771
FXUS02 KWBC 230722
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
221 AM EST TUE JAN 23 2024
VALID 12Z FRI JAN 26 2024 - 12Z TUE JAN 30 2024
...EXCESSIVE RAINFALL/FLOODING THREAT OVER THE SOUTH TO CONTINUE
LATE WEEK FROM THE GULF COAST STATES TO THE SOUTHERN
APPALACHIANS...
..OVERVIEW
A SIGNIFICANT AND PROTRACTED RAINFALL EVENT IS EXPECTED TODAY
THROUGH SATURDAY WITH HEAVY RAIN/CONVECTION AND RUNOFF THREATS
AMID A SLOW TO TRANSLATE AND AMPLIFIED PATTERN, WITH PRIMARY FOCUS
TO REFORM AND SPREAD FROM SOUTHEAST TEXAS THROUGH THE LOWER
MISSISSIPPI/TENNESSEE VALLEYS AND GULF COAST STATES THROUGH THE
SOUTHERN APPALACHIANS AND VICINITY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM A
COMPOSITE BLEND OF REASONABLY WELL CLUSTERED GUIDANCE FROM THE 18
UTC GFS AND 12 UTC ECMWF/UKMET/CANADIAN FOR FRIDAY INTO SUNDAY.
FORECAST SPREAD IN THIS PERIOD HAS DECREASED, BOLSTERING FORECAST
CONFIDENCE. THIS BLENDED SOLUTION IS OVERALL QUITE COMPATIBLE WITH
ENSEMBLES, THE NATIONAL BLEND OF MODELS AND WPC CONTINUITY. OPTED
TO INCLUDE SOME INPUT FROM THE GEFS/ECMWF ENSEMBLE MEANS INTO
EARLY NEXT WEEK TO BUILD A BASELINE FORECAST AMID GRADUALLY
GROWING FORECAST SPREAD. A SIMILAR COMPOSITE OF LATEST GUIDANCE
FROM THE 00 UTC CYCLE OVERALL SEEMS TO FAVORABLY REMAIN IN LINE.
..WEATHER/HAZARDS HIGHLIGHTS
AN AMPLIFIED UPPER RIDGE WILL BUILD OVER THE WEST COAST BY FRIDAY
THAT SHOULD PROVE SLOW TO SHIFT EASTWARD ACROSS A WARMER AND
STABILIZED WEST THROUGH NEXT TUESDAY. A SERIES OF AMPLIFIED
EASTERN PACIFIC SYSTEMS WILL LIFT OFFSHORE AND BRING AN AXIS OF
LONG FETCH MOISTURE UP ON THE WESTERN PERIPHERY OF THE SHIELDING
RIDGE, WITH MAIN FOCUS INTO FAVORED TERRAIN WITHIN COASTAL AREAS
FROM THE PACIFIC NORTHWEST TO NORTHERN CALIFORNIA. WPC EXCESSIVE
RAINFALL OUTLOOKS (ERO) FOR DAY4/FRIDAY AND DAY5/SATURDAY OFFER
MARGINAL RISK THREAT AREAS OVER NW CALIFORNIA/SW OREGON AND THE
OLYMPICS TO HIGHLIGHT BEST GUIDANCE SIGNALS AND LEADS INTO
ADDITIONAL WET COASTAL WEATHER POTENTIAL LATER WEEKEND INTO EARLY
NEXT WEEK.
A SIGNIFICANT RAINFALL EPISODE OVER THE SOUTH WILL LINGER INTO
FRIDAY/SATURDAY AS DEEP MOISTURE FEED IN ADVANCE OF THE LAST MAJOR
SOUTHERN STREAM SHORTWAVE IN THE SERIES WORKS ACROSS THE REGION
AND LIFTS ENERGETICALLY NORTHEASTWARD ON THE WESTERN PERIPHERY OF
A SLOW TO RECEDE SOUTHEAST/EAST DOWNSTREAM UPPER RIDGE. A
REMAINING THREAT FOR LEADING HEAVY RAIN AND THUNDERSTORMS THROUGH
THE GULF COAST STATES INTO THE SOUTHEAST/SOUTHERN APPALACHIANS AND
VICINITY WITH SYSTEM APPROACH/PASSAGE AND ENHANCED FRONTAL
WAVE/DEEPENING LOW FOCUS HAS PROMPTED ISSUANCE OF A DAY 4/FRIDAY
SLIGHT RISK AREA ERO OVER THE CENTRAL GULF COAST STATES WITH A
SURROUNDING MARGINAL RISK AREA DAY4/FRIDAY EXTENDING UP
THROUGH/LEE OF THE SOUTHERN APPALACHIANS DAY 5/SATURDAY. AREAS IN
VICINITY OF THE TRACK OF THE INITIALLY CLOSED UPPER CENTER MAY
ALSO SEE LOCALLY HEAVIER DOWNPOURS AS HIGHLIGHTED BY THE
DAY4/FRIDAY MARGINAL RISK AREA ERO OVER OKLAHOMA/NORTH TEXAS. THIS
LIFTING/SHEARING OF THIS FEATURE FAVORS A MODERATE PRECIPITATION
SWATH NORTHEASTWARD ACROSS THE MID-SOUTH AND OHIO VALLEY THROUGH
THE CENTRAL APPALACHIANS, MID-ATLANTIC AND NEW ENGLAND THROUGH THE
WEEKEND. WHILE WITHIN A WIDESPREAD AND SIGNIFICANTLY WARMER
PATTERN, ENOUGH COOLED AIR MAY REMAIN IN PLACE TO ALLOW POTENTIAL
FOR SOME SNOW ALONG WITH SOME WINDY CONDITIONS ON THE FAR NORTHERN
EDGE OF THE BROAD PRECIPITATION SHIELD INTO THE INTERIOR NORTHEAST
BY SUNDAY AS AIDED WITH A DEEPENING LOW TRACK UP/OFF THE EAST
COAST. THIS STORM SHOULD BECOME STRONG ENOUGH TO BE A MARITIME
HAZARD OFF THE MID-ATLANTIC THEN NEW ENGLAND SUNDAY INTO MONDAY.
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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