321
FXUS02 KWBC 050650
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 AM EST MON DEC 05 2022
VALID 12Z THU DEC 08 2022 - 12Z MON DEC 12 2022
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
BLEND OF THE 18 UTC GFS, 12 UTC ECMWF/CANADIAN AND LATEST
GEFS/ECMWF ENSEMBLE MEANS ALONG WITH THE 01 UTC NATIONAL BLEND OF
MODELS. HOWEVER, APPLIED BLEND WEIGHTS STRONGLY TOWARD REASONABLY
CLUSTERED MODEL GUIDANCE FOR THURSDAY AND THEN SLOWLY RAMPED UP
INPUT FROM THE ENSEMBLE MEANS INTO THE WEEKEND AND EARLY NEXT WEEK
AMID STEADILY GROWING FORECAST SPREAD AND UNCERTAINTY. USAGE OF
THE ENSEMBLE MEANS IS MORE PROBLEMATIC THAN USUAL GIVEN THE
GEFS/ECMWF ENVELOPE OF FORECASTS BECOME MORE OUT OF SYNC THAN
NORMAL LATER PERIOD FROM THE EAST-CENTRAL PACIFIC INTO THE LOWER
48, WITH NO CLEAR SIGNAL TO DIFFERENTIATE IN A DATA SENSITIVE
PATTERN. ACCORDINGLY, PATTERN EVOLUTION PREDICTABILITY SEEMS BELOW
NORMAL FROM THE WEEKEND INTO EARLY NEXT WEEK, MAINLY DUE TO SMALL
TO LARGER SCALE DIFFERENCES WITH ASPECTS OF THE DIGGING OF TROUGH
ENERGY INTO THE WEST AND SUBSEQUENT DOWNSTREAM PROGRESSION.
OVERALL, THE AFOREMENTIONED FORECAST GUIDANCE STRATEGY ACTS TO
MAINTAIN MAX WPC PRODUCT CONTINUITY. THE LATEST 00 UTC MODELS
OFFER QUITE POOR RUN TO RUN CONTINUITY AND LIMITED COMMON TRENDS
FROM THE WEEKEND INTO EARLY NEXT WEEK, FURTHER LOWERING FORECAST
CONFIDENCE IN THIS PERIOD.
..WEATHER/HAZARD HIGHLIGHTS
EJECTION OF ENERGETIC UPPER TROUGH ENERGIES AND LEAD FRONTAL
MOISTURE POOLING IS EXPECTED TO SPREAD A SWATH OF MODERATELY HEAVY
RAINS THROUGH THE OHIO VALLEY STATES AND CENTRAL
APPALACHIANS/MID-ATLANTIC THURSDAY/FRIDAY, POSSIBLY AIDED FRIDAY
INTO SATURDAY BY UNCERTAIN/MODERATE COASTAL LOW GENESIS. THE
MODELS SEEM TO REASONABLY SHOW A POTENTIALLY 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 SNOW/ICE DURING THIS PERIOD ON THE COOLED NORTHERN
PERIPHERY OF THIS PRECIPITATION SHIELD FROM THE MIDWEST THROUGH
THE NORTHEAST.
MEANWHILE UPSTREAM, AMPLE SYSTEM ENERGIES DIGGING SOUTHEASTWARD
FROM THE GULF OF ALASKA ARE SLATED TO WORK INTO THE WEST
THURSDAY/FRIDAY AND RENEW MODERATELY HEAVY PRECIPITATION CHANCES
INTO THE NORTHWEST AND NORTHERN CALIFORNIA TO INCLUDE A THREAT FOR
ENHANCED TERRAIN/MOUNTAIN SNOWS THAT WILL SPREAD OVER AN UNSETTLED
WEST/ROCKIES. THE PATTERN SEEMS TO THEN OFFER AN EMERGING MODERATE
SETUP FOR RAINFALL OVER THE EAST-CENTRAL U.S. NEXT WEEKEND INTO
EARLY NEXT WEEK AS WESTERN U.S. UPPER TROUGH ENERGIES WORK
UNCERTAINLY 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, BUT GUIDANCE
REMAINS ALL OVER THE PLACE FROM RUN TO RUN WITH SYSTEM FOCUS
AND/OR EXISTENCE.
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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