Strong Wind in California, September 19, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
1008 AM PDT WED SEP 19 2007

.UPDATE...
UPDATED TO PUSH PRECIPITATION COVERAGE MOSTLY INTO WESTERN LASSEN
AND NORTHERN WASHOE COUNTIES FOR THIS AFTERNOON. WITH THE UPPER LOW
DROPPING DUE SOUTH ALONG THE NORTHERN CALIFORNIA COAST TODAY...THE
COMBINATION OF THE COLD FRONT AND BEST UPPER FORCING IN THE
NORTHEAST QUADRANT OF THE UPPER LOW WILL REMAIN OVER EXTREME
NORTHERN AND WESTERN AREAS OF THE CWA TODAY. THE MAIN STORY SOUTH OF
THE COLD FRONT WILL BE THE WIND...WHICH IS ALREADY GUSTING CLOSE TO
70 MPH ON THE SIERRA CREST AND AROUND 50 MPH AT THE DL BLISS RAWS AT
6900 FEET IN THE TAHOE ZONE. HOLD ONTO YOUR HATS SNYDER
&&

.PREVIOUS SHORT TERM...ISSUED AT 304 AM PDT
AN UPPER LOW NOW OVER THE OLYMPIC PENINSULA WILL CONTINUE TO MOVE
SOUTH ALONG THE WA/OR COAST THIS MORNING.  A JET MAX JUST WEST OF
THE LOW WILL HELP TO DEEPEN IT AND MOVE IT QUICKLY TO THE SOUTH.
THE MEDIUM RANGE MODELS HAVE COME MORE INTO LINE DURING THE LAST
COUPLE OF RUNS.  THE GFS...ECMWF...UKMET AND CANADIAN ALL BRING THE
UPPER LOW TO NRN CALIFORNIA BY 00Z THURSDAY.  THE LOW IS PROGGED BY
THE MODELS TO BECOME CUT OFF FROM THE UPPER FLOW BY 00Z FRIDAY.
EVEN BY THIS TIME THE MODELS ARE REMARKABLY SIMILAR IN BRINGING THE
500 MB LOW TO THE CNTRL CALIFORNIA COAST.  THE GFS AND UKMET ARE
SLIGHTLY FARTHER WEST WITH THE LOW...TAKING IT TO NEAR PT CONCEPTION
BY 00Z FRIDAY.  THE MODELS BEGIN TO FILL THE LOW ON FRIDAY BUT KEEP
IT STATIONARY NEAR THE CNTRL CA COAST.

WINDS HAVE ALREADY STARTED TO INCREASE IN THE HIGHER ELEVATIONS OF
THE SIERRA AND CARSON RANGE THIS MORNING.  WINDS BETWEEN 8K AND 10K
FT HAVE BEEN GUSTING TO 40-50 MPH.  SFC WINDS SHOULD DECREASE BY 00Z
THIS EVENING.  WIND GUSTS TO 45 MPH ARE POSSIBLE TODAY...ESPECIALLY
IN THE IMMEDIATE LEE OF THE SIERRA.  PRECIPITATION SHOULD SPREAD
ACROSS MOST OF THE KREV CWFA THIS AFTN.  WITH SFC TEMPERATURES ONLY
MAKING IT INTO THE MID 70S ACROSS WRN NEVADA...AND THE COLD POOL
ASSOCIATED WITH THE UPPER LOW REMAINING TO THE WEST OVER CNTRL
CALIFORNIA...INSTABILITY SHOULD BE NEGLIGIBLE ACROSS THE CNTRL
SIERRA AND WRN NEVADA.  AS A RESULT HAVE REMOVED MENTION OF TSTMS
FROM THE FORECAST FOR TODAY.  HOWEVER WILL CONTINUE MENTION OF
SHRA.  THE DEFORMATION ZONE IN THE NE QUAD OF THE UPPER LOW WILL BE
OVER THE NRN SIERRA AND NRN NEVADA TONIGHT.  WITH THIS UPPER LVL
FORCING PRECIP WILL BE LIKELY IN THE NWRN ZONES TONIGHT FROM TAHOE
NORTH.  WILL CONTINUE WITH A CHANCE OF SHRA OVER THE REMAINDER OF
THE CWFA.  THE UPPER LOW WILL REMAIN FAIRLY STATIONARY THROUGH
FRIDAY SO WILL CONTINUE WITH MENTION OF CHC AND SLIGHT CHC SHRA
ACROSS THE AREA BOTH DAYS.  SNOW LEVELS WILL DROP TO ARND 6K FT IN
THE SIERRA TONIGHT.  SOIL TEMPERATURES HOWEVER ARE AROUND 65 F OVER
MUCH OF THE REGION SO ANY SNOWFALL SHOULD NOT ACCUMULATE VERY
QUICKLY.  OHARA

.LONG TERM...SATURDAY THROUGH TUESDAY...
THERE IS DECENT CONSENSUS THIS MORNING IN EJECTION OF UPPER LOW
SATURDAY AND THEN MOVING IT EAST AS AN OPEN TROUGH SUNDAY. THERE IS
REASONABLE CONFIDENCE THAT AS UPPER LOW MOVES INTO NEVADA SATURDAY
THERE WOULD BE AN INCREASING PROBABILITY OF PRECIPITATION WITH BOTH
THE GFS/ECMWF INDICATING WIDESPREAD BAND OF PRECIPITATION DEVELOPING
ACROSS THE NORTHERN SIERRA INTO NORTHWEST NEVADA ON THE LOWS
NORTHWEST QUADRANT WHERE LARGE SCALE ASCENT WAS INDICATED. THERE MAY
BE SOME TIMING AND PLACEMENT ADJUSTMENTS NECESSARY AS THE EXACT
TRACK OF UPPER LOW IS ASCERTAINED. HOWEVER IT SEEMED PRUDENT TO
PLACE SOME HIGHER POPS/QPF DURING AT LEAST ONE PERIOD AND CURRENT
RUNS OF THE GFS/ECMWF WERE USED AS GUIDANCE. POPS WERE RAISED TO
LIKELY OVER NORTHERN AND WESTERN AREAS OF THE FORECAST AREA SATURDAY
WHILE A CHANCE OF SHOWERS/SLIGHT CHANCE OF THUNDER WAS KEPT FURTHER
EAST UNDERNEATH UPPER LOW WHERE STEEP LAPSE RATES AND NEGATIVE LI/S
SUPPORT MORE CONVECTIVE PRECIPITATION. TEMPERATURES WERE COOLED A
FEW DEGREES IN THE NORTHWEST AREA ALTHOUGH THESE READINGS MAY BE TOO
HIGH IF BAND OF STEADY RAIN DOES DEVELOP. IN ADDITION...ANOTHER
BLANKET OF SNOW WOULD COVER THE HIGH SIERRA AS SNOW LEVELS LOWER TO
AROUND 8000 FEET. UPPER LOW TO OPEN AND MOVE EAST SATURDAY NIGHT AND
SUNDAY WITH DECREASING SHOWERS. BUILDING HEIGHTS WILL BRING A
WARMING AND DRYING TREND GOING INTO EARLY NEXT WEEK. HOHMANN
&&

.AVIATION...
SCATTERED SHOWERS WILL MOVE INTO NORTHEAST CALIFORNIA AND NORTHWEST
NEVADA THIS MORNING AND THEN SPREAD THIS AFTERNOON AS A COLD FRONT
PROGRESSES SOUTH THROUGH THE AREA. GENERALLY VFR EXCEPT THERE WILL
BE LOCAL MVFR CONDITIONS/MT TOP OBSCUREMENT OVER NORTHEAST
CALIFORNIA AND TAHOE BASIN. MAIN IMPACT TODAY WILL BE SOUTHWEST TO
WEST WIND AS SURFACE PRESSURE/THERMAL GRADIENT TIGHTEN. WIDESPREAD
GUSTS 30KT LIKELY WITH LOCAL GUSTS TO 40KT. WINDS WILL DIMINISH BY
LATE EVENING. AREAS OF MVFR CONDITIONS IN CEILINGS WILL BECOME MORE
PROBABLE IN THE TAHOE BASIN TONIGHT AND EARLY THURSDAY UNDER PERIOD
OF HEAVIER RAIN/SHOWERS. HOHMANN
&&

.FIRE WEATHER...
STRONG COLD FRONT WILL PUSH ACROSS THE REGION TODAY AND BRING WITH
IT GUSTY WINDS. SOUTH TO SOUTHWEST WINDS AHEAD OF THE FRONT WILL
INCREASE LATE MORNING AND THEN SHIFT TO A MORE WEST DIRECTION DURING
THE AFTERNOON BEHIND FRONT. WIND GUSTS WILL APPROACH 35-40 MPH WITH
LOCAL GUSTS TO 50 MPH IN WIND PRONE AREAS. THE GFS CONTINUES TO SHOW
A MINIMUM IN RH AT H7 ACROSS THE WARNING AREA WHILE THE ECMWF HAS
THIS FEATURE FURTHER TO THE SOUTH. HUMIDITY IS GOING TO BE A
MARGINAL FACTOR WITH MINIMUM VALUES LIKELY TO BE REACHED EARLY
AFTERNOON BEFORE RISING...ESPECIALLY BEHIND FRONT. WHILE THE
COMBINATION OF WIND AND HUMIDITY COULD BRIEFLY REACH CRITICAL
LEVELS...IT IS GOING TO BE THE STRONG WINDS AND COLD FRONTAL PASSAGE
THAT WILL WARRANT MAINTAINING THE RED FLAG WARNING. HUMIDITY LEVELS
WILL EASILY RISE TO MUCH HIGHER VALUES BY MID EVENING TO MITIGATE
CRITICAL FIRE WEATHER CONDITIONS ALTHOUGH WINDS WILL LIKELY STAY UP
UNTIL AROUND MIDNIGHT. COOLER AND WETTER CONDITIONS WILL FOLLOW
THURSDAY INTO THE WEEKEND. HOHMANN
&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...RED FLAG WARNING FROM 10 AM TO 8 PM PDT WEDNESDAY FOR
       NVZ453-459.

     WIND ADVISORY FROM 10 AM TO 8 PM PDT WEDNESDAY FOR NVZ001>004.

CA...RED FLAG WARNING FROM 10 AM TO 8 PM PDT WEDNESDAY FOR CAZ273.

     WIND ADVISORY FROM 10 AM TO 8 PM PDT WEDNESDAY FOR CAZ072-073.

&&

HTTP://WEATHER.GOV/RENO