641
FXUS02 KWBC 180746
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
346 AM EDT SUN OCT 18 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 AND COASTAL
FLOODING IMPACTS TO THE EAST COAST MID-TO-LATE WEEK. A CUTOFF LOW
WILL BRING EXCESSIVE RAINFALL CONCERNS FROM SOUTHERN CALIFORNIA TO
THE FOUR CORNERS STATES MID-TO-LATE WEEK AS WELL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THERE'S GOOD AGREEMENT ON THE AMPLIFICATION OF A MID-LEVEL CUT-OFF
LOW IN THE EAST PACIFIC MID-WEEK, FOLLOWED BY THE WEAKENING OF IT
AS IT ENTERS THE WESTERN U.S. BY LATE WEEK. THE EXACT SPEED OF THE
DISTURBANCE REMAINS IN QUESTION BUT HAS IMPROVED OVER THE LAST FEW
RUNS. THE AMPLITUDE AND LOCATION OF A DOWNSTREAM UPPER RIDGE OVER
THE CENTRAL U.S. IS CAPTURED VERY WELL BY MOST OF THE AVAILABLE
GUIDANCE. MODELS CONTINUE TO TREND FARTHER AWAY FROM THE EAST
COAST WITH THE LOCATION OF THE NOR'EASTER MID-WEEK.
THE ECAIFS AND EURO MEAN WERE FAVORED IN THE BLEND BETWEEN DAYS 4
AND 7 DUE TO NOTABLE RUN-TO-RUN INCONSISTENCIES IN THE
DETERMINISTIC EURO AND GFS.
..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 LATE THIS WEEKEND
BEFORE DRIFTING BACK TOWARD THE MAINLAND EARLY IN THE 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 WEEK. THIS SYSTEM COULD
GENERATE HIGH ELEVATION SNOW FOR PORTIONS OF THE NORTHERN
ROCKIES/INTERMOUNTAIN WEST LATE WEEK.
TEMPERATURES WILL BE AROUND AVERAGE FOR THE EAST COAST, ABOVE
AVERAGE OVER THE PLAINS AND MISSISSIPPI VALLEY/MIDWEST, AND
GENERALLY BELOW AVERAGE IN THE WEST BENEATH PERSISTENT UPPER
TROUGHING.
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
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