180
FXUS02 KWBC 051900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SUN JAN 5 2025
VALID 12Z WED JAN 08 2025 - 12Z SUN JAN 12 2025
..ARCTIC BLAST PERSISTS FOR THE CENTRAL/EASTERN U.S. THIS WEEK
..OVERVIEW
A QUIETER WEATHER PATTERN IS EXPECTED TO DEVELOP MID-WEEK WITH
ONLY LIGHT PRECIPITATION FORECAST ACROSS THE NATION, EXCEPT FOR IN
THE GREAT LAKES WHERE COLD NORTHWESTERLY FLOW WILL REJUVENATE LAKE
EFFECT SNOWS. HEAVIER PRECIPITATION WILL RETURN LATER THIS WEEK AS
A FRONTAL SYSTEM MOVES INTO THE WEST AND LOW PRESSURE DEVELOPS
ALONG THE GULF COAST. THE FRONTAL SYSTEM IN THE WEST WILL APPROACH
THE COAST ON FRIDAY AND MOVE ACROSS THE REGION THIS WEEKEND WITH
WIDESPREAD PRECIPITATION FROM THE NORTHWEST TO THE NORTHERN AND
CENTRAL ROCKIES. THE GULF SYSTEM IS FORECAST TO BRING WIDESPREAD
PRECIPITATION FROM THE GULF COAST TO THE SOUTHEAST LATE THIS WEEK,
AND PRECIPITATION MAY SPREAD UP THE EAST COAST AS IT MOVES OFFSHORE
THIS WEEKEND. THERE IS A SIGNIFICANT AMOUNT OF UNCERTAINTY
SURROUNDING THE EVOLUTION OF THE SYSTEM AS IT MOVES TOWARDS THE
EAST COAST, AND THE TIMING AND LOCATION OF THIS SYSTEM WILL BE
IMPORTANT FOR DETERMINING IMPACTS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON THE WEATHER PATTERN
THROUGH MID-WEEK, BUT MODEL SPREAD INCREASES SIGNIFICANTLY FRIDAY
THROUGH THE WEEKEND AS THEY TRY TO RESOLVE THE LOW PRESSURE SYSTEM
EVOLUTION OVER THE SOUTHEAST AND EAST COAST. THE ECMWF HAS SHOWN
THE BEST RUN-TO-RUN CONSISTENCY WITH THIS FEATURE WHILE THE GFS HAS
TENDED TO FLIP FLOP A BIT, AND THE CMC AND UKMET SEEM TO BE THE
FURTHEST FROM THE GENERAL MODEL CONSENSUS AND THE ENSEMBLE MEAN
SOLUTIONS. THE 00Z ECMWF AND 06Z GFS WERE IN GOOD AGREEMENT THE
TRACK AND PLACEMENT OF THE SURFACE LOW, BRINGING IT ACROSS THE
CAROLINAS AND STRENGTHENING THE LOW OFFSHORE OF THE NORTHEAST. THE
12Z GUIDANCE HAS COME IN A BIT WEAKER, AND IS FAVORING A MORE
EASTWARD TRACK, WHICH WOULD PULL THE SYSTEM AWAY FROM THE COAST AND
REDUCE POTENTIAL IMPACTS FOR THE MID-ATLANTIC AND NORTHEAST. DUE
TO SPREAD/UNCERTAINTY AND LOW PREDICTABILITY, CONFIDENCE IS LOW IN
THE FORECAST ALONG THE EAST COAST FOR SATURDAY AND SUNDAY.
A GENERAL MODEL BLEND OF THE DETERMINISTIC GFS/ECMWF/CMC/UKMET WAS
USED FOR THE FIRST TWO DAYS OF THE PERIOD (WEDNESDAY AND
THURSDAY), WITH MORE WEIGHT PLACED ON THE GFS AND ECMWF. FOR FRIDAY
ONWARDS, THE CMC AND UKMET WERE REMOVED FROM THE BLEND AND THE
ECENS AND GEFS ENSEMBLE MEANS WERE ADDED IN INCREASING AMOUNTS.
..WEATHER/HAZARDS HIGHLIGHTS
MID-WEEK, THE QUIETER WEATHER PATTERN WILL RESULT IN LIMITED
PRECIPITATION HAZARDS. LAKE EFFECT SNOWS WILL PERIODICALLY BE
REJUVENATED BY DEEP COLD SURGES, AND LIGHT TO MODEST PRECIPITATION
WILL FOCUS DOWN THROUGH THE ROCKIES AND NORTH-CENTRAL U.S. WITH AN
EMERGING SURFACE SYSTEM. THERE WILL ALSO BE CHANCES FOR
PRECIPITATION OVER PORTIONS OF THE SOUTHWEST AND SOUTHERN PLAINS
UNDERNEATH AN UPPER CLOSED LOW THAT WILL MOVE SOUTH OVER THIS
REGION. PRECIPITATION CHANCES WILL INCREASE OVER THE SOUTHERN
PLAINS, LOWER MISSISSIPPI VALLEY, AND GULF COAST BY THURSDAY AS
ENERGY FROM THE UPPER LOW SPREADS NORTHEAST. ANOMALOUS MOISTURE
WILL FOCUS OVER THE WESTERN GULF COAST AS A LOW PRESSURE SYSTEM
STRENGTHENS OVER THE WESTERN GULF, AND HEAVY PRECIPITATION WILL BE
POSSIBLE IN PORTIONS OF TEXAS AND LOUISIANA. LATEST MODEL TRENDS
SHOW INCREASING PRECIPITATION IN THIS REGION, SO A MARGINAL RISK
AREA WILL LIKELY BE ADDED TO THE DAY 5/THURSDAY EXCESSIVE RAINFALL
OUTLOOK TO ACCOUNT FOR LOCALIZED FLOOD POTENTIAL.
WHILE THE GULF LOW STRENGTHENS, COLD AIR IN PLACE OVER THE
SOUTHERN PLAINS MAY SUPPORT SOME MIXED/ICY WINTRY PRECIPITATION
WEDNESDAY AND THURSDAY DURING THE OVERNIGHT HOURS. TEMPERATURES
WILL DROP BELOW FREEZING OVERNIGHT FOR MOST OF THE STATE, AND EVEN
PORTIONS OF SOUTH TEXAS COULD BE COLD ENOUGH FOR SOME ICY
PRECIPITATION. WINTRY PRECIPITATION WILL MOVE NORTHEAST WITH THE
SYSTEM TOWARDS THE TENNESSEE VALLEY AND CENTRAL/SOUTHERN
APPALACHIANS ON FRIDAY.
AS THE GULF SYSTEM PROGRESSES, PRECIPITATION WILL SPREAD ACROSS
THE SOUTHEAST ON FRIDAY AND EXPAND NORTH ACROSS THE EASTERN THIRD
OF THE NATION FRIDAY INTO THE WEEKEND. HEAVY PRECIPITATION
POTENTIAL WILL BE STRONGLY DEPENDENT ON THE TIMING AND PLACEMENT OF
THE LOW PRESSURE SYSTEM, WHICH IS HIGHLY UNCERTAIN AT THIS TIME.
IF THE LOW MOVES QUICKLY OFFSHORE AND STRENGTHENS AWAY FROM THE
COAST, THEN IMPACTS WILL BE LIMITED, AND IMPACTS WILL BE MORE
LIKELY WITH A SLOWER LOW THAT STRENGTHENS CLOSER TO THE U.S.
COASTLINE.
THE WEATHER PATTERN WILL FAVOR THE CONTINUATION OF WELL BELOW
NORMAL TEMPERATURES EAST OF THE ROCKIES THROUGH AT LEAST THIS
WEEKEND. NOTABLE COLD IS POSSIBLE IN THE FAR NORTHERN TIER, BUT
THIS SHOULD NOT BE RECORD BREAKING. TEMPERATURE ANOMALIES OF 10-20
DEGREES BELOW NORMAL ARE ALSO LIKELY FROM THE CENTRAL PLAINS AND
MID-MISSISSIPPI/OHIO VALLEYS THROUGH THE APPALACHIANS, ESPECIALLY
AS TEMPERATURES REMAIN QUITE COLD FOR SNOW COVERED AREAS FROM A
MAJOR LEAD SHORT RANGE WINTER STORM. MEANWHILE, UPPER RIDGING IN
THE WESTERN U.S. WILL OFFER SLIGHTLY ABOVE NORMAL TEMPERATURES
PRIOR TO POSSIBLE BREAKDOWN LATER PERIOD THAT WOULD SUPPORT
ORGANIZED RAIN/TERRAIN SNOW POTENTIAL FROM THE NORTHWEST TO THE
ROCKIES.
DOLAN/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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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