049
FXUS02 KWBC 021832
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
131 PM EST MON JAN 02 2023
VALID 12Z THU JAN 05 2023 - 12Z MON JAN 09 2023
...HEAVY PRECIPITATION THREATS INTO CALIFORNIA LIKELY RESUME THIS
WEEKEND...
...GUIDANCE/PREDICTABILITY ASSESSMENT AND WEATHER/HAZARD
HIGHLIGHTS...
GLOBAL GUIDANCE CONTINUES TO AGREE TO WEAKEN A DEEP CYCLONE OFF
THE PACIFIC NORTHWEST COAST ON THURSDAY AND SET UP A MEAN LOW
FARTHER NORTHWEST THAT PERSISTS INTO NEXT WEEK, KEEPING AN ACTIVE
PATTERN FOR THE WEST COAST (PARTICULARLY CALIFORNIA) AS SHORTWAVE
ENERGY ROUNDS THE LOW. PRECIP FROM THE MIDWEEK ATMOSPHERIC RIVER
AHEAD OF THE CYCLONE OVER CALIFORNIA PERSISTS THURSDAY BEFORE A
BRIEF REPRIEVE FRIDAY. MANY AREAS, ESPECIALLY BURN SCARS, ARE
LIKELY TO BE SENSITIVE TO ADDITIONAL RAINFALL BY THEN GIVEN THE
AMPLE RECENT AND FORECAST RAINFALL. AN EXPERIMENTAL DAY 4
EXCESSIVE RAINFALL OUTLOOK (ERO) "SLIGHT" RISK AREA ALONG WITH
HIGH PROBABILITIES FOR SIERRA SNOWFALLS IN THE WPC WINTER WEATHER
OUTLOOK (WWO) PERSIST. 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, THERE IS STILL UNCERTAINTY OF
TIMING, STRENGTH, AND PLACEMENT OF PACIFIC LOWS/FRONTAL SYSTEMS
BRINGING THE NEXT SURGES OF MOISTURE INTO THE WEST COAST AND MAY
BE NOTEWORTHY IN CALIFORNIA, PARTICULARLY FROM RECENT GFS RUNS
(INCLUDING THE 12Z FROM TODAY) AS WELL AS THE CMC AND UKMET WHILE
THE ECMWF KEEPS FORCING/PRECIPITATION OFFSHORE.
SOME UNCERTAINTY REMAINS WITH A FRIDAY RE-INVIGORATION OF LOW
PRESSURE OVER NEW ENGLAND FRIDAY. RECENT GFS RUNS (INCLUDING THE
12Z FROM TODAY) HAVE A MORE NEGATIVELY TILTED UPPER LOW OVER THE
EASTERN GREAT LAKES WHICH ALLOWS A STRONGER COASTAL LOW OFF NEW
ENGLAND AND SNOW OVER MUCH OF THE NORTHEAST FRIDAY/FRIDAY NIGHT.
MEANWHILE THE LATEST CMC/UKMET/ECMWF HAVE A WEAKER/MORE
PROGRESSIVE FLOW THAT DOES NOT RESULT IN MUCH LATE WORK WEEK
PRECIP OVER THE NORTHEAST. HOWEVER, MEMBERS OF THE ECENS AND CMCE
HAVE A SIMILAR FEATURE, SO THIS IS SOMETHING TO MONITOR AND A
REASON WHY THE FORECAST TRENDS FROM DETERMINISTIC GUIDANCE TO
ENSEMBLES ON DAY 5. MEANWHILE, LEAD UPPER-LEVEL TROUGHING MOVING
THROUGH THE INTERMOUNTAIN WEST IS FORECAST TO REACH THE GREAT
PLAINS BY SATURDAY AND HELP DEVELOP A MODEST FRONTAL WAVE THAT IS
SUBSEQUENTLY FORECAST TO TRACK EAST, BUT WITH LATITUDINAL
UNCERTAINTY WITH GUIDANCE TAKING IT OVER THE MIDWEST OR TENNESSEE
VALLEY THIS WEEKEND. IN GUIDANCE HAS IT 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 INTO FRIDAY BEFORE WPC
GUIDANCE PREFERENCES BEGIN TO SWITCH TO A GEFS/ECMWF/CMCE ENSEMBLE
MEAN PREFERENCE AMID MODESTLY GROWING FORECAST SPREAD THROUGH THE
REST OF THIS MEDIUM RANGE PERIOD.
SLIGHTLY WARMER THAN NORMAL CONDITIONS GENERALLY PREVAIL FOR THE
NORTHWEST, CENTRAL, AND EASTERN SECTIONS OF THE CONUS FRIDAY INTO
NEXT WEEK WHILE TEMPERATURES IN THE SOUTHWEST ARE NEAR TO BELOW
NORMAL UNDER TROUGHING.
JACKSON
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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