119
FXUS02 KWBC 241851
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
150 PM EST SAT FEB 24 2024
VALID 12Z TUE FEB 27 2024 - 12Z SAT MAR 02 2024
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST MODEL GUIDANCE CONTINUES TO STRUGGLE FINDING A CONSENSUS ON
UPCOMING SPLIT STREAM FLOW REGIME NEXT WEEK OVER THE CONUS. TWO
CAMPS HAVE EMERGED WITH THE ECMWF/UKMET AND ECENS MEAN DEPICTING
DISTINCT NORTHERN AND SOUTHERN STREAM FLOW WITH A PROGRESSIVE,
QUICK MOVING NORTHERN STREAM TROUGH TRAVERSING THE NORTHERN TIER
OF THE COUNTRY FROM COAST TO COAST THROUGH THE EARLY-MIDDLE
FORECAST PERIOD, FOLLOWED BY A SOUTHERN STREAM WAVE THAT BEGINS AS
A CLOSED LOW OFF THE CALIFORNIA COAST THEN TRACKING FROM THE
SOUTHWEST TOWARDS THE MIDWEST THROUGH NEXT WEEK. MEANWHILE, THE
CMC/GFS AND GEFS MEAN HAVE GENERALLY CONTINUED TO SHOW LESS PHASE
SEPARATION BETWEEN THE TWO STREAMS, AND IN SOME CASES HAVE THE
NOTED NORTHERN/WEAKER SOUTHERN STREAM ENERGIES PHASE TOGETHER. THE
PRIOR DAY'S 12Z AND LATEST 00Z RUN OF THE GFS DID SHOW A TREND
TOWARDS MORE FLOW SEPARATION SIMILAR TO THE OTHER GUIDANCE
CLUSTER. HOWEVER, THE 06Z AND MOST RECENT UPDATED 12Z RUN REVERSED
THIS TREND AND SHIFTED BACK TOWARDS A SLOWER NORTHERN STREAM
TROUGH WHICH THEN PHASES WITH THE SOUTHERN STREAM WAVE OVER THE
CENTRAL U.S. THE MACHINE LEARNING MODEL SUITE FROM THE ECMWF WAS
THE FIRST TO CATCH ON TO THIS SPLIT FLOW PATTERN SEVERAL DAYS AGO
AND CONTINUES TO BACK THIS SOLUTION, PROVIDING CONFIDENCE TO
SUPPORT THE ECMWF/UKMET AND ECENS MEAN CLUSTER. DESPITE SOME
TIMING DIFFERENCES, PARTICULARLY WITH RESPECT TO A SLOWER SOUTHERN
STREAM SHORTWAVE, THE LATEST RUN OF THE ICON ALSO SHOWS SUPPORT
FOR THE FLOW SEPARATION, AS WELL AS THE 00Z CMC ENSEMBLE MEAN.
OTHERWISE, THE NEXT FEATURE OF INTEREST UPSTREAM LATER NEXT
WEEK/EARLY NEXT WEEKEND WILL BE A DEEP UPPER-LEVEL TROUGH DIGGING
SLOWLY ALONG THE WEST COAST ALLOWING FOR MULTI-DAY MOIST PACIFIC
FLOW TRANSLATING SOUTHWARD. BOTH THE DETERMINISTIC AND ENSEMBLE
GUIDANCE ARE IN GOOD GENERAL AGREEMENT ON THE THIS EVOLUTION.
THE UPDATED WPC FORECAST USED A SIMILAR BLEND TO THE PRIOR
FORECAST CONSISTING OF THE ECMWF/UKMET WITH A CONTRIBUTION FROM
THE ECENS MEAN EARLY IN THE PERIOD GIVEN THE GUIDANCE AND THOUGHT
PROCESS ON THE UPCOMING PATTERN REMAINED SIMILAR. FOLLOWING THE
REMOVAL OF THE TIME-LIMITED UKMET, THE BLEND FOR THE LATER PERIOD
RELIED ON THE ECMWF/ECENS MEAN AS WELL AS CONTINUITY. THE
PROGRESSIVE NATURE OF THE FLOW LEADS TO MORE SIGNIFICANT
TIMING/PLACEMENT CHANGES OF SHORTWAVE ENERGIES AND ASSOCIATED
SURFACE FRONTAL SYSTEMS IN THIS TIMEFRAME, AND THE INCLUSION OF
SOME CONTINUITY HELPS TO LIMIT MORE DRASTIC CHANGES WITH
INHERENTLY LOWER PREDICTABILITY.
..OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
AN UPPER RIDGE TRAVERSING THE CENTRAL AND EASTERN U.S. FOR THE
FIRST HALF OF NEXT WEEK WILL SPREAD MUCH ABOVE NORMAL TEMPERATURES
FROM THE PLAINS THROUGH THE MIDWEST AND THEN THE EAST. AN EMERGING
PRECIPITATION PATTERN DEVELOPS INTO TUESDAY/WEDNESDAY FROM THE
MIDWEST/GREAT LAKES THROUGH THE EAST TO INCLUDE SOME MODERATELY
HEAVY ACTIVITY. SPC ALSO SHOWS SOME RISK FOR SEVERE WEATHER IN
THIS PERIOD WITH POSSIBLE FOCUS ACROSS THE MID-MISSISSIPPI AND
TENNESSEE VALLEYS AND VICINITY. A POST-FRONTAL SURGE OF A COLD
CANADIAN HIGH PRESSURE IN THE WAKE OF LOW SYSTEM PASSAGE ALSO
OFFERS SOME WRAP-BACK ENHANCED SNOW POTENTIAL FROM THE UPPER
MIDWEST AND GREAT LAKES THROUGH THE NORTHEAST.
MEANWHILE, NORTHERN AND WEAKER SOUTHERN-STREAM TROUGHING FROM THE
PACIFIC LOOK TO SEPARATELY TRACK INTO THE WEST. THE NORTHERN
STREAM TROUGH WILL BRING COOLER TEMPERATURES, ELEVATION-DEPENDENT
RAIN/SNOW, AND WINDY CONDITIONS THROUGH PARTS OF THE INTERMOUNTAIN
WEST/ROCKIES THROUGH TUESDAY PASSAGE, WHILE SOUTHERN STREAM SYSTEM
EJECTION MAY BRING SOME LIGHT PRECIPITATION THE SOUTHWEST, THEN
SOUTHERN ROCKIES/PLAINS INTO MIDWEEK. DOWNSTREAM TRANSLATION MAY
THEN SUPPORT SYSTEM GENESIS, WITH LEAD RETURN MOISTURE SET TO FUEL
INCREASING RAIN/CONVECTIVE CHANCES ACROSS THE SOUTH LATER NEXT
WEEK INTO NEXT WEEKEND.
FARTHER UPSTREAM, A GROWING GUIDANCE SIGNAL IN SUPPORT OF
AMPLIFYING UPPER TROUGH DEVELOPMENT OVER THE EAST PACIFIC/WEST
COAST SEEMS TO INCREASINGLY SUPPORT CHANCES FOR SOME MODERATE TO
HEAVIER PRECIPITATION FOCUS INTO THE PACIFIC NORTHWEST MID-LATER
WEEK THAT MAY SHIFT DOWN THE COAST THROUGH CALIFORNIA LATER WEEK
AND NEXT WEEKEND TO MONITOR. A WPC DAY 5/WEDNESDAY EXCESSIVE
RAINFALL OUTLOOK MARGINAL RISK AREA WAS INTRODUCED FOR COASTAL
AREAS OF THE PACIFIC NORTHWEST TO USHER IN THIS EMERGING WET
PATTERN. THIS INCLUDES HEAVY SNOW THREATS INLAND OVER FAVORED
TERRAIN/MOUNTAINS ACROSS THE NORTHWEST/NORTHERN ROCKIES AND DOWN
WITH SOME EMPHASIS DOWN THROUGH THE SIERRA LATER PERIOD.
AS FOR ANOMALOUS TEMPERATURES, THE CENTRAL U.S. WILL SEE QUITE
WARM TEMPERATURES EARLY NEXT WEEK UNDERNEATH AN UPPER RIDGE.
TEMPERATURES OF 20-35 DEGREES ABOVE AVERAGE WILL EXPAND FROM THE
PLAINS THROUGH THE MIDWEST INTO TUESDAY. WIDESPREAD WELL ABOVE
NORMAL AND RECORD-BREAKING TEMPERATURES WILL SPREAD EASTWARD
ACROSS THE EASTERN U.S. THROUGH MIDWEEK. THE UPPER TROUGH AND WELL
DEFINED COLD FRONT PRESSING SOUTHWARD AND EASTWARD SHOULD THEN
COOL TEMPERATURES DOWN CLOSER TO NORMAL OR A FEW DEGREES BELOW
ACROSS THESE BROAD REGIONS, BUT UNSEASONABLE WARMTH SHOULD REBOUND
LATER WEEK AND THE WEEKEND BACK OVER THE CENTRAL STATES.
PUTNAM/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, 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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