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309
AGUS76 KRSA 271841
HMDRSA

HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
930 AM PST THU NOV 27 2014

...PERIODS OF RAIN AND SNOW TO MOVE THROUGH THE REGION OVER THE NEXT
WEEK...
...UNSETTLED PATTERN STARTING MONDAY...

.24 HOUR PRECIPITATION TOTALS (ENDING NOV 27 AT 400 AM PST)...

THE REGION REMANIED DRY THROUGH EARLY THIS MORNING.


.METEOROLOGICAL CONDITIONS (THU AM - WED AM)...

SATELLITE THIS MORNING SHOWS A NARROW BAND OF MOISTURE MOVING
THROUGH SOUTHERN OREGON...WITH A WELL DEFINED DRY SLOT JUST BEHIND.
WHILE PRECIP HAS BEGUN FALLING ON THE OREGON SIDE OF THE
BORDER...EXPECT THE PRECIP TO HANG JUST OUT OF OUR AREA UNTIL LATER
IN THE DAY. THE FRONT IS FORECAST TO REMAIN STATIONARY THROUGH THE
EARLY AFTERNOON...FINALLY EDGING SOUTH IN THE EVENING AND OVERNIGHT
HOURS. DID GO A LITTLE FASTER WITH THIS SOUTHWARD MARCH THAN MODEL
CONSENSUS...FEELING IT IS JUST TOO CLOSE NOT TO.

FRIDAY SHOULD SEE THIS FRONTAL SYSTEM CONTINUING TO MOVE...PROPELLED
FINALLY BY A VORT MAX THRUST AHEAD BY THE UPPER JET. THE NARROW
MOISTURE PLUME ORIENTED ALONG THE FRONT WILL FOLLOW ALONG PRETTY
WELL IN SYNC...ALLOWING FOR MODERATE PRECIP TO MOVE THROUGH MUCH OF
NORTHERN CA NORTH OF I-80 THROUGH THE DAY FRIDAY. THE FRONT IS
EXPECTED TO HANG UP A LITTLE LONGER IN A W-E ORIENTATION FROM THE
RUSSIAN-NAPA BASINS INTO THE NORTHERN SIERRA AND FEATHER R BASIN...
GENERALLY ALONG THE I-80 CORRIDOR. THIS SYSTEM MANAGES TO HOLD
TOGETHER QUITE WELL THROUGH THE NIGHT INTO SATURDAY MORNING...WHEN
MODELS AGREE ON A LATE MORNING/EARLY AFTERNOON PERIOD OF MODERATE TO
HEAVY PRECIP OVER THE SANTA CRUZ MTNS...CUTTING OFF JUST S OF
MONTEREY BAY. BEHIND THE FRONT A SHOWERY PATTERN HOLDS TOGETHER IN A
MOIST AND RELATIVELY UNSTABLE AIRMASS.

WHILE MODELS BEGIN TO DIVERGE SIGNIFICANTLY COME SUNDAY...THEY DO AT
LEAST AGREE UPON A WET PATTERN FOR THE DAY. A WEAK S/WV TROUGH MOVES
THROUGH THE MOIST WESTERLY FLOW...TAKING AIM AGAIN AT AN AREA FROM
THE SF BAY SOUTH THROUGH THE CENTRAL COAST...AND INLAND INTO THE
SIERRA AROUND THE TAHOE BASIN. THE INLAND INTRUSION IS MORE
PRONOUNCED ON THE 27/00Z EC AND 27/12Z CANADIAN THAN IT IS ON THE
27/12Z GFS...AND IS ALL BUT IGNORED ON THE 27/12Z NAM. THE GFS
BRINGS A WAVE INLAND FURTHER NORTH AND LATER IN THE DAY INSTEAD.
THIS TIME PERIOD REALLY BEGINS THE LOW CONFIDENCE PORTION OF THE
FORECAST.

MOVING INTO MONDAY...A VIGOROUS UPPER LOW SHOULD BEGIN MOVING CLOSER
TOWARDS THE WEST COAST...THOUGH TO VARYING DEGREES AND STRENGTHS
DEPENDING ON MODEL AND RUN. CURRENT GFS CENTERS THE LOW NEAR
135W/36N ON MONDAY MORNING...WHILE THE EC IS MUCH FURTHER WEST AT
141W/31N. WHILE IT DOES NOT EXTEND QUITE AS FAR...AT THE END OF ITS
RUN...THE NAM PLACEMENT IS MORE SIMILAR TO THE GFS...WHILE IT IS
INTERESTING TO NOTE THE CANADIAN IS MORE SIMILAR TO THE EC. THESE
DIFFERENCES BRING UP A SIGNIFICANT DIFFERENCE IN POSSIBILITIES FOR
THE GENERAL PATTERN THROUGH MOST OF NEXT WEEK.

THE EC SOLUTION BRINGS LIGHT WARM FRONTAL PRECIP INTO NORTHERN CA ON
MONDAY AS WEAK RIDGING AMPS UP JUST OF THE WEST COAST IN RESPONSE TO
THE STRONG UPPER LOW FURTHER WEST. TUESDAY REMAINS MOSTLY DRY...AND
PRECIP FINALLY BEGINS TO MOVE INLAND ON WEDNESDAY. THE UPPER LOW
ENDS UP TRACKING TO THE NE...AND ONLY A WEAK FRONTAL PASSAGE MARKS
ITS WAY THROUGH CA WED AND THURS WHILE THE BULK OF THE ENERGY PASSES
TO THE NORTH.

THE GFS SOLUTION IS MUCH MORE DYNAMIC OVER THE REGION...POSITIVELY
TILTING THE TROUGH ASSOCIATED WITH THE UPPER LOW INTO NORTHERN CA BY
MONDAY NIGHT...AND BRINGING MODERATE TO HEAVY PRECIP INTO THE NORTH
COAST. THIS SYSTEM VERY SLOWLY MOVES INLAND OVERNIGHT AND INTO
TUESDAY MORNING...GRADUALLY ELONGATED AND BRINGING WIDESPREAD
MODERATE TO HEAVY PRECIP TO COASTAL AREAS PRETTY MUCH ALL THE WAY TO
SAN DIEGO. THE SHASTA BASIN SHOULD ALSO SEE AN UPTICK IN PRECIP
TUESDAY AFTERNOON AS SOUTHERLY FLOW UP THE SACRAMENTO VALLEY
INCREASES...FOLLOWED BY THE ENTIRETY OF THE WEST SIDE OF THE SIERRA
AS THE FLOW TURNS SOUTHWEST. BY WEDNESDAY MORNING...THE UPPER LOW
SHOULD PUSH EAST OF THE AREA...LEAVING A SHOWERY DAY BEHIND.

SO...THE BIG QUESTION STILL REMAINS WHICH MODEL TO TRUST. THE
CURRENT FORECAST LEANS MORE TOWARDS THE QUICKER GFS...BUT CONFIDENCE
CONTINUES TO BE MUCH LOWER THAN NORMAL...WITH THE WEATHER NEXT WEEK
STILL VERY MUCH UP IN THE AIR.


.HYDROLOGICAL CONDITIONS...

ALL RIVERS WILL REMAIN NEAR CURRENT LEVELS THROUGH THE DAY TODAY.
PRECIPITATION FORECAST FOR FRIDAY AND INTO THIS COMING WEEKEND WILL
RESULT IN MINOR RISES IN RIVERS LEVELS ALONG THE NORTHERN COAST OF
CALIFORNIA AND IN THE UPPER SACRAMENTO RIVER SYSTEM.

ALTHOUGH THE UNCERTAINTY IS HIGH ... THERE IS THE POSSIBILITY FOR
MORE SIGNIFICANT RAINFALL AND RISES IN RIVER LEVELS BEGINNING ON
TUESDAY. THE EEL RIVER WATERSHED IS ONE REGION THAT MAY SEE SOME
MAJOR RISES TUEDAY THROUGH WEDNESDAY.

ALL RIVERS ARE CURRENTLY FORECAST TO REMAIN BELOW MONITOR LEVELS
THROUGH THE NEXT FIVE DAYS.


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

JM/PF

$$



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