620
FXUS02 KWBC 221849
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
148 PM EST SUN JAN 22 2023
VALID 12Z WED JAN 25 2023 - 12Z SUN JAN 29 2023
...HEAVY SNOW THREAT FROM THE OHIO VALLEY/GREAT LAKES TO THE
INTERIOR NORTHEAST FOR WEDNESDAY/THURSDAY...
..SYNOPTIC OVERVIEW
THERE CONTINUES TO BE STRONG SUPPORT FOR THE DEVELOPMENT OF A WELL
ORGANIZED LOW PRESSURE SYSTEM TO TRACK ACROSS THE OHIO VALLEY TO
THE NORTHEAST U.S. WEDNESDAY/THURSDAY THAT WILL BE THE MAIN STORY
MAKING WEATHER HEADLINES DURING THIS FORECAST PERIOD, WITH A
WIND-DRIVEN RAIN NEAR THE COAST AND MODERATE TO HEAVY SNOW FROM
NORTHERN PORTIONS OF THE OHIO VALLEY/GREAT LAKES ACROSS INTERIOR
PORTIONS OF THE NORTHEAST. THIS WILL BE IN RESPONSE TO AN
AMPLIFIED SHORTWAVE TROUGH ALOFT THAT WILL QUICKLY EXIT THE EAST
COAST BY FRIDAY. IN THE WAKE OF THIS STORM WILL BE A WEAKER
ALBERTA CLIPPER THAT WILL TRACK SOUTHEAST ACROSS THE GREAT LAKES
REGION ON FRIDAY WITH A TRAILING COLD FRONT BEHIND IT. FRONTAL
PASSAGE WILL DROP A COLD CANADIAN AIRMASS INTO THE LOWER 48, WITH
SHORTWAVE PASSAGES/HEIGHT FALLS TO COMBINE WITH UPSLOPE FETCH TO
SPREAD SOME TERRAIN ENHANCED SNOWS DOWN ACROSS NORTH-CENTRAL PARTS
OF THE INTERMOUNTAIN WEST/ROCKIES/HIGH PLAINS. ENERGIES DUG INTO
THE WEST THEN EJECT DOWNSTREAM TO SUPPORT A NEW SYSTEM THAT MAY
ORGANIZE LATE PERIOD OVER THE SOUTHERN PLAINS AS THE COLD CANADIAN
AIRMASS SINKS INCREASINGLY DOWN ACROSS OUR FINE NATION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF SEEMINGLY WELL CLUSTERED AND CONSISTENT
GUIDANCE FROM THE 06 UTC GFS, 00 UTC ECMWF/UKMET/CANADIAN, THE 13
UTC NATIONAL BLEND OF MODELS (NBM) AND WPC CONTINUITY WEDNESDAY
INTO FRIDAY IN AN ACTIVE PATTERN WITH ABOVE NORMAL PREDICTABILITY.
12 UTC GUIDANCE NOW ALSO REMAINS IN LINE WITH THIS FORECAST
STRATEGY.
HOWEVER, THERE REMAINS AMPLE CONCERNS HEADING INTO NEXT WEEKEND
WITH THE DISPARATE MODEL HANDLING OF COMPLEX ALASKA/GULF OF ALASKA
SYSTEM ENERGIES IN THE MODELS DOWN INTO THE WESTERN U.S. TO THE
LEE OF AN AMPLIFIED EASTERN PACIFIC UPPER RIDGE, AND ALSO WITH
EVEN LESS CERTAIN UNDERCUTTING EASTERN PACIFIC SYSTEM ENERGIES AND
PHASING ISSUES MAINLY FROM THE GFS. ACCORDINGLY PREFER AN ENSEMBLE
MEAN SOLUTION TO MITIGATE SOME OF THESE DIFFERENCES AND RUN TO RUN
VARIATIONS. OF THE ENSEMBLE SYSTEMS, PREFER THE ECMWF ENSEMBLE
MEAN WHOSE MORE AMPLIFIED UPPER TROUGH DEVELOPMENT DOWN THROUGH
THE WEST COAST SEEMS TO FIT BEST WITH CONSIDERING UPSTREAM UPPER
RIDGE AMPLITUDE, RECENT MODEL TRENDS, WPC CONTINUITY AND PATTERN
HISTORY.
..WEATHER/HAZARD HIGHLIGHTS
THE NEXT MAJOR STORM SYSTEM IS FORECAST TO TRACK NORTHEAST ACROSS
THE OHIO VALLEY ON WEDNESDAY, REACHING THE NORTHEAST U.S. BY
THURSDAY AS A NEW SURFACE LOW IS FORECAST TO DEVELOP NEAR THE
COAST AND BECOMES THE DOMINANT LOW. THE BEST HEAVY RAINFALL
POTENTIAL EXISTS FROM THE FLORIDA PANHANDLE INTO SOUTHERN GEORGIA
WITH THUNDERSTORMS ALONG A GULF MOISTURE POOLING TRAILING COLD
FRONT AND UP INTO COASTAL AREAS OF THE NORTHEAST WITH ENHANCED
ATLANTIC INFLOW WITH THE LOW. THERE IS POTENTIAL FOR SOME 1 TO
LOCALLY 2 INCH RAINFALL TOTALS. MEANWHILE THERE WILL LIKELY BE A
NOTEWORTHY SWATH OF WINTRY WEATHER FROM THE NORTHERN OHIO
VALLEY/EASTERN GREAT LAKES ON WEDNESDAY, WHERE A SWATH OF ENHANCED
DEFORMATION ZONE SNOWS WILL BE POSSIBLE. HEAVY SNOW IS
ADDITIONALLY LIKELY ACROSS THE APPALACHIANS THROUGH INTERIOR AREAS
OF THE NORTHEAST AS THE SECONDARY LOW DEVELOPS, WITH GALES UP THE
COAST AS THE LOW CONTINUES TO INTENSIFY. MUCH OF THIS SNOW WILL
BE FALLING OVER AREAS EXPECTED TO GET SIGNIFICANT ACCUMULATIONS
FROM THE LEAD STORM ON SUNDAY-MONDAY.
A BROAD EXPANSE OF BELOW AVERAGE TEMPERATURES ARE EXPECTED FROM
THE INTERMOUNTAIN WEST TO THE CENTRAL GULF COAST ON WEDNESDAY AND
ONWARD IN THE WAKE OF THE EASTERN U.S. LOW PRESSURE SYSTEM, WITH
MILD AIR ALONG THE EAST COAST PRIOR TO FRONTAL PASSAGE. A RETURN
TO MUCH COLDER CONDITIONS IS LOOKING LIKELY ACROSS THE NORTHERN
PLAINS AND UPPER MIDWEST AS AN ARCTIC AIRMASS MOVES IN BEHIND THE
DEPARTING CLIPPER LOW, WITH HIGHS RUNNING UP TO 15-25 DEGREES
BELOW NORMAL POTENTIALLY ACROSS PORTIONS OF MONTANA, THE DAKOTAS,
AND NEBRASKA ON SUNDAY. COLD AIR WILL ALSO EVENTUALLY FILTER
THROUGH THE NORTHWEST/INTERMOUNTAIN WEST. MEANWHILE DOWNSTREAM,
MILD CONDITIONS WILL LIKELY RETURN TO MUCH OF THE SOUTHERN AND
EASTERN U.S. WITH SOME RETURN FLOW OFF THE GULF OF MEXICO.
HAMRICK/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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