524
FXUS02 KWBC 060701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST TUE DEC 06 2022
VALID 12Z FRI DEC 09 2022 - 12Z TUE DEC 13 2022
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
BLEND OF BEST CLUSTERED GUIDANCE FROM THE 18 UTC GFS/GEFS AND 12
UTC ECMWF/ECMWF ENSEMBLE MEAN ALONG WITH WPC CONTINUITY AND THE 01
UTC NATIONAL BLEND OF MODELS, APPLYING THE BULK OF BLEND WEIGHTS
TO THE MODELS FRIDAY BEFORE TRANSITIONING TO MOSTLY ENSEMBLE MEANS
BY EARLY NEXT WEEK.
..WEATHER/HAZARD HIGHLIGHTS
ORGANIZED UPPER SHORTWAVE TROUGH PASSAGE AND LEAD FRONTAL MOISTURE
POOLING MAY SPREAD A SWATH OF MODERATELY HEAVY RAINS THROUGH THE
CENTRAL APPALACHIANS/MID-ATLANTIC FRIDAY, WITH COASTAL ACTIVITY
LINGERING THIS WEEKEND WITH UNCERTAIN/MODERATE COASTAL LOW
GENESIS. SOME RECENT MODELS SHOW POTENTIAL FOR A MORE AMPLE QPF
SIGNATURE THAN THE NBM GIVEN SUPPORT, ALBEIT WITH LESS THAN
STELLAR RUN TO RUN AXIS PLACEMENT. THERE IS ALSO SOME POTENTIAL
FOR A SWATH OF SOME SNOW/ICE DURING THIS PERIOD ON THE COOLED
NORTHERN PERIPHERY OF THIS PRECIPITATION SHIELD.
MEANWHILE UPSTREAM, AMPLE SYSTEM ENERGIES DIGGING SOUTHEASTWARD
FROM THE GULF OF ALASKA ARE SLATED TO CONTINUE TO WORK ACROSS THE
WEST COAST INTO THE WEST FRIDAY AND RENEW MODERATELY HEAVY
PRECIPITATION CHANCES INTO THE NORTHWEST AND CALIFORNIA TO INCLUDE
A THREAT FOR ENHANCED TERRAIN/MOUNTAIN SNOWS THAT WILL SPREAD OVER
AN UNSETTLED AND COOLED INTERMOUNTAIN WEST/ROCKIES. SYSTEM
EJECTION THEN OFFER AN EMERGING SETUP FOR MODERATE TO HEAVY
RAINFALL WITH SOME POTENTIAL FOR RUNOFF ISSUES CENTERED OVER THE
SOUTHERN PLAINS AND MID-LOWER MS/TN VALLEYS NEXT WEEKEND AS
WESTERN U.S. UPPER TROUGH ENERGIES EJECT DOWNSTREAM AS RETURN GULF
MOISTURE INTERCEPTS A DEVELOPING/WAVY FRONTAL SYSTEM.
THE PATTERN ALSO SEEMS FAVORABLE FOR RENEWED MODERATELY HEAVY
PRECIPITATION INCLUDING TERRAIN/MOUNTAIN ENHANCED SNOWS INLAND
INTO THE NORTHWEST/WEST AGAIN BY NEXT WEEKEND AS ADDITIONAL
NORTHEAST PACIFIC SYSTEM ENERGIES WORK INLAND INTO THE UNSETTLED
REGION. THE SPREAD IN THE GUIDANCE HAS PERSISTENTLY BEEN ALL OVER
THE PLACE FROM RUN TO RUN WITH SYSTEM FOCUS, ESPECIALLY AFTER
ABOUT 4/5 DAYS INTO THE FORECAST PERIOD, BUT THE MODELS HAVE
OVERALL TRENDED SLIGHTLY TOWARD AMPLIFICATION/LESS PROGRESSION.
ACCORDINGLY, DOWNSTREAM PROPAGATION OF THE MAIN SYSTEM OUT FROM
THE WEST INTO THE EAST-CENTRAL U.S. IS DELAYED A BIT EARLY NEXT
WEEK COMPARED TO CONTINUITY, BUT HAS POTENTIAL FOR SUFFICIENT
AMPLITUDE TO SUPPORT MODERATE CYCLO/FRONTOGENESIS AND A RENEWED
RETURN FLOW OF GULF MOISTURE TO SUPPORT AN EXPANDING AREA OF
PRECIPITATION. NBM QPF SEEMS OVERDONE WITH COVERAGE/AMOUNTS GIVEN
UNCERTAINTIES SO TARGETED THIS FOR CHANGE, BUT THERE IS
NONETHELESS AN EMERGING THREAT FOR HEAVIER CONVECTIVE RAINS
PERHAPS CENTERED OVER THE MID-LOWER MS VALLEY/LOWER OH VALLEY.
THERE IS MEANWHILE ALSO A THREAT FOR SOME SNOW/ICE ON THE
NORTHERN/NORTHWESTERN PERIPHERY OF THE PRECIPITATION SHIELD OVER
THE NORTH-CENTRAL U.S..
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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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