449
NGUS86 KRSA 012038
HCMRSA
HYDROMETEOROLOGICAL COORDINATION MESSAGE
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
130 PM PDT TUE APR 1 2025
..LOW PRESSURE MOVES FROM NW TO SE ACROSS THE REGION TONIGHT
..PRECIP BECOMES SCATTERED WED-THU WITH A WEAK SYSTEM SUN
METEOROLOGICAL CONDITIONS (SHORT TERM: TUE PM - FRI AM)
AREAS OF SHOWERS CONTINUE TO STREAM MAINLY FROM NORTHWEST TO
SOUTHEAST ACROSS NORTHERN/CENTRAL CA AND NORTHERN NV AS A
DISTURBANCE BEGINS TO MOVE FROM THE OR COASTAL WATERS OVER NORTHERN
CA. STILL EXPECTING THE POSSIBILITY OF AFTERNOON AND EARLY EVENING
THUNDERSTORMS AS FORCING BECOMES MORE FAVORABLE AND INSTABILITY
INCREASES PRIMARILY WHERE BREAKS IN THE CLOUDS HAVE OCCURRED. LOOK
FOR THE S/WV TROF TO CONTINUE TO TRACK SOUTHEAST ACROSS CA THROUGH
TONIGHT BEFORE SWINGING EASTWARD ACROSS THE LOWER COLORADO RIVER
BASIN. FROM 01/18Z THROUGH 02/12Z...BEST PRECIP TOTALS LOOK TO FALL
OVER THE SIERRA BETWEEN THE AMERICAN RIVER BASIN TO THE NORTH AND
TUOLUMNE RIVER BASIN TO THE SOUTH WITH 0.50 TO 1.25-INCH (LOCAL TO
1.50-INCHES). AS MENTIONED WITH THE MORNING FORECAST...DEPENDING ON
THE COVERAGE OF CONVECTIVE CELLS...LOCALIZED HIGHER AMOUNTS ARE
POSSIBLE UNDER STRONGER SHOWERS/THUNDERSTORMS. ALSO...LOOK FOR
FREEZING LEVELS TO BOTTOM OUT OVERNIGHT WITH A BROAD AREA OF 2500-
TO 5000-FEET...LOWEST NORTHWEST AND HIGHEST SOUTHEAST.
WITH THE BROAD UPR TROF CONTINUING ACROSS THE WEST FOR WEDNESDAY
INTO EARLY THURSDAY...LOOK FOR THE POTENTIAL FOR SCATTERED SHOWERS
TO CONTINUE IN THE DRIER NORTHERLY FLOW ALOFT. PRECIP SHOULD FOCUS
OVER THE SIERRA AND PORTIONS OF COASTAL SOUTHERN CA...ALONG WITH
POINTS EAST ACROSS NV. FINALLY BY THE END OF THE FORECAST PERIOD...A
NARROW WAVELENGTH UPR RIDGE WILL APPROACH THE COASTAL
WATERS...BRINGING DRY CONDITIONS AND INCREASING FREEZING LEVELS TO
THE REGION.
METEOROLOGICAL CONDITIONS (LONG TERM: FRI AM - MON AM)
LITTLE CHANGES TO THE AFTERNOON FORECAST FOR SLIGHT DECREASES IN
AMOUNTS AND COVERAGE OVER SRN SIERRA AND SRN CA AND EASTERN NV ON
FRIDAY AND OVER NW CA DURING THE DAY SUNDAY. 12Z MODELS AND
ENSEMBLES STILL SHOW VARIABILITY WITH THE SYSTEM SUNDAY INTO MONDAY
OVER THE NORTH.
UPPER LEVEL TROUGH MOVES SE THROUGH THE REGION ON FRIDAY AS
SHORTWAVE RIDGING BUILDS IN BEHIND IT. ISOLATED LIGHT PRECIP IS
POSSIBLE OVER THE SRN SIERRA AND OVER SRN CA (MAINLY OVER SAN
BERNARDINO MTNS AND SOUTH INTO THE SAN DIEGO COUNTY MTNS) AND OVER
NV ON FRIDAY. PRECIP AMOUNTS GENERALLY EXPECTED TO BE LESS THAN A
TENTH OF AN INCH. SHORTWAVE RIDGING OVER THE REGION ON SATURDAY
BETWEEN SYSTEMS AS THE TROUGH MOVES THROUGH THE FOUR CORNERS REGION
AND ANOTHER LOW PRESSURE SYSTEM APPROACHES THE WEST COAST. DRY AND
WARMER CONDITIONS EXPECTED ON SATURDAY.
THERE IS STILL VARIABILITY IN THE TIMING, STRENGTH AND TRACK OF THE
LOW PRESSURE SYSTEM FOR SUNDAY. THIS SYSTEM MAY TAP INTO SOME
MOISTURE WITH A PW PLUME NEAR AN INCH OF THE NRN CA COAST. THE 12Z
GFS IS FASTER AND FARTHER NORTH THAN THE 12Z EC (HAS FRONT ALONG THE
NRN CA COAST SUNDAY NIGHT) AND MOVES THE ASSOCIATED FRONT THROUGH
DURING THE DAY SUNDAY AND TROUGH INTO THE PAC NW/NRN CA SUNDAY
NIGHT. ENSEMBLE MEMBERS ALSO SHOW VARIABILITY. 24 HR QPF 50TH
PERCENTILE CLUSTERS ENDING AT 12Z TUESDAY RANGE FROM DRY OVER THE
REGION IN 29% OF THE ENSEMBLE MEMBERS (CANADIAN 45%, GFS 23% AND EC
29%) TO 0.5-1.5 INCHES ALONG THE NW CA COAST AND SRN OR CASCADES AND
PRECIP INTO THE SHASTA BASIN IN 43% OF THE ENSEMBLE MEMBERS
(CANADIAN 25%, GFS 60%, EC 40%). THE OTHER 28% OF THE ENSEMBLE
MEMBERS (CANADIAN 30% GFS 17% AND EC 34%) ARE IN BETWEEN WITHE PRECIP
CONFINED TO THE NW CA COAST WITH UP TO AROUND AN INCH. THE FORECAST
USES A BLEND OF THE LATEST NBM WITH WPC AND SOME PREVIOUS FORECAST.
THIS DECREASED PRECIP AMOUNTS AND EXTENT INLAND DURING THE DAY
SUNDAY. PRECIP POSSIBLE ALONG THE NRN CA COAST DURING THE DAY
SUNDAY AND SPREADING SOUTH AND EAST OVER NRN CA (MAINLY ALONG THE
COAST AND HIGHER TERRAIN) SUNDAY NIGHT. PRECIP AMOUNTS AROUND 0.25-
0.75 INCHES ALONG THE NW CA COAST AND AROUND A QUARTER OF AN INCH OR
LESS OVER THE SRN OR CASCADES AND AROUND A TENTH OF AN INCH OR LESS
FOR THE SHASTA BASIN, NRN SIERRA AND RUSSIAN BASIN.
HIGH TEMPERATURES GENERALLY NEAR NORMAL TO AROUND 15 DEGREES BELOW
NORMAL (WARMEST OVER NRN CA) FRIDAY AFTERNOON AND WARM TO NEAR
NORMAL TO 10 DEGREES ABOVE NORMAL FOR NRN CA AND NEAR NORMAL TO
AROUND 10 DEGREES BELOW NORMAL FOR CENTRAL AND SRN CA AND NV
SATURDAY AND NEAR NORMAL TO AROUND 10 DEGREES ABOVE NORMAL OVER THE
REGION ON SUNDAY (A LITTLE COOLING OVER NW CA). LOW TEMPERATURES
GENERALLY NEAR NORMAL FOR THE REGION FRIDAY NIGHT AND WARM TO NEAR
NORMAL TO 10 DEGREES ABOVE NORMAL SATURDAY NIGHT AND TO ABOVE NORMAL
TO AROUND 12 DEGREES ON SUNDAY NIGHT.
FREEZING LEVELS AROUND 5000-7000 FT EXCEPT UP TO 9000 FT OVER NRN CA
COAST FRIDAY MORNING AND RISE TO AROUND 7500-11,000 FT (SE-NW) OVER
CA AND AROUND 6500-8500 FT OVER NV (HIGHEST IN THE NW). FREEZING
LEVEL AROUND 8000-11,000 FT OVER CA/NV ON SUNDAY MORNING AND DROP TO
AROUND 5000-8000 FT OVER SRN OR AND NRN CA AND 8000-12,000 FT OVER
CENTRAL AND SRN CA AND AROUND 7500-11,000 FT OVER NV (LOWEST IN THE
NW) SUNDAY 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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