306
FXUS02 KWBC 172000
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 PM EDT SAT OCT 17 2026
VALID 12Z TUE OCT 20 2026 - 12Z SAT OCT 24 2026
..POTENT NOR'EASTER TO BRING MARITIME AND EAST COASTAL IMPACTS
..SOUTHERN CALIFORNIA/SOUTHWEST/ROCKIES HEAVY PRECIPITATION
..OVERVIEW
A DEVELOPING NOR'EASTER IS EXPECTED TO BRING WIND, RAIN AND
COASTAL FLOODING IMPACTS TO THE EAST COAST INTO MID-LATER NEXT
WEEK. A CUTOFF LOW WILL BRING EXCESSIVE RAINFALL CONCERNS FROM
SOUTHERN CALIFORNIA TO THE FOUR CORNERS STATES MID-LATER NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THERE'S IS GOOD SIGNAL FOR CLOSED MID-LEVEL LOWS TO DEVELOP ALONG
THE EAST AND WEST COASTS, WHILE A RIDGE AMPLIFIES IN BETWEEN OVER
THE CENTRAL U.S.. MODELS CONTINUE TO TEETER BACK AND FORTH WITH THE
POSITIONING OF THE EAST COAST LOW. WPC PROGS OFFER A DEEPENING LOW
WITH POSITION SLIGHTLY ON THE WESTWARD SIDE OF THE BROAD ENVELOPE
OF GUIDANCE SOLUTIONS GIVEN UPPER FLOW AMPLITUDE. THIS SOLUTION IS
CLOSE TO THE ECMWF AND ECMWF/CANADIAN ENSEMBLE MEANS.
GUIDANCE CLUSTERING HAS IMPROVED TO A DEGREE WITH THE DEVELOPMENT
AND EVOLUTION OF THE EAST PACIFIC TO WEST/SOUTHWEST ONWARD MAIN
SYSTEM, BOLSTERING FORECAST GUIDANCE, BUT LOCAL DETAILS REMAIN
LESS CERTAIN. A COMPOSITE GUIDANCE BLEND NOW SEEMS MORE REASONABLE.
..WEATHER/HAZARDS HIGHLIGHTS
A SLOW MOVING NOR'EASTER OFFERS A PROTRACTED THREAT FOR STRONG
WINDS, POTENTIALLY HEAVY RAIN AND COASTAL FLOODING/STORMY MARITIME
CONDITIONS FROM THE COASTAL MID-ATLANTIC TO ALONG/OFF THE
NORTHEAST. THE MID-LATITUDE CYCLONE RESPONSIBLE FOR THESE HAZARDS
IS FORECAST TO INTENSIFY OFF THE CAROLINAS THIS WEEKEND BEFORE
DRIFTING BACK TOWARD THE MAINLAND EARLY NEXT WEEK. PERSISTENT
ONSHORE FLOW SHOULD GENERATE STRONG WINDS WITH GUSTS EXCEEDING 40
KTS POSSIBLE ALONG THE IMMEDIATE COASTLINE. BEACH EROSION IS ALSO
LIKELY FROM THE AFOREMENTIONED STRONG ONSHORE FLOW. THIS DEVELOPING
STORM ALSO OFFERS POTENTIAL SUBTROPICAL TRANSITION TO MONITOR NEXT
WEEK AS PER NHC. OVERALL, PLEASE REFER TO WPC'S KEY MESSAGES ON
OUR WEBSITE FOR MORE INFORMATION: WWW.WPC.NCEP.NOAA.GOV.
A SHORTWAVE PASSING SOUTH OF THE GULF OF ALASKA IS FORECAST TO
DIG/AMPLIFY INTO A CUT-OFF LOW OVER THE EASTERN PACIFIC JUST OFF
THE WEST COAST MIDWEEK. THE DEPTH AND SPEED OF THIS SYSTEM WILL
DETERMINE HOW MUCH MOISTURE IT CAN PULL INTO THE REGION. THE LATEST
TRENDS SUGGEST AN INCREASING LIKELIHOOD FOR ANOMALOUS MOISTURE TO
BE PULLED INTO THE WEST. THIS MOISTURE WILL THEN INTERACT WITH A
FRONTAL SYSTEM AND PRODUCE SCATTERED TO ISOLATED THUNDERSTORMS
OVER PORTIONS OF THE FOUR CORNERS. HEAVY RAINFALL MAY OCCUR AS WELL
WITH SOME EXTREME FORECAST INDEX SHIFT OF TAIL SIGNALS SHOWING UP
ACROSS SOUTHERN CALIFORNIA THROUGH THE SOUTHWEST. SOME HIGH
ELEVATION SNOWFALL IS ALSO LIKELY FOR THE SIERRA THROUGH PARTS OF
THE INTERMOUNTAIN WEST TO THE ROCKIES WITH SLOW PROGRESSION. SYSTEM
EMERGENCE THROUGH THE ROCKIES INTO THE PLAINS WILL FAVOR THE SPREAD
OF THE RAINFALL SHIELD AND EMERGING PLAINS CONVECTION LATE PERIOD.
ANOTHER SHORTWAVE DIVING SOUTH THROUGH BRITISH COLUMBIA WILL SEND A
COLD FRONT INTO THE NORTHWEST MID-TO-LATE NEXT WEEK. THIS SYSTEM
COULD GENERATE HIGH ELEVATION SNOW FOR PORTIONS OF THE NORTHERN
ROCKIES/INTERMOUNTAIN WEST LATE NEXT WEEK.
KEBEDE/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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page