872
FXUS02 KWBC 040700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST WED DEC 4 2024
VALID 12Z SAT DEC 07 2024 - 12Z WED DEC 11 2024
...RETURN FLOW TO FUEL EMERGING RAINFALL FROM THE WEST-CENTRAL
GULF COAST TO THE APPALACHIANS THIS WEEKEND TO EARLY NEXT WEEK...
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM A
COMPOSITE OF REASONABLY CLUSTERED GUIDANCE FROM THE LATEST
GUIDANCE GFS/ECMWF/UKMET/CANADIAN MODELS THAT HAVE GOOD ENSEMBLE
SUPPORT AND CONTINUITY. PIVOTED TO THE MOST COMPATIBLE SOLUTIONS OF
THE ECMWF/ECMWF ENSEMBLE MEAN AND CANADIAN/CANADIAN ENSEMBLE MEAN
AT LONGER TIME FRAME TO MAINTAIN BEST CONTINUITY AMID OTHERWISE GROWING
FORECAST SPREAD.
..WEATHER/HAZARDS HIGHLIGHTS
ARCTIC AIR THAT HAS PERSISTED OVER THE EAST-CENTRAL U.S. WILL
MODERATE BY THIS WEEKEND AS AMPLIFIED UPPER TROUGHING FINALLY
LIFTS OUT AFTER A PROLONGED TIME PERIOD. NEVERTHELESS, LAKE EFFECT
SNOW IS LIKELY TO BE ONGOING INTO EARLY SATURDAY IN THE WAKE OF A
STRONG CLIPPER-TYPE SYSTEM. BY EARLY NEXT WEEK, TEMPERATURES SHOULD
BE NEAR TO A LITTLE ABOVE AVERAGE ACROSS MUCH OF THE EASTERN U.S..
MEANWHILE, EMERGING MOIST RETURN FLOW FROM THE GULF OF MEXICO AS
AMBIENT HIGH PRESSURE OVER THE SOUTH RETREATS TO THE EAST WILL
SUPPORT INCREASING COVERAGE OF SHOWERS AND THUNDERSTORMS, SOME OF
WHICH COULD BE HEAVY, FROM THE WEST-CENTRAL GULF COAST STATES UP
THROUGH THE SOUTHERN APPALACHIANS THIS WEEKEND THROUGH EARLY NEXT
WEEK. IN TERMS OF THE WPC EXCESSIVE RAINFALL OUTLOOK, MAINTAINED A
DAY 4/SATURDAY MARGINAL RISK AREA CENTERED OVER SOUTHEAST TEXAS TO
COVER EVENT GENESIS. INTRODUCED MARGINAL AND SLIGHT RISK AREAS FOR
DAY 5/SUNDAY INTO MONDAY CENTERED OVER THE LOWER MISSISSIPPI
VALLEY AS CONVECTION ERUPTS IN A FAVORED RIGHT ENTRANCE REGION OF
THE UPPER JET PATTERN TO FAVOR TRAINING/REPEAT CELLS AS STRONG
MOISTURE FLUX FROM THE CENTRAL GULF CONTINUES AHEAD OF AN
APPROACHING MAIN COLD FRONT.
UPSTREAM, MODERATLY HEAVY TERRAIN ENHANCED PRECIPITATION IS
EXPECTED TO DEVELOP THIS WEEKEND OVER THE PACIFIC NORTHWEST WITH
ENERGETIC UPPER TROUGH PASSAGE AND LONG LEAD MOISTURE FEED.
TERRAIN ENHANCED SNOWS WILL THEN SPREAD INCREASINGLY INLAND ACROSS
THE NORTHWEST TO THE NORTH-CENTRAL ROCKIES WITH COLD FRONTAL
PASSAGE OVER THE WEST INTO EARLY NEXT WEEK. EXPECT A NICE WARMING
TREND IN ADVANCE OF THIS FRONT OUT FROM THE WEST THROUGH OVER THE
CENTRAL U.S. THIS WEEKEND/EARLY NEXT WEEK PRIOR TO COOLING
PASSAGE.
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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