272
FXUS02 KWBC 241859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EST WED JAN 24 2024
VALID 12Z SAT JAN 27 2024 - 12Z WED JAN 31 2024
..OVERVIEW
ORGANIZED RAINFALL TO LIFT UP THE LENGTH OF THE EASTERN SEABOARD
AND VICINITY WITH A DEEPENING LOW PRESSURE SYSTEM/COASTAL LOW
TRACK THIS WEEKEND MAY ALSO PRODUCE A SWATH OF ACCUMULATING
INTERIOR NORTHEAST SNOWS BY SUNDAY. FARTHER UPSTREAM, A LONG
DURATION UNSETTLED PATTERN IS LIKELY TO PERSIST THROUGH THE NEXT
WEEK WITH FOCUS FROM NORTHERN CALIFORNIA THROUGH THE PACIFIC
NORTHWEST. THE REMAINDER OF THE NATION IN BETWEEN SHOULD
EXPERIENCE A TRANQUIL BREAK FROM SIGNIFICANT RECENT BOUTS OF COLD
AIR/WINTRY CONDITIONS TO INUNDATING WET WEATHER, INSTEAD IN A
RELATIVELY WARM AND DRY LATE JANUARY PATTERN.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 12Z MODEL GUIDANCE SUITE IS IN GOOD OVERALL AGREEMENT ON THE
SYNOPTIC SCALE, INCLUDING THE POTENT SOUTHERN STREAM SHORTWAVE
TROUGH FOR THIS WEEKEND. THERE HAS BEEN AN OVERALL SLOWER TREND
IN THE GUIDANCE COMPARED TO THE 00Z CYCLE, WITH THE SURFACE LOW
DEPARTING THE EAST COAST LATER SUNDAY EVENING COMPARED TO EARLIER
FORECASTS. LOOKING AHEAD TO EARLY NEXT WEEK, THE GFS/GEFS MEAN
ARE FARTHER WEST WITH THE AXIS OF THE UPPER RIDGE ACROSS THE
NORTHERN ROCKIES, WHEREAS THE CMC/ECMWF ARE MORE DISPLACED TO THE
EAST. THERE IS GENERALLY GOOD AGREEMENT THAT A LARGE UPPER TROUGH
WITH A POTENTIAL ATMOSPHERIC RIVER WILL APPROACH THE WEST COAST
TOWARDS THE MIDDLE OF NEXT WEEK, BUT MORE UNCERTAINTY RESIDES
ACROSS THE UPPER MIDWEST WITH A TROUGH DROPPING SOUTHWARD FROM
CENTRAL CANADA. THE FRONTS/PRESSURES FORECAST WAS PRIMARILY
DERIVED FROM A MULTI-DETERMINISTIC MODEL BLEND THROUGH SUNDAY,
FOLLOWED BY GRADUALLY INCREASING PERCENTAGES OF THE ENSEMBLE MEANS
GOING INTO THE FIRST HALF OF NEXT WEEK.
..WEATHER/HAZARDS HIGHLIGHTS
DEEP LAYERED SOUTHERLY FLOW IN ADVANCE OF A SLOW MOVING AND
AMPLIFIED EASTERN PACIFIC UPPER TROUGH WILL LIFT DEEP AND LONG
FETCH MOISTURE UP ACROSS THE EASTERN PACIFIC AND INTO NORTHERN
CALIFORNIA AND ALSO WESTERN OREGON AND THE OLYMPIC PENINSULA.
THIS WILL FUEL A PROTRACTED WET PERIOD OVER THE NEXT WEEK, WITH
CONDITIONS ERODING OVER TIME WITH THE CUMULATIVE BUILDING OF
RAINFALL TOTALS. LIFTING SYSTEMS EMBEDDED WITHIN THE LARGER SCALE
FLOW WILL PERIODICALLY ENHANCE ACTIVITY RIDING THE WESTERN
PERIPHERY OF AN AMPLIFIED DOWNSTREAM UPPER RIDGE OVER THE WEST,
AND MAY OVER TIME LEAD TO RUNOFF ISSUES MAINLY FOR FAVORED FACING
TERRAIN. THE WPC EXCESSIVE RAINFALL OUTLOOKS (EROS) FOR DAY
4/SATURDAY AND DAY 5/SUNDAY SHOW SMALL MARGINAL RISK THREAT AREAS
CENTERED OVER NW CALIFORNIA/SW OREGON AND FOR BOTH DAYS OVER THE
OLYMPICS TO HIGHLIGHT BEST GUIDANCE SIGNALS AND TOPOGRAPHY.
AN ONGOING AND SIGNIFICANT RAINFALL EPISODE OVER THE SOUTH WILL
FINALLY END SATURDAY. DEEP 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. A REMAINING THREAT FOR HEAVY
RAIN UP FROM THE SOUTHEAST THROUGH THE SOUTHERN APPALACHIANS AND
VICINITY WITH SYSTEM APPROACH/PASSAGE AND DEEPENING LOW FOCUS HAS
PROMPTED A DAY 4/SATURDAY ERO MARGINAL RISK AREA. 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 OVER THE INTERIOR
NORTHEAST BY 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/HAMRICK
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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