297
FXUS02 KWBC 060758
PMDEPD
EXTENDED FORECAST DISCUSSION...AMENDED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 AM EST SAT JAN 6 2024
VALID 12Z TUE JAN 9 2024 - 12Z SAT JAN 13 2024
***INTENSE LOW PRESSURE TO BRING WIDESPREAD RAIN, WIND, AND SNOW
FOR MUCH OF THE EASTERN HALF OF THE NATION THROUGH WEDNESDAY,
FOLLOWED BY AN ARCTIC AIRMASS SETTLING SOUTH ACROSS THE NORTHERN
PLAINS***
..GENERAL OVERVIEW
THE WEATHER PATTERN ACROSS THE CONTINENTAL U.S. WILL CONTINUE TO
BE EXTREMELY ACTIVE WITH MULTIPLE HIGH IMPACT WEATHER EVENTS
EXPECTED NEXT WEEK. THE FIRST AND BIGGEST EVENT WILL BE THE
RAPIDLY DEEPENING SURFACE LOW ACROSS THE SOUTH-CENTRAL U.S. THAT
WILL QUICKLY REACH THE GREAT LAKES AND NORTHEAST BY WEDNESDAY
MORNING, WITH WIDESPREAD HEAVY RAIN AND STRONG WINDS ACCOMPANYING
IT, AND POTENTIAL BLIZZARD CONDITIONS NORTHWEST OF THE LOW TRACK.
ONCE THIS STORM DEPARTS, AN ARCTIC FRONT WILL HERALD THE ARRIVAL
OF THE COLDEST TEMPERATURES SO FAR THIS SEASON ACROSS THE
NORTH-CENTRAL U.S. WITH A PATTERN CHANGE EMERGING. THERE ARE ALSO
INCREASING PROSPECTS FOR ANOTHER WELL ORGANIZED STORM SYSTEM TO
DEVELOP OVER THE DEEP SOUTH/GULF COAST REGION BY THE END OF THE
WEEK THAT COULD VERY WELL PRODUCE MORE IMPACTFUL WEATHER FOR THE
EASTERN U.S. BY SATURDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE NOW AGREES VERY WELL ON THE INTENSITY
AND OVERALL EVOLUTION OF THE MAJOR EASTERN U.S. STORM SYSTEM
DURING THE TUESDAY-WEDNESDAY TIME PERIOD, AND THE CMC HAS TRENDED
CLOSER TO THE MODEL CONSENSUS COMPARED TO YESTERDAY, WHERE THIS
SOLUTION WAS WELL SOUTH OF THE OTHER GUIDANCE. THE MODELS AGREE
THAT THE LOW SHOULD BOTTOM OUT IN THE HIGH 970S TO LOW 980S FOR
PRESSURE. FOR THE PACIFIC SYSTEM MOVING IN ACROSS THE
NORTHWESTERN U.S., SOME DIFFERENCES BECOME APPARENT AS THE
SHORTWAVE REACHES THE GREAT LAKES, WITH THE UKMET WEAKER AND MORE
SUPPRESSED WITH THE SURFACE LOW. LOOKING AHEAD TO THE END OF THE
WEEK, THE CMC IS FASTER WITH THE SOUTHERN STREAM SHORTWAVE
EJECTING ACROSS THE SOUTHERN PLAINS, AND THE GFS IS THE SLOWER AND
STRONGER SOLUTION WITH THE ECMWF BETWEEN THESE TWO SOLUTIONS.
THIS TROUGH WILL BE THE MAIN DRIVER FOR THE NEXT ORGANIZED STORM
TO AFFECT THE EASTERN U.S. BY THE END OF THE FORECAST PERIOD. THE
FRONTS/PRESSURES WERE PRIMARILY DERIVED FROM A MULTI-DETERMINISTIC
MODEL BLEND THROUGH WEDNESDAY, AND THEN A GRADUALLY INCREASING
PERCENTAGE OF THE ENSEMBLE MEANS TO ACCOUNT FOR 40-50% OF THE
FORECAST BY NEXT SATURDAY.
..WEATHER/HAZARDS HIGHLIGHTS
CONFIDENCE CONTINUES TO INCREASE FOR A HIGHLY IMPACTFUL EVENT
SPANNING FROM TEXAS TO THE GREAT LAKES AND NORTHEAST U.S. EARLY IN
THE WEEK AS A SURFACE LOW BECOMES ANOMALOUSLY STRONG OVER ARKANSAS
AND THEN LIFTS NORTHEAST TOWARDS THE EASTERN GREAT LAKES BY
WEDNESDAY MORNING. HEAVY RAINFALL WILL INDEED BE ONE OF THE
THINGS MAKING WEATHER HEADLINES AS A VERY STRONG LOW LEVEL JET
ADVECTS DEEP GULF OF MEXICO MOISTURE NORTHWARD ACROSS THE EAST
COAST STATES ON TUESDAY. WIDESPREAD 1-3 INCH RAINFALL TOTALS ARE
LIKELY FROM THE SOUTHERN APPALACHIANS TO SOUTHERN NEW ENGLAND,
WITH SCATTERED HIGHER AMOUNTS POSSIBLE. THE NEW DAY 4 OUTLOOK
CONTINUES WITH A SLIGHT RISK AREA STRETCHED FROM THE SOUTHERN
APPALACHIANS TO SOUTHERN NEW ENGLAND, AND MAINTAINING THE EXISTING
MODERATE RISK AREA BETWEEN PHILADELPHIA AND NEW YORK CITY, WHERE
THERE IS A STRONG SIGNAL FOR 2 TO 3 INCH RAINFALL TOTALS DURING
THIS TIME WITH IMPRESSIVE IVT VALUES EXPECTED FROM THE WESTERN
ATLANTIC. PARTS OF THIS REGION MAY ALSO HAVE SOME SNOW ON THE
GROUND AT THE ONSET OF THIS EVENT, AND THIS WILL TEND TO BE AN
AGGRAVATING FACTOR IN THE FLOODING POTENTIAL ALONG WITH REDUCED
FLASH FLOOD GUIDANCE. A BROADER MARGINAL RISK AREA INCLUDES ALL
AREAS FROM SOUTHERN GEORGIA TO SOUTHERN NEW HAMPSHIRE.
IN ADDITION TO THE HEAVY RAINFALL WILL BE THE INCREASING THREAT OF
STRONG TO SEVERE THUNDERSTORMS IN THE WARM SECTOR OF THE LOW WHERE
THE BEST COMBINATION OF KINEMATICS AND INSTABILITY WILL EXIST, AND
THIS IS EXPECTED FROM NORTHERN FLORIDA TO SOUTHEASTERN NORTH
CAROLINA ON TUESDAY. ON THE NORTHWEST SIDE OF THE LOW WILL BE THE
INCREASING PROSPECTS FOR AN IMPACTFUL WINTER STORM FROM NORTHERN
MISSOURI TO MICHIGAN, AND GIVEN THE STRONG PRESSURE GRADIENT
EXPECTED, THERE WILL LIKELY BE SOME BLIZZARD CONDITIONS AT TIMES.
WIDESPREAD WINDY CONDITIONS ARE EXPECTED ACROSS MUCH OF THE
EASTERN HALF OF THE NATION TUESDAY AND GOING INTO WEDNESDAY WITH
WINDS GUSTING 30-50 MPH AT TIMES, AND PERHAPS EVEN HIGHER ACROSS
THE HIGHEST TERRAIN OF THE CENTRAL/SOUTHERN APPALACHIANS.
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 NEXT WEEK FOR A GOOD PORTION OF THE
WEST. THERE IS A MODERATE TO LOCALLY HEAVIER PRECIPITATION SIGNAL
FOCUS 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.
LOOKING AHEAD TO THE FRIDAY-SATURDAY TIME PERIOD, IT IS LOOKING
MORE LIKELY THAT ANOTHER POTENTIALLY STRONG LOW PRESSURE SYSTEM
COULD AFFECT SIMILAR AREAS OF THE CENTRAL AND EASTERN U.S.
COMPARED TO THE LOW ON TUESDAY, TRACKING FROM TEXAS TO THE GREAT
LAKES BASED ON THE LATEST GUIDANCE. THIS WOULD ONCE AGAIN
INCREASE THE POTENTIAL FOR STRONG THUNDERSTORMS, HEAVY RAINFALL,
AND WINTER WEATHER TO CLOSE OUT THE WEEK, AND THIS WILL CONTINUE
TO BE MONITORED CLOSELY.
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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