455
FXUS02 KWBC 070658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 AM EST SUN JAN 7 2024
VALID 12Z WED JAN 10 2024 - 12Z SUN JAN 14 2024
...ANOTHER LOW PRESSURE SYSTEM IS LIKELY TO CLOSE OUT THE WORK
WEEK ACROSS THE CENTRAL AND EASTERN U.S. WITH MORE WIND, SNOW, AND
HEAVY RAIN, AND AN ARCTIC BLAST FOR THE NORTHERN PLAINS...
..GENERAL OVERVIEW
THE POWERFUL LOW PRESSURE SYSTEM THAT HAMMERS THE EASTERN U.S.
EARLY IN THE WEEK IS EXPECTED TO REACH SOUTHERN ONTARIO BY
WEDNESDAY MORNING, WITH THE COLD FRONT EXITING THE EAST COAST
EXCEPT FOR NEW ENGLAND, WHERE STRONG ONSHORE FLOW WILL PRODUCE
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, A PATTERN CHANGE 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 00Z MODEL GUIDANCE SUITE REMAINS IN GOOD OVERALL AGREEMENT ON
THE EXITING LOW PRESSURE SYSTEM ACROSS THE NORTHEAST U.S. ON
WEDNESDAY, ALTHOUGH THE GFS IS A LITTLE SLOWER WITH PIVOTING THE
AXIS OF THE UPPER TROUGH ACROSS NEW ENGLAND COMPARED TO THE
ECMWF/CMC. THE 00Z CMC HAS TRENDED IN LINE WITH THE MODEL
CONSENSUS, BUT AT THE TIME OF FRONTS/PRESSURES PREPARATION, THE
12Z CMC WAS CONSIDERABLY FASTER WITH THE TRAILING TROUGH OVER THE
MIDWEST AND OHIO VALLEY THROUGH THURSDAY, SO THE MODEL BLEND WAS
INITIALIZED FROM A GFS/ECMWF/UKMET BLEND THROUGH THE END OF THE
WEEK. FOR THE NEXT SYSTEM DEVELOPING ACROSS THE SOUTHERN PLAINS
FRIDAY, THE GFS IS SLOWER AND MORE AMPLIFIED WITH THE 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 BY FRIDAY NIGHT). BOTH THE EC AND GEFS
ENSEMBLE MEANS ARE BETWEEN THESE TWO SOLUTIONS, AND THEREFORE
THESE SERVED AS A GOOD PROXY FOR THE EXPECTED LOCATION OF THE
SURFACE LOW. MODEL SPREAD BECOMES HIGH ACROSS THE EASTERN PACIFIC
AND ADJACENT PORTIONS OF THE WEST GOING INTO NEXT WEEKEND, AND
THIS LEADS TO BELOW AVERAGE CONFIDENCE FOR THAT REGION. THE
ENSEMBLE MEANS ACCOUNTED FOR 40-60% OF THE FORECAST BLEND GOING
INTO NEXT WEEKEND TO ACCOUNT FOR THE GROWING MODEL DIFFERENCES.
..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 SOME SNOWPACK. GIVEN SOME EXISTING
UNCERTAINTY IN SNOW LEVELS AND OVERALL PRECIPITATION TYPE, A BROAD
MARGINAL RISK AREA FOR DAY 4 IS 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 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. HEAVY RAIN AND STRONG THUNDERSTORMS ARE ALSO
LIKELY FOR MUCH OF THE DEEP SOUTH AND EXTENDING EASTWARD ACROSS
PORTIONS OF THE CAROLINAS.
IN TERMS OF TEMPERATURES, AN ARCTIC BLAST IS EXPECTED FOR THE
NORTHERN PLAINS TO CLOSE OUT NEXT WEEK WITH WIDESPREAD SUBZERO
LOWS FOR THE DAKOTAS AND INTO MONTANA, AND HIGHS ONLY IN THE 0S
AND 10S FOR MANY OF THOSE SAME AREAS, WITH ANOMALIES UPWARD TO 30
DEGREES BELOW NORMAL. SOME SUBZERO HIGHS ARE LIKELY FOR NORTHERN
MONTANA INTO NORTH DAKOTA. UPSTREAM, A CONTINUED SERIES OF HIGHLY
DYNAMIC PACIFIC SYSTEMS WILL MAINTAIN AND PERIODICALLY REJUVENATE
A HIGHLY UNSETTLED/WINTRY PATTERN NEXT WEEK FOR A GOOD PORTION OF
THE WEST. THERE IS A MODERATE TO LOCALLY HEAVIER PRECIPITATION
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
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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