599
FXUS02 KWBC 190805
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
405 AM EDT MON OCT 19 2026
VALID 12Z THU OCT 22 2026 - 12Z MON OCT 26 2026
..LINGERING NOR'EASTER OFFERS EAST COAST MARITIME IMPACTS
..SOUTHERN CALIFORNIA/SOUTHWEST/ROCKIES HEAVY PRECIPITATION
..OVERVIEW
A LINGERING NOR'EASTER WILL BRING WIND AND COASTAL FLOODING
IMPACTS TO THE EAST COAST INTO MID-LATE WEEK. A CUTOFF LOW WILL
SUPPORT HEAVY RAINFALL FROM SOUTHERN CALIFORNIA TO THE FOUR
CORNERS STATES MID-TO-LATE WEEK ALONG WITH SOME MOUNTAIN SNOWS.
ASSOCIATED ACTIVITY WILL SPREAD THROUGH THE WEST ROCKIES AND THEN
WORK DOWNSTREAM WITH PLAINS SYSTEM GENESIS. THERE IS ALSO AN
EMERGING ONSHORE WET PATTERN FOR FLORIDA TO MONITOR LATE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS ARE IN GOOD AGREEMENT ON THE OVERALL SYNOPTIC EVOLUTION OF
THE MID-LEVEL PATTERN BEGINNING MID-WEEK. THE AMPLITUDE OF A
WESTERN ATLANTIC TROUGH IS THE MOST UNCERTAIN ASPECT OF THE LATE
WEEK PORTION OF THE MEDIUM RANGE. BEYOND THAT, THE TIMING/SPEED OF
ANOTHER WEST COAST TROUGH CARRIES THE MOST MODEL DISPERSION THIS
WEEKEND.
THE AIGFS IS FAVORED IN THE DAYS 3-7 BLEND WITH OTHER PIECES OF
GUIDANCE USED LESS CONSISTENTLY. THE ENSEMBLE MEANS MAKE UP 60% OF
THE BLEND BY DAY 5, DUE TO GROWING VARIANCE WITH RESPECT TO AN
INCOMING SHORTWAVE OUT OF BRITISH COLUMBIA. THE ENSEMBLE MEAN
MAINTAIN FAVORABLE WEIGHTING THROUGH THE END OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
A NOR'EASTER WILL OFFER THREATS FOR HIGH WINDS AND COASTAL
FLOODING WITH STORMY MARITIME CONDITIONS FROM THE COASTAL MID-
ATLANTIC TO OFF THE NORTHEAST. THE STORM WILL INTENSIFY OFF THE
CAROLINAS OVER THE NEXT FEW DAYS AND BRING STRONG WINDS BACK
TO THE COASTLINE INTO MID-LATE WEEK TO PROTRACT A THREAT FOR BEACH
EROSION. THE STORM OFFERS POTENTIAL SUBTROPICAL TRANSITION TO
MONITOR LATER WEEK PER NHC. 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 INTO MIDWEEK AND WORK INLAND INTO CALIFORNIA AND
THE SOUTHWEST LATER WEEK. ANOMALOUS MOISTURE WILL FEED INTO THE
WEST TO SUPPORT INCREASINGLY WIDESPREAD RAIN/THUNDERSTORMS OVER THE
REGION AND THROUGH THE GREAT BASIN/ROCKIES. THERE'S A SLIGHT RISK
(AT LEAST 15% CHANCE) OF EXCESSIVE RAINFALL LEADING TO FLASH
FLOODING FOR PORTIONS OF THE FOUR CORNERS REGION, WITH A STRONG
SIGNAL FOR HEAVY RAINFALL OVER THE SAN JUAN MOUNTAINS AS WELL AS
THE GENERAL SOUTHWESTERN COLORADO AREA PEAKING ON THURSDAY. THE
SLOW MOVING SYSTEM WILL THEN EJECT DOWNSTREAM AND LEAD CYCLE/FRONTS
GENESIS AND RETURN FLOW SHOULD SUPPORT EMERGING
SHOWERS/THUNDERSTORMS OVER THE PLAINS BY NEXT WEEKEND, ALBEIT STILL
WITH TIMING UNCERTAINTY TO NAVIGATE.
UPSTREAM, A CLOSED LOW WITH AMPLE UPPER TROUGHING WILL DIG FROM
THE GULF OF ALASKA TO APPROACH THE NORTHWEST AND/OR OFFSHORE LATE
WEEK. THIS SYSTEM COULD GENERATE MODERATE PRECIPITATION INCLUDING
HIGH ELEVATION SNOWS INTO THE NORTHWEST AS DEPENDENT ON ULTIMATE
INLAND PENETRATION TO MONITOR WITH UPCOMING GUIDANCE.
MEANWHILE, MEAN UPPER TROUGH DEVELOPMENT AND LINGERING DOWN THOUGH
THE SOUTHEAST U.S. MAY LEAD INTO A WET ONSHORE FLOW PERIOD FOR
ESPECIALLY SOUTHERN FLORIDA LATE PERIOD INTO NEXT WEEK. AN UPPER
RIDGE WILL AMPLIFY OVER THE CENTRAL U.S. LEADING TO ABOVE AVERAGE
TEMPERATURES ACROSS THE REGION THROUGH THIS WEEKEND.
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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