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150
AGUS76 KRSA 301619
HMDRSA

HYDROMETEOROLOGICAL DISCUSSION NATIONAL WEATHER SERVICE / CALIFORNIA
NEVADA RFC / SACRAMENTO CA 920 AM PDT THU OCT 30 2014

...SIGNIFICANT SYSTEM TO BRING PRECIP TO MOST OF THE REGION TONIGHT
THROUGH SATURDAY...

.24 HOUR PRECIPITATION TOTALS (ENDING OCT 30 AT 500 AM PDT)...

A STATIONARY FRONT ALIGNED NEAR THE CA/ORE BORDER AND BACK WSW
OFFSHORE WAS THE FOCUSING MECHANISM FOR LIGHT PRECIP EARLY IN THE
PERIOD OVER THE SMITH AND KLAMATH RIVER BASINS. AMOUNTS WERE
GENERALLY LESS THAN 0.10-INCH.


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

STRONG UPPER LEVEL LOW PRESSURE SYSTEM CONTINUES TO DEVELOP OVER THE
GULF OF ALASKA...WITH A BAROCLINIC LEAF PATTERN FORMING AHEAD OF THE
FRONTAL SYSTEM JUST OFF THE PACIFIC NORTHWEST COASTLINE. DOWNSTREAM
RIDGE AXIS IS CURRENTLY OVER UTAH...WITH SOUTHWEST FLOW OVER CA
BEGINNING TO STREAM HIGH CLOUDS INTO MUCH OF THE REGION. VERY STRONG
UPPER JET IS CURRENTLY ALIGNED ALONG 132W IN A GENERALLY SSW-NNE
ORIENTATION WITH A CORE OF 120-KT WINDS. THIS CORE IS EXPECTED TO
STRENGTHEN AS THE SYSTEM MOVES TOWARDS THE CA COAST TONIGHT TO NEAR
150-KTS. IN ADDITION...A WELL ORGANIZED MOISTURE PLUME WHICH EXTENDS
AS FAR WEST AS THE HAWAIIAN ISLANDS WILL CONTINUE TO FEED INTO THIS
STORM...WITH AMOUNTS GENERALLY AROUND 1-1.2" REACHING THE COASTLINE.

FOR TODAY...EXPECT THE FRONTAL SYSTEM TO REMAIN JUST OFFSHORE FOR
THE MAJORITY OF THE DAY...WITH JUST LIGHT PRECIP FORECAST FOR THE
NORTH COAST THROUGH THE EARLY EVENING. EXPECT HEAVIER PRECIP TO
BEGIN IN EARNEST LATE TONIGHT INTO FRIDAY MORNING...AS THE FRONTAL
BAND MOVES INTO THE NORTH COAST AND FURTHER INLAND. HEAVIEST PRECIP
WILL INITIALLY BE FOCUSED ALONG THE NORTH COAST FROM AROUND CAPE
MENDOCINO NORTHWARD...WITH LIGHTER AMOUNTS BOTH FURTHER SOUTH
TOWARDS THE RUSSIAN R BASIN AND FURTHER INLAND INTO THE UPPER
KLAMATH.

BY FRIDAY MORNING...THE FRONT IS EXPECTED TO MOVE FURTHER INLAND...
BRINGING HEAVY PRECIP TO THE REMAINDER OF THE NORTH COAST FROM CAPE
MENDOCINO SOUTH TOWARDS THE SF BAY...AND INLAND TO THE UPPER KLAMATH
AND SHASTA REGION. FAVORABLE SOUTHERLY FLOW AND GOOD INLAND PWAT
PENETRATION WILL AID IN UPSLOPE ENHANCEMENT OVER THE WESTERN SIDE OF
SHASTA WILL BRING HIGHER AMOUNTS TO THAT AREA AS WELL AS THE
NORTHERN SACRAMENTO VALLEY FRIDAY MORNING. AS THE AFTERNOON
PROGRESSES...THE FRONT WILL PUSH EAST INTO THE NORTHERN SIERRA...
AND SOUTH INTO THE CENTRAL COAST. MODELS HOLD THIS FRONT AND
ASSOCIATED MOISTURE TOGETHER QUITE WELL DURING THIS TIME...AND FEEL
MODERATE TO HEAVY PRECIP WILL BE A REAL CONCERN FOR THESE AREAS AS
WELL. HEAVIEST PERIOD FOR THE CENTRAL COAST APPEARS TO BE FRIDAY
EVENING...AS THE UPPER JET TAKES A W-E SHIFT AND MOST FAVORABLE
ONSHORE DYNAMICS SET UP OVER SAN LUIS OBISPO AND SANTA BARBARA
COUNTIES. MODERATE TO HEAVY PRECIP IS ALSO EXPECTED TO MOVE INTO THE
CENTRAL AND SOUTHERN SIERRA DURING THIS TIME...WITH EACH THE GFS...
ECMWF...AND NAM-WRF SHOWING A BULLSEYE OVER THE SIERRA FROM JUST
SOUTH OF TAHOE TO AROUND MAMMOTH FROM LATE FRIDAY EVENING INTO
SATURDAY MORNING. CURRENT PRECIP MAY ALSO BE UNDERDONE OVER VENTURA
AND LOS ANGELES COUNTIES...AS THE 30/12Z GFS IS COMING IN WETTER
OVER THOSE AREAS THAN PREVIOUSLY INDICATED. PRECIP SHOULD MAKE IT
ALL THE WAY INTO SAN DIEGO COUNTY DURING THIS TIME.

ON SATURDAY MORNING...EXPECT PRECIP TO BEGIN CLEARING UP OVER THE
NORTH COAST ON THE BACK SIDE OF THE UPPER TROUGH...WHOSE AXIS IS
EXPECTED TO SHIFT OVER THE CA/NV BORDER BY THIS TIME. FOCUS OF
PRECIP SATURDAY MORNING SHOULD SHIFT TO OVER NEVADA...WHERE STRONG
DIVERGENCE JUST AHEAD OF THE TROUGH WILL TAKE ADVANTAGE OF THE
FORECAST 0.5-0.75" PWAT AMOUNTS THAT MAKE IT INTO NEVADA. 0.5-1.25"
PRECIP AMOUNTS ARE LIKELY OVER MUCH OF NORTHERN NEVADA.  RESIDUAL
MODERATE SHOWERS SHOULD ALSO CONTINUE OVER THE CENTRAL AND SOUTHERN
SIERRA SAT AM WITH THE TROF AXIS DYNAMICS OVERHEAD...BUT WEAKEN AS
THE AFTERNOON PROGRESSES AND THE TROF MOVES TO THE EAST. SCATTERED
SHOWERS MAY ALSO CONTINUE OVER THE CENTRAL VALLEY OF CA THROUGH THE
AFTERNOON IN THE COLD POOL BEHIND THE TROUGH...BUT SHOULD BE WIDELY
SCATTERED.

BY SATURDAY EVENING...THE TROUGH WILL TAKE ON A NEGATIVE TILT...WITH
ONLY A FEW SHOWERS STILL REMAINING OVER NORTHERN NEVADA. EVEN THESE
WILL DIMINISH BY SUNDAY MORNING.

FREEZING LEVELS WILL BEGIN HIGH TODAY...BUT QUICKLY LOWER TO AROUND
6000-7000-FT AS THE FRONT MOVES INTO THE NORTH COAST TONIGHT. EXPECT
EVEN FURTHER LOWERING ON FRIDAY AS THE TROUGH AXIS MOVES CLOSER TO
THE COAST. BY FRIDAY NIGHT...EXPECT FREEZING LEVELS AROUND 4500-5500-
FT ON THE NORTH COAST AND AROUND 5500-6500-FT OVER THE NORTHERN
SIERRA. IN THE COLD POOL JUST BEHIND THE PASSAGE OF THE TROUGH
AXIS...COLDEST FREEZING LEVELS WILL DROP TO AROUND 4500-5500-FT
ACROSS THE NORTHERN HALF OF THE STATE...AND TO AROUND 6-7-KFT OVER
THE CENTRAL AND SOUTHERN SIERRA AND SOUTHERN CA.


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

THE INITIAL S/WV TROF WILL HAVE EJECTED TO THE NE...BUT A SECONDARY
S/WV TROF WILL DROP SSE JUST EAST OF THE SIERRA CREST ON SUNDAY.
THERE IS NOT A LOT OF MOISTURE AVAILABLE FOR THIS SYSTEM...SO AT
BEST EXPECT SOME SCATTERED LIGHT PRECIP MAINLY OVER NEVADA.

INTO MONDAY...THIS S/WV TROF WILL EXIT ACROSS THE LOWER COLORADO
RIVER BASIN AND MOVE SLOWLY EAST ACROSS ARIZ. AT THE SAME TIME...AN
UPR RIDGE CENTERED JUST NORTH AND EAST OF HAWAII WILL NUDGE TOWARD
THE WEST COAST AND EXPAND OVER THE NORTHERN ROCKIES AND WEST-CENTRAL
CANADA. THIS WILL DIRECT THE NEXT MOISTURE PLUME NORTH OF THE REGION
TOWARD THE PACNW. THE SOUTHERN EXTENT WILL IMPACT THE KLAMATH AND
SMITH RIVER BASINS LATE MONDAY INTO TUESDAY BEFORE RETREATING BACK
NORTH LATE TUESDAY INTO EARLY WEDNESDAY.


.HYDROLOGICAL CONDITIONS...

PRECIPITATION FORECAST FOR TONIGHT INTO SATURDAY IS EXPECTED TO
PRODUCE MINOR RISES TO RIVERS AND STREAMS IN THE COASTAL...AND
NORTHERN CENTRAL VALLEY DRAINAGES OF CALIFORNIA.

ALL RIVERS AND STREAMS IN THE CNRFC FORECAST AREA ARE CURRENTLY
BELOW...AND ARE EXPECTED TO REMAIN BELOW MONITOR LEVELS THROUGH THE
WEEKEND.


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

DRK/JM/DRK/AT

$$




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