415
FXUS02 KWBC 031859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EST TUE JAN 03 2023
VALID 12Z FRI JAN 06 2023 - 12Z TUE JAN 10 2023
...SIGNIFICANT HEAVY PRECIPITATION THREATS FOR CALIFORNIA TO
RESUME THIS WEEKEND AND EARLY NEXT WEEK...
19Z UPDATE: THE OVERALL UPPER LEVEL PATTERN OVER MUCH OF THE
CONTINENTAL U.S. WILL BE A BIT MORE COMPLICATED THAN USUAL, WITH
MULTIPLE SHORTWAVES WITHIN RELATIVELY WELL DEFINED NORTHERN AND
SOUTHERN STREAM FLOWS. THE 12Z MODEL GUIDANCE SUITE HAS A GOOD
GENERAL DEPICTION ON FRIDAY, BUT MORE NOTEWORTHY DIFFERENCES
APPEAR BY THE WEEKEND WITH THE TIMING OF THE SHORTWAVE TROUGH
ACROSS THE MIDWEST. THE EASTERN PACIFIC WILL CONTINUE TO BE
EXTREMELY ACTIVE WITH POTENTIALLY 3 WELL DEFINED LOW PRESSURE
SYSTEMS APPROACHING THE WEST COAST WITH MORE ATMOSPHERIC RIVER
EVENTS EXPECTED. IN TERMS OF THE QPF, AMOUNTS HAVE TRENDED A
LITTLE HIGHER SINCE THE PREVIOUS FORECAST, BUT SLIGHTLY LOWER THAN
THE NBM. THE PREVIOUS FORECAST DISCUSSION IS APPENDED BELOW FOR
REFERENCE. /HAMRICK
...GUIDANCE/PREDICTABILITY ASSESSMENT AND WEATHER/HAZARD
HIGHLIGHTS...
THIS FRIDAY SHOULD SERVE AS A RELATIVELY LIGHT PRECIPITATION OVER
MOST OF THE WEST GIVEN SHORTER TERM FORECASTS, BUT EJECTING
IMPULSES MAY PRODUCE SOME CENTRAL GREAT BASIN/ROCKIES SNOWS WHILE
DEEP LAYERED/MOIST SOUTHERLY FLOW UP ALONG/OFF THE WEST COAST
SHOULD BEGIN TO PRODUCE SOME ENHANCED PRECIPITATION FOR FAVORED
AREAS OF COASTAL NORTHERN CALIFORNIA AND THE PACIFIC NORTHWEST.
THE WPC EXPERIMENTAL DAY 5 EXCESSIVE RAINFALL OUTLOOK (ERO) RENEWS
BY SATURDAY A "SLIGHT" RISK AREA FOR NORTHERN CALIFORNIA. THE
THREAT FOR ADDITIONAL ROUNDS OF HEAVY RAINFALL WITH AMPLE RUNOFF
ISSUES ARE LIKELY TO PERSIST AND EXPAND SOUTHWARD OVER THE STATE
SUNDAY THROUGH TUESDAY IN A DANGEROUSLY WET PATTERN WITH MULTIPLE
RIVERS OF MOISTURE WORKING INLAND AHEAD OF A SERIES OF
UNCERTAIN/DEEPENED EASTERN PACIFIC STORMS. MANY AREAS, ESPECIALLY
BURN SCARS, ARE LIKELY TO BE SENSITIVE TO ADDITIONAL RAINFALL
GIVEN THE AMPLE RECENT AND FORECAST RAINFALL. HIGH PROBABILITIES
FOR SIERRA SNOWFALLS ARE ALSO DEPICTED IN THE WPC WINTER WEATHER
OUTLOOK (WWO) SUNDAY-TUESDAY. GUIDANCE ALSO SHOWS SOME FAVORABLE
FLOW INTO THE NORTHWEST FOR ESPECIALLY SOUTHWARD FACING TERRAIN
AND MODEST SHORTWAVE/TERRAIN ENHANCED SNOW POTENTIAL WORKING INTO
THE GREAT BASIN.
ELSEWHERE, GUIDANCE SOLUTIONS HAVE BECOME BETTER CLUSTERED WITH A
FRIDAY RE-INVIGORATION OF LOW PRESSURE OVER NEW ENGLAND AS A
SUPPORTING CLOSED UPPER TROUGH/LOW PASSAGES ACROSS THE REGION.
THIS MAY SUPPORT SOME PLOW-ABLE SNOWS ACROSS INTERIOR NEW ENGLAND
AS WRAPPING MOISTURE IS SQUEEZED OUT IN A COOLING ENVIRONMENT.
MEANWHILE, UPPER-LEVEL TROUGHING MOVING THROUGH THE WEST IS
FORECAST TO REACH THE PLAINS BY SATURDAY AND HELP DEVELOP A MODEST
SURFACE FRONTAL WAVE THAT MAY SUBSEQUENTLY TRACK WITH SOME
UNCERTAINTY EASTWARD ACROSS THE MID-MISSISSIPPI VALLEY TO THE
MID-ATLANTIC THIS WEEKEND. COMPARED TO THE MODELS, THE NBM STILL
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 TO THE MID-ATLANTIC THIS WEEKEND AND THE
SOUTH/SOUTHEAST INTO EARLY NEXT WEEK. WPC QPF AND WEATHER GRIDS
WERE ACCORDINGLY ADJUSTED.
OVERALL, A COMPOSITE BLEND OF BEST CLUSTERED GUIDANCE FROM THE
LATEST GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS SEEMS TO PROVIDE A
REASONABLE FORECAST BASIS FRIDAY INTO SATURDAY BEFORE WPC GUIDANCE
PREFERENCES SWITCH IN EARNEST TO THE COMPATIBLE GEFS/ECMWF
ENSEMBLE MEANS AMID MODESTLY GROWING FORECAST SPREAD THROUGH THE
REST OF THIS FORECAST PERIOD.
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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