935
FXUS02 KWBC 210620
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
220 AM EDT WED OCT 21 2026
VALID 12Z SAT OCT 24 2026 - 12Z WED OCT 28 2026
...SOUTHERN ROCKIES TO SOUTHERN HIGH PLAINS HEAVY RAIN THREAT THIS
WEEKEND...
...HEAVY RAIN THREAT FOR PORTIONS OF SOUTH FLORIDA COAST THIS
WEEKEND...
..OVERVIEW
UNSETTLED WEATHER CONTINUES ACROSS PORTIONS OF THE FOUR
CORNERS,SOUTHERN ROCKIES, AND SOUTHERN HIGH PLAINS, WHERE A SLOW-
MOVING TROUGH AND ASSOCIATED MOISTURE TRANSPORT BRINGS HEAVY
RAINFALL CONCERNS FROM THE WEEKEND INTO EARLY NEXT WEEK. AS THE
PACIFIC UPPER LOW APPROACHES THE PACIFIC NORTHWEST, ADDITIONAL
PRECIPITATION MAY DEVELOP THROUGH LATE WEEKEND, WHILE PERSISTENT
ONSHORE FLOW MAINTAINS HEAVY RAINFALL OVER PORTIONS OF SOUTH
FLORIDA COAST. THE SHORTWAVE AND FRONTAL BOUNDARY OVER THE
NORTHERN TIER MAY BRING CHANCES FOR RAINFALL ACROSS THE NORTHERN
PLAINS INTO THE UPPER MIDWEST/GREAT LAKES INTO EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE MODEL GUIDANCE CONTINUES TO SUPPORT AN UPPER TROUGH ACROSS
WESTERN U.S. EARLY IN THE PERIOD, WITH INCREASING POTENTIAL FOR THE
TROUGH TO SPLIT INTO A NORTHERN AND SOUTHERN COMPONENT. THE
SOUTHERN STREAM OF ENERGY SHOULD HELP MAINTAIN ASCENT AND MOISTURE
TRANSPORT ACROSS THE SOUTHWEST AND SOUTHERN ROCKIES, WHILE MODELS
SHOW HIGHER UNCERTAINTY ON THE NORTHERN STREAM AS IT PROGRESSES
EASTWARD. FURTHERMORE, ALTHOUGH THE GFS/GEFS SEEMS TO SHOW BETTER
AGREEMENT WITH THE ECMWF AND CMC, OVERALL MODEL CONSENSUS CONTINUE
TO SHOW UNCERTAINTIES WITH THE EVOLUTION OF THE SHORTWAVE ENERGY
OVER NORTHEASTERN PACIFIC THROUGH THE WEEKEND. DIFFERENCES IN
AMPLITUDE, TIMING AND INLAND PROGRESSION COULD SUBSTANTIALLY
INFLUENCE SENSIBLE WEATHER. A FARTHER SOUTH SOLUTION WOULD FAVOR
MORE WIDESPREAD PRECIPITATION ACROSS THE PACIFIC NORTHWEST AND
NORTHERN CALIFORNIA, WHILE A MORE OFFSHORE SOLUTIONS WOULD ALLOW
FOR GREATER RIDING AND DRIER CONDITIONS OVER PORTIONS OF THE WEST.
THEREFORE, THE FORECAST WAS INFLUENCES BY A MULTI-MODEL BLEND OF
THE ECMWF/CMC/GFS THROUGH THE FIRST PORTION OF THE PERIOD. THE
ENSEMBLE MEANS WERE INCORPORATED TOWARDS THE LATE PERIOD TO BRING
A REASONABLE COMPROMISE WHERE THE DETERMINISTIC SOLUTIONS DIVERGE.
..WEATHER/HAZARDS HIGHLIGHTS
THE UPPER TROUGH AND ASSOCIATED MOISTURE TRANSPORT SHOULD SUPPORT
PERIODS OF SHOWERS AND THUNDERSTORMS FROM SATURDAY INTO EARLY NEXT
WEEK ACROSS PORTIONS OF THE THE FOUR CORNERS INTO THE PLAINS AND
EVENTUALLY THE UPPER MISSISSIPPI VALLEY AS THE TROUGH MOVES
EASTWARD. FAVORABLE LARGE- SCALE ASCENT, COMBINED WITH SUFFICIENT
DEEP MOISTURE AND LIFT, MAY PRODUCE LOCALLY HEAVY RAINFALL ACROSS
PORTIONS OF NEW MEXICO INTO THE SOUTHERN/CENTRAL HIGH PLAINS. THE
GREATEST CONCERN WOULD BE IN AREAS WHERE REPEATED CONVECTION
DEVELOPS THAT CAN LEAD TO LOCALIZED FLASH FLOODING. THEREFORE, THE
RISK FOR EXCESSIVE RAINFALL CONTINUES FOR PORTIONS OF NEW MEXICO
AND TEXAS INTO THE SOUTHERN/CENTRAL HIGH PLAINS THROUGH THE
WEEKEND.
ACROSS THE NORTHWEST, THE UPPER LOW/TROUGH FROM THE GULF OF ALASKA
WILL APPROACH THE PACIFIC NORTHWEST BY LATE WEEKEND AND WILL BRING
ONSHORE FLOW. THIS WILL INCREASE PRECIPITATION CHANCES ACROSS THE
PACIFIC NORTHWEST THROUGH THE WEEKEND INTO MONDAY. HIGHER
ELEVATIONS COULD EXPERIENCE A WINTRY MIX, DEPENDING ON THE THERMAL
PROFILE AND SNOW LEVELS. ACROSS THE NORTHERN TIER, A SHORTWAVE MAY
PROGRESS EASTWARD ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST
EARLY NEXT WEEK, ACCOMPANIED BY A SURFACE FRONTAL BOUNDARY. THIS
MAY SUPPORT PERIOD OF SHOWERS, FOLLOWED BY COOLER AIR. ELSEWHERE,
THE PERSISTENT EASTERLY FLOW WILL TRANSPORT MOISTURE ACROSS
SOUTHERN FLORIDA, PRODUCING SHOWERS AND THUNDERSTORMS. REPEATED
RAINFALL OVER URBANIZED AREAS AND LOCATIONS WITH POOR DRAINAGE
COULD LEAD TO LOCALIZED FLASH FLOODING CONCERNS THROUGH THE
WEEKEND.
OUDIT
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