379
FXUS02 KWBC 110701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT MON MAR 11 2024
VALID 12Z THU MAR 14 2024 - 12Z MON MAR 18 2024
...HEAVY SNOWS POSSIBLE ACROSS PARTS OF THE CENTRAL-SOUTHERN
ROCKIES ON THURSDAY INTO FRIDAY...
..HEAVY RAINFALL POTENTIAL RETURNS TO THE SOUTH LATE THIS WEEK
..OVERVIEW
THE GENERAL FLOW OVER THE CONUS WILL TREND MUCH MORE AMPLIFIED
DURING THE MEDIUM RANGE PERIOD AS TROUGHING OVER THE WEST DIGS
SOUTHWARD AND CLOSES OFF A DEEP UPPER LOW OVER THE SOUTHWEST WHICH
MEANDERS IN PLACE FOR MUCH OF THE PERIOD. THIS WOULD PROMOTE A
MULTI-DAY PERIOD OF HEAVY RAINFALL POTENTIAL ACROSS PARTS OF THE
SOUTHERN U.S. LATE THIS WEEK AND INTO THE WEEKEND. ELSEWHERE,
NORTHERN STREAM ENERGY WILL AMPLIFY ACROSS THE UPPER MIDWEST/GREAT
LAKES NEXT WEEKEND, AS A STRONG RIDGE SHIFTS OVER THE WEST COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THERE REMAINS GOOD AGREEMENT ON THE OVERALL LARGE SCALE VERY
AMPLIFIED PATTERN IN THE LATEST GUIDANCE/ENSEMBLES, BUT STILL SOME
CONSIDERABLE DIFFERENCES IN THE DETAILS WITH IMPLICATIONS ON
SENSIBLE WEATHER IMPACTS, ESPECIALLY CONCERNING QPF AMOUNTS AND
COVERAGE ACROSS THE SOUTH. THERE IS LOTS OF UNCERTAINTY REGARDING
MULTIPLE STREAMS OF ENERGY THROUGH THE UPPER MIDWEST/GREAT LAKES
FRIDAY-MONDAY. FOR FRIDAY-SATURDAY, THE ECMWF, GFS, AND ENSEMBLES
SEEM REASONABLY CLUSTERED, BUT THE CMC WAS NOTABLY
FASTER/DIFFERENT WITH ONE SHORTWAVE AS IT DROPPED INTO THE UPPER
MIDWEST. RECENT RUNS OF THE ECMWF (INCLUDING TONIGHTS NEW 00Z RUN)
SUGGESTS A MORE DIGGING SHORTWAVE NEXT SUNDAY-MONDAY WHICH MAY BE
ENOUGH TO PICK UP THE SOUTHWEST LOW AND BEGIN TO BRING THAT ENERGY
EASTWARD BY EARLY MONDAY. AT THIS POINT, THERE IS BETTER SUPPORT
(FROM THE ENSEMBLES AND ECMWF-BASED AI MODELS) FOR MORE SEPARATION
OF THE TWO STREAMS ALLOWING THE UPPER LOW TO LINGER IN PLACE OVER
THE SOUTHWEST/FAR NORTHERN MEXICO THROUGH AT LEAST MONDAY.
HOWEVER, SOME PRIOR RUNS OF THE GFS HAVE SHOWN A SIMILAR EVOLUTION
TO THE CURRENT ECMWF SO THERE IS STILL A GREAT DEAL OF
UNCERTAINTY. GIVEN THE BETTER SUPPORT FOR SOME LINGERING
ENERGY/LOW TO HOLD BACK, THE WPC PROGS FOR DAYS 6 AND 7 TRENDED
AWAY FROM THE ECMWF LATE PERIOD AND MORE TOWARDS THE ENSEMBLE
MEANS WITH THE GFS. THE EARLY PERIODS USED A BLEND OF THE ECMWF,
CMC, AND GFS (BEFORE THE ABOVE NOTED ISSUES WITH THE CMC). THE
UKMET WAS NOT USED IN THE BLEND TONIGHT AS IT WAS MUCH STRONGER
WITH INITIAL ENERGY EJECTING INTO THE PLAINS ON THURSDAY. OVERALL,
GOOD CONTINUITY WAS MAINTAINED WITH THE PREVIOUS WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
A WINTER STORM WILL BE ONGOING ACROSS PARTS OF THE
CENTRAL-SOUTHERN ROCKIES AS THE PERIOD BEGINS THURSDAY, WITH
POSSIBLY SIGNIFICANT SNOWFALL IN THE HIGHEST TERRAIN OF COLORADO,
AND MORE UNCERTAIN POTENTIAL FOR NOTABLE SNOWS ACROSS THE FRONT
RANGE URBAN CORRIDOR AS WELL. SNOWS SHOULD SHIFT SOUTHWARD INTO
NEW MEXICO BY FRIDAY. MEANWHILE, A FRONT DRAPED ACROSS THE MIDWEST
WILL SUPPORT SOME INCREASING PRECIPITATION ON THURSDAY AND
ALTHOUGH THERE WILL BE AMPLE MOISTURE AND INSTABILITY PRESENT NEAR
THE FRONT FOR EFFICIENT RAINFALL TO DEVELOP, DRY ANTECEDENT
CONDITIONS SHOULD KEEP THE OVERALL EXCESSIVE RAINFALL RISK TO
SUB-MARGINAL LEVELS. TO THE SOUTH, MOISTURE STREAMING AHEAD OF THE
STAGNANT LOW OVER THE SOUTHWEST WILL SUPPORT A LIKELY MULTI-DAY
HEAVY RAINFALL THREAT ACROSS THE SOUTH. THERE REMAINS PLENTY OF
UNCERTAINTY IN THE EXACT PLACMENT OF THE HIGHEST QPF, BUT THERE IS
SUPPORT IN THE DYNAMICS FOR FAIRLY BROAD SLIGHT RISK AREAS ON THE
DAYS 4 AND 5 EXCESSIVE RAINFALL OUTLOOKS. FOR DAY 4, THE SLIGHT
EXTENDS FROM NORTHEAST TEXAS/SOUTHEAST OKLAHOMA AND COVERING MUCH
OF ARKANSAS, WITH A SHIFT TO THE SOUTH AND EAST ON DAY 5 MORE INTO
LOUISIANA AND THE CENTRAL GULF COAST STATES. SEVERE WEATHER IS
ALSO A THREAT WITH THIS CONVECTIVE ACTIVITY PER THE STORM
PREDICTION CENTER WITH A SEVERE WEATHER AREA DELINEATED FOR PARTS
OF THE SOUTHERN PLAINS ON THURSDAY. SOME HEAVY RAINFALL POTENTIAL
MAY EXTEND NORTHWARD ALONG THE BOUNDARY INTO THE SOUTHERN/CENTRAL
APPALACHIANS AND THE MID-ATLANTIC AND THIS POTENTIAL IS COVERED
WITH A MARGINAL RISK ON DAY 5/FRIDAY. HEAVY RAINFALL SHOULD
CONTINUE INTO PARTS OF THE SOUTHEAST THIS WEEKEND AS WELL.
MEAN RIDGING ALOFT OVER THE EAST-CENTRAL AND EASTERN U.S. WILL
SUPPORT AN EXPANSIVE AREA OF ABOVE NORMAL TEMPERATURES TO THE EAST
OF THE ROCKIES. THE CORE OF WARMEST ANOMALIES SHOULD COVER PARTS
OF THE UPPER MIDWEST AND UPPER GREAT LAKES ON WEDNESDAY, WITH
HIGHS POTENTIALLY REACHING 20-30 DEGREES ABOVE NORMAL.
TEMPERATURES WILL TREND WARMER INTO THE SOUTH AND EAST MID TO LATE
NEXT WEEK AS WELL WITH DAYTIME HIGHS WELL INTO THE 70S TO NEAR 80
FOR SOME. OVER THE WEST, MODERATELY BELOW AVERAGE HIGHS AND
NEAR/ABOVE AVERAGE LOWS WILL SHIFT FROM THE NORTHWEST ON WEDNESDAY
INTO THE GREAT BASIN/FOUR CORNERS THURSDAY AND BEYOND.
TEMPERATURES ALONG THE IMMEDIATE WEST COAST SHOULD BEGIN TO
REBOUND AGAIN BY NEXT FRIDAY-SATURDAY AS STRONG RIDGING BUILDS IN
ALOFT.
SANTORELLI
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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