Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
930 AM PST THU NOV 20 2014

...PRECIP TO SWEEP THROUGH THE AREA TODAY FOLLOWED BY A STRONGER
SYSTEM FRIDAY AND SATURDAY...
...WEAK SYSTEM TO CLIP THE NORTH EARLY NEXT WEEK...

.24 HOUR PRECIPITATION TOTALS (ENDING NOV 20 AT 400 AM PST)...

A WEAKENING NEGATIVELY TILTED UPR TROF MOVED ACROSS THE REGION
YESTERDAY. BEST AMOUNTS WERE OBSERVED ALONG THE COAST FROM THE
GOLDEN GATE NORTHWARD WITH 0.50- TO 1.00-INCH WITH SOME LOCAL
AMOUNTS REACHING 1.25- TO 1.50-INCHES OVER THE FAVORABLE WEST FACING
SLOPES ACROSS THE EEL...LOWER KLAMATH...AND SMITH RIVER BASINS.
INLAND OVER THE SHASTA DRAINAGE...CREST OF THE SOUTHERN OREGON
CASCADES...AND AREA NEAR LASSEN NP TOTALS WERE GENERALLY FROM 0.33-
TO 0.67-INCH.

MOVING SOUTH ACROSS THE HEART OF THE SF BAY AREA DOWN ALONG THE
CENTRAL CA COAST...AND THEN INLAND OVER THE SOUTHERN SACRAMENTO AREA
TO THE CENTRAL SIERRA TOTALS WERE GENERALLY FROM A FEW HUNDREDTHS OF
AN INCH TO 0.25-INCH.

A FEW HUNDREDTHS WERE ALSO OBSERVED OVER EXTREME NW NEV/NE CA AND
THE DRIER LOCATIONS OF THE UPPER KLAMATH BASIN.


.METEOROLOGICAL CONDITIONS (SHORT TERM: THU AM - SUN AM)...

THE NEXT WAVE OF PRECIP IS UPON US THIS MORNING...WITH AN UPPER LOW
SEEN ON WATER VAPOR IMAGERY CENTERED AROUND 200-NM WSW OF CAPE
MENDOCINO...WITH A FRONTAL SYSTEM CURRENTLY MOVING THROUGH THE NORTH
COAST. THIS WIDE BAND OF PRECIP EXTENDS FROM OFF THE WEST COAST EAST
INLAND TO AROUND I-5...AND AS FAR SOUTH AS THE SF BAY. ECHOES CAN BE
SEEN OFFSHORE FROM MONTEREY BAY...AND EXPECT PRECIP TO MOVE IN AS
SCHEDULED THROUGH THE MORNING HOURS. PRECIPITABLE WATER PLUME IS NOT
SUPER IMPRESSIVE WITH THIS SYSTEM...AND GPS IPW SENSORS CONFIRM PWAT
AMOUNTS ALONG THE NORTH COAST SITTING AROUND 0.6-0.8"...LOWER THAN
YESTERDAY`S PEAK OF AROUND 1".

EXPECT THE UPPER TROUGH TO CONTINUE PUSHING THROUGH DURING THE
AFTERNOON AND EVENING HOURS...WITH THE FRONT BRINGING PRECIP INTO
THE NORTHERN AND CENTRAL SIERRA THIS AFTERNOON...AS WELL AS INTO THE
CENTRAL COAST AND SAN JOAQUIN VALLEY. IT DOES FALL APART QUICKLY AS
IT DROPS FURTHER SOUTH AND THE MOISTURE FEED IS CUT OFF DURING THE
EVENING. WHILE PRECIP IS EXPECTED TO COME TO A CLOSE BY MIDNIGHT
OVER THE NORTHERN HALF OF THE STATE...A FEW SHOWERS ARE STILL
POSSIBLE OVER SOUTHERN CA AS THE UPPER LOW TRACKS SOUTH THROUGH THE
SE CA DESERTS EARLY FRIDAY MORNING. IT SHOULD FINALLY EJECT TO THE
SOUTHEAST LATER FRIDAY MORNING. FREEZING LEVELS ARE CURRENTLY
SITTING AT AROUND 8000-FT THIS MORNING...BUT ARE EXPECTED TO FALL TO
AROUND 6500-FT DURING THE AFTERNOON AND EVENING HOURS AS THE UPPER
LOW MOVES THROUGH. THIS FALL WILL LIKELY OCCUR AFTER THE MAIN BAND
MOVES THROUGH...HOWEVER...AND EXPECT THE MAJORITY OF WHAT FALLS
TODAY TO BE LIQUID.

THE THIRD AND STRONGEST SYSTEM IS STILL SET TO ARRIVE IN THE NORTH
FRIDAY AFTERNOON...RIGHT ON THE HEELS OF THE UPPER LOW`S EXIT. THIS
SYSTEM IS DRIVEN BY A WARM AIR ADVECTIVE PATTERN... WITH THE REGION
IN A FAVORABLE POSITION RELATIVE TO THE STRONG 150-KT UPPER JET AND
FUELED BY A BROAD 1.5" PWAT PLUME DIRECTED AT THE NORTH COAST.
MODELS SHOW VERY STRONG ISENTROPIC LIFT OVER THE NORTH COAST FROM 0-
12Z FRIDAY NIGHT...AND IN A BAND FROM THE RUSSIAN/NAPA BASINS EAST
INTO THE NORTHERN SIERRA FROM 06-18Z SATURDAY. WINDS ARE ALSO QUITE
FAVORABLE...WITH 850-MB WINDS EXPECTED TO HIT 40-50-KTS OUT OF THE
SW OVER THE NORTH COAST...AND 30-40-KTS OUT OF WEST INTO THE
NORTHERN SIERRA. WHILE MODELS HAVE BACKED OFF SLIGHTLY ON PRECIP
EXPECTED OVER THESE AREAS DURING THAT TIME...FEEL THAT THE DYNAMICS
ARE STILL MORE THAN AMPLE TO PRODUCE MODERATE TO LOCALLY HEAVY
PRECIP...AND WOULD NOT BE SURPRISED TO SEE THE FORECAST TOTALS
INCREASE OVER THE NEXT COUPLE OF UPDATES.

FREEZING LEVELS ON FRIDAY INTO SATURDAY MORNING WILL REMAIN FAIRLY
HIGH DUE TO THE NATURE OF THE PRECIP PATTERN...GENERALLY ABOVE 9000-
FT. BY SATURDAY NIGHT...SHOULD SEE THEM TAKE A DIP DOWN TO AROUND
5000-6000-FT OVER THE NORTH COAST AND TO AROUND 7000-FT OVER THE
NORTHERN SIERRA. UNFORTUNATELY FOR SNOW PACK...BY THE TIME THE Z
LEVELS FALL...ONLY SHOWERY PRECIP SHOULD REMAIN.

THROUGH THE MORNING HOURS ON SATURDAY...THE MAIN SLUG OF PRECIP IS
EXPECTED TO MOVE DOWN INTO THE CENTRAL COAST AND CENTRAL AND
SOUTHERN SIERRA...AS WELL AS INTO NORTHERN NEVADA. THE PIECE MOVING
INTO THE CENTRAL COAST SHOULD JUST RESULT IN LIGHT SHOWERS...WHILE
THE INLAND PIECES IN THE SIERRA AND OVER NEVADA SHOULD PRODUCE MORE
MODERATE TOTALS. A FINAL S/WV MOVING THROUGH THE WESTERLY FLOW
PATTERN SHOULD PRODUCE ANOTHER UPTICK IN SHOWERS OVERNIGHT OVER THE
NORTH COAST AND UPPER KLAMATH BEFORE WEAKENING AND PUSHING EAST
SUNDAY MORNING.


.METEOROLOGICAL CONDITIONS (LONG TERM: SUN AM - WED AM)...

NOT THE BEST AGREEMENT AMONGST THE MEDIUM RANGE MODELS WITH THE
PLACEMENT OF THE UPR RIDGE THE KEY FOR THE EARLY TO MIDDLE OF THE
WEEK TIME PERIOD. CONFIDENCE OF PRECIP NEXT WEEK IS FAIRLY LOW AT
THIS POINT. CURRENTLY...WPC FAVORS A COMBINATION OF THE EC AND
NAEFS...WHILE DISCOUNTING THE GFS/GEFS.

INITIALLY...A S/WV TROF WILL MOVE TOWARD THE PACNW WITH THE UPR
RIDGE PUMPING UP OFFSHORE BETWEEN 130W AND 140W. THIS WILL BRING
LIGHT PRECIP TO FAR NORTHERN AREAS NEAR THE CA/ORE BORDER AND INLAND
OVER FAR NORTHERN NEV. THIS SYSTEM WILL SHIFT INLAND AND THEN DIVE
SE ACROSS THE EASTERN GREAT BASIN ON ITS WAY TO THE SOUTHERN ROCKIES.

NEXT SLUG OF MOISTURE WILL ADVECT FROM THE NEAR THE HAWAIIAN ISLANDS
AND FOLLOW THE PERIPHERY OF THE UPR RIDGE ON ITS WAY TOWARD THE
PACNW...CLIPPING FAR NORTHERN CA. A WARM FRONT MOVING OVER THE
CA/ORE BORDER AREA WILL BRING LIGHT PRECIP TO THIS AREA ON
MONDAY...WHILE INTO TUESDAY A S/WV TROF DIVING SOUTH ALONG THE WEST
COAST OF ALASKA/BC WILL MOVE TOWARD THE PACNW. THIS WILL PUSH THE
MOISTURE PLUME SOUTH TOWARD NORTHERN CA...AND AN INCREASE IN PRECIP
OVER THE CA/ORE BORDER AREA LATER TUESDAY INTO EARLY WEDNESDAY.

ALL OF THIS DEPENDS ON THE EC/NAEFS GETTING THE OVERALL PATTERN
CORRECT. IF THE GFS TURNS OUT TO BE THE MODEL TO FOLLOW...THE UPR
RIDGE AXIS WILL BE CLOSER TO THE COAST WITH DRY CONDITIONS
PREVAILING AND SYSTEMS DIVING IN FROM THE NORTH MOVING OFF FARTHER
TO THE EAST OF THE AREA.


.HYDROLOGICAL CONDITIONS...

SMALL RISES HAVE BEEN OBSERVED AND WILL CONTINUE IN MANY OF THE
NORTH COAST RIVERS OVER THE NEXT 24 HOURS.  LARGER RISES WILL COME
OVER THE WEEKEND FOR NORTHERN CA COAST AND SACRAMENTO VALLEY RIVER
LOCATIONS DUE TO THE HEAVIER RAIN EXPECTED FRIDAY MORNING THROUGH
EARLY SUNDAY MORNING.

HOWEVER, ALL RIVER LEVELS ARE EXPECTED TO STAY WELL BELOW MONITOR
STAGE THROUGH THE FORECAST PERIOD.


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

DRK/JM/DRK/BW

$$



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