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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