292
FXUS02 KWBC 250659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST THU JAN 25 2024
VALID 12Z SUN JAN 28 2024 - 12Z THU FEB 01 2024
..OVERVIEW
A STORM SYSTEM FORECAST TO EXIT AN INUNDATED SOUTH SATURDAY WILL
LIFT TO THE MID-ATLANTIC COAST AROUND SUNDAY NIGHT BEFORE EXITING
AS A COASTAL STORM. FOR SUNDAY INTO EARLY MONDAY, THE DEEPENING
SYSTEM SEEMS LIKELY TO PRODUCE A WRAPPED SWATH OF WELL ORGANIZED
PRECIPITATION FROM THE UPPER OHIO VALLEY/CENTRAL APPALACHIANS
THROUGH THE MID-ATLANTIC INTO NEW ENGLAND, WITH INTERIOR SNOWS
POSSIBLE FROM THE CENTRAL APPALACHIANS THROUGH INTERIOR
PENNSYLVANIA/NEW YORK/NEW ENGLAND. FAR UPSTREAM, PORTIONS OF THE
WEST COAST WILL ALSO BE RATHER UNSETTLED AT TIMES WITH MULTIPLE
ROUNDS OF RAIN EXPECTED FOR PACIFIC NORTHWEST WELL INTO NEXT WEEK,
LEADING INTO A LARGER ATMOSPHERIC RIVER EVENT SIGNAL NEXT MIDWEEK
FARTHER SOUTHWARD DOWN THE COAST INTO CALIFORNIA TO MONITOR FOR
SEVERITY AND IMPACT. MEANWHILE, A RELATIVELY QUIET WEATHER PATTERN
SHOULD BE IN PLACE FOR MUCH OF THE REST OF THE LOWER 48.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LAST FEW MODEL CYCLES HAVE BEEN IN GOOD AGREEMENT ON THE
SYNOPTIC SCALE INTO NEXT WEEK, ALBEIT WITH AN OVERALL SLOWER
GUIDANCE TREND. THERE IS GENERALLY GOOD AGREEMENT THAT A LARGE
EASTERN PACIFIC UPPER TROUGH WITH A LEAD ATMOSPHERIC RIVER FOCUS
INTO COASTAL WASHINGTON/OLYMPICS INTO EARLY NEXT WEEK WILL WORK
MORE IN EARNEST TOWARD CALIFORNIA THROUGH NEXT MIDWEEK. THERE ARE
LINGERING DIFFERENCES WITH WEATHER FOCUS OF A MAIN SURFACE LOW TO
TRACK UP/OFF THE EASTERN SEABOARD SUNDAY INTO MONDAY, BUT THE
SYSTEM SEEMS DEEP ENOUGH TO WARRANT A MODERATE INCREASE IN QPF
VERSUS WPC CONTINUITY. LATER, QUITE A BIT OF UNCERTAINTY DEVELOPS
OVER THE CENTRAL TO EASTERN U.S. WITH A SERIES OF UPPER IMPULSES
DROPPING FROM CANADA, ALBEIT IN A RELATIVELY TRANQUIL WEATHER
REGIME. ACCORDINGLY, THE WPC FORECAST WAS PRIMARILY DERIVED FROM A
MULTI-DETERMINISTIC MODEL BLEND VALID FOR SUNDAY AND MONDAY,
TRANSITIONING TUESDAY AND FOR NEXT WEDNESDAY AND THURSDAY TO THE
MORE COMPATIBLE ENSEMBLE MEANS AMID GROWING FORECAST SPREAD AND
MODEL RUN TO RUN CONSISTENCY ISSUES AS NOTED.
..WEATHER/HAZARDS HIGHLIGHTS
DEEP LAYERED SOUTHERLY FLOW IN ADVANCE OF A SLOW MOVING AND
AMPLIFIED EASTERN PACIFIC UPPER TROUGH WILL LIFT AND CHANNEL DEEP
AND LONG FETCH MOISTURE UP ACROSS THE EASTERN PACIFIC, WITH EARLY
NEXT WEEK FOCUS LIKELY SHIFTED NORTHWARD OVER THE PACIFIC
NORTHWEST ON THE WESTERN PERIPHERY OF AN AMPLIFIED UPPER RIDGE
DOWNSTREAM OVER THE WEST. THIS WILL FUEL A PROTRACTED WET PERIOD
NEXT WEEK, WITH CONDITIONS ERODING WITH THE CUMULATIVE BUILDING OF
RAINFALL TOTALS. SYSTEMS EMBEDDED WITHIN THE LARGER SCALE FLOW
WILL PERIODICALLY ENHANCE ACTIVITY, AND MAY OVER TIME LEAD TO
RUNOFF ISSUES MAINLY FOR FAVORED FACING TERRAIN. THE WPC EXCESSIVE
RAINFALL OUTLOOKS (EROS) FOR DAY 4/SUNDAY AND DAY 5/MONDAY NOW
SHOW SMALL MARGINAL RISK THREAT AREAS CENTERED OVER THE OLYMPICS
TO HIGHLIGHT BEST MODEL GUIDANCE SIGNALS AND TOPOGRAPHICAL
FORCING. IT IS IMPORTANT TO AGAIN NOTE THAT THE SLOW APPROACH OF A
LARGE EASTERN PACIFIC MEAN UPPER TROUGH IS EXPECTED TO ACT TO
REFOCUS A LEAD ATMOSPHERIC RIVER MORE IN EARNEST TOWARD CALIFORNIA
AROUND NEXT MIDWEEK WITH THE POTENTIAL FOR HEAVY RAINFALL AND
GROWING RUNOFF ISSUES.
AN ONGOING AND SIGNIFICANT RAINFALL EPISODE OVER THE GULF COAST
REGION WILL FINALLY TAPER OFF SATURDAY. GULF OF MEXICO TO ATLANTIC
MOISTURE FEED AHEAD OF THE LAST MAJOR SOUTHERN STREAM SHORTWAVE IN
THE SERIES WILL LIFT NORTHEASTWARD ON THE WESTERN PERIPHERY OF AN
AMPLIFIED DOWNSTREAM UPPER RIDGE. THE LIFTING OF THIS FEATURE AND
LOW ALSO FAVORS A MODERATE WRAPPED PRECIPITATION SWATH ACROSS THE
OHIO VALLEY, APPALACHIANS AND MID-ATLANTIC THROUGH THE NORTHEAST
THIS WEEKEND. WHILE WITHIN A WIDESPREAD AND SIGNIFICANTLY WARMER
PATTERN, ENOUGH COOLED AIR MAY REMAIN IN PLACE TO ALLOW FOR SNOW
ALONG WITH SOME WINDY CONDITIONS ON THE NORTHERN EDGE OF THE BROAD
PRECIPITATION SHIELD FROM THE CENTRAL APPALACHIANS THROUGH THE
INTERIOR NORTHEAST SUNDAY AS AIDED WITH A DEEPENING LOW TRACK
UP/OFF THE EAST COAST. THIS EMERGING COASTAL STORM WILL ALSO OFFER
A MARITIME RISK OFFSHORE 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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