High Wind in California, April 19 to 20, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
233 AM PDT SAT APR 19 2008

...STRONG WINDS TODAY AND THEN COLD TEMPERATURES SUNDAY...

.SHORT TERM...
AN UNSETTLED PATTERN THROUGH THE SHORT TERM.  WINDS THIS MORNING
HAVE DECOUPLED FAIRLY WELL ACROSS THE REGION.  SURFACE WINDS ARE
GENERALLY LESS THAN 10 MPH ALTHOUGH WINDS AT THE RIDGE TOPS CONTINUE
TO GUST TO OVER 50 MPH.  THE COOLING TEMPERATURES AT THE SFC WITH
THE NIGHTTIME INVERSION ARE HELPING TO KEEP THE STRONGER WINDS FROM
MIXING TO THE SFC.

WINDS WILL BE THE MAIN CONCERN FOR TODAY.  DAYTIME HEATING WILL
COMBINE WITH INCREASING WIND SPEEDS ALOFT TO BRING STRONGER WINDS TO
THE SFC STARTING LATER THIS MORNING.  AN UPPER LOW PRESSURE SYSTEM
NOW OVER SWRN BRITISH COLUMBIA WILL BEGIN TO MOVE TO THE SOUTH
TODAY.  AN UPPER LEVEL JET NOW SHOWING UP ON SATELLITE IMAGERY WILL
HELP TO PULL THIS SYSTEM TO THE SOUTH.  WIND SPEEDS SHOULD BE AT
THEIR GREATEST AROUND 06Z SUNDAY.  THE NAM AND GFS BOTH SHOW 700 MB
WIND SPEEDS OF NEAR 50 KTS OVER THE CNTRL SIERRA BETWEEN THE TAHOE
BASIN AND MONO COUNTY AT THAT TIME.  THESE STRONGER WINDS SHOULD
MOVE THROUGH MONO COUNTY BY 12Z AS THE UPPER JET MAX MOVES SOUTH.
WILL CONTINUE WITH THE HIGH WIND WARNINGS AND WIND ADVISORIES FOR
TODAY.

NEXT CONCERN IS THE SHARPLY COLDER WEATHER ON SUNDAY.  THE MAIN COLD
POOL ALOFT SHOULD REMAIN NORTH OF OUR AREA THROUGH MONDAY BEFORE THE
UPPER LOW STARTS TO MOVE EAST.  HOWEVER...NLY FLOW WEST OF THE UPPER
LOW WILL ADVECT COLD AIR INTO THE REGION.  TEMPERATURES AT 700 MB
ARE PROGGED TO DROP TO AROUND -15C OVER THE TAHOE BASIN BY 12Z
SUNDAY.  TEMPERATURES AT 850 MB...AROUND GROUND LEVEL...SHOULD REACH
BELOW FREEZING OVER MOST OF THE KREV CWFA FOR CLOSE TO 6 HOURS
SATURDAY NIGHT...MAINLY BETWEEN 09Z AND 15Z.  SIMILAR SITUATION FOR
SUNDAY NIGHT BUT COLDEST PERIOD SHOULD BE SLIGHTLY LONGER BETWEEN
06Z AND 15Z.

TEMPERATURES SHOULD WARM UP QUICKLY ON MONDAY AS RIDGING BUILDS INTO
THE WRN CONUS AND SYNOPTIC FLOW BACKS TO A MORE WLY DIRECTION.  AFTN
HIGH TEMPERATURES ON MONDAY SHOULD BE AROUND 10 DEGREES WARMER THAN
THOSE ON SUNDAY.  HOWEVER THESE READINGS WILL STILL BE AROUND 10
DEGREES COOLER THAN NORMAL FOR MID APRIL.  OHARA

.LONG TERM...TUESDAY THROUGH FRIDAY...
MODELS IN THE MEDIUM RANGE DIVERGE QUITE A BIT BY THURSDAY. GFS IS
THE MOST PROGRESSIVE FOR THE PERIOD AND IS AN OUTLIER AMONG ITS
ENSEMBLE. EURO IS MORE IN LINE WITH THE GFS ENSEMBLE AND ALSO ITS
ENSEMBLE PER HPC. PREFER TO LEAN TOWARDS ITS SOLUTION THROUGH
WEDNESDAY WITH MORE OF A LEAN TOWARD THE GFS ENSEMBLE BEYOND.

TUESDAY SHOULD BE A DAY OF SHORT WAVE RIDGING...BUT IT WILL STILL BE
A BIT COOL AS H7 TEMPS ARE STILL NEAR -6 C AND INCREASING MID AND
HIGH CLOUDS AHEAD OF AN EAST PACIFIC SYSTEM WILL RETARD HEATING.
GOING WITH EURO...THAT SYSTEM ARRIVES TUE NIGHT INTO WED AND IT WILL
HAVE SOME DECENT MOISTURE TO WORK WITH. WILL CONTINUE WITH DAY SHIFT
IDEAS OF GENERAL CHC POPS EXCEPT SOUTH OF I-80 AND EAST OF 395 IN
WESTERN NV. H7 TEMPS REMAIN QUITE COOL SO SNOW LEVELS WILL BE A BIT
LOW...5500-6000 FEET. OF COURSE IF SOMEHOW THE GFS IS RIGHT...IT
COULD BE QUITE A BIT WARMER WITH LITTLE IN THE WAY OF PRECIP.

THURSDAY/FRIDAY...SYSTEM EXITS WITH DEEPENING SYSTEM IN THE GULF OF
ALASKA NEAR 140W. THIS SHOULD BUILD A RIDGE OVER THE WEST THROUGH
THE PERIOD. EURO IS STILL A BIT SLOW WITH THIS IDEA AND APPEARS TOO
SLOW. GFS ENSEMBLE LOOKS GOOD AND WILL SEE TEMPS RISE CLOSE TO 70 IN
WRN NV VALLEYS AND IN THE UPPER 50S SIERRA BY FRIDAY. AGAIN...IF THE
OUTLIER GFS SOLUTION IS RIGHT...IT COULD BE 5-10 DEGREES WARMER.
WALLMANN

&&

.AVIATION...
MAIN CONCERN THIS MORNING WILL BE LLWS AS VALLEYS FOR THE MOST PART
HAVE DECOUPLED XCP KTRK. WINDS OFF THE SURFACE ARE RUNNING AROUDN
30-40 KTS ATTM. LLWS SHOULD CONTINUE UNTIL AROUND 16Z WHEN MIXING
WILL BEGIN TO OCCUR AND VALLEY WINDS INCREASE. STRONGEST WINDS WILL
BE FROM 20-00Z FOR THE TERMINALS THEN GRADUALLY DECREASE AS THE
FRONT PASSES AND DIRECTION GRADUALLY SHIFTS FROM NEAR 230 THROUGH
300. EXCEPTION WILL BE KTVL WHERE LOCAL DRAINAGE EFFECTS WILL KEEP
WINDS FROM A 200 DIRECTION AT ALL TIMES.

OTHER CONCERN WITH INCREASE IN WINDS WILL BE BLOWING DUST...MAINLY
FOR KLOL. WITH WINDS A MORE WEST DIRECTION THAN MONDAYS EVENT...MORE
DUST FROM THE BLACK ROCK/SMOKE CREEK DESERTS COULD BE ADVECTED INTO
THE AREA BY 22Z. WILL GO WITH OCCASIONAL DECREASES TO NEAR 1SM...BUT
THERE IS ABOUT A 25 PCT CHANCE IT COULD BE 1/4SM OR LESS AT TIMES.

AS FAR AS PRECIP/CIGS...DO NOT SEE MUCH IMPACT XCP NEAR KTRK NEAR
03Z WHERE CIGS COULD REACH 2KFT AND VIS DOWN TO 3SM IN -SHSN.
WALLMANN

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WIND ADVISORY FROM 11 AM TO 11 PM PDT TODAY FOR NVZ002>004.

     HIGH WIND WARNING FROM 11 AM TODAY TO 5 AM PDT SUNDAY FOR
     NVZ001.

CA...WIND ADVISORY FROM 11 AM TO 11 PM PDT TODAY FOR CAZ072.

     HIGH WIND WARNING FROM 11 AM TODAY TO 5 AM PDT SUNDAY FOR
     CAZ073.
&&

HTTP://WEATHER.GOV/RENO