478
FXUS02 KWBC 041856
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 PM EST SAT JAN 4 2025
VALID 12Z TUE JAN 7 2025 - 12Z SAT JAN 11 2025
..ARCTIC BLAST AFFECTS CENTRAL/EASTERN U.S. NEXT WEEK
19Z UPDATE: THE 12Z GUIDANCE, INCLUDING THE CMC, HAS TRENDED
TOWARDS THE CUT-OFF UPPER LOW SOLUTION NEAR THE SOUTHWESTERN U.S.,
WHEREAS YESTERDAY IT WAS STILL MORE DISAGREEABLE WITH HOW IT WOULD
EVOLVE. AT THE TIME OF FRONTS/PRESSURES PREPARATION, THE 00Z CMC
STILL HAD SOME DIFFERENCES WITH THE MODEL CONSENSUS WITH THE ARCTIC
SURFACE HIGH DISPLACED AND ALSO A SLOWER NORTHERN STREAM UPPER
TROUGH PASSAGE ACROSS THE GREAT LAKES AND OHIO VALLEY REGION LATE
IN THE WEEK. THEREFORE, THE WPC FORECAST WAS HEDGED MORE IN THE
DIRECTION OF THE ECMWF/UKMET/GFS, ALONG WITH SOME PREVIOUS
CONTINUITY FOR THE TUESDAY-THURSDAY TIME PERIOD, AND THEN GRADUALLY
INCREASED CONTRIBUTIONS FROM THE GEFS AND EC MEANS TO ABOUT HALF BY
FRIDAY/SATURDAY.
THE 13Z NBM, SIMILAR TO YESTERDAY, IS MUCH TOO LIGHT WITH EXPECTED
LAKE EFFECT SNOWS FOR THE MIDDLE OF THE WEEK, SO THE QPF WAS MAINLY
BASED ON THE GFS/ECMWF WITH SOME UPWARD ADJUSTMENT FROM THERE.
ELSEWHERE ACROSS THE CONTINENTAL U.S. THE NBM WAS MORE REASONABLE
AND BLENDED WITH SOME OPERATIONAL GFS/ECMWF AND A LITTLE LESS OF
THE CMC. IT IS IMPORTANT TO NOTE A GENERAL UPWARD TREND IN QPF THIS
CYCLE FOR THE END OF NEXT WEEK WITH A POTENTIAL LOW PRESSURE SYSTEM
DEVELOPING OVER THE NORTHERN GULF, AND THIS COULD BE THE NEXT
IMPACTFUL WEATHER SYSTEM TO MONITOR IF TRENDS CONTINUE UPWARD IN
FUTURE MODEL RUNS. STAY TUNED FOR ADDITIONAL INFORMATION AS THE
EVENT BECOMES MORE RESOLVED IN THE DAYS AHEAD. THE PREVIOUS
FORECAST DISCUSSION IS APPENDED BELOW FOR REFERENCE. /HAMRICK
---------------------------
..OVERVIEW
THE WEATHER PATTERN FOR NEXT 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 IS ALSO AN
UNCERTAIN SIGNAL FOR EXTENT OF FAR SOUTH-CENTRAL U.S. RAIN/WINTER
PRECIPITATION DEVELOPMENT INTO LATER NEXT WEEK TO MONITOR.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE FORECAST SPREAD AND UNCERTAINTY OVERALL SEEM LESS OF AN
ISSUE THAN NORMAL WELL INTO MED-RANGE TIME SCALES, INCLUDING FOR
THE LATEST 00 UTC CYCLE. A COMPOSITE OF BEST CLUSTERED GFS/ECMWF
MODEL AND ENSEMBLE SOLUTIONS ALONG WITH THE NATIONAL BLEND OF
MODELS (NBM) FOR THE MOST PART SEEMS TO PROVIDE A CONSISTENT AND
REASONABLE FORECAST BASIS. THIS SOLUTION MAINTAINS GREAT WPC
PRODUCT CONTINUITY AND REMAINS BEST IN LINE WITH MACHINE LEARNING
GUIDANCE. ALTERNATELY, LESS SUPPORTED BUT STILL PLAUSIBLE RECENT
CANADIAN RUNS HAVE BEEN THE LEAST ALIGNED WITH THIS COMPOSITE WITH
DEVELOPMENT OF A LESS AMPLIFIED/MORE PROGRESSIVE SOUTHERN STREAM
AND A MORE AMPLIFIED/LESS PROGRESSIVE NORTHERN STREAM IN SPLIT FLOW
AS SYSTEMS DIG TO THE LEE OF FULL LATITUDE UPPER RIDGING BUILT
ALONG/OFF THE WEST COAST OF NORTH AMERICA.
..WEATHER/HAZARDS HIGHLIGHTS
GREAT LAKE EFFECT SNOWS WILL BE PERIODICALLY REJUVENATED WITH DEEP COLD
SURGES NEXT WEEK GIVEN AMPLE FLOW AMPLITUDE. 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 NEXT WEEK, AND
EVENTUALLY THE 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 A SEPARATED
SOUTHERN STREAM. AN EMERGING PRECIPITATION PATTERN MAY UNFOLD INTO
LATER NEXT WEEK, AND WITH COLD AIR IN PLACE FROM TEXAS EASTWARD,
SOME AREAS MAY NEED TO MONITOR ANY ONSET OF WINTRY PRECIPITATION.
IN TERMS OF THE EXCESSIVE RAINFALL OUTLOOKS, NO RISK AREAS ARE
WARRANTED FOR EITHER DAY 4 OR DAY 5 GIVEN A PAUCITY OF DEEP
MOISTURE ACROSS THE COUNTRY.
COLDER THAN NORMAL TEMPERATURES ARE LIKELY 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 NEXT
WEEK, 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.
SCHICHTEL/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 (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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