561
FXUS02 KWBC 211842
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM 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
MODELS CONTINUE TO SHOW INCREASING CLUSTERING ON THE FORECAST
THROUGH MUCH OF THE MEDIUM RANGE PERIOD, AT LEAST THE FIRST HALF.
THERE IS GOOD AGREEMENT THAT A COMPACT UPPER LOW MAY MEANDER OVER
THE SOUTHWEST WILL LIFT INTO THE NORTHERN PLAINS/UPPER MIDWEST NEXT
WEEK, WITH MINOR TIMING AND DETAIL DIFFERENCES. MOST OF THE
UNCERTAINTY OF THE PERIOD CONTINUES TO SURROUND A DEEP UPPER LOW
THAT SHOULD EVENTUALLY MOVE INTO THE PACIFIC NORTHWEST EARLY NEXT
WEEK. MODELS CONTINUE TO SHOW SOME CONSIDERABLE TIMING AND
EVOLUTION DIFFERENCES. RECENT CMC AND UKMET RUNS ARE TOO FAST WITH
THIS, AND THE NEW 12Z GFS TODAY TRENDED MORE OFFSHORE WITH THE LOW
AND STRONGER WITH A SHORTWAVE INTO THE NORTH-CENTRAL U.S.. THE
ECMWF, EC-AIFS, 06Z GFS, AND ENSEMBLE MEANS SEEM TO SHOW A MIDDLE
GROUND AND IS THE PREFERRED BLEND AT THIS POINT. THIS IS ALSO
CONSISTENT WITH THE PREVIOUS WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
THE SOUTHWEST 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. 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. 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 WITH INCREASED
PRECIPITATION CHANCES ACROSS THE PACIFIC NORTHWEST THROUGH THE
WEEKEND INTO MONDAY. SHOWERS WILL DEVELOP FROM THE PLAINS TO THE
UPPER MISSISSIPPI VALLEY AND GREAT LAKES ALONG FRONTAL BOUNDARIES
AHEAD OF THE SOUTHWEST LOW AS IT WEAKENS AND LIFTS NORTHEASTWARD.
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.
SANTORELLI/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
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