822
FXUS02 KWBC 060713
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
213 AM EST MON JAN 6 2025
VALID 12Z THU JAN 09 2025 - 12Z MON JAN 13 2025
..ARCTIC BLAST PERSISTS FOR THE CENTRAL/EASTERN U.S. THIS WEEK
..OVERVIEW
LINGERING COLD NORTHWESTERLY FLOW WILL STILL SUPPORT GREAT LAKE
EFFECT SNOWS INTO LATER THIS WEEK. MEANWHILE, ORGANZIED
PRECIPITATION WILL RETURN LATER THIS WEEK AS A FRONTAL SYSTEM MOVES
INTO THE WEST AND LOW PRESSURE DEVELOPS OFF 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
DOWNSTREAM GULF SYSTEM IS TRICKER GIVEN UNCERTAIN SOUTHERN STREAM
UPPER TROUGH ENERGY EJECTION FROM THE SOUTHWEST U.S./NORTHERN
MEXICO. THE PATTERN EVENTUALLY DOES SEEM TO SUPPORT THE DEVELOPMENT
OF 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 OVER THE GULF
AND ESPECIALLY AS IT MOVES TOWARDS/UP THE EAST COAST AND WESTERN
ATLANTIC, AND THE TIMING AND LOCATION OF THIS SYSTEM WILL BE
IMPORTANT FOR DETERMINING IMPACTS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
RECENT MODELS AND ENSEMBLES CONTINUE THROUGH THE LATEST 00 UTC
VERSIONS TO OFFER QUITE A RUN OF LESS THAN STELLAR CYCLE TO CYCLE
FORECAST CONTINUITY, WITH SYSTEM TIMINGS AND SPLIT FLOW
PHASINGS/INTERACTIONS VARIANCES THAT SPAN THE ENTIRE MED-RANGE
FORCAST PERIOD. GIVEN GREATER THAN NORMAL UNCERTAINTIES, OPTED TO
INVOKE AN ENSEMBLE MEAN AND COMPOSITE FORECAST PLAN APPROACH WITH
USAGE OF GUIDANCE FROM A BLEND OF THE GEFS/ECMWF ENSEMBLE MEAN AND
THE NATIONAL BLEND OF MODELS. THIS SEEMS TO BEST CAPTURE GUIDANCE
THAT BEST MAINTAINS WPC PRODUCT AND THREAT MESSAGING CONTINUITY
WITH DEPICTION OF ONE POSSIBLE SUBSET OF SYSTEM TIMINGS, ALBEIT IN
REASONABLY SIMILAR MAIN GUIDANCE STORM TRACKS.
..WEATHER/HAZARDS HIGHLIGHTS
LAKE EFFECT SNOWS WILL PERIODICALLY BE REJUVENATED BY DEEP COLD
SURGES INTO LATER THIS WEEK AS LIGHT TO MODEST PRECIPITATION WILL
FOCUS DOWN THROUGH THE ROCKIES AND NORTH-CENTRAL U.S. WITH AN
FORCASSURFACE SYSTEM GENESIS. THERE WILL ALSO BE CHANCES FOR
PRECIPITATION OVER PORTIONS OF THE SOUTHWEST AND SOUTHERN PLAINS
WITH RETURN FLOW RESPONSE AS AN UPPER CLOSED LOW SETTLES AND
APPROACHES. 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. WHILE DEEPEST
INSTABILITY AND HEAVIEST RAINS MAY FOCUS OFFSHORE, GUIDANCE SHOWS
AMPLE WESTERN THEN CENTRAL GULF COAST STATE PRECIPITATION
POTENTIAL, SO MARGINAL RISK AREAS HAVE BEEN INTRODUCED TO THE DAY
4/THURSDAY AND DAY 5/FRIDAY WPC EXCESSIVE RAINFALL OUTLOOK TO
ACCOUNT FOR LOCALIZED FLOOD POTENTIAL.
WHILE THE GULF LOW MODERATLY STRENGTHENS,COLD AIR WELL IN PLACE
OVER THE SOUTHERN PLAINS MAY SUPPORT SOME MIXED/ICY WINTRY
PRECIPITATION INTO THURSDAY. 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 MAY TRANSLATE WITH THE SYSTEM TOWARDS THE TENNESSEE
VALLEY AND CENTRAL/SOUTHERN APPALACHIANS/SOUTHEAST ON FRIDAY.
AS THE GULF SYSTEM PROGRESSES, PRECIPITATION MAY EXPAND
NORTHEASTWARD ACROSS THE EAST FRIDAY INTO SATURDAY. 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 THIS WEK FOR SNOW COVERED AREAS
FROM AN ONGOING MAJOR LEAD WINTER STORM. MEANWHILE, UPPER RIDGING
IN THE WESTERN U.S. WILL OFFER SLIGHTLY ABOVE NORMAL TEMPERATURES
PRIOR TO BREAKDOWN HEADING INTO THE WEEKEND.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page