741
FXUS02 KWBC 071847
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
147 PM EST SUN JAN 07 2024
VALID 12Z WED JAN 10 2024 - 12Z SUN JAN 14 2024
...ANOTHER MAJOR STORM TO IMPACT THE EAST-CENTRAL TO EASTERN U.S.
WITH SNOW/RAIN/WIND THREATS AS AN ARCTIC BLAST DIGS THROUGH THE
NORTH-CENTRAL U.S....
..GENERAL OVERVIEW
THE POWERHOUSE LOW PRESSURE SYSTEM THAT HAMMERS THE EASTERN U.S.
EARLY IN THE WEEK IS EXPECTED TO REACH SOUTHERN ONTARIO BY
WEDNESDAY MORNING, WITH A TRAILING COLD FRONT EXITING THE EAST
COAST EXCEPT FOR NEW ENGLAND, WHERE LINGERING STRONG ONSHORE FLOW
WILL OFFER HEAVY RAIN AND HIGH WINDS. AN IMPROVING WEATHER TREND
COMMENCES IN THE WAKE OF THIS STORM SYSTEM GOING INTO THURSDAY
ACROSS THE EASTERN U.S. AS HIGH PRESSURE BRIEFLY SETTLES IN.
HOWEVER, ANOTHER POTENT LOW PRESSURE SYSTEM LIKELY GETS ORGANIZED
ACROSS THE SOUTH-CENTRAL U.S. BY FRIDAY MORNING IN RESPONSE TO AN
AMPLIFYING UPPER TROUGH APPROACHING FROM THE ROCKIES, AND THIS LOW
SHOULD TRACK IN THE GENERAL DIRECTION OF THE OHIO VALLEY AND GREAT
LAKES REGION BY NEXT WEEKEND WITH MORE BAD WEATHER EXPECTED FOR
MANY AREAS. IN ADDITION, PATTERN VARIANCE WILL RESULT IN A STRONG
ARCTIC FRONT HERALDING THE COLDEST WEATHER OF THE SEASON THUS FAR
ACROSS MUCH OF THE NORTH-CENTRAL U.S. FOR THE SECOND HALF OF THE
WEEK AND BEYOND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00/06 UTC MODEL GUIDANCE SUITE REMAINS IN GOOD OVERALL
AGREEMENT ON THE EXITING LOW PRESSURE SYSTEM ACROSS THE NORTHEAST
U.S. ON WEDNESDAY, ALTHOUGH THE GFS/UKMET REMAIN A TAD SLOWER WITH
PIVOTING THE AXIS OF THE UPPER TROUGH ACROSS NEW ENGLAND COMPARED
TO THE ECMWF/CMC. THE 12 UTC GFS/UKMET HAVE TRENDED TOWARD THE
ECMWF/CMC. FOR THE NEXT MAIN SYSTEM DEVELOPING ACROSS THE SOUTHERN
PLAINS FRIDAY, THE GFS AND TO A LESSER EXTENT THE UKMET REMAIN
SLOWER AND MORE AMPLIFIED WITH THE SUPPORTING UPPER TROUGH
COMPARED TO THE MUCH MORE PROGRESSIVE ECMWF/CMC, AND THEREFORE
CONSIDERABLE TIMING DIFFERENCES WITH THE SURFACE LOW TRACK (GFS
SLOWEST AND ECMWF FASTEST). THE ECMWF AND GEFS ENSEMBLE MEANS
REMAIN BETWEEN THESE TWO SOLUTIONS, ALBEIT WITH THE GEFS MEAN
SLIGHTLY LESS PROGRESSIVE THAN THE ECMWF ENSEMBLE MEAN. EVEN SO,
AN ENSEMBLE MEAN COMPOSITE STILL SEEM TO SERVE AS A GOOD PROXY FOR
THE EXPECTED DETERMINISTIC LOCATION OF THE SURFACE LOW WITHIN A
BROAD ENVELOPE OF PLAUSIBLE TIMING SOLUTIONS. ENERGY DIGGING TO
THE LEE OF EAST PACIFIC HIGH AMPLITUDE RIDGING TENDS TO SUPPORT
THE LESS PROGRESSIVE SOLUTIONS, WHILE VARIABLE SMALLER WAVELENGTH
SPACING WITH INDIVIDUAL SYSTEMS EMBEDDED WITHIN THE LARGER FLOW
TEND TO SUPPORT THE MORE PROGRESSIVE SIDE OF THE FORECAST
ENVELOPE. 12 UTC GUIDANCE FORECAST SPREAD HAS DECREASED TO A
DEGREE, BUT IS TILL AMPLE. HOWEVER, IT IS IMPORTANT TO NOTE THAT
DESPITE THESE UNCERTAIN TIMING DIFFERENCES, THERE CONTINUES TO BE
A GREATER THAN NORMAL SIGNAL FOR ANOTHER MAJOR SYSTEM AND
ASSOCIATED WEATHER THREATS TO DEVELOP IN A CONTINUATION OF A
HIGHLY FAVORABLE PATTERN, BUT AT THIS POINT NOT QUITE AS POTENT AS
THE LEAD EARLY WEEK STORM.
..WEATHER/HAZARDS HIGHLIGHTS
HEAVY RAIN AND STRONG WINDS WILL LIKELY BE ONGOING ACROSS CENTRAL
AND EASTERN PORTIONS OF NEW ENGLAND WEDNESDAY MORNING INTO THE
AFTERNOON AHEAD OF THE STRONG COLD FRONT EXITING THE EAST COAST.
AN IMPRESSIVE SOUTH-SOUTHEASTERLY LOW LEVEL JET AHEAD OF THE FRONT
WILL LIKELY MIX DOWN ENOUGH TO PRODUCE SURFACE WIND GUSTS IN
EXCESS OF 50 MPH AT TIMES ACROSS MAINE, AND STORM FORCE WINDS
ACROSS THE COASTAL WATERS. RAINFALL WILL BE MAXIMIZED ACROSS THE
UPSLOPE PORTIONS OF THE NORTHERN APPALACHIANS OF MAINE WHERE 1 TO
2 INCHES OF RAINFALL IS LIKELY, AND MUCH OF THIS WILL LIKELY BE
FALLING OVER AREAS WITH SNOWPACK. GIVEN SOME EXISTING UNCERTAINTY
IN SNOW LEVELS AND OVERALL PRECIPITATION TYPE, A BROAD MARGINAL
RISK AREA FOR DAY 4/WEDNESDAY REMAINS PLANNED, ALTHOUGH THIS COULD
EVENTUALLY BE UPGRADED TO A SLIGHT RISK ONCE THINGS BECOME MORE
CERTAIN. FOR THE DAY 5 PERIOD THURSDAY, NO RISK AREAS ARE PLANNED
FOR THIS FORECAST CYCLE.
LOOKING AHEAD TO THE FRIDAY-SATURDAY TIME PERIOD, ANOTHER
POTENTIALLY STRONG LOW PRESSURE SYSTEM IS LOOKING INCREASINGLY
LIKELY AND THIS COULD AFFECT SIMILAR AREAS OF THE CENTRAL AND
EASTERN U.S. COMPARED TO THE LOW ON TUESDAY/WEDNESDAY, TRACKING
FROM TEXAS TO THE GREAT LAKES BASED ON THE LATEST 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. FOCUS SLATED TO THEN
WORK ACROSS THE APPALACHIANS INTO THE INTERIOR NORTHEAST WITH
SYSTEM PROGRESSION SHOULD ALSO AGAIN FAVOR LAKE EFFECT SNOWS IN
THE WAKE. HEAVY RAIN AND STRONG THUNDERSTORMS ARE ALSO LIKELY FOR
MUCH OF THE SOUTH/SOUTHEAST LIKELY FRIDAY, BEFORE LIFTING ROBUSTLY
UP THE EASTERN SEABOARD SATURDAY. WET ANTECEDENT CONDITIONS ACROSS
THESE AREAS SUGGEST MORE WIDESPREAD RUNOFF ISSUES TO MONITOR.
IN TERMS OF TEMPERATURES, AN ARCTIC BLAST IS EXPECTED FOR THE
NORTHERN PLAINS/ROCKIES TO CLOSE OUT THE WEEK WITH WIDESPREAD
DOUBLE DIGIT BELOW ZERO LOWS FOR THE DAKOTAS AND INTO MONTANA, AND
SOME SUBZERO HIGHS, WITH ANOMALIES AS MUCH AS 40 DEGREES BELOW
NORMAL. COLD CANADIAN AIR WILL ALSO DIG WEST OF THE DIVIDE TROUGH
THE INTERMOUNTAIN WEST AND ALSO SPREAD DOWN ACROSS THE CENTRAL TO
EAST-CENTRAL U.S., DRIVEN/MODIFIED IN THE WAKE AND BETWEEN MAIN
STORM PASSAGES.
UPSTREAM, A CONTINUED SERIES OF HIGHLY DYNAMIC GULF OF
ALASKA/WESTERN CANADIAN DIGGING SYSTEMS WILL MAINTAIN AND
PERIODICALLY REJUVENATE A HIGHLY UNSETTLED/WINTRY PATTERN THIS
WEEK FOR A GOOD PORTION OF THE WEST. THERE IS A MODERATE SIGNAL TO
SPREAD DOWN FROM THE PACIFIC NORTHWEST TO NORTH-CENTRAL CALIFORNIA
INTO THE SIERRA. THERE SHOULD ALSO BE WIDESPREAD TERRAIN/MOUNTAIN
FOCUSING SNOWS FURTHER INLAND ACROSS THE INTERMOUNTAIN WEST INTO
THE ROCKIES WITH CONTINUED SYSTEM PROGRESSIONS.
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 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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