724
FXUS02 KWBC 110708
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
307 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
POSSIBLY SIGNIFICANT WINTER STORM ACROSS THE COLORADO ROCKIES ON
THURSDAY, AND 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 TONIGHT'S 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 LONG-DURATION 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 PLACEMENT 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 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 FROM THE MIDWEST INTO THE
NORTHEAST, WITH HIGHS POTENTIALLY REACHING 15-20+ DEGREES ABOVE
NORMAL. TEMPERATURES ACROSS THE EAST WILL TREND COOLER WITH TIME
AFTER THURSDAY, BUT STILL GENERALLY ABOVE NORMAL THROUGH THE
WEEKEND. OVER THE WEST, MODERATELY BELOW AVERAGE HIGHS AND
NEAR/ABOVE AVERAGE LOWS WILL SHIFT INTO THE GREAT BASIN/FOUR
CORNERS THURSDAY AND BEYOND. TEMPERATURES ALONG THE IMMEDIATE WEST
COAST SHOULD INCREASE BY FRIDAY AND THROUGH THE WEEKEND AS STRONG
RIDGING BUILDS IN ALOFT. BELOW AVERAGE TEMPERATURES WILL ALSO
SPREAD FROM THE NORTH-CENTRAL U.S. INTO THE MISSISSIPPI VALLEY AND
EVENTUALLY THE MIDWEST THIS WEEKEND/EARLY NEXT WEEK AS NORTHERN
STREAM TROUGHING MOVES THROUGH THE REGION.
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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