252
FXUS02 KWBC 020656
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 AM EST MON JAN 02 2023
VALID 12Z THU JAN 05 2023 - 12Z MON JAN 09 2023
...RENEWED HEAVY PRECIPITATION THREATS TO BREACH THE WEST COAST
WITH THE MOST SIGNIFICANT EPISODE WEDNESDAY-THURSDAY IN
CALIFORNIA...
...GUIDANCE/PREDICTABILITY ASSESSMENT AND WEATHER/HAZARD
HIGHLIGHTS...
MODELS AND ENSEMBLES AGREE TO BRING A RATHER DEEP CYCLONE TOWARD
BUT OFF THE PACIFIC NORTHWEST COAST ON THURSDAY. THE BULK OF THE
ATMOSPHERIC RIVER MOISTURE AHEAD OF THE CYCLONE IS FORECAST TO BE
PRECIPITATED WHILE SHIFTING SOUTHWARD OVER CALIFORNIA WITH
CULMINATION ON THURSDAY. MANY AREAS, ESPECIALLY BURN SCARS, ARE
LIKELY TO BE SENSITIVE TO ADDITIONAL RAINFALL BY THEN GIVEN THE
AMPLE RECENT RAINFALL IN ADDITION TO THE RAIN EXPECTED DURING THE
SHORT RANGE PERIOD. WPC HAS ISSUED AN EXPERIMENTAL MEDIUM RANGE
EXCESSIVE RAINFALL OUTLOOK (ERO) "SLIGHT" RISK AREA ALONG WITH
HIGH PROBABILITIES FOR SIERRA SNOWFALLS IN THE WPC WINTER WEATHER
OUTLOOK (WWO). GUIDANCE ALSO SHOWS SOME FAVORABLE FLOW INTO THE
PACIFIC NORTHWEST FOR ESPECIALLY SOUTHWARD FACING TERRAIN AND
PERIODIC SHORTWAVE/TERRAIN ENHANCED SNOW POTENTIAL FARTHER INLAND
ACROSS THE INTERMOUNTAIN WEST TOWARD THE ROCKIES WITH SYSTEM
TRANSLATIONS. BY THE WEEKEND, A COUPLE OF UNCERTAIN PACIFIC
LOWS/FRONTAL SYSTEMS ARE FORECAST TO BRING THE NEXT SURGES OF
MOISTURE INTO THE WEST COAST OF NOTE, BUT ARE NOT EXPECTED TO BE
WITH THE GUSTO OF THE LEAD EVENT.
GUIDANCE ALSO REMAINS VARIED WITH EMPHASIS IN DEPICTION OF A LOW
PRESSURE WAVE SLIDING OFF THE NEW ENGLAND COAST AS LINGERING
SURFACE TROUGHING EXTENDING WEST INTO THE GREAT LAKES AS COLDER
AIR ARRIVES FROM EASTERN CANADA ON THURSDAY. A LINGERING UPPER
WAVE/LOW MAY INTERACT WITH THE SURFACE TROUGH AND THE COLD AIR TO
DELIVER A PERIOD OF SNOW OR MIXED PRECIPITATION ACROSS THE
INTERIOR NORTHEAST INTO FRIDAY. MEANWHILE, LEAD UPPER-LEVEL
TROUGHING MOVING THROUGH THE INTERMOUNTAIN WEST IS FORECAST TO
REACH THE CENTRAL PLAINS BY SATURDAY AND HELP DEVELOP A MODEST
FRONTAL WAVE THAT IS SUBSEQUENTLY FORECAST TO TRACK GENERALLY
TOWARD THE GREAT LAKES THEN OFF THE EAST COAST BY MONDAY. COMPARED
TO THE MODELS AND CONSIDERING SYSTEM DEVELOPMENT, THE 01 UTC NBM
SEEMS TO BE MISSING THE MODEST PRECIPITATION POTENTIAL THAT MAY
PRODUCE SOME LIGHT WINTRY WEATHER OVER THE MIDWEST AS WELL AS A
TRAILING AREA OF SHOWERS DOWN TROUGH THE SOUTH-CENTRAL U.S. AS
WELL AS DOWNSTREAM INTO THE MID-ATLANTIC. WPC QPF AND ASSOCIATED
WEATHER GRIDS WERE ADJUSTED TO ACCOMMODATE.
OVERALL, A COMPOSITE BLEND OF THE GFS/ECMWF/CANADIAN/UKMET SEEMS
TO PROVIDE A REASONABLE FORECAST BASIS THURSDAY INTO FRIDAY BEFORE
WPC GUIDANCE PREFERENCE SWITCHES TO THE STILL COMPATIBLE
GEFS/ECMWF ENSEMBLE MEANS AMID MODESTLY GROWING FORECAST SPREAD
THROUGH THE REST OF THIS MEDIUM RANGE PERIOD. THIS SOLUTION
MAINTAINS REASONABLE WPC PRODUCT CONTINUITY AND CONSISTENCY.
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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