124
FXUS02 KWBC 201924
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
324 PM EDT TUE OCT 20 2026
VALID 12Z FRI OCT 23 2026 - 12Z TUE OCT 27 2026
...SOUTHERN ROCKIES TO SOUTHERN HIGH PLAINS HEAVY RAIN THREAT THIS
WEEKEND...
..OVERVIEW
AN UPPER-LEVEL TROUGH AND ASSOCIATED MOISTURE PLUME WILL BRING A
THREAT FOR HEAVY RAINFALL TO PARTS OF THE SOUTHERN ROCKIES TO
SOUTHERN HIGH PLAINS THIS WEEKEND INTO EARLY NEXT WEEK. THIS TROUGH
SHOULD SPLIT NEXT WEEK WITH A SHORT WAVE/SURFACE FRONT RACING
ACROSS THE NORTHERN TIER AND WEAK ENERGY LINGERING OVER THE
SOUTHWEST. ANOTHER PACIFIC SHORTWAVE MAY MOVE INTO THE NORTHWEST
BRINGING PRECIPITATION ACROSS THE REGION NEXT WEEK. ACROSS THE
SOUTHEAST, ONSHORE FLOW WILL SUPPORT ADDITIONAL RAINFALL ACROSS
ESPECIALLY SOUTHEAST FLORIDA THROUGH MUCH OF THE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS PRETTY WELL CLUSTERED FOR THE BEGINNING OF THE
PERIOD FEATURING AN ELONGATED WESTERN TROUGH THAT SPLITS WITH A
SHORTWAVE MOVING THROUGH THE NORTHERN TIER INTO EARLY NEXT WEEK AND
A WEAK UPPER LOW LINGERING OVER THE SOUTHWEST. THE GREATEST SOURCE
OF UNCERTAINTY DURING THE PERIOD SURROUNDS SHORTWAVE ENERGY MOVING
OUT OF THE GULF OF ALASKA WITH A LIKELY CUTOFF LOW FORMING OFF THE
BRITISH COLUMBIA COAST THIS WEEKEND. THERE IS A LOT OF RUN TO RUN
VARIABILITY ON THE EVOLUTION OF THIS, WHETHER THE LOW AMPLIFIES AND
MOVES INTO THE NORTHWEST U.S. LATE PERIOD OR LINGERS OFF THE
BRITISH COLUMBIA COAST. THIS IMPACTS THE DOWNSTREAM EVOLUTION OF
THE PATTERN OVER THE NORTH-CENTRAL U.S. AS WELL AND THE STRENGTH OF
A SHORTWAVE AND ALSO RIDGING OVER THE WEST. THE EC-AIFS AND CMC
BRING THE UPPER LOW FARTHER SOUTH INTO THE NORTHWEST, RESULTING IN
AMPLIFIED TROUGHING OVER THE WEST LATE PERIOD, WHILE THE GFS AND
ECMWF ARE LESS EXCITED ABOUT THIS, WITH MORE RIDGING OVER THE WEST.
ENSEMBLES ARE ALSO PRETTY SPLIT, RESULTING IN A HIGHLY UNCERTAIN
FORECAST. THE WPC FORECAST TODAY LEANED PRETTY HEAVY ON THE
ENSEMBLE MEANS LATE PERIOD, WHICH SEEMED TO BE A FAIRLY GOOD MIDDLE
GROUND SOLUTION FOR NOW, AND CONSISTENT WITH THE PREVIOUS WPC
FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
ACROSS THE WESTERN U.S., THE UPPER TROUGH WILL CONTINUE TO SUPPORT
PERIODS OF RAIN AND EMBEDDED THUNDERSTORMS ACROSS THE FOUR CORNERS
REGION BY LATE WEEK. ANOMALOUS MOISTURE TRANSPORT INTO THE REGION,
COMBINED WITH ASCENT ASSOCIATED WITH THE LINGERING UPPER LOW AND
FORCING, COULD PRODUCE LOCALLY HEAVY RAINFALL, ESPECIALLY INTO THE
WEEKEND ACROSS THE SOUTHERN ROCKIES TO HIGH PLAINS REGION. ANY
PERSISTENCE OF DEEP MOISTURE AND SLOW STORM MOTION WOULD INCREASE
THE POTENTIAL FOR EXCESSIVE RUNOFF, PARTICULARLY OVER VULNERABLE
TERRAIN AND BURN SCARS. THEREFORE, A MARGINAL RISK OF EXCESSIVE
RAINFALL FOR PORTIONS OF THE NEW MEXICO INTO WESTERN TEXAS
CONTINUES FOR FRIDAY, WHILE A SLIGHT RISK IS INTRODUCED FOR
SATURDAY ACROSS PORTIONS OF NEW MEXICO AND TEXAS INTO THE
SOUTHERN/CENTRAL HIGH PLAINS.
FURTHER NORTH, AN UPPER LOW/TROUGH DIGGING SOUTHEASTWARD FROM THE
GULF OF ALASKA MAY MOVE INTO THE NORTHWEST BY LATER IN THE WEEKEND.
DEPENDING ON THE EVOLUTION, THIS MAY BRING INCREASED PRECIPITATION
CHANCES TO AT LEAST THE PACIFIC NORTHWEST. ELSEWHERE, A BROAD
UPPER TROUGH EXTENDING TOWARDS THE WESTERN ATLANTIC MAY SUPPORT
PERSISTENT EASTERLY FLOW AND MOISTURE TRANSPORT INTO FLORIDA.
PERIODS OF SHOWERS AND THUNDERSTORMS COULD DEVELOP ALONG THE
FLORIDA COAST, WITH RAINFALL POTENTIALLY BECOMING MORE WIDESPREAD
ACROSS THE SOUTHERN PENINSULA IF ONSHORE FLOW PERSISTS. REPEATED
RAINFALL OVER URBANIZED AREAS AND LOCATIONS WITH POOR DRAINAGE
COULD LEAD TO LOCALIZED FLASH FLOODING CONCERNS THROUGH THE WEEKEND
INTO EARLY NEXT WEEK.
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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