333
FXUS02 KWBC 111907
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
307 PM EDT SAT OCT 11 2025
VALID 12Z TUE OCT 14 2025 - 12Z SAT OCT 18 2025
...LOCALLY HEAVY RAIN AND FLASH FLOODING REMAIN A THREAT FOR PARTS
OF THE SOUTHWEST NEXT WEEK...
..HEAVIER RAIN AND MOUNTAIN SNOW FOR CALIFORNIA
..OVERVIEW
AN AMPLIFIED PATTERN WILL FAVOR A STORMY PERIOD FOR MUCH OF THE
WEST WITH WELL BELOW TEMPERATURES. THIS WILL BRING MODEST RAIN TO
CALIFORNIA AND SIGNIFICANT SNOW FOR THE SIERRA ON TUESDAY
(ESPECIALLY ABOVE 6500FT). THIS WILL SPREAD ACROSS THE
INTERMOUNTAIN WEST MIDWEEK AND PERHAPS LINGER THROUGH MUCH OF THE
WEEK AS THE SYSTEM SLOWLY MOVES EASTWARD/NORTHEASTWARD. OVER THE
CENTRAL AND EASTERN STATES, THE COASTAL STORM IN THE SHORT TERM
WILL PULL AWAY FROM THE NORTHEAST AND MILDER AIR WILL BE PREVALENT
AS UPPER RIDGING BUILDS AHEAD OF THE WESTERN TROUGHING.
..GUIDANCE/PREDICTABILITY ASSESSMENT
FOR THE FIRST HALF OF THE PERIOD, THE MODELS REMAINED IN GOOD
AGREEMENT AND MULTI-MODEL BLEND SUFFICED AS A STARTING POINT. BY
AROUND THURSDAY, THERE WAS A NOTABLE DIVERGENCE OF OPINION IN HOW
QUICKLY TO LIFT THE WESTERN TROUGH: MOST DYNAMICAL MODELS WERE
QUICKER WHILE THE AI MODELS/ENSEMBLES WERE SLOWER. THE
PREVIOUS/OVERNIGHT SHIFT WAS NICELY IN BETWEEN THE TWO CAMPS, AND
HAVE FAVORED CONTINUITY FOR NEXT FRI/SAT FOR NOW. THE FLOW IS
SOMEWHAT COMPLICATED BY INCOMING NORTHERN STREAM SHORTWAVES LATER
IN THE WEEK NEXT WEEK WHICH COULD MODULATE THE SHAPE/AXIS OF THE
TROUGH OR SPLIT IT INTO MULTIPLE SHORTWAVES. THE 13Z NBM WAS THE
BASIS FOR THE SENSIBLE WEATHER GRIDS BUT WITH MODIFICATION BY NEXT
FRI/SAT TO ACCOUNT FOR THE SLOWER PREFERENCE. IN THE
CENTRAL/EASTERN STATES, A SLOWER WESTERN TROUGH WOULD DELAY THE
RIDGE AXIS FROM MOVING EASTWARD BUT AGAIN THIS COULD BE COMPLICATED
BY NORTHERN STREAM SHORTWAVES THROUGH EASTERN CANADA. CONFIDENCE
IN THE FORECAST STARTED ABOVE AVERAGE WITH A TREND TO NEAR/BELOW
AVERAGE BY THE END OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
OVER THE NORTHEAST, THE COASTAL STORM AND ITS EFFECTS (BLUSTERY
WINDS, HIGH SURF, AND ABOVE NORMAL TIDES) WILL PULL AWAY FROM THE
COAST AT THE START OF THE PERIOD. FOCUS WILL BE ON THE WEST AS THE
INCOMING UPPER LOW THAT WILL BRING IN THE RAIN/SNOW TO CALIFORNIA
WILL BE UNDERWAY ON TUESDAY. A MARGINAL RISK IN THE EXCESSIVE
RAINFALL OUTLOOK IS NOTED FOR AREAS BETWEEN SAN FRANCISCO AND LOS
ANGELES. HEAVY SNOW IS LIKELY IN THE SIERRA ABOVE 6500-7000FT. IN
ADDITION, ANOTHER MARGINAL RISK AREA EXISTS OVER NEW MEXICO WHERE
MOISTURE LEVELS REMAIN HIGH.
INTO WEDNESDAY, THE SYSTEM WILL CONTINUE SOUTHEASTWARD AND PUSH
THE RAIN/SNOW INTO THE INTERMOUNTAIN WEST, WITH A CONTINUED THREAT
OVER NEW MEXICO WHERE ANOTHER MARGINAL RISK AREA IS IN PLACE. MUCH
OF THE WEST WILL SEE AT LEAST SOME RAIN OR SNOW, WITH SNOW LEVELS
LOWERING AS COLDER AIR MOVES IN. TEMPERATURES WILL BE WELL BELOW
NORMAL TUE-WED (BY 10-20 DEG) WITH SOME SLIGHT MODERATION FOR THE
REST OF THE WEEK, BUT STILL STAYING COOLER THAN NORMAL.
FOR THE CENTRAL STATES, SOUTHWESTERLY FLOW WILL INCREASE THE
CHANCES OF LIGHT TO MODEST RAIN LATE TUESDAY INTO WEDNESDAY OVER
THE NORTHERN PLAINS INTO THE UPPER MIDWEST CLOSER TO THE JET
STREAM. HOWEVER, MILD AND MOISTURE-LADEN AIR TO THE SOUTH (CENTRAL
TO SOUTHERN PLAINS) WILL SUPPORT AT LEAST ISOLATED SHOWERS AND
PERHAPS SOME STORMS AHEAD OF THE WESTERN/ROCKIES SYSTEM. MUCH OF
THE SOUTHEAST WILL REMAIN DRY AND WARM THROUGH THE PERIOD WITH
TEMPERATURES WELL INTO THE 80S AND LOW 90S (SOUTH TX).
FRACASSO
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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