Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 171653
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HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
850 AM PST WED DEC 17 2014

...RAIN AND SNOW CONTINUES INTO THE WEEKEND...
...LOOK FOR DRYING CONDITIONS TO SET UP EARLY NEXT WEEK...


.24 HOUR PRECIPITATION TOTALS (ENDING DEC 17 AT 400 AM PST)...

A S/WV TROF MOVED THROUGH THE REGION BEGINNING YESTERDAY
AFTERNOON...BRINGING MODERATE PRECIP TO MOST OF THE REGION. WHILE
LESS THAN A QUARTER OF AN INCH FELL IN SOUTHERN OREGON AND THE SMITH
BASIN...AMOUNTS INCREASED OVER THE REST OF THE NORTH COAST. OVER THE
EEL R BASIN...1-2" PRECIP FELL THROUGH THE EARLY MORNING HOURS. THE
RUSSIAN PICKED UP AROUND 1-1.5"...AND THE NAPA RECEIVED 0.5-1"
PRECIP. FURTHER SOUTH...THE SANTA CRUZ AND SANTA LUCIA MTNS MEASURED
0.75-1.25" PRECIP. THE TRANSVERSE RANGES OVER SOUTHERN CA RECEIVED
AROUND 0.5-1" PRECIP...EXCEPT OVER THE SAN GABRIELS N OF GLENDALE
WHERE 1.5-2" PRECIP WAS REPORTED. MTNS IN SAN DIEGO COUNTY RECEIVED
AROUND 0.5-1". COASTAL AND VALLEY LOCATIONS IN SRN CA MEASURED
AROUND 0.25-0.75" PRECIP.

FURTHER INLAND OVER THE SHASTA DRAINAGE AS WELL AS THE FEATHER R
BASIN...1-1.5" PRECIP WAS REPORTED WITH UP TO 2" ALONG FAVORED
SLOPES OF THE WESTERN SIDE. OVER THE AMERICAN R BASIN AROUND 0.5-
0.75" PRECIP WAS MEASURED WITH SIMILAR AMOUNTS OVER THE CENTRAL
SIERRA. THE SOUTHERN SIERRA PICKED UP A MERE 0.1-0.3" PRECIP. OVER
THE SACRAMENTO VALLEY...0.5-0.75" PRECIP WAS RECORDED...WITH UP TO
AN INCH IN SOME LOCATIONS. THE SAN JOAQUIN VALLEY RECEIVED 0.1-0.4"
PRECIP THROUGH THE EARLY AM HOURS.

EAST OF THE SIERRA CREST...LESS THAN 0.2" PRECIP FELL...WITH JUST A
FEW HUNDREDTHS AROUND THE RENO AREA. AROUND 0.05-0.1" WAS RECORDED
OVER SCATTERED AREAS IN NORTHERN NEVADA.


.METEOROLOGICAL CONDITIONS (SHORT TERM: WED AM - SAT AM)...

WV/IR IMAGERY INDICATES ONE S/WV TROF MOVING ACROSS SOUTHERN CA
WHILE WEAKER ONE IS CROSSING FROM NE CA INTO NW NEV. OFFSHORE...THE
NEXT DISTURBANCE IS DROPPING INTO THE GENERAL UPR TROF ALONG THE
WEST COAST. THIS S/WV TROF IS LOCATED NEAR 40N/130W. 88-D MOSAIC IS
SHOWING SCATTERED PRECIP ASSOCIATED WITH EACH OF THESE FEATURES WITH
THE HEAVIEST SINCE 17/12Z FALLING ACROSS THE HIGHER TERRAIN FROM SW
SAN BERNARDINO COUNTY SOUTH TO SAN DIEGO COUNTY. PRECIP GAGES IN
THIS AREA SHOW AMOUNTS GENERALLY IN THE 0.33- TO 0.50-INCH RANGE
WITH A FEW LOCALIZED AREAS NEARING 0.75-INCH.

AS THE S/WV TROF MOVES OUT OF SOUTHERN CA ON ITS WAY TOWARD
AZ...PRECIP WILL BE ON THE DECREASE. THE S/WV TROF FARTHER NORTH
NEAR THE CA/NEV BORDER WILL WEAKEN AS IT MOVES OFF TOWARD THE NE.
ATTENTION WILL BE ON THE OFFSHORE S/WV TROF DROPPING SE ALONG THE
NORTH COAST...BECOMING ELONGATED AND WEAKENING AS IT MOVES INLAND.
LOOK FOR WIDESPREAD LIGHT PRECIP TO SPREAD ACROSS NORTHERN CA WITH
SCATTERED LIGHT PRECIP EXPECTED FOR CENTRAL CA.

INTO THU...THIS S/WV TROF WILL MOVE OFF TOWARD THE EAST WITH A
FAIRLY QUICK MOVING UPR RIDGE SLIDING ACROSS THE REGION. THIS WILL
BRING DRY CONDITIONS TO MUCH OF THE AREA...EXCEPT FOR SOME SCATTERED
LIGHT WAA PRECIP OVER PORTIONS OF EXTREME NORTHERN CA.

NEXT SYSTEM WILL ARRIVE ON FRIDAY. SOME DIFFERENCES AMONGST THE
MODELS IN TERMS OF STRENGTH OF THE COLD FRONT AS IT MOVES ACROSS
NORTHERN CA AND THEN DISSIPATES OVER CENTRAL CA. FOR NOW...FOLLOWED
FAIRLY CLOSE TO THE 17/09Z SREF...WHICH OFFERS A DECENT COMPROMISE.
BEST PRECIP WILL FALL OVER AREAS NEAR OR NORTH OF I-80 DURING THE
FIRST HALF OF FRIDAY...AND THEN PRECIP WILL FALL APART AS THE S/WV
TROF MOVES INLAND.


.METEOROLOGICAL CONDITIONS (LONG TERM: SAT AM - TUE AM)...

BY SATURDAY MORNING...THE FRONTAL SYSTEM IS EXPECTED TO WASH OUT
OVER SOUTHERN CA...WITH JUST THE EC HOLDING TOGETHER SOME NORTH
SLOPE SHOWERS OVER THE SANTA MONICA AND SAN GABRIEL MTNS. THE NEXT
SYSTEM FOLLOWS QUICKLY ON ITS HEELS HOWEVER...WITH PRECIP EXPECTED
TO INCREASE OVER THE NORTH COAST THROUGH THE MORNING HOURS. AFTER A
BRIEF PERIOD OF MODERATE PRECIP LATER SAT AFTERNOON INTO EARLY
EVENING...THIS SYSTEM IS HANG ON ALONG FAR NORTHERN AREAS THROUGH
SUNDAY MORNING...FINALLY EXITING DURING THE AFTERNOON AND EVENING
HOURS. PRECIP SHOULD REMAIN CONFINED TO THE NORTH COAST...SHASTA
DRAINAGE...UPPER KLAMATH...AND NORTHERN NEVADA.

BY MONDAY...HIGH PRESSURE OFF THE WEST COAST WILL DOMINATE THE
PATTERN. MOSTLY DRY CONDITIONS ARE EXPECTED TO PREVAIL WITH THE
EXCEPTION OF SOME LIGHT SCATTERED SHOWERS POSSIBLE OVER THE NORTHERN
PERIMETER OF NV LATE MON PM ASSOCIATED W THE DIRTY RIDGE. A POSSIBLE
INSIDE SLIDER REMAINS ON THE HORIZON FOR CHRISTMAS EVE AND DAY TO
BRING RAIN AND SNOW SHOWERS TO THE REGION.


.HYDROLOGICAL CONDITIONS...

THE WET WEATHER PATTERN CONTINUES TO PRODUCE PERIODIC RISES ON MOST
CALIFORNIA RIVERS TODAY.  THESE FLUCTUATING RIVER CONDITIONS WITH
MANY FLOWS ABOVE SEASONAL NORMALS ARE EXPECTED TO CONTINUE INTO THE
WEEKEND BUT WITH MORE OF A NORTHERN AND CENTRAL CALIFORNIA FOCUS.
ON THE SACRAMENTO RIVER...OVERFLOW INTO THE SUTTER BYPASS IS
OCCURRING OR EXPECTED TO OCCUR AT COLUSA AND TISDALE WEIRS FOR THE
NEXT FEW DAYS.  A RISE TO JUST BELOW MONITOR STAGE ON THE SAN DIEGO
RIVER AT FASHION VALLEY IS EXPECTED TODAY.

ALL OTHER RIVER STAGES ARE EXPECTED TO REMAIN BELOW MONITOR LEVELS
FOR THE NEXT FEW DAYS.

MORE INFORMATION ON THE CNRFC WEBSITE AT HTTP://WWW.CNRFC.NOAA.GOV

JM/DRK/JM/AM

$$



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