328
FXUS02 KWBC 050711
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
211 AM 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
THE WEATHER PATTERN INTO MID-LATER THIS WEEK ACROSS MUCH OF THE
NATION WILL QUIET DOWN IN TERMS OF PRECIPITATION ASIDE FROM
PERIODIC GREAT LAKE EFFECT SNOW ENHANCEMENT WITH REINFORCEMENT OF
WIDESPREAD ARCTIC FLOW AND SOME AREAS OF MAINLY LIGHT PRECIPITATION
IN THE WESTERN AND CENTRAL U.S., BUT MUCH COLDER THAN AVERAGE
TEMPERATURES WILL PERSIST IN MOST AREAS FROM THE ROCKIES EASTWARD.
THERE THEN REMAINS AN UNCERTAIN SIGNAL FOR EXTENT OF SOUTH-CENTRAL
U.S. RAIN/WINTER PRECIPITATION DEVELOPMENT TO MONITOR THAT LEADS
INTO A POTENTIALLY STORMY/WINTRY PATTERN OUT THROUGH THE SOUTH AND
EAST CAOST TO MONITOR HEADING INTO/THROUGH NEXT WEEKEND AS GUIDANCE
IS HAVING TROUBLE WITH PROGRESSIONS AND POTENTIAL INTERACTIONS OF
MAIN SYSTEMS WITHIN SEPARATED NORTHERN AND SOUTHERN STREAM FLOWS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE SOLUTIONS REMAIN REASONABLY WELL CLUSTERED
VALID FOR WEDNESDAY/THURSDAY AND A GFS/ECMWF/CANADIAN/UKMET
COMPOSITE MODEL BLEND SEEMS TO MITIGATE MUCH OF LINGERING SMALLER
SCALE VARIANCES IN WELL DEFINED SPLIT FLOW OVER THE NATION AS CONSISTENT
WITH INDIVIDUAL UNCERTAINTIES. HOWEVER, FORECAST SPREAD AND CYCLE
TO CYCLE CONTINUITY ISSUES HAVE SIGNIFICANTLY INCREASED HEADING
INTO AND THROUGH NEXT WEEKEND IN POTENTIALLY MORE ACTIVE FLOW AS
GUIDANCE GRAPPLES WITH MAJOR STREAM PHASING AND SYSTEM TIMING/FOCUS
DIFFERENCES IN A PATTERN WITH RAPIDLY LOWERING PREDICTABILITY OVER
TIME. THIS SEEMS EVIDENT WITH THE MODELS, ENSEMBLES AND MACHINE
LEARNING GUIDANCE. ACCORDINGLY, WPC MEDIUM RANGE PRODUCTS VALID
FOR THIS TIME FRAME WERE PRIMARILY DERIVED FROM THE NATIONAL BLEND
OF MODELS AS ADJUSTED MAINLY TOWARD THE ECMWF ENSEMBLE MEAN AS THIS
COMBINATION SEEMED TO BEST MAINTAIN WPC CONTINUITY AND REASONINGS
PENDING UPCOMING STABILIZATION OF A MORE COMMON GUIDANCE SIGNAL.
THE LATEST 00 UTC GUIDANCE CYCLE DOES NOT SEEM TO YET PROVIDE THIS.
..WEATHER/HAZARDS HIGHLIGHTS
IT DOES STILL REMAIN THE CASE THAT GREAT LAKE EFFECT SNOWS WILL BE
PERIODICALLY REJUVENATED WITH DEEP COLD SURGES THIS WEEK GIVEN
ONGOING FLOW SUPPORT. THE NBM RUNS REMAIN CHARACTERISTICALLY
UNDERDONE WITH THIS POTENTIAL, LEADING TO MANUAL CORRECTIVE
ADJUSTMENTS. LIGHT TO MODEST PRECIPITATION INCLUDING ELEVATION SNOW
WILL SPREAD FOCUS DOWN THROUGH THE ROCKIES AND NORTH-CENTRAL U.S.
WITH AN EMERGING SURFACE SYSTEM. FARTHER SOUTH, THERE ARE SOME
CHANCES FOR PRECIPITATION FROM THE SOUTHWEST TO SOUTHERN PLAINS AND
LOWER MISSISSIPPI VALLEY AND VICINITY DEPENDENT ON UNCERTAIN
TIMING/EJECTION OF ENERGIES IN AN AT LEAST QUITE SEPARATED
SOUTHERN STREAM AND AMPLIFYING NORTHERN STREAM FLOW. AN EMERGING
PRECIPITATION PATTERN MAY UNFOLD INTO LATER WEEK, AND WITH COLD
AIR IN PLACE FROM TEXAS EASTWARD, SOME AREAS MAY NEED TO MONITOR ONSET
OF WINTRY PRECIPITATION. IN TERMS OF THE WPC EXCESSIVE RAINFALL
OUTLOOKS, NO RISK AREAS SEEMED WARRANTED FOR EITHER DAY 4/WEDNESDAY
OR DAY 5/THURSDAY GIVEN A PAUCITY OF DEEP MOISTURE AND INSTABILITY
ACROSS THE COUNTRY, BUT GUIDANCE SUGGESTS HEAVIER PRECIPITATION
POTENTIAL TO MONITOR OVER THE WEST GULF COAST STATES. THERE ARE
THEN A FEW SUBSEQUENT DOWNSTREAM HAZARDOUS SCENARIOS OVER THE
AMBIENT COLD SOUTH AND EAST COAST STATES TO MONITOR HEADING
INTO/THROUGH NEXT WEEKEND. THESE PRIMARILY REVOLVE AROUND QUITE
UNCERTAIN APPROACH AND INTERACTIONS OF ORGANIZED SYSTEMS IN TWO
STREAMS. SOME GUIDANCE SHOW A THREAT FOR POTENTIALLY SIGNIFICANT
WINTER STORM DEVELOPMENT AND TRACK VERSUS MUCH MORE BENIGN
SOLUTIONS. WILL CONTINUE TO MONITOR FOR A STRONGER SIGNAL, BUT FOR
NOW IT SEEMS PRUDENT TO PREPARE/RECOGNIZE FOR THE THREAT POTENTIAL.
COLDER THAN NORMAL TEMPERATURES WILL PERSIST ACROSS THE CENTRAL
AND EASTERN U.S. UNDERNEATH ROUNDS OF UPPER TROUGHING AND WITH COLD
SURFACE HIGH PRESSURE SYSTEMS. NOTABLE COLD IS POSSIBLE IN THE FAR
NORTHERN TIER, WITH HIGH TEMPERATURES BARELY REACHING 0F AND LOWS
IN THE -10S FOR SOME AREAS. THIS SHOULD NOT BE RECORD BREAKING, BUT
THE COLD COULD STILL BE HAZARDOUS AS WIND CHILL VALUES MAY DIP
INTO THE -20S AND -30S. 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 ALSO SUPPORT ORGANIZED
RAIN/TERRAIN SNOW POTENTIAL ACROSS THE PACIFIC NORTHWEST/NORTHWEST.
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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