083
FXUS02 KWBC 090734
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 AM EST TUE JAN 09 2024
VALID 12Z FRI JAN 12 2024 - 12Z TUE JAN 16 2024
...ANOTHER MAJOR STORM TO IMPACT THE EAST-CENTRAL TO EASTERN U.S.
WITH SNOW/RAIN/WIND THREATS FOLLOWED BY AN ARCTIC BLAST THROUGH
MUCH OF THE NORTH-CENTRAL U.S....
..GENERAL OVERVIEW
AN UPPER TROUGH OVER THE GREAT PLAINS WILL AMPLIFY WHILE IT
PROPAGATES THROUGH THE MIDWEST AND INTO SOUTHEASTERN CANADA THIS
WEEKEND. AT THE SURFACE, CYCLOGENESIS AND A RAPIDLY INTENSIFYING
MID-LATITUDE CYCLONE WILL TAKE SHAPE OVER THE SOUTHERN PLAINS AND
LOWER MISSISSIPPI VALLEY ON FRIDAY. THIS SYSTEM WILL CONTINUE TO
INTENSIFY AS IT MOVES INTO THE MIDWEST AND NORTHEAST ON SATURDAY.
MEANWHILE, A POTENT UPPER LOW WILL BREAK-DOWN AN EAST PACIFIC
RIDGE AND MAKE ITS WAY INTO THE NORTHWEST THIS WEEKEND. ARCTIC
HIGH PRESSURE WILL BUILD IN ACROSS THE CENTRAL U.S. BEHIND THE
DEPARTING STORM IN THE EAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST NUMERICAL MODELS ARE QUITE DISPERSED IN THEIR HANDLING
OF THE OVERALL EVOLUTION OF THE SYNOPTIC PATTERN OVER THE LOWER 48
DURING THE MEDIUM RANGE PERIOD. THERE'S PLENTY OF RUN-TO-RUN
VARIANCE IN THE DETERMINISTIC EURO WITH RESPECT TO THE INCOMING
EAST PAC LOW ON DAY 3. THE 12Z UKMET/CMC AND 18Z GFS ARE ALSO ALL
OVER THE PLACE WITH THEIR PLACEMENTS OF THAT SYSTEM SO THIS
SYSTEM'S DETAILS ARE YET TO BE CONSIDERED CERTAIN. THE MODELS ARE
IN REASONABLE AGREEMENT ABOUT THE EVOLUTION OF THE WOUND UP
EASTERN U.S. STORM THROUGH DAY 5. A GENERAL MODEL BLEND CONSISTING
OF THE 12Z EC/UKMET/CMC AND 18Z GFS WERE UTILIZED ON DAY 3. THE
UKMET WAS REMOVED ON DAY 4 DUE TO ITS SIGNIFICANT DIVERGENCE FROM
THE REST OF THE GUIDANCE REGARDING THE SHORTWAVE ENERGY IN THE
EAST PAC/NORTHWEST U.S.. THE CANADIAN IS DROPPED FROM THE DAY 5
BLEND IN PLACE OF THE 12Z ECE AND 18Z GEFS BECAUSE IT (CMC) HAS
THE PARENT LOW CENTERED OVER THE UPPER MIDWEST WHILE THE EC AND
GFS AND CANADIAN ENSEMBLE HAVE IT MUCH FARTHER NORTH IN CANADA.
THE CANADIAN ENSEMBLE IS INTRODUCED BRIEFLY ON DAY 6 AND REMOVED
ON DAY 7.
..WEATHER/HAZARDS HIGHLIGHTS
THE ACTIVE PERIOD CONTINUES THROUGH THIS WEEKEND, BEGINNING WITH
YET ANOTHER MAJOR STORM OVER THE EAST-CENTRAL TO EASTERN U.S. THIS
FRIDAY. A DEEP MID-LATITUDE CYCLONE WILL PRODUCE A SWATH OF HEAVY
SNOW AND STRONG WINDS FROM EASTERN MISSOURI THROUGH THE GREAT
LAKES ON FRIDAY, AND INTO NEW ENGLAND ON FRIDAY NIGHT WITH
LINGERING LAKE EFFECT SNOW OCCURRING ON THE BACKSIDE OF THE ARCTIC
COLD FRONT DOWNWIND LAKES ERIE AND ONTARIO ON SATURDAY. SOME LIGHT
TO MODERATE SNOW MAY OCCUR DOWN THROUGH THE CENTRAL APPALACHIANS
ON FRIDAY NIGHT AND SATURDAY AS WELL. RAIN SHOWERS AND SCATTERED
THUNDERSTORMS ARE LIKELY FROM THE MIDWEST TO THE MID-ATLANTIC AND
SOUTHEAST/GULF COAST WITHIN THE WARM SECTOR OF THE STORM ON
FRIDAY. THE STORM PREDICTION CENTER HIGHLIGHTS A 15% PROBABILITY
OF SEVERE THUNDERSTORMS FROM EASTERN LOUISIANA ACROSS THE
SOUTHEAST, CAROLINAS AND INTO SOUTHERN VIRGINIA. SOME HEAVY
RAINFALL IS POSSIBLE OVER PARTS OF THE CENTRAL MIDWEST FRIDAY
AFTERNOON WHERE SOME INSTABILITY MAY CREEP IN, LEADING TO THE
THREAT OF EXCESSIVE RAINFALL. THIS THREAT IS MARGINAL (AT LEAST
5%). AS THE SYSTEM PROGRESSES EASTWARD FRIDAY NIGHT THE
NORTHEAST/SOUTHERN NEW ENGLAND COAST MAY BECOME AN AREA OF FOCUSED
HEAVY RAINFALL. A SLIGHT RISK OF EXCESSIVE RAINFALL (AT LEAST 15%)
IS IN EFFECT FOR THE AREA ENCOMPASSING THE I-95 CORRIDOR BETWEEN
BALTIMORE AND WESTERN RHODE ISLAND WHERE FAVORABLE JET DYNAMICS
AND MOISTURE FLUX WILL BE PRESENT. HEAVY RAINFALL OVER EXISTING
SNOWPACK IN NORTHEASTERN PENNSYLVANIA INTO NORTHERN NEW JERSEY,
SOUTHERN NEW YORK AND SOUTHERN NEW ENGLAND MAY ALSO CONTRIBUTE TO
THE FLASH FLOODING THREAT. THE DEEPENING CYCLONE OVER THE GREAT
LAKES WILL DRIVE ANOTHER HIGH WIND THREAT ACROSS THE NORTHEASTERN
QUADRANT OF THE COUNTRY ON SATURDAY.
AN ARCTIC HIGH PRESSURE WILL DESCEND ON THE CENTRAL U.S. FOLLOWING
THE AMPLIFIED EASTERN SYSTEM THIS WEEKEND. AN ARCTIC AIRMASS WILL
ADVECT INTO THE NORTH-CENTRAL TO CENTRAL U.S. AS A RESULT. THIS
AIRMASS WILL BRING WITH IT HIGHS FROM THE TEENS TO NEGATIVE TEENS
THIS WEEKEND THROUGH THE MIDDLE OF NEXT WEEK. MEANWHILE, A POTENT
EAST PAC SHORTWAVE LOW WILL BREAK THROUGH AN ENTRENCHED UPPER
RIDGE OVER BRITISH COLUMBIA AND THE PACIFIC NORTHWEST. DESPITE
MODEL UNCERTAINTY, THIS SYSTEM IS STILL EXPECTED TO DIRECT
SUBTROPICAL MOISTURE INTO THE WEST THIS FRIDAY AND SATURDAY. THE
RESULT WILL BE HEAVY TO EXCESSIVE RAINFALL ALONG THE NORTHWEST
COAST, FROM SOUTHERN WASHINGTON TO NORTHERN CALIFORNIA, AND HEAVY
SNOW ACROSS THE CASCADES, OLYMPICS, THE INTERMOUNTAIN WEST AND
COLORADO ROCKIES.
KEBEDE
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 FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES 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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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