Hydrometeorological Discussion
Issued by NWS California-Nevada RFC

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AGUS76 KRSA 281734
HMDRSA

HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
930 AM PST FRI NOV 28 2014

...PERIODS OF RAIN AND SNOW TO DOMINATE THE FORECAST THROUGH NEXT
WEEK...

.24 HOUR PRECIPITATION TOTALS (ENDING NOV 28 AT 400 AM PST)...

A NEARLY-STATIONARY FRONTAL BOUNDARY BROUGHT LIGHT PRECIPITATION TO
FAR NW CA AND SRN OREGON.  AMOUNTS WERE 0.1-0.2" IN SRN OREGON AND
JUST 0.01" IN FAR NW CA.


.METEOROLOGICAL CONDITIONS (SHORT TERM: FRI AM - MON AM)...

RADAR THIS MORNING IS FINALLY GETTING ACTIVE OVER THE FORECAST
AREA...WITH THE NEARLY STATIONARY LINE THAT SAT JUST NORTH OF THE
CA/OR BORDER FOR MOST OF YESTERDAY AND LAST NIGHT BEGINNING TO TAKE
ITS SOUTHWARD MARCH. MODERATE PRECIP HAS ALREADY MOVED THROUGH THE
SMITH BASIN...AND IS TAKING A TURN INTO THE UPPER KLAMATH THEN
SOUTHWEST TOWARDS CAPE MENDOCINO  AND THE EEL R BASIN. PRECIP RATES
ARE GENERALLY 0.1-0.2" PER HOUR ALONG THE MAIN FRONTAL BAND.

FAIRLY GOOD MODEL AGREEMENT THROUGH THE SHORT TERM WILL TAKE THE
FRONT THROUGH NORTHERN CA THROUGH THE DAY TODAY...SAGGING AS FAR
SOUTH AS THE I-80 CORRIDOR BY MIDNIGHT. A VORT MAX PUSHING THROUGH
THE FLOW PATTERN SHOULD CAUSE A BUMP IN PRECIP ALONG THE SF BAY AND
NE INTO THE FEATHER R BASIN EARLY SATURDAY MORNING...THEN DROP A BIT
FURTHER SOUTH INTO THE SANTA CRUZ MTNS AND EAST INTO THE AMERICAN R
BASIN BY LATE MORNING. FAVORABLE JET DYNAMICS COULD ALSO GET A BUMP
IN PRECIP ALONG THE NORTH COAST AGAIN SATURDAY MORNING. THE SYSTEM
SHOULD CONTINUE TO PRODUCE SCATTERED SHOWERS THROUGH THE REST OF THE
DAY OVER NORTHERN CA SATURDAY AS THE FRONT QUICKLY WASHES OUT AND A
MOIST AIRMASS IS LEFT BEHIND.

WHILE A STRONG UPPER LOW PRESSURE SYSTEM BEGINS TO GAIN STEAM OUT
OVER THE EASTERN PACIFIC AROUND 37N/143W SUNDAY MORNING...A S/WV
TROUGH IS PROPELLED INTO NORTHERN CA. EACH OF THE MODELS TRIES TO
BRING A STREAK OF HEAVY PRECIP THROUGH THE REGION DURING THE EARLY
MORNING HOURS SUN...BUT EACH PLACES IT A BIT DIFFERENTLY. THE EC
DRAGS THIS THROUGH THE SANTA CRYZ AND SANTA LUCIA MTNS...THEN INLAND
INTO THE CENTRAL SIERRA. THE NAM IS A BIT FURTHER NORTH...SOAKING
THE RUSSIAN/NAPA BASINS...AND THE GFS KEEPS THIS FEATURE OFFSHORE.
LEANED A BIT MORE TOWARDS THE EC SOLUTION FOR THIS ONE. THE BULK OF
THE DAY ON SUNDAY WILL BE WET WITH SCATTERED LIGHT TO MODERATE
SHOWERS OVER THE MAJORITY OF NORTHERN AND CENTRAL CA. CANNOT RULE
OUT THE POSSIBILITY OF SOME LIGHT PRECIP OVER SOUTHERN CA AS WELL
ALONG THE SOUTHERN EDGE OF THIS FEATURE DURING THE LATER AFTERNOON
HOURS. SHOWERS WILL CONTINUE INTO THE OVERNIGHT PERIOD...BUT MAINLY
FOCUSED ON THE NORTHERN QUARTER OF THE REGION.


.METEOROLOGICAL CONDITIONS (LONG TERM: MON AM - THU AM)...

ALL MODELS HAVE SHOWN INCONSISTENCIES BETWEEN RUNS AND FROM ONE
MODEL TO THE NEXT.  THE GFS IS THE ONLY MODEL SHOWING A BAND OF
MODERATE-HEAVY PRECIP MOVING INTO THE NORTH COAST MON NIGHT INTO TUE
MORNING AND IS THE FASTEST MODEL WITH THE PROGRESSION OF WAVES OF
PRECIP THROUGH THE EXTENDED PERIOD.  THE OLD 12 UTC ECMWF IS IN GOOD
AGREEMENT WITH THE LATEST 00 UTC GEM RUN, BUT THE LATEST 00 UTC
ECMWF IS FASTER AND NOW JUST A LITTLE SLOWER THAN THE GFS OVERALL.
ECMWF ENSEMBLE MEANS AGREE WELL WITH THE DETERMINISTIC RUN.  WE
LEANED HEAVILY ON THE ECMWF SOLN FOR THIS MORNING`S FORECAST,
ALTHOUGH CONFIDENCE IN TIMING IS STILL LOW AT THIS POINT.

EXPECT AN ONSHORE FLOW AND LIGHT LINGERING SHOWERS TO PERSIST INTO
MON MORNING ACROSS MAINLY COASTAL AND HIGHER-ELEVATION PORTIONS OF
NRN CA AS WELL AS ACROSS SRN OREGON.  SHOWERS ARE EXPECTED TO WIND
DOWN GRADUALLY THROUGH MON NIGHT.  FOR TUE, AN UPPER LOW IS EXPECTED
DRIFT SLOWLY EWD AND APPROACH 130W.  A COLD FRONT IS EXPECTED TO
PUSH INTO THE CNTRL CA COAST BY TUE AFTERNOON, WITH PLENTY OF UPPER
DIVERGENCE AHEAD OF THE FRONT AND INTO FAR NRN CA AS WELL.  AS THE
FRONT PUSHES INLAND TUE, THERE IS A POTENTIAL FOR MODERATE TO HEAVY
PRECIPITATION FOR PARTS OF NRN AND CNTRL CA, WITH HIGHER AMOUNTS
ALSO IN SRN CA HIGHER TERRAIN AS S TO SW WINDS AND PW VALUES IN
EXCESS OF 1.3" COMBINE FOR GOOD OROGRAPHIC ENHANCEMENT.

AS THE INITIAL ROUND OF PRECIP MOVES INTO NV AND DOWN INTO SW CA,
EXPECT THE UPPER LOW TO APPROACH NRN CA, WITH THE ECMWF AGAIN
DEVELOPING GOOD UPPER DIVERGENCE OVER NRN CA AHEAD OF THE UPPER LOW.
ONSHORE FLOW IS ALSO EXPECTED TO CONTINUE DURING THIS TIME FRAME.
THE RESULT IS EXPECTED TO BE ANOTHER ROUND OF MODERATE TO HEAVY
PRECIP OVER MAINLY NRN CA ON WED, ESPECIALLY FOR THE SIERRA AND
FAVORED COASTAL AREAS.  PRECIP SHOULD BEGIN TO GRADUALLY WIND DOWN
THROUGH WED NIGHT AS THE WAVE ALOFT QUICKLY PUSHES TO THE NE.

EXPECT 7000-8000 FT FREEZING LEVELS RISING TO 8000-9000 FT WITH THE
LIGHT PRECIP ONGOING MON INTO MON NIGHT.  TUE, FREEZING LEVELS ARE
EXPECTED TO BE AROUND 9500-10,000 FT ACROSS NRN CA/NV AND ABOVE
11,000 IN SRN CA.  BY WED MORNING, LEVELS FALL TO AROUND 7500-8500
FT IN NRN/CNTRL CA/NV AND 10,000 FT AND ABOVE IN SRN CA.


.HYDROLOGICAL CONDITIONS...

PERIODIC RAIN EXPECTED ACROSS MUCH OF CALIFORNIA AND NEVADA WELL
INTO NEXT WEEK WILL PRODUCE MINOR AND SOME MODERATE RISES ON MANY
RIVERS AND STREAMS.  ALL STAGES ARE EXPECTED TO REMAIN BELOW MONITOR
LEVELS THROUGH THE WEEKEND.


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

KL/JM/KL/AM

$$



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