174
FXUS02 KWBC 081955
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
355 PM EDT THU OCT 8 2026
VALID 12Z SUN OCT 11 2026 - 12Z THU OCT 15 2026
...ISAIAS WILL BRING HEAVY RAINFALL AND POTENTIAL FLASH FLOODING
ACROSS PARTS OF THE MID-ATLANTIC AND NORTHEAST THROUGH SUNDAY...
...REMNANTS OF RACHEL TO INCREASE HEAVY RAINFALL POTENTIAL ACROSS
THE SOUTHWEST AND INTERMOUNTAIN WEST THIS WEEKEND INTO EARLY NEXT
WEEK...
..PATTERN OVERVIEW
HEAVY RAINFALL ALONG WITH FLASH FLOODING POTENTIAL FOR THE MID-
ATLANTIC AND NORTHEAST REGION THROUGH SUNDAY AS THE REMNANTS OF
ISAIAS LIFT NORTHEASTWARDS. MEANWHILE, REMNANT ENERGY AND TROPICAL
MOISTURE FROM RACHEL WILL ABSORB INTO THE AMPLIFIED WESTERN TROUGH
TO BRING WIDESPREAD RAINFALL FROM THE SOUTHWEST TO GREAT BASIN AND
ROCKIES/PLAINS. ADDITIONALLY, CHANCES FOR WIDESPREAD SNOW ARRIVES
FOR THE HIGH ELEVATIONS OF THE NORTHERN ROCKIES THIS WEEKEND INTO
EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST SUITE OF GUIDANCE MAINTAINS DECENT AGREEMENT ON THE
LARGE SCALE PATTERN FOR THE EXTENDED PERIOD FEATURING A TROUGH
TRACKING SOUTHEASTWARD AND INTERACTING WITH MOISTURE FROM THE
TROPICAL SYSTEM RACHEL. THE MODELS HAVE BEEN PERSISTENT IN
CAPTURING THE PROGRESSION OF THE NORTHERN-STREAM WAVE. UNCERTAINTY
REMAINS WITH HOW QUICKLY THE WESTERN TROUGH EJECTS INTO THE PLAINS
AND HOW STRONGLY IT AMPLIFIES AS IT INTERACTS WITH THE DEVELOPING
RIDGE DOWNSTREAM. CONFIDENCE IS LOWER CONCERNING THE TIMING AND
AMPLITUDE OF SHORTWAVES BY MID-PERIOD. THE ENSEMBLE MEANS AND THE
AI GUIDANCE SEEMS TO HAVE A BETTER HANDLE ON SOME OF THE SMALLER-
SCALE DIFFERENCES. THE FORECAST FAVORED A MULTI-MODEL BLEND
APPROACH THROUGH THE EARLY NEXT WEEK, WITH INCREASING RELIANCE ON
ENSEMBLE MEANS AND AI GUIDANCE WHERE DETERMINISTIC SOLUTIONS
DIVERGE.
..WEATHER/HAZARDS HIGHLIGHTS
THE HEAVY RAINFALL CONCERNS FROM SUNDAY INTO MONDAY WILL BE
ASSOCIATED WITH THE LINGERING TROPICAL MOISTURE FROM ISAIAS. THE
REMNANTS OF ISAIAS PROCEED NORTHEASTWARD FROM THE MID- ATLANTIC,
WITH RAINFALL GRADUALLY BECOMING MORE STRATIFORM AND SHIFTING
OFFSHORE. SOME LOCALLY MODERATE TO HEAVY RAINFALL COULD PERSIST
ACROSS PORTIONS OF THE NORTHEAST AND MID- ATLANTIC ON SUNDAY INTO
MONDAY, LEADING TO ISOLATED FLASH FLOODING RISK. THE HIGHER
LIKELIHOOD FOR FLASH FLOODING WILL OCCUR PARTICULARLY WHERE THE
CIRCULATION INTERACTS WITH FRONTAL BOUNDARIES AND WHERE REPEATED
CONVECTION DEVELOPS.
ACROSS THE WEST, THE REMNANTS OF RACHEL AND THE ASSOCIATED WESTERN
TROUGH WILL CONTINUE INTERACT, LEADING TO WIDESPREAD HEAVY
RAINFALL AND LOCALIZED FLASH FLOODING FROM THE SOUTHWEST INTO THE
GREAT BASIN, ROCKIES, AND EVENTUALLY THE NORTHERN PLAINS SUNDAY
INTO MONDAY. FURTHERMORE, COLD AIR SURGING BEHIND THE COLD FRONT
WILL LOWER SNOW LEVELS, LEADING TO ACCUMULATING SNOW OVER HIGHER
ELEVATIONS OF THE NORTHERN ROCKIES THROUGH MONDAY CAUSING POSSIBLE
MINOR TO MODERATE IMPACTS. MOMENTS OF WET AND HEAVY SNOW MAY CAUSE
IMPACTS TO POWER LINES AND TREES.
ANOTHER SHORTWAVE PROGRESSES EASTWARD ACROSS THE NORTHERN-
TIER, BRINGING ANOTHER CHANCE FOR SHOWERS ALONG A FRONTAL BOUNDARY
ACROSS THE NORTHERN/CENTRAL ROCKIES AND PLAINS AND UPPER MIDWEST
ON MONDAY INTO TUESDAY. FARTHER SOUTH ACROSS THE SOUTHWEST INTO THE
ROCKIES AND CENTRAL/SOUTHERN PLAINS, RENEWED CHANCES FOR HEAVY
RAINFALL DEVELOPS AS TROPICAL MOISTURE FROM SIMON MOVES NORTHWARD
INTO THE AREA. THE MOISTURE WILL MOVE NORTHEASTWARD ALONG THE
FRONTAL BOUNDARY, SPREADING WIDESPREAD SHOWERS ACROSS THE ROCKIES,
PLAINS, AND MIDWEST.
CAMPBELL/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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