450
NGUS86 KRSA 211422
HCMRSA
HYDROMETEOROLOGICAL COORDINATION MESSAGE
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
720 AM PDT TUE OCT 21 2025
...MOSTLY DRY CONDITIONS THROUGH THURS, ASIDE FROM SCATTERED
SHOWERS/T-STORMS OVER THE SRN SIERRA/NV WEDS AS A LOW MOVES
THROUGH...
...MORE WIDESPREAD PRECIP EXPECTED FRI-SUN ACROSS NRN CA AS TROPICAL
MOISTURE IS STEERED TOWARDS THE WEST COAST...
METEOROLOGICAL CONDITIONS (TUE AM - MON AM)
AN UPPER LOW CONTINUES TO APPROACH FROM THE SOUTHWEST WHILE ANOTHER
MOVES ACROSS THE GULF OF ALASKA ON THE NORTHWEST SIDE OF A RIDGE.
DRY CONDITIONS EXPECTED TODAY ACROSS THE REGION UNDER HIGH PRESSURE
WITH THE LOW SET TO REACH POINT CONCEPTION TOMORROW MOVING INLAND
ACROSS SOUTHERN CA THROUGHOUT THE DAY. AS THE LOW TRAVELS INLAND,
EXPECT IT DROP SOME SHOWERS AND THUNDERSTORMS. BEST CHANCES OVER THE
SOUTHERN SIERRA AND EASTWARD INTO NV. POSSIBLE FOR SOME LINGERING
SHOWERS THURSDAY MORNING AS THE LOW EXITS INTO THE FOUR CORNERS.
MODELS CONTINUE TO DEPICT TROPICAL MOISTURE FUNNELING INTO THE WEST
COAST IN BETWEEN A RIDGE NORTH OF THE HAWAIIAN ISLANDS AND THE LOW
IN THE GULF OF ALASKA FRIDAY AND INTO THE WEEKEND. THE FIRST BURST
OF TROPICAL MOISTURE WILL BE CARRIED INTO THE PACNW/NRN CA ALONG A
COLD FRONT ON FRIDAY. MODELS HAVE SLOWED DOWN THE ARRIVAL TIME OF
THE FRONT ONCE AGAIN PUSHING IT BACK UNTIL LATER FRIDAY MORNING. THE
ECMWF REMAINS A BIT AHEAD OF THE GFS TIMING WISE BUT FOR NOW SHOWERS
ARE EXPECTED TO REACH THE NORTH COAST MID MORNING/EARLY AFTERNOON.
PRECIP IS THEN FORECAST TO SPREAD INLAND INTO SHASTA THE REST OF THE
DAY AND DOWN INTO THE NORTHERN SIERRA/NORTH BAY OVERNIGHT. BOTH
MODELS THEN SHOW A SURFACE LOW AND UPPER TROUGH REACHING THE PACNW
SOME TIME SATURDAY MORNING AS MOISTURE CONTINUES TO MOVE ALONG A
SIMILAR TRAJECTORY. THERE REMAINS SOME UNCERTAINTY REGARDING THE
PATH OF THE MOISTURE PLUME AND HOW FAR SOUTH IT WILL REACH. THE
MAJORITY OF THE PRECIP IS FORECAST NORTH OF I-80, BUT THERE IS
DISAGREEMENT ON EXACTLY HOW FAR NORTH. ENSEMBLES ARE IN RELATIVELY
GOOD AGREEMENT ON THE HEAVIEST AMOUNTS ALONG THE NORTH COAST WITH
POINTS OF DISAGREEMENT ON HOW FAR SOUTH AND INLAND TO CARRY SOME OF
THE HIGHER VALUES. BOTTOM LINE, EXPECT TROPICAL MOISTURE AND SOME
EMBEDDED DISTURBANCES TO BRING PERIODS OF HEAVY PRECIP TO PARTS OF
NORTHERN CA FRIDAY AND OVER THE WEEKEND.
OFFICIAL QPF SLOWED DOWN THE NBM AND WPC GUIDANCE A LITTLE TO FALL
MORE IN LINE WITH THE DET GFS/ECMWF AND THE ENSEMBLE TREND TOWARDS
SLOWER ARRIVAL TIMING FRIDAY. THE REST OF THE FORECAST WAS GENERALLY
A BLEND OF WPC THE NBM AND OCCASIONALLY SOME OF THE WEST WRF. QPF
FOR WEDNESDAY SHOULD BE AROUND 0.10-0.50" OVER THE CENTRAL/SOUTHERN
SIERRA AND LESSER AMOUNTS ACROSS CENTRAL/SRN NV. EXPECT HIGHER
TOTALS UNDER THUNDERSTORMS. FOR THE REST OF THE PERIOD (FRIDAY-
SUNDAY): 2-3.50" NORTH COAST (3-5" SMITH BASIN), 1-2.30" SHASTA,
0.75-1.75" NORTHERN SIERRA, 0.10-0.75" CENTRAL SIERRA AND THE REST
OF NRN CA, 0.10-0.75" NORTH BAY, AND A FEW HUNDREDTHS TO 0.25" FOR
THE BAY AREA AND SOUTHERN SIERRA.
FREEZING LEVELS TO START FRIDAY STILL NORTH OF 12.5 KFT FOR MOST OF
THE REGION LOWERING INTO SATURDAY TO 6-10.5 KFT NORTH OF I-80 AND 10-
13.5 KFT FROM I-80 TO THE SOUTHERN SIERRA. LOWER LEVELS WILL SPREAD
A BIT FURTHER SOUTH THE REST OF SATURDAY DOWN TO 5-9 KFT NORTH OF I-
80 IN THE EVENING AND HOVERING AROUND THERE THROUGH SUNDAY. HIGHER
FREEZING LEVELS WILL BEGIN TO BUILD BACK IN FROM WEST TO EAST INTO
MONDAY.
PLEASE NOTE: THIS PRODUCT MAY NOT BE ROUTINELY UPDATED. PLEASE REFER
TO THE FOLLOWING PRODUCT ISSUED BY THE CNRFC
WWW.CNRFC.NOAA.GOV/DAILY-BRIEFING FOR A GRAPHICAL SUMMARY OF WEATHER
AND HYDROLOGIC CONDITIONS.
QPF GRAPHICS ARE AVAILABLE AT WWW.CNRFC.NOAA.GOV/QPF.PHP
*********************** CONTACT INFORMATION ************************
CNRFC OFFICE HOURS PHONE: 1 (916) 979-3056 EXTENSION 338
AFTER-HOURS CALLING SERVICE: 1 (800) 218-0858
LEAVE NAME...OFFICE...AND PHONE NUMBER
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