380
FXUS02 KWBC 311909
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SAT DEC 31 2022
VALID 12Z TUE JAN 03 2023 - 12Z SAT JAN 07 2023
...WINTER STORM THREAT ACROSS THE UPPER MIDWEST ON TUESDAY AS A
HEAVY RAIN/SEVERE WEATHER THREAT WORKS ACROSS THE SOUTHEAST IN
WEDNESDAY...
...MORE ROUNDS OF MODERATE TO HEAVY PRECIPITATION FOR THE WEST
WITH FOCUS ACROSS CALIFORNIA...
..OVERVIEW
A DEEPENED LOW PRESSURE SYSTEM WITH A FORECAST TRACK ACROSS THE
NORTHERN U.S. WILL LIKELY SUPPORT A LINGERING HEAVY SNOW THREAT
FOR THE UPPER MIDWEST TUESDAY, WHILE HEAVY RAIN, FLASH FLOODING,
AND SEVERE WEATHER APPEAR LIKELY ACROSS THE SOUTH TUESDAY INTO
WEDNESDAY. MEANWHILE, THE WEST SHOULD SEE ADDITIONAL ROUNDS OF
MODERATE TO HEAVY PRECIPITATION NEXT WEEK WITH HIGHEST AMOUNTS
MAINLY ACROSS CALIFORNIA.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES OFFER A REASONABLY SIMILAR LARGER SCALE
PATTERN EVOLUTION THROUGH THE MEDIUM-RANGE. HOWEVER, THE ECMWF HAS
SHOWN QUITE A BIT OF UNCERTAINTY REGARDING WHETHER A DEEP CYCLONE
WILL FORM AND TRACK OFF THE COAST OF THE PACIFIC NORTHWEST BY
ABOUT THURSDAY. THE MOST TWO RECENT RUNS HAVE SETTLED INTO A
CYCLOGENESIS SCENARIO IN GOOD AGREEMENT WITH THE REST OF THE
GUIDANCE. ACROSS THE NORTHERN U.S., THE ECMWF HAS BEEN
CONSISTENTLY FORECASTING A MORE SOUTHERLY TRACK WITH THE CYCLONE
ASSOCIATED WITH THE WINTER STORM. OTHER GUIDANCE HAVE TRENDED
TOWARD THE ECMWF SOLUTION. ACROSS THE NORTHEAST, THE ECMWF
CONTINUE TO SUPPORT MORE SURFACE TROUGHING ON THURSDAY WHICH WILL
LEAD TO WINTRY WEATHER IMPLICATIONS. ACROSS THE SOUTHEAST, MODELS
HAVE CONTINUED TO SHOW A DOWNWARD TREND IN THE QPF AHEAD OF A COLD
FRONT TUE-WED. IT APPEARS THAT THE THREAT OF HEAVY RAIN HAS
DECREASED FARTHER INLAND, LEAVING THE FLORIDA PANHANDLE TO BE THE
AREA MOST SUSCEPTIBLE TO HEAVY RAIN DUE TO INTERACTION WITH A WEAK
COASTAL FRONT.
ACCORDINGLY, THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY
DERIVED FROM A BLEND OF THE 00Z ECMWF, 06Z GFS, AND 00Z CMC AND
THEIR ENSEMBLE MEANS BUT LEANING TOWARD THE 00Z ECMWF/00Z EC MEANS
THROUGH THE MEDIUM-RANGE FORECAST PERIOD WITH MANUAL ADJUSTMENTS
NEAR CYCLONE CENTERS TO ENSURE REASONABLE DEPTH.
..WEATHER/HAZARD HIGHLIGHTS
A DEEPENED LOW STORM TRACK ACROSS THE NORTH-CENTRAL U.S. WILL
SHIFT AN AXIS OF COMMA-HEAD SNOWS ACROSS THE UPPER MIDWEST
TUESDAY, ALONG WITH INCREASINGLY WINDY CONDITIONS AND AN ICY
TRANSITIONAL ZONE. GUIDANCE IS CONVERGING ON THE ECMWF SOUTHERLY
TRACK SOLUTION, BOLSTERING FORECAST CONFIDENCE. INFLOW EAST OF THE
LOW AND LINGERING COLD AIR MAY ALSO SUPPORT SOME SNOW/ICE
DOWNSTREAM ACROSS THE UPPER GREAT LAKES AND NORTHERN NEW ENGLAND.
MEANWHILE FARTHER SOUTH, THE FRONTAL SYSTEM ASSOCIATED WITH THIS
LOW AND FAVORABLE GULF MOISTURE/INSTABILITY AND RIGHT ENTRANCE
REGION UPPER JET LIFT SHOULD SUPPORT MODERATE TO HEAVY RAINFALL
BUT RECENT MODEL QPFS HAVE TRENDED DOWNWARD IN THIS AREA.
THEREAFTER, A TRAILING FRONTAL LOW PRESSURE SYSTEM COULD DEVELOP
AND SPREAD SOME MODERATE TO HEAVY RAIN UP THE MID-ATLANTIC STATES
TO COASTAL NEW ENGLAND. SOME WINTRY PRECIPITATION IS ALSO
POSSIBLE FROM THE CENTRAL APPALACHIANS INTO THE INTERIOR NORTHEAST.
ADDITIONAL ROUNDS OF PRECIPITATION ARE ALSO EXPECTED TO CONTINUE
ALONG THE WEST COAST AS THE WEEK PROGRESSES, BUT PRIMARILY WITH A
FOCUS ON CALIFORNIA. THERE IS QUITE A BIT OF UNCERTAINTY WITH THE
TIMING OF ADDITIONAL HEAVY PRECIPITATION EVENTS AT THIS POINT
GIVEN THE VARIED SHORTWAVE PROGRESSIONS AND SURFACE SYSTEM FOCUS,
BUT AMOUNTS LOOK TO TREND UPWARD BY WEDNESDAY-THURSDAY ACROSS
CALIFORNIA AS A STRONGER FRONTAL SYSTEM APPROACHES FROM THE
PACIFIC WITH ANOTHER POTENTIAL ATMOSPHERIC RIVER EVENT GIVEN THE
SIGNAL FOR A STRONG FETCH OF MOISTURE WITH THE SYSTEM. MANY AREAS
ARE LIKELY TO BE SENSITIVE TO ADDITIONAL RAINFALL BY THEN GIVEN
THE AMPLE RECENT RAINFALL AND ADDITIONAL RAIN DURING THE SHORT
RANGE PERIOD. THERE IS ALSO A MULTI-DAY THREAT FOR HEAVY SNOW THAT
WILL FOCUS OVER THE SIERRA, BUT ALSO TO A LESSER EXTENT SPREAD
NORTHWARD THROUGH THE CASCADES AND WITH SOME GUSTO INLAND ACROSS
THE INTERMOUNTAIN WEST TOWARD THE ROCKIES OVER TIME WITH SYSTEM
TRANSLATION.
MILDER THAN AVERAGE TEMPERATURES FOR WINTER WILL BE WIDESPREAD
ACROSS THE EASTERN HALF OF THE COUNTRY FOR EARLY NEXT WEEK. LOWS
OF AROUND 15-30F ABOVE AVERAGE AND HIGHS AROUND 10-20F ABOVE
AVERAGE WILL BE COMMON, EVEN REACHING 20-30F ANOMALIES IN THE OHIO
VALLEY/GREAT LAKES TUESDAY AND THE NORTHEAST ON WEDNESDAY. DAILY
RECORDS FOR WARM LOWS COULD BE WIDESPREAD FOR PARTS OF THE CENTRAL
AND EASTERN U.S., WHILE DAILY RECORD HIGHS ARE POSSIBLE AS WELL
ESPECIALLY IN THE OHIO VALLEY. MEANWHILE IN THE WEST, THE OVERALL
WET/SNOWY PATTERN WILL TEND TO KEEP DAYTIME TEMPERATURES AROUND
5-10F BELOW NORMAL. AS THE LARGE-SCALE UPPER TROUGH MOVES THROUGH
THE WESTERN U.S. INTO THE PLAINS, NEAR TO BELOW AVERAGE
TEMPERATURES ARE EXPECTED TO WORK THEIR WAY FROM WEST TO EAST
ACROSS THESE AREAS.
KONG/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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