066
NGUS86 KRSA 212110
HCMRSA
HYDROMETEOROLOGICAL COORDINATION MESSAGE
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
115 PM PST FRI FEB 21 2025
..PRECIP SPREADS ACROSS NW CA AND SW OR THIS WEEKEND INTO MONDAY
METEOROLOGICAL CONDITIONS (SHORT TERM: FRI PM - MON AM)
ONE DISTURBANCE IS MAKING ITS WAY ACROSS SOUTHERN BC AND THE PACIFIC
NORTHWEST THIS AFTERNOON...WHILE A POSITIVELY TILTED UPR RIDGE
EXTENDS FROM OFF THE SOUTHERN CA COAST TO THE NORTH-NORTHEAST OVER
NORTHERN CA AND THE INTERIOR OF THE PACIFIC NORTHWEST. DRY
CONDITIONS WILL PERSIST INTO EARLY SATURDAY...UNTIL A DEEPER
MOISTURE PLUME EXTENDING FROM THE WEST-CENTRAL PACIFIC REACHES THE
WEST COAST BETWEEN THE PACIFIC NORTHWEST AND NORTHERN CA.
WAA/ISENTROPIC LIFT WILL RAMP UP WITH LOWERED CONDENSATION PRESSURE
DEFICITS...BRINGING AN INCREASE IN PRECIP ACROSS NORTHWEST CA AND
SOUTHWEST OR AS 1.00-INCH PW VALUES INTERSECT THE COAST. BEST TOTALS
STILL APPEAR TO BE OVER THE SMITH RIVER BASIN WITH THE EVENING AND
OVERNIGHT PERIODS ON SATURDAY INTO EARLY SUNDAY APPEARING TO BE THE
MOST ACTIVE...AS THE 21/12Z HREF SHOWS PROBABILITIES OF GREATER THAN
1.00-INCH IN EACH OF THE 6-HOUR PERIODS ENDING AT 23/06Z AND 23/12Z
INCREASING WITH NEAR CERTAINTY FOR THE OVERNIGHT HOURS. THE MOISTURE
PLUME WILL NARROW AND LIFT NORTHWARD ON SUNDAY DECREASING PRECIP
THROUGH THE DAY.
TOTALS THROUGH SUNDAY 12Z WILL GENERALLY BE IN THE RANGE OF 4.50- TO
6.00-INCHES FOR THE SMITH RIVER BASIN...DROPPING OFF RATHER RAPIDLY
INLAND AND TO THE SOUTH. OVER THE LOWER KLAMATH RIVER BASIN...EXPECT
1.00- TO 2.00-INCHES AND 0.10- TO 1.00-INCH OVER THE EEL RIVER
BASIN. INLAND OVER THE CREST OF THE SOUTHERN OR CASCADES...AMOUNTS
WILL BE IN THE RANGE OF 1.00- TO 2.00-INCHES...WITH ABOUT 0.25- TO
0.75-INCH ABOVE SHASTA DAM. FREEZING LEVELS DURING THE DURATION OF
THE PRECIP LOOK TO RANGE FROM 7000- TO 9000-FEET.
OVERALL CHANGES FROM THE MORNING FORECAST SHOW A SLIGHTLY INCREASE
IN AMOUNTS FROM CAPE MENDOCINO NORTHWARD TO THE CA/OR BORDER AND
INLAND OVER THE CREST OF THE SOUTHERN OR CASCADES...GENERALLY
SHOWING PLUS 0.10- TO PLUS 0.33-INCH.
METEOROLOGICAL CONDITIONS (LONG TERM: MON AM - THU AM)
INCREASED PRECIP AMOUNTS FOR MONDAY AROUND A TENTH OF AN INCH FOR
THE SMITH BASIN OTHERWISE LITTLE CHANGE FOR PRECIP AMOUNTS MONDAY
INTO TUESDAY MORNING.
A SHORTWAVE TROUGH MOVES INTO THE PAC NW/B.C. AND BRUSHES THE NORTH
MONDAY INTO EARLY TUESDAY BRINGING A CHANCE OF SHOWERS TO SRN OR AND
PORTIONS OF NRN CA. PW PLUME AIMED AT NRN CA COAST WITH AROUND 0.8
INCH PW ALONG THE COAST ON MONDAY MORNING THEN DROPS SOUTH AND
ERODES AND RETREATS OFF OF CENTRAL CA COAST MONDAY EVENING. SHOWERS
WILL BE ALONG THE NW CA COAST AND SRN OR MONDAY MORNING AND WILL
SPREAD INLAND INTO THE SHASTA BASIN AND SOUTH DOWN THROUGH THE EEL
BASIN DURING THE DAY MONDAY INTO MONDAY EVENING. LINGERING SHOWERS
POSSIBLE OVERNIGHT INTO TUESDAY MORNING. THE CURRENT FORECAST IS A
BLEND OF LATEST NBM AND WPC AND SOME OF PREVIOUS FORECAST. PRECIP
AMOUNTS FOR 12Z MONDAY INTO 12Z TUESDAY ARE FORECAST TO BE AROUND
0.75-1.5 INCHES FOR THE SMITH BASIN AND AROUND A HALF AN INCH FOR
THE SRN OR CASCADES AND KING RANGE AND AROUND A QUARTER OF AN INCH
OR LESS FOR THE SHASTA BASIN AND EEL BASINS AND LESS THAN A TENTH OF
AN INCH FOR THE FEATHER AND RUSSIAN BASINS. PRECIP AMOUNTS FOR EARLY
TUESDAY ARE EXPECTED TO BE AROUND A TENTH OF AN INCH OR LESS ALONG
THE NW CA COAST AND SRN OR CASCADES. THERE IS STILL SOMEWHAT LOW
CONFIDENCE IN AMOUNTS AND THE SOUTHERN AND EASTERN EXTENT OF PRECIP
FOR MONDAY INTO EARLY TUESDAY DUE TO DIFFERENCES IN MODELS AND
ENSEMBLE MEMBERS. ON THE 24 HR QPF CLUSTERS ENDING 12Z TUESDAY HAVE
LESS THAN A QUARTER (22%- GFS53% AND EC 12%) OF THE ENSEMBLE MEMBERS
HAVE A TENTH OF AN INCH OR LESS FOR THE SHASTA BASIN AND ONLY UP TO
AN INCH FOR THE SMITH BASIN AND NO PRECIP SOUTH OF PT ARENA. THE
OTHER CLUSTERS SHOW 1.5 TO 2 INCHES FOR THE SMITH BASIN AND UP TO AN
INCH FOR THE SHASTA BASIN.
THE TROUGH MOVES EAST OF THE REGION AND RIDGE OF HIGH PRESSURE
BUILDS INTO THE REGION TUESDAY AFTERNOON INTO WEDNESDAY FOR DRY
CONDITIONS. ANOTHER SHORTWAVE TROUGH BEHIND THE RIDGE THAT MAY SPLIT
WITH A CLOSED LOW POSSIBLY DEVELOPING OVER THE EASTERN PACIFIC
OFFSHORE OF THE CA COAST ON WEDNESDAY NIGHT. THE MODELS VARY ON
TIMING AND STRENGTH AND TRACK OF THIS TROUGH/LOW BUT WILL BRING A
CHANCE OF SHOWERS TO PORTIONS OF CA, MAINLY OVER CENTRAL AND SRN CA,
LATER NEXT WEEK. THE 12Z GFS IS QUICKER BRINGING IN THE SOUTHERN
PORTION OF THE TROUGH/LOW TO COAST OF CA NEAR BAY AREA THURSDAY
AFTERNOON AND INLAND INTO CENTRAL CA/NV BY FRIDAY. 12Z EC FORMS A
CLOSED LOW WITH SOUTHERN HALF OF TROUGH AND SPINS OFFSHORE THEN INTO
SRN CA LATE FRIDAY INTO SATURDAY.
FREEZING LEVELS AROUND 7000-8000 FT ALONG SRN OR CASCADES AND NW CA
COAST AND 8000-13,000 FT (N-S) ELSEWHERE MONDAY MORNING THEN DROP TO
AROUND 4000-5000 FT NEAR THE ORCA BORDER AND AROUND 6000-12,000 FT N-
S ELSEWHERE MONDAY NIGHT. FREEZING LEVELS RISE TO AROUND 8000-13,000
FT OVER CA BEHIND THE TROUGH AND LOWER TO AROUND 6000-11,000 FT OVER
NV TUESDAY NIGHT. FREEZING LEVELS AROUND 10,000 FT AND HIGHER FOR
THE REGION UNDER HIGH PRESSURE BY WEDNESDAY NIGHT.
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
KOZLOWSKI/OSBORNE
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