608
FXUS02 KWBC 051857
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 PM EST MON DEC 05 2022
VALID 12Z THU DEC 08 2022 - 12Z MON DEC 12 2022
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE OVERALL PATTERN FOR THE NEXT WEEK WILL BE TRANSITIONING FROM A
WEST COAST TROUGH/SOUTHEAST RIDGE TO A MORE BROAD TROUGH WITH A
GENERALLY SOUTHWEST FLOW REGIME ACROSS THE CONUS. HOWEVER DUE TO
THE DEGREE OF SPREAD WITH THE TIMING, LOCATION, AND AMPLITUDE
DIFFERENCES SHORTLY AFTER THE INITIAL PERIOD, CONFIDENCE IN ANY OF
THE SPECIFICS IS BELOW AVERAGE. THE WPC MEDIUM RANGE PRODUCT SUITE
WAS PRIMARILY DERIVED FROM A BLEND OF THE ECWMF/GFS WITH LESSER
WEIGHTING OF THE CMC/UKMET TO START AND AS THE TIME GOES ON THE
INCLUSION AND WEIGHTING OF THE ECWMF ENSEMBLE/GEFS MEANS WERE
INCREASED- ENDING THE WITH 50% MEANS/50% DETERMINISTIC BY THE END
OF THE FORECAST. THIS HELPED MAINTAIN CONTINUITY AND REDUCE THE
NOISE WITHIN THE GUIDANCE. ADDITIONALLY, IT LED TO A BIT OF A SLOW
DOWN IN THE FRONTAL PROGRESSION ACROSS THE CENTRAL CONUS FOR DAYS
5-7 WHEN COMPARED TO THE PREVIOUS FORECAST. AS PREVIOUSLY NOTED,
THE 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.
..WEATHER/HAZARD HIGHLIGHTS
ENERGETIC IMPULSES ARE EXPECTED TO EJECT FROM THE UPPER-LEVEL
TROUGH ACROSS THE CENTRAL U.S AND WITH LEAD FRONTAL MOISTURE
POOLING WILL SPREAD A SWATH OF MODERATELY HEAVY RAINS THROUGH THE
OHIO VALLEY STATES AND CENTRAL APPALACHIANS/MID-ATLANTIC THURSDAY
AND FRIDAY. IT MAY LINGER 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. SOME OF THE RAINS MOVING ACROSS
THE TENNESSEE/OHIO VALLEYS THROUGH FRIDAY MORNING, HAVE INCREASED
SOIL SATURATION FROM RECENT RAINFALL, MAY REACH OR EXCEED LOCAL
FLASH FLOOD GUIDANCE AND SEE ISOLATED AREAS OF FLASH FLOODING. THE
ELEVATED RISK FOR RUNOFF AND FLASH FLOODING WILL SHIFT TO PORTIONS
OF THE APPALACHIANS AND THE DELMARVA REGION INTO SATURDAY MORNING
AS THE AREA OF RAIN SHIFTS EASTWARD.
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. THE SPREAD IN THE
GUIDANCE HAS PERSISTENTLY BEEN ALL OVER THE PLACE FROM RUN TO RUN
WITH SYSTEM FOCUS AND/OR EXISTENCE. THE RAINFALL AMOUNTS AND
LOCATION OF THIS PRECIPITATION MAY CHANGE SIGNIFICANTLY OVER THE
NEXT FEW DAYS AS THE MODELS WORK OUT VARIOUS ISSUES.
CAMPBELL/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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