428
NGUS86 KRSA 081438
HCMRSA
HYDROMETEOROLOGICAL COORDINATION MESSAGE
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
740 AM PDT THU MAY 8 2025
...MOSTLY DRY CONDITIONS AND ABOVE NORMAL TEMPERATURES THROUGH
SATURDAY AS HIGH PRESSURE BUILDS OVERHEAD...
...A LARGE COLDER SYSTEM IS EXPECTED TO BRING PRECIP TO THE
REGION LATE SUN THRU EARLY NEXT WEEK...
METEOROLOGICAL CONDITIONS (THU AM - WED AM)
DRY CONDITIONS ACROSS THE REGION THIS MORNING AS AN UPPER RIDGE
BUILDS OVERHEAD. BEHIND THIS RIDGE, A LARGE UPPER LOW IS TRAVELING
ACROSS THE GULF OF ALASKA. THIS LOW WILL EVENTUALLY MAKE ITS WAY TO
CA TO BRING THE NEXT ROUND OF PRECIP. HIGH PRESSURE WILL CONTINUE
OUR WARMING TREND TODAY WITH ABOVE NORMAL TEMPERATURES IN THE
FORECAST BY ABOUT 5 TO 15 DEG F. TPW IMAGERY SHOWS SOME LINGERING
MOISTURE OVER PARTS OF CA (0.50-0.75") AS A FRONT CONTINUES TO
TRAVERSE THE AREA. THIS MAY GENERATE A SHOWER/THUNDERSTORM OR TWO
OVER THE SIERRA LATER TODAY, BUT NOTHING SIGNIFICANT IS EXPECTED.
THE RIDGE WILL CONTINUE TO BUILD IN OVERHEAD THE REST OF THE WEEK
KEEPING DRY CONDITIONS IN PLACE AND ALLOWING TEMPERATURE ANOMALIES
TO RISE TO +10 TO +20 DEG F FOR FRIDAY AND SATURDAY.
A TROUGH WILL DEVELOP OFF THE SOUTH SIDE OF THE GULF LOW ON SATURDAY
HEADED TOWARDS THE WEST COAST. THIS WILL ALLOW SOME INITIAL COOLING
OVER THE NORTH COAST FOR SATURDAY WHILE AS MENTIONED BEFORE THE REST
OF CA/NV WILL SEE ABOVE NORMAL TEMPERATURES. THE CORE OF THE LOW
WILL THEN SHIFT TO THE SOUTH THROUGHOUT SUNDAY SENDING SHOWERS INTO
CA. THE TIMING OF PRECIP HAS SLOWED DOWN SINCE YESTERDAY, AND MODELS
CONTINUE TO DISAGREE ON THE DETAILS OF THIS SYSTEM. ENSEMBLES OF 500
MB HEIGHT PATTERNS ARE DIVIDED AS WELL ON THE TIMING AND POSITIONING
OF THE LOW INTO EARLY NEXT WEEK. FOR NOW, THE MAJORITY OF THE PRECIP
FOR SUNDAY IS FORECAST TO STAY NORTH OF CAPE MENDOCINO ASIDE FROM
LIGHTER SHOWERS REACHING SONOMA COUNTY. BOTH THE GFS AND ECMWF SHOW
THE LOW MOVING INLAND INTO THE PACNW ON MONDAY WHILE TROUGHING DIGS
INTO NRN CA. PRECIP TO SPREAD INTO CENTRAL CA THROUGHOUT THE DAY.
TROUGHING WILL DIG DEEPER INTO THE REGION INTO TUESDAY WITH SHOWERS
POSSIBLE OVER PARTS OF SRN CA. THE TROUGH SHOULD BEGIN TO EXIT INTO
THE FOUR CORNERS BY THE AFTERNOON WITH SHOWERS LINGERING INTO EARLY
WEDNESDAY (MAINLY OVER THE SIERRA AND EASTWARD). AS THE LOW/TROUGH
MOVES OVERHEAD, THUNDERSTORMS WILL ALSO BE POSSIBLE. ENSEMBLE SPREAD
REGARDING THE QPF REMAINS SIMILAR TO YESTERDAY WITH 24 HR QPF VALUES
AT ARCATA ANYWHERE FROM 0" TO NEARLY 2" BETWEEN THE GFS/ECMWF. THERE
IS DECENT AGREEMENT ON A SYSTEM IMPACTING THE AREA LATE THIS WEEKEND
INTO EARLY NEXT WEEK, BUT LOW CONFIDENCE ON THE TIMING AND AMOUNTS
OF PRECIP.
ALL THE QPF IN THE FORECAST, ASIDE FROM A COUPLE HUNDREDTHS OVER THE
SIERRA, IS FOR THE EXTENDED WITH THE BEST DAY FOR PRECIP LIKELY TO
BE MONDAY. HIGHEST AMOUNTS OVER THE NORTHERN/CENTRAL SIERRA AND THE
SMITH BASIN. QPF 12Z SUN-12Z WEDS: 0.50-1" NORTH COAST/NRN SIERRA,
0.25-0.75" SHASTA, 0.10-0.75" CENTRAL SIERRA, A FEW HUNDREDTHS TO
0.25" SOUTHERN SIERRA AND THE REST OF NRN CA, AND LESS THAN A TENTH
FOR COASTAL SRN CA.
IN ADDITION TO PRECIPITATION, THE SYSTEM WILL LOWER TEMPERATURES
FROM NW TO SE STARTING SUNDAY WHEN MUCH OF THE CA COAST WILL DROP TO
BELOW NORMAL. THIS TREND WILL CONTINUE INTO MONDAY WITH WIDESPREAD
ANOMALIES OF -5 TO -15 DEG F. COOLER TEMPERATURES WILL PERSIST FOR
TUESDAY AS WELL. FREEZING LEVELS WILL DROP FROM 10-13.5 KFT OR SO
THIS WEEK TO 5.5-10 KFT NORTH OF I-80 SUNDAY AFTERNOON. LOWER
FREEZING LEVELS WILL SPREAD ACROSS THE REGION EARLY NEXT WEEK DOWN
TO 4.5-8 KFT NORTH OF I-80 MID MONDAY MORNING, THESE LOWER LEVELS
WILL PUSH AS FAR SOUTH AS MONTEREY COUNTY BY THE EVENING. FREEZING
LEVELS TO BOTTOM OUT EARLY TUESDAY AT 4.5-7.5 KFT NORTH OF POINT
CONCEPTION BEFORE REBOUNDING FROM SW TO NE AS THE SYSTEM EXITS INTO
WEDNESDAY.
PLEASE NOTE: THIS PRODUCT MAY NOT BE ROUTINELY UPDATED THIS
SUMMER. 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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