471
FXUS02 KWBC 220701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST MON JAN 22 2024
VALID 12Z THU JAN 25 2024 - 12Z MON JAN 29 2024
...EXCESSIVE RAINFALL/FLOODING THREAT TO CONTINUE LATE WEEK FROM
THE LOWER MISSISSIPPI/TENNESSEE VALLEYS TO THE GULF COAST
STATES/SOUTHERN APPALACHIANS...
..OVERVIEW
A SIGNIFICANT RAINFALL EVENT IS ON TAP WITH MULTIPLE DAYS OF HEAVY
RAIN AND RUNOFF THREATS AMID A SLOW TO TRANSLATE AND AMPLIFIED
PATTERN THIS WEEK, WITH PRIMARY FOCUS FROM SOUTHEAST TEXAS THROUGH
THE LOWER MISSISSIPPI/TENNESSEE VALLEYS AND GULF COAST STATES TO
THE SOUTHERN APPALACHIANS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF REASONABLY WELL CLUSTERED GUIDANCE FROM RECENT
RUNS OF THE GFS/ECMWF/UKMET/CANADIAN FOR THURSDAY INTO SATURDAY
WHOSE SOLUTIONS SEEM QUITE OVERALL QUITE COMPATIBLE WITH
GEFS/ECMWF/CANADIAN/NAEFS ENSEMBLES AND THE NATIONAL BLEND OF
MODELS AND WPC CONTINUITY IN A PATTERN WITH ABOVE AVERAGE
PREDICTABILITY. PREFER TO SWITCH TO THE ENSEMBLE MEANS TO BUILD A
BASELINE FORECAST ONWARD INTO EARLY NEXT WEEK AMID GROWING
FORECAST SPREAD BUT APPLIED BLEND WEIGHTING EMPHASIS TOWARD ECMWF
ENSEMBLES WHOSE SOMEWHAT GREATER AMPLITUDE INTO THESE LONGER TIME
FRAMES SEEMS MORE LIKELY IN THIS TYPE OF FLOW PATTERN.
..WEATHER/HAZARDS HIGHLIGHTS
THE PACIFIC NORTHWEST/NORTHERN CALIFORNIA WILL SEE PERIODS OF
MODERATE RAINS INTO MID-LATER WEEK WITH MULTIPLE PACIFIC SYSTEM
APPROACHES. DIGGING ENERGIES INTO A MEAN UPPER TROUGH OVER THE
WEST SHOULD ALLOW FOR SOME PRECIPITATION TO WORK INLAND TO THE
NORTH-CENTRAL INTERMOUNTAIN WEST/ROCKIES EARLY THIS PERIOD TO
INCLUDE SOME ENHANCED TERRAIN/MOUNTAIN SNOWS. UPPER RIDGE BUILDING
UP/INLAND THROUGH THE WEST COAST HEADING INTO THE WEEKEND SHOULD
INCREASINGLY LIMIT MOST ACTIVITY WITH A MORE NORTHWARD TO OFFSHORE
FOCUS. HOWEVER IN THIS TRANSITION, CHANNELED/DEEPENED MOISTURE
FEED MAY FOCUS LOCALLY HEAVY RAINFALL INTO FAVORED SOUTHERLY
FACING TERRAIN OF THE OLYMPICS AND VICINITY, PROMPTING
INTRODUCTION OF A DAY 5/FRIDAY EXCESSIVE RAINFALL OUTLOOK MARGINAL
RISK AREA. THIS AREA LOOKS TO BE A FOCUS FOR MORE ENHANCED
MOISTURE AND RAINFALL THROUGH NEXT WEEKEND.
A SIGNIFICANT RAINFALL EPISODE WILL LINGER LATER WEEK INTO THE
WEEKEND AS DEEP MOISTURE FEED IN ADVANCE OF SEVERAL EJECTING
SHORTWAVE TROUGHS AND FRONTAL WAVES SHOULD PROVE SLOW TO SPREAD
HEAVY RAIN AND THUNDERSTORMS THROUGH THE LOWER
MISSISSIPPI/TENNESSEE VALLEYS AND GULF COAST STATES INTO THE
SOUTHEAST/SOUTHERN APPALACHIANS AND VICINITY. THESE WILL FUEL
GROWING FLOODING CONCERNS GIVEN SIGNIFICANT REPEAT/TRAINING
POTENTIAL AND A SIGNAL IN THE GUIDANCE FOR LOCALLY HEAVY DAILY
TOTALS. WPC DAY 4/THURSDAY AND DAY 5/FRIDAY EXCESSIVE RAINFALL
OUTLOOKS HAVE SLIGHT RISK AND SURROUNDING MARGINAL RISK AREAS FROM
THE LOWER MISSISSIPPI VALLEY AND GULF COAST STATES TO THE SOUTHERN
APPALACHIANS GIVEN SLOW PATTERN TRANSLATION WITH FAVORABLE UPPER
SUPPORT, DEEP MOISTURE RETURN, AND REPEAT ACTIVITY SIGNATURE. AS
CONFIDENCE INCREASES IN BOTH THE AXIS OF HEAVIEST RAINFALL AS WELL
AS POTENTIAL OVERLAP WITH RAINFALL ON TUESDAY AND WEDNESDAY
LEADING TO WETTER ANTECEDENT CONDITIONS, A HIGHER RISK THRESHOLD
MAY BE NEEDED. A SWATH OF MORE MODERATE RAINS IS ALSO SET TO
SPREAD UP ACROSS THE OHIO VALLEY/GREAT LAKES AND THE EAST INTO
LATER WEEK AS ENHANCED WITH FRONTAL WAVE DEVELOPMENTS, AND GIVEN
MUCH WARMER TEMPERATURES AND SNOWMELT AS APPLICABLE, AREAL AND
STREAM FLOODING MAY BECOME A CONCERN. HOWEVER, UNCERTAINTY REMAINS
WITH THESE WAVES AS WELL AS THE EXTENT AND FOCUS OF SEEMINGLY
MODEST COASTAL WAVES NEXT WEEKEND INTO EARLY NEXT WEEK. WINTRY
PRECIP SHOULD BE LIMITED TO THE FAR NORTHERN U.S. TIER AND MORE
EARNESTLY INTO SOUTHERN CANADA AS WARM AIR SPREADS FARTHER NORTH.
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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