW PROBABILITIES OVER NORTHWEST TO
NORTHERN INTERMOUNTAIN/ROCKIES TERRAIN/MOUNTAINS. ACTIVITY WILL
SPREAD INTO THE PLAINS LATER NEXT WEEKEND WITH CYCLOGENESIS AND
FRONTOGENESIS OVER THE CENTRAL HIGH PLAINS BEING BLOCKED BY A
HIGHLY AMPLIFIED OMEGA BLOCKING PATTERN THAT IS FORECAST TO SET UP
ACROSS THE U.S. FROM COAST TO COAST.
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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