703
FXUS02 KWBC 080659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST MON JAN 8 2024
VALID 12Z THU JAN 11 2024 - 12Z MON JAN 15 2024
...ANOTHER MAJOR STORM TO IMPACT THE EAST-CENTRAL TO EASTERN U.S.
WITH SNOW/RAIN/WIND THREATS AND AN ARCTIC BLAST ENVELOPS MUCH OF
THE NORTH-CENTRAL PLAINS...
..GENERAL OVERVIEW
IN THE WAKE OF THE DEPARTING SURFACE LOW EXITING THE NORTHEAST
U.S. LATE WEDNESDAY, AN IMPROVING WEATHER TREND COMMENCES GOING
INTO THURSDAY ACROSS THE EASTERN U.S. AS HIGH PRESSURE BRIEFLY
SETTLES IN ACROSS THE REGION. HOWEVER, THIS WILL BE RATHER SHORT
LIVED AS THE EXTREMELY ACTIVE WEATHER PATTERN CONTINUES WITH
ANOTHER POTENT LOW PRESSURE SYSTEM GETTING BETTER ORGANIZED ACROSS
THE SOUTH-CENTRAL U.S. BY FRIDAY MORNING IN RESPONSE TO AN
AMPLIFYING UPPER TROUGH APPROACHING FROM THE ROCKIES. THIS LOW
SHOULD TRACK IN THE GENERAL DIRECTION OF THE OHIO VALLEY AND GREAT
LAKES REGION BY SATURDAY WITH MORE BAD WEATHER EXPECTED FOR MANY
AREAS THAT WILL BE HAMMERED EARLIER IN THE WEEK. IN ADDITION, A
STRONG ARCTIC FRONT WILL HERALD THE COLDEST WEATHER OF THE SEASON
THUS FAR ACROSS MUCH OF THE NORTH-CENTRAL U.S. FOR THE SECOND HALF
OF THE WEEK AND GOING INTO THE WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
FOR THE NEXT BIG SYSTEM DEVELOPING ACROSS THE SOUTHERN PLAINS
FRIDAY, THE MODELS ALL AGREE THAT A POTENT SOUTHERN STREAM
TROUGH/SHORTWAVE EXITING THE ROCKIES THURSDAY WILL BEGIN ACQUIRING
NEGATIVE TILT BY FRIDAY EVENING ACROSS THE MIDWEST, ALLOWING RAPID
SURFACE CYCLOGENESIS TO OCCUR. THE GUIDANCE HAS ALSO SHOWN A
STRONGER TREND WITH THE SURFACE LOW AS IT APPROACHES THE GREAT
LAKES, WITH BOTH THE GFS AND ECMWF INDICATING CENTRAL PRESSURE
CLOSE TO 970 MB OVER EASTERN MICHIGAN, AND THE CMC IS SHOWING MORE
OF A TRIPLE POINT LOW DEVELOPMENT BY SATURDAY EVENING ACROSS NEW
ENGLAND. ELSEWHERE ACROSS THE NATION, THE CMC BECOMES MORE OUT OF
PHASE WITH THE MODEL CONSENSUS FROM THE WEST COAST TO THE PLAINS,
AND A MUCH STRONGER UPPER LOW OVER SOUTH-CENTRAL CANADA. THE
GUIDANCE NOW AGREES BETTER ON A SHORTWAVE APPROACHING THE PACIFIC
NORTHWEST LATE SATURDAY THAT WILL EVENTUALLY MOVE INLAND ACROSS
THE INTERMOUNTAIN WEST, WITH THE GFS GENERALLY INDICATING A MORE
PROGRESSIVE SOLUTION. FOR FRONTS AND PRESSURES, A
MULTI-DETERMINISTIC BLEND SUFFICED AS A STARTING POINT IN THE
FORECAST PROCESS, WITH MORE WEIGHTING TOWARDS THE GFS/ECMWF. THE
USE OF THE ENSEMBLE MEANS WAS GRADUALLY INCREASED TO ABOUT 40-50%
BY SUNDAY INTO MONDAY. FOR THE LAKE EFFECT SNOW LATER IN THE
FORECAST PERIOD, THE NBM APPEARED TOO LOW WITH AMOUNTS, SO THE QPF
WAS ROUGHLY DOUBLED FOR THIS REGION.
..WEATHER/HAZARDS HIGHLIGHTS
UNFORTUNATELY, ANOTHER STRONG LOW PRESSURE SYSTEM IS FORECAST TO
RAPIDLY DEVELOP OVER THE SOUTH-CENTRAL U.S. BY THURSDAY NIGHT INTO
EARLY FRIDAY, AND THIS COULD AFFECT SIMILAR AREAS OF THE CENTRAL
AND EASTERN U.S. COMPARED TO THE LOW IN THE SHORT RANGE FORECAST
PERIOD, TRACKING FROM NORTHERN TEXAS TO THE OHIO VALLEY AND THEN
THE EASTERN GREAT LAKES BASED ON THE LATEST MODEL GUIDANCE. THERE
WILL LIKELY BE A BAND OF SIGNIFICANT SNOW EXTENDING FROM MISSOURI
TO MICHIGAN ASSOCIATED WITH THE DEFORMATION ZONE/WRAPPING MOISTURE
NORTHWEST OF THE SURFACE LOW, AND THE HIGHEST PROBABILITIES OF
THIS ARE GENERALLY SOUTHEAST OF THE HIGHEST SNOWFALL TOTALS
EXPECTED WITH THE SYSTEM EARLY IN THE WEEK. GIVEN THE STRONG
PRESSURE GRADIENT THAT WILL BE IN PLACE, MANY PLACES COULD
EXPERIENCE BLIZZARD CONDITIONS. WITH STRONG COLD AIR ADVECTION IN
THE WAKE OF THIS LOW PRESSURE SYSTEM, LAKE EFFECT SNOW IS EXPECTED
TO INCREASE DOWNWIND OF THE GREAT LAKES BY THE WEEKEND, AND
POTENTIALLY HEAVY AT TIMES. ADDITIONAL ROUNDS OF HEAVY RAIN AND
STRONG TO SEVERE THUNDERSTORMS ARE ALSO LIKELY FOR MUCH OF THE
SOUTH/SOUTHEAST GOING INTO FRIDAY, AND THEN SPREADING QUICKLY
NORTHEASTWARD ALONG THE EAST COAST GOING INTO FRIDAY NIGHT AND
SATURDAY. THIS RAINFALL WILL ALSO BE FALLING OVER HIGHLY
SATURATED SOILS OWING TO RECENT RAINFALL, AND GIVEN THE QPF SIGNAL
FOR SOME 1-2 INCH RAINFALL TOTALS ACROSS PORTIONS OF THE
MID-ATLANTIC AND NORTHEAST, A SLIGHT RISK OF EXCESSIVE RAINFALL IS
PLANNED FOR THE DAY 5 PERIOD ON FRIDAY/FRIDAY NIGHT FROM EASTERN
PA TO WESTERN MA, AND A BROADER MARGINAL RISK AREA EXTENDING
SOUTHWARD ALONG THE SPINE OF THE APPALACHIANS AND A SEPARATE AREA
ACROSS PORTIONS OF KY AND TN.
IN TERMS OF TEMPERATURES, AN ARCTIC BLAST IS EXPECTED FOR THE
NORTHERN PLAINS/ROCKIES TO CLOSE OUT THE WEEK WITH WIDESPREAD
DOUBLE DIGIT SUBZERO LOWS FOR THE DAKOTAS AND INTO MONTANA, AND
SOME SUBZERO HIGHS, WITH ANOMALIES AS MUCH AS 30-40 DEGREES BELOW
NORMAL AND THE POTENTIAL FOR SOME DAILY RECORD LOWS. THE ARCTIC
AIRMASS WILL ALSO DROP SOUTHWARD WEST OF THE CONTINENTAL DIVIDE
THROUGHOUT THE CENTRAL AND NORTHERN INTERMOUNTAIN WEST, AND ALSO
SPREAD DOWN ACROSS THE CENTRAL TO EAST-CENTRAL U.S. OVER TIME, BUT
MODIFIED AS IT PROGRESSES SOUTHEASTWARD.
UPSTREAM, A CONTINUED SERIES OF HIGHLY DYNAMIC GULF OF
ALASKA/WESTERN CANADIAN AMPLIFYING SYSTEMS WILL MAINTAIN AND
PERIODICALLY REJUVENATE A HIGHLY UNSETTLED AND WINTRY PATTERN LATE
THIS WEEK FOR A GOOD PORTION OF THE WEST. THERE IS A STRONG
SIGNAL IN THE GUIDANCE FOR THIS SHORTWAVE ENERGY TO SPREAD DOWN
FROM THE PACIFIC NORTHWEST TO NORTH-CENTRAL CALIFORNIA INTO THE
SIERRA. THERE SHOULD ALSO BE WIDESPREAD TERRAIN/MOUNTAIN ENHANCED
SNOWS FARTHER INLAND ACROSS THE INTERMOUNTAIN WEST INTO THE
ROCKIES WITH CONTINUED SYSTEM PROGRESSIONS.
HAMRICK
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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