842
FXUS02 KWBC 260656
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 AM EST SUN NOV 26 2023
VALID 12Z WED NOV 29 2023 - 12Z SUN DEC 03 2023
..OVERVIEW
AN UPPER LOW OVER/NEAR HUDSON BAY WILL ALLOW FOR GENERAL TROUGHING
WITH SOME EMBEDDED SHORTWAVES THROUGH THURSDAY ACROSS THE GREAT
LAKES AND NORTHEAST. THIS PATTERN WOULD SUPPORT SOME ONGOING LAKE
EFFECT SNOWS, LOCALLY ENHANCED IN SPOTS. AN UPPER LOW OFF THE
CALIFORNIA COAST ON WEDNESDAY SHOULD SHIFT INLAND ACROSS THE
SOUTHWEST WITH ITS SHORTWAVE ENERGY EVENTUALLY SHIFTING EAST INTO
THE CENTRAL U.S. BRINGING POTENTIAL FOR WIDESPREAD MODERATE TO
HEAVY RAINFALL ACROSS PARTS OF THE SOUTH-CENTRAL U.S. INTO THE
SOUTHEAST. THE NEXT SYSTEM MOVES INTO THE WEST THURSDAY-FRIDAY
PROMOTING AMPLIFIED TROUGHING SHIFTING ACROSS THE WEST NEXT
WEEKEND AND A BUILDING RIDGE DOWNSTREAM ACROSS THE SOUTHEAST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
OVERALL, THE GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE
SYNOPTIC SCALE PATTERN THROUGH MUCH OF THE PERIOD. THERE ARE SOME
LINGERING DIFFERENCES IN THE DETAILS PERTAINING TO INDIVIDUAL
SHORTWAVES THROUGH THE GREAT LAKES/NORTHEAST AND THE INITIAL
SHORTWAVE SHIFTING ACROSS THE MIDWEST LATE IN THE WEEK, BUT FOR
THE MOST PART, A BLEND OF THE DETERMINISTIC GUIDANCE GAVE A GOOD
STARTING POINT FOR DAYS 3-4/WEDNESDAY-THURSDAY. BY FRIDAY, THERE
ARE SOME MORE NOTABLE DIFFERENCES WITH TIMING AND STRENGTH OF THE
NEXT SHORTWAVE INTO THE PACIFIC NORTHWEST AND A LOT OF LINGERING
UNCERTAINTY IN THE PATTERN GOING INTO NEXT WEEKEND. THE GFS HAS
BEEN FAIRLY CONSISTENT IN SHOWING A LESS AMPLIFIED SHORTWAVE THAT
PROGRESSES MORE EASTERLY ACROSS THE NORTHWEST/NORTHERN ROCKIES.
MEANWHILE, THE CMC AND ECMWF SHOW MUCH MORE DIGGING OF THIS TROUGH
INTO CALIFORNIA AND THE SOUTHWEST AND MORE AMPLIFICATION OF THE
PATTERN NEXT WEEKEND AS THE TROUGH PROGRESSES INTO THE CENTRAL
U.S., WHICH IS MORE WIDELY SUPPORTED BY THE ENSEMBLE GUIDANCE AS
WELL. BEYOND DAY 4, THE WPC BLEND INCORPORATED INCREASING AMOUNTS
OF THE ENSEMBLE GUIDANCE THROUGH NEXT WEEKEND, WITH STILL SOME
MODEST ECMWF AND CMC FOR A LITTLE BIT OF ADDED SYSTEM DEFINITION.
..WEATHER/HAZARDS HIGHLIGHTS
FAVORABLE WESTERLY COLD FLOW OVER THE STILL RELATIVELY WARM GREAT
LAKES WILL CONTINUE TO PROMOTE SOME LOCALLY ENHANCED LAKE EFFECT
SNOWS THROUGH THURSDAY ESPECIALLY DOWNWIND OF LAKES ERIE AND
ONTARIO, BUT NOT NEARLY AS HEAVY AS IS EXPECTED IN THE SHORT RANGE
PERIOD. ELSEWHERE, SHORTWAVE ENERGY INTO THE MID-SOUTH AND A WARM
FRONT LIFTING THROUGH THE GULF OF MEXICO WILL ALLOW FOR INCREASING
MOISTURE AND INSTABILITY ACROSS THE GULF COAST/SOUTHEAST REGION,
WITH INCREASING CONFIDENCE IN SOME WIDESPREAD MODERATE TO HEAVY
RAINFALL BEGINNING THURSDAY AND LASTING INTO NEXT WEEKEND. AMOUNTS
AND TIMING REMAIN QUITE UNCERTAIN STILL, BUT THERE WAS ENOUGH
SUPPORT FOR A MARGINAL RISK ON THE DAY 5 (THURSDAY) EXCESSIVE
RAINFALL OUTLOOK FROM EASTERN TEXAS INTO THE LOWER MISSISSIPPI
VALLEY. OUT WEST, PRECIPITATION WILL INCREASE THURSDAY INTO NEXT
WEEKEND AS A SHORTWAVE OR TWO MOVE THROUGH THE REGION, WITH SOME
PRECIPITATION REACHING SOUTHWARD INTO CALIFORNIA AND THE
SOUTHWEST. THE HEAVIEST PRECIPITATION (COASTAL RAIN AND MOUNTAIN
SNOW) WILL BE ACROSS THE WASHINGTON/OREGON COAST AND CASCADES NEXT
WEEKEND.
THE EAST COAST SHOULD START OUT WITH BELOW NORMAL TEMPERATURES ON
WEDNESDAY, BUT SHOULD MODERATE BACK TOWARDS NORMAL BY THURSDAY.
MEAN TROUGHING ACROSS THE INTERIOR WEST SHOULD ALLOW FOR COOLER
THAN NORMAL TEMPERATURES LASTING INTO NEXT WEEKEND. ELSEWHERE,
THERE IS SIGNAL FOR A PERIOD OF ABOVE NORMAL TEMPERATURES ACROSS
THE NORTHERN PLAINS ON WEDNESDAY, WITH DAYTIME HIGHS 10-15 DEGREES
ABOVE AVERAGE, BUT AS RIDGING BUILDS INTO THE MIDWEST AND EASTERN
U.S. LATER THIS WEEK, ABOVE NORMAL TEMPERATURES SHOULD EXPAND WITH
TIME WITH MUCH OF THE NORTHERN PLAINS TO MIDWEST AND SOUTHEAST
ABOVE NORMAL BY NEXT WEEKEND.
SANTORELLI
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES ARE AT:
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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