050
FXUS02 KWBC 040659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST WED JAN 04 2023
VALID 12Z SAT JAN 07 2023 - 12Z WED JAN 11 2023
...SIGNIFICANT HEAVY PRECIPITATION THREATS FOR CALIFORNIA TO RENEW
THIS WEEKEND AND EARLY NEXT WEEK...
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE OVERALL UPPER LEVEL PATTERN OVER MUCH OF THE CONTINENTAL U.S.
WILL BE A BIT MORE COMPLICATED THAN USUAL, WITH MULTIPLE UNCERTAIN
EMBEDDED SHORTWAVES WITHIN RELATIVELY WELL DEFINED NORTHERN AND
SOUTHERN STREAM FLOWS. THE EASTERN PACIFIC WILL CONTINUE TO BE
EXTREMELY ACTIVE WITH WITH A SERIES OF DEEEPENED LOW PRESSURE
SYSTEMS APPROACHING THE WEST COAST WITH MORE ATMOSPHERIC RIVER
EVENTS EXPECTED. THE UPPER LEVEL RIDGE OVER THE INTERMOUNTAIN WEST
FOR MOST OF THE FORECAST PERIOD WILL TEND TO LIMIT HOW FAR
INLAND/DIMINSHED THESE STORM SYSTEMS GET INTO AT LEAST EARLY NEXT
WEEK.
ACCORDINGLY, THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY
DERIVED FROM A COMPOSITE BLEND OF MID-LARGER SCALE COMPATIBLE
GUIDANCE FROM THE 18 UTC GFS/GEFS MEAN, 12 UTC
ECMWF/CANADIAN/ECMWF ENSEMBLE MEAN, WPC CONTINUITY AND THE 01 UTC
NATIONAL BLEND OF MODELS (NBM). WPC PREFERRED BLEND WEIGHTING
SHIFTS IN FAVOR OF THE MORE COMPATIBLE ENSEMBLE MEANS AT LONGER
TIME FRAMES BY TUESDAY IN AN EFFORT TO BEST MITIGATE RAMPANT
SMALLER SCALE VARIANCES CONSISTENT WITH PREDICTABILITY. THE LATEST
00 UTC GUIDANCE SUITE GENERALLY REMAINS IN LINE WITH THIS FORECAST
PLAN.
..WEATHER/HAZARD HIGHLIGHTS
THE WPC EXPERIMENTAL DAY 4/5 EXCESSIVE RAINFALL OUTLOOKS (EROS)
RENEWS SATURDAY AND SUNDAY "SLIGHT" RISK AREAS CENTERED OVER
NORTHERN CALIFORNIA. THE THREAT FOR ADDITIONAL ROUNDS OF HEAVY
RAINFALL WITH AMPLE RUNOFF ISSUES THAT MAY EXPAND SOUTHWARD ARE
LIKELY TO PERSIST THROUGH EARLY NEXT WEEK IN A DANGEROUSLY WET
PATTERN WITH MULTIPLE RIVERS OF MOISTURE WORKING INLAND AHEAD OF A
SERIES OF UNCERTAIN/DEEPENED EASTERN PACIFIC STORMS. THIS
CONTINUES A PATTERN FAVORABLE TO PRODUCE A MAJOR WIDESPREAD
EPISODE. 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)
SATURDAY-NEXT WEDNESDAY. GUIDANCE ALSO SHOWS SOME FAVORABLE FLOW
INTO THE NORTHWEST FOR ESPECIALLY SOUTHWARD FACING TERRAIN. THERE
IS ALSO MORE MODEST SHORTWAVE/TERRAIN ENHANCED SNOW POTENTIAL TO
WORK INTO THE GREAT BASIN, PERHAPS ESPECIALLY EARLY-MID NEXT WEEK
WITH A BETTER MAINTAINED SYSTEM PUSH INLAND ACROSS THE REGION.
MEANWHILE, UPPER-LEVEL TROUGHING MOVING THROUGH THE WEST IS
FORECAST TO REACH THE PLAINS AND HELP DEVELOP A MODEST SURFACE
FRONTAL WAVE TO SUBSEQUENTLY TRACK WITH SOME UNCERTAINTY EASTWARD
ACROSS THE MID-MISSISSIPPI VALLEY TO THE MID-ATLANTIC SATURDAY
INTO MONDAY. COMPARED TO THE MODELS, THE NBM STILL SEEMS TO BE
MISSING SOME MODEST PRECIPITATION POTENTIAL THAT MAY PRODUCE SOME
LIGHT WINTRY WEATHER FOR PARTS OF THE OHIO VALLEY THROUGH THE
APPALACHIANS AS WELL AS A TRAILING AREA OF RAINFALL DOWN TROUGH
THE SOUTH-CENTRAL U.S. THIS WEEKEND AND MODESTLY TO THE SOUTHEAST
INTO EARLY NEXT WEEK. WPC QPF AND WEATHER GRIDS WERE ACCORDINGLY
ADJUSTED. GUIDANCE HAS TRENDED HEAVIER WITH ACTIVITY ACROSS
EASTERN TX AND THE LOWER MS VALLEY WHERE SOME DOWNPOURS MAY LEAD
TO LOCAL RUNOFF ISSUES.
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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