740
FXUS02 KWBC 230703
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
203 AM EST MON JAN 23 2023
VALID 12Z THU JAN 26 2023 - 12Z MON JAN 30 2023
...HEAVY SNOW THREAT FROM THE OHIO VALLEY/GREAT LAKES TO THE
INTERIOR NORTHEAST FOR WEDNESDAY/THURSDAY...
..SYNOPTIC OVERVIEW
A WELL ORGANIZED LOW PRESSURE SYSTEM WILL TRACK ACROSS THE OHIO
VALLEY TO THE NORTHEAST THROUGH THIS PERIOD THROUGH THURSDAY, 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. FOLLOWING THIS SYSTEM WILL BE A RELATIVELY WEAK
ALBERTA CLIPPER THAT STREAMS ACROSS THE GREAT LAKES REGION FRIDAY
WITH AN ASSOCIATED TRAILING COLD FRONT. COLDER AIR WILL FILTER
INTO THE CONUS 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
SOUTHWARD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST RUNS OF THE GLOBAL GUIDANCE AND THEIR RESPECTIVE
ENSEMBLE MEANS CONTINUE TO SHOW ABOVE AVERAGE PREDICTABILITY
THROUGH MOST OF THE EXTENDED FORECAST PERIOD. HOWEVER THERE ARE
STILL SOME DIFFERENCES TOWARD THE LATTER PERIODS WITH HOW TO
RESOLVE 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.
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF SEEMINGLY WELL CLUSTERED AND CONSISTENT
GUIDANCE FROM THE 18/00 UTC GFS, 00 UTC ECMWF/UKMET/CANADIAN/EC
ENSEMBLE MEAN AND THE 01 UTC NATIONAL BLEND OF MODELS (NBM). THIS
APPROACH HELPED MAINTAIN SOME FORECAST TO FORECAST CONTINUITY.
..WEATHER/HAZARD HIGHLIGHTS
THE LEADING MAJOR STORM SYSTEM IS EXPECTED TO LIFT NORTHEAST
ACROSS THE OHIO VALLEY WEDNESDAY, REACHING THE NORTHEAST U.S.
THURSDAY AS A NEW SURFACE LOW IS FORECAST TO DEVELOP NEAR THE
COAST AND BECOMES THE DOMINANT LOW. CONCENTRATED AREAS OF MODERATE
TO HEAVY RAINFALL WILL LIKELY FOCUS FROM THE FLORIDA PANHANDLE TO
SOUTHERN GEORGIA. THIS IS WHERE GULF OF MEXICO MOISTURE WILL BE
POOLING IN PROXIMITY TO THE TRAILING FRONT WHICH MAY YIELD 1 TO 2+
INCHES. FURTHER NORTH, A SWATH OF WINTRY WEATHER IS ANTICIPATED
FROM THE NORTHERN OHIO VALLEY/EASTERN GREAT LAKES. 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.
CAMPBELL/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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