High Wind and Strong Wind in Nevada, December 12 to 13, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
930 PM PST FRI DEC 12 2008

.UPDATE...
AVIATION SECTION ALSO UPDATED.

WINDS INCREASING A BIT SLOWER THAN ANTICIPATED. STRONG COLD FRONT
STILL ON TRACK TO MOVE THROUGH THE AREA WITH THE FRONT NEAR THE
OREGON BORDER CURRENTLY TO RENO-TAHOE 12-14Z AND SOUTHERN ZONES BY
20Z. COLD AIR RAPIDLY FILTERING IN ALOFT WITH SLIDE MTN ALREADY 23
DEGS. GUT FEELING IS THAT CURRENT WIND FORECAST IS OVERDONE...AND
PEAK GUSTS WILL BE NEAR 60-65 MPH IN THE VALLEY TO NEAR 75 MPH
FOOTHILLS. IT WOULD BE AN EXTREMELY RARE EVENT IF WE HAVE WINDS AS
HIGH AS FORECAST WITH SUCH COLD AIR ALREADY IN PLACE ASIDE FROM
RIDGES WHICH WILL STILL LIKELY GUST OVER 100 MPH. THAT SAID...THE
TROP FOLD IS JUST BEGINNING TO MOVE INTO THE AREA AND THAT IS THE
WILD CARD. WHILE GUT IS SAYING WINDS ARE TOO STRONG...THIS MESOSCALE
FORCING COULD RESULT IN THE BRIEF PERIOD OF VERY STRONG WINDS.
THEREFORE...WILL KEEP CURRENT FCST AS IS FOR NOW. WALLMANN

&&

.PREV DISCUSSION...ISSUED AT 249 PM

...HIGH WIND EVENT TONIGHT INTO SATURDAY...
...PERIODS OF SNOW THROUGH NEXT WEEK...

SHORT TERM (TONIGHT-MONDAY NIGHT)...

IMPRESSIVE SATELLITE PRESENTATION OF INTENSIFYING CYCLONE OVER PAC
NW THIS AFTN. THIS IS THE SYSTEM THAT WILL DROP SE AND AFFECT US FOR
THE NEXT 24-36 HOURS. WINDS HAVE BEEN SLOW TO PICK UP TODAY WITH LOW
LEVEL STABLE LAYER IN PLACE, BUT WITH RAPIDLY INCREASING THERMAL AND
PRESSURE GRADIENTS ASSOC WITH APPROACHING COLD FRONT...WINDS WILL
RAMP UP STARTING THIS EVENING. VERTICAL STABILITY PROFILE, PRESENCE
OF TROP FOLD, AND INCREASING 700MB/250MB FLOW CONTINUE TO INDICATE
LIKELIHOOD FOR DAMAGING WIND EVENT FROM RNO SOUTH INTO MONO CO FROM
ROUGHLY 6Z-18Z/SAT.

GIVEN THESE INGREDIENTS AND A GOOD STANDING WAVE SIGNATURE IN LOCAL
WRF MODEL...POTENTIAL IS THERE FOR HIGH-END WIND GUSTS AOA 100 MPH
IN WIND PRONE VALLEYS AND AREAS DOWNWIND OF SIERRA MOUNTAIN GAPS.
HAVE MADE A FEW TWEAKS TO DELAY THE ONSET OF STRONGEST WINDS A
COUPLE HOURS FROM ONGOING FORECAST. LATEST WRF SHOWING SLIGHTLY
LESS VICIOUS WINDS FOR RNO AREA COMPARED TO PREVIOUS RUNS, BUT AM
NOT BUYING INTO THAT GIVEN INGREDIENTS FOR HIGH WINDS IN PLACE.
ELSEWHERE, SOLID ADVISORY WIND GUSTS ARE EXPECTED WITH AREAS OF
BLOWING DUST LIKELY GIVEN RECENT DRY SPELL.

WINDS SHOULD SUBSIDE GRADUALLY BY SATURDAY EVENING BEHIND THE FRONT.
STRONG FRONTOGENESIS ALOFT (700-400MB) WILL HELP CREATE A BAND OF
SNOW NEAR THE FRONT TONIGHT AS IT MOVES SOUTH THRU THE AREA.
ALREADY SEEING A NICE BAND OF PRECIP OVER SRN OREGON NEAR MFR.
HAVE INCREASED POPS IN NRN ZONES THIS EVENING AS A RESULT. GFS AND
SREF SHOW THE BAND BREAKING APART BY THE TIME IT HITS I-80/US 50
CORRIDOR LATE TONIGHT, AS STRONGEST FORCING ZIPS EAST INTO ERN
NV/UT. THERE COULD BE LIGHT SNOW ACCUMS IN VALLEY AREAS BY SAT
MORNING, BUT WITH WIND BEING THE MAJOR THREAT, WILL NOT ISSUE
WINTER ADVISORIES AND SIMPLY MENTION SNOW IN THE EXISTING WIND
PRODUCTS. SCT TO NUMEROUS SNOW SHOWERS WILL CONTINUE INTO SATURDAY
WITH ENHANCED INSTABILITY AND COLD POOL ALOFT. MAYBE A FEW ICE
PELLET SHOWERS?

NEXT PERIOD OF INTEREST IS SUNDAY NIGHT INTO MONDAY. CONSENSUS OF
MODELS INCLUDING THE ECMWF AND SREF SHOW A SECOND DECENT WAVE
DROPPING SOUTH ALONG THE COAST INTO NRN CA THEN. WITH MORE OF AN
ONSHORE COMPONENT...THE SIERRA MAY PICK UP A DECENT AMOUNT OF SNOW
DURING THIS PERIOD. STABILITY PROFILES ARE SUGGESTIVE OF GOOD
SPILLOVER INTO WRN NV WITH THIS FEATURE. POTENTIAL IS THERE FOR A
FEW INCHES IN WRN NV WITH A FOOT OR MORE IN THE HIGH SIERRA. HAVE
INCREASED POPS AND QPF/SNOW AMOUNTS ACCORDINGLY. WILL NOT ISSUE ANY
HEADLINES AT THIS TIME DUE TO IMMINENT WIND THREAT.

WE HAVE POSTED AN ONLINE BRIEFING DETAILING SOME OF THE IMPACTS FROM
THIS STORM...ON OUR WEBSITE AT WEATHER.GOV/RENO. PEOPLE SHOULD BE
PREPARING FOR HIGH WINDS BY REMOVING/SECURING OUTDOOR OBJECTS
INCLUDING FURNITURE AND HOLIDAY DECORATIONS. THE HIGH WINDS MAY
RESULT IN TRAVEL RESTRICTIONS...ESPECIALLY ALONG US 395. THE HIGHEST
THREAT FOR TRAVEL PROBLEMS SPECIFICALLY DUE TO SNOW IN THE SIERRA
APPEARS TO BE LATE SUNDAY INTO MONDAY WITH THAT SECOND SYSTEM,
THOUGH SOME LIGHT ACCUMS TONIGHT AND SATURDAY COULD STILL RESULT IN
DELAYS.

NOTE TO USERS: WE WILL LIKELY SEND UP A SPECIAL 6Z SOUNDING THIS
EVENING TO SAMPLE THE ENVIRONMENT AHEAD OF THE FRONT AND TO MONITOR
THE STABILITY/WIND PROFILES ALOFT. THE 12Z SOUNDING, DEPENDING ON
HOW INTENSE THE WINDS GET AT THE NWS OFFICE, MAY BE DELAYED OR
CANCELLED FOR SAFETY REASONS.

CS

.LONG TERM /TUESDAY THROUGH FRIDAY/...

MODELS ARE IN SLIGHTLY BETTER AGREEMENT TODAY REGARDING THE LONG
TERM...HOWEVER THERE IS STILL LOWER THAN AVERAGE CONFIDENCE IN THE
DETAILS. THERE IS EXPECTED TO BE LINGERING SHORTWAVE ENERGY OVER THE
CENTRAL CALIFORNIA COAST ON TUESDAY HOWEVER THE STRENGTH OF THIS
ENERGY IS STILL UNCERTAIN. EITHER WAY THIS ENERGY WILL INTERACT WITH
THE UNSTABLE AIRMASS OVER THE CWA TO CONTINUE AT LEAST SHOWER
ACTIVITY THROUGH TUESDAY NIGHT. MODELS NOW AGREE ON SHORTWAVE
RIDGING OVER THE PACNW WEDNESDAY...BUT IT IS UNCERTAIN HOW FAR SOUTH
AND EAST THIS WILL PUSH THE PREVIOUSLY MENTIONED SHORTWAVE ENERGY.
WEDNESDAY AND WEDNESDAY NIGHT ARE CURRENTLY THE BEST CHANCES FOR A
BREAK IN THE ACTIVE WEATHER...HOWEVER KEPT WITH AROUND CLIMO POPS TO
COVER THE MODEL UNCERTAINTY.

MODELS ARE NOW COMING INTO BETTER AGREEMENT ON THE NEXT SYSTEM
DIGGING OUT OF WRN CANADA LATE IN THE WEEK. THIS LOW COULD BE THE
MORE SIGNIFICANT SNOW PRODUCER FOR THE SIERRA HOWEVER IT IS STILL
SEVERAL DAYS OUT. THIS SYSTEM LOOKS TO HAVE A BETTER MOISTURE TAP
AND A BETTER OVERRUNNING SETUP AHEAD OF IT. THE BEST CHANCES FOR
PRECIP FROM THIS SYSTEM WILL BE THURSDAY NIGHT INTO THE WEEKEND.
TELECONNECTIONS FOR THIS PATTERN OF HIGH HEIGHT ANOMALIES OVER THE
ALEUTIAN ISLANDS FAVOR TROUGHINESS ALONG THE WEST COAST AND ABOVE
NORMAL PRECIP...SO THE ACTIVE WEATHER PATTERN IS EXPECTED TO
CONTINUE DESPITE POOR MODEL PERFORMANCE. JORDAN

&&

.AVIATION...

WINDS SLOWER TO MATERIALIZE AND GUT FEELING IS WINDS WILL BE LIGHTER
THAN EXPECTED. STILL EXPECT SW WIND GUSTS 45-50KTS FOR
KTVL-KTRK-KRNO BETWEEN 08-12Z...BUT ACTUAL DURATION OF THAT STRENGTH
LIKELY TO BE ONLY 2 HRS. THERE WILL STILL BE PLENTY OF TURBULENCE
NEAR THE SIERRA WITH A STANDING MTN WAVE. ALSO...KRNO WILL BE IN THE
ROTOR AT TIMES...WHICH IS WHY THERE IS SOME NORTHEAST WINDS SHOWN IN
THE TAF. AS A RESULT...LLWS MAY NOT ALWAYS BE FROM THE WSW...BUT
FROM THE NORTHEAST IN THE ROTOR ITSELF

AS THE FRONT PASSES THE WINDS WILL SWITCH TO THE NORTHWEST AND
DECREASE SIGNIFICANTLY HOWEVER GUSTS OVER 30 KTS ARE STILL LIKELY.
SNOW SHOWERS WITH RAPIDLY DROPPING TEMPERATURES ARE EXPECTED BEHIND
THE FRONT AFTER 12Z. SHOWERS AT KRNO AND KLOL WILL BE VERY SHORT
LIVED WITH LITTLE ACCUMULATION...HOWEVER PERIODS OF MVFR CONDITIONS
CAN BE EXPECTED AT KTVL AND KTRK 12-18Z. WALLMANN/JORDAN

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WIND ADVISORY UNTIL 1 AM PST SATURDAY FOR NVZ005.

     HIGH WIND WARNING UNTIL 1 PM PST SATURDAY FOR NVZ001.

     HIGH WIND WARNING UNTIL 7 AM PST SATURDAY FOR NVZ002-003.

     WIND ADVISORY UNTIL 7 AM PST SATURDAY FOR NVZ004.

CA...WIND ADVISORY UNTIL 1 AM PST SATURDAY FOR CAZ070-071.

     HIGH WIND WARNING UNTIL 1 PM PST SATURDAY FOR CAZ073.

     HIGH WIND WARNING UNTIL 7 AM PST SATURDAY FOR CAZ072.

&&

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