Lake Wind Advisory 7, NWS Reno, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
215 PM PDT SUN SEP 2 2007

.SHORT TERM...

FOCUS OF THE FIRST 3 DAYS IS ON EVOLUTION OF UPPER TROF NEAR 41N
143W (1250MI WNW OF RNO). OPERATIONAL MODELS ARE SUGGESTING A
SLOWER PROGRESSION...AND SREF DEPICTS HIGH SPREADS ON THE WRN SIDE
OF MEAN TROF...INDICATING POTENTIAL FOR A SLOWER SOLN TO OCCUR.

DRY AND RELATIVELY STABLE AIRMASS TODAY WILL SHOW A TREND TOWARD
DESTABILIZATION/MOISTENING WITH APPROACH OF THIS TROF. GIVEN
RELATIVELY MEAGER CLOUD ENHANCEMENT THUS FAR...HAVE REMOVED SLT CHCS
FOR TSRA ACROSS SRN ZONES THIS AFTN/EVE. FOR MON AFTN/EVE...HAVE
EXPANDED THE ISOLD TSRA FROM MONO/MINERAL COUNTIES UP INTO ERN
CHURCHILL. TUES-TUES NIGHT WILL BE THE MOST CHALLENGING PERIOD WITH
TROF NEARING. GFS SHOWS A VEIL OF MID LEVEL CLOUDS STREAMING ACROSS
THE CWA TUES...WHICH WITH SOME SLIGHT INSTABILITY SHOULD RESULT IN
ISOLD SHRA/TSRA FROM MONO COUNTY UP INTO GREAT BASIN AREAS.

SHOWERS MAY BECOME MORE COMMON ACROSS NRN 1/2 THE CWA AS POTENT
UPPER WAVE TRACKS THROUGH THE AREA...DYNAMIC TROPOPAUSE WITHIN TROF
AXIS DOWN TO BELOW 600MB TUES NIGHT. MAY NEED TO CONSIDER RAISING
POPS INTO CHC CATEGORY IF SYSTEM CONTINUES TO DEMONSTRATE THIS
INTENSITY. ALONG THESE LINES MAIN STORY WILL LIKELY BE STRONG
WINDS...SREF MEAN SHOWING 700MB WINDS AOA 35KTS FROM 9Z TO
21Z/TUES. GFS HAS SIMILAR NUMBERS...NAM EVEN HIGHER. EVEN THOUGH
GUSTS WILL BE MARGINAL TOMORROW...WITH THE ENHANCED LABOR DAY
BOATING TRAFFIC WILL ISSUE A LAKE WIND ADVISORY FOR MON AFTN/EVE.
GIVEN CURRENT MODEL TRENDS...WE MAY NEED TO CONSIDER A FULL WIND
ADVISORY FOR TUESDAY ACROSS MUCH OF THE CWA.

SYSTEM TRANSLATES DOWNSTREAM OF THE CWA WED INTO WED NIGHT...WITH
PRECIP CHCS AND WINDS DIMINISHING. TEMPS WILL BE SUBSTANTIALLY
COOLER TUES AND WED (BELOW NORMAL HIGHS POSSIBLE?).

CS

.LONG TERM...THURSDAY THROUGH SUNDAY...

RIDGE REBUILDING OFF THE WEST COAST WITH HEIGHT RISES OVER THE
FORECAST AREA WILL BRING WARMER TEMPS BACK TO THE REGION WITH TEMPS
BACK INTO THE LOWER 90S FOR MOST VALLEYS IN THE EXTENDED PERIOD.
WHILE A WEAKNESS IN THE RIDGE IS STILL INDICATED OVER ERN CA-WRN NV
THURS-FRI...THE FORECAST POSITION OF THE WEAK UPR LOW OFF THE CA
COAST IS TOO FAR OFFSHORE WITH ITS DEFORMATION ZONE REMAINING WEST
OF THE FORECAST AREA. WITHOUT THIS DYNAMIC FORCING...TSTM FORMATION
WILL BE UNLIKELY ALTHOUGH SOME AFTERNOON CUMULUS SHOULD FORM IN THE
SOUTH ZONES EACH DAY.

NEXT WEEKEND LOOKS MUCH MORE BENIGN ON ALL GUIDANCE SOURCES AS THE
TROPICAL MOISTURE FROM LANDFALLING TS/HURRICANE HENRIETTE IN NWRN
MEXICO LOOKS TO STAY WELL EAST AND SOUTH OF THE FORECAST
AREA...WHILE NORTHERN STREAM SHORTWAVES TRACK MORE EAST NEAR THE
US-CANADA BORDER. WEAK LOW OFF THE CA COAST IS NOW BEING SHOWN TO
RETROGRADE FARTHER OFFSHORE...LEAVING THE FORECAST AREA IN A WEAK
FLOW PATTERN THAT WILL SUPPORT SOME PM CUMULUS BUILDUPS ESPECIALLY
NEAR THE SIERRA CREST AND IN MINERAL-MONO CONVERGENCE ZONE...BUT
MARGINAL INSTBY AND WARM CAPPING LAYER ALOFT WILL LIMIT THE
POTENTIAL FOR TSTM DEVELOPMENT. MJD

&&

.AVIATION...

VFR CONDITIONS THROUGH MONDAY. ISOLD TSTMS WITH BRIEF MVFR CONDS AND
OUTFLOW GUSTS TO 35 KT PSBL BTWN 21Z-03Z MONDAY SOUTH OF FALLON TO
COLEVILLE LINE. MJD

&&

.FIRE WEATHER...

DRY AIR IS BACK...WITH HUMIDITIES LAST NIGHT ONLY DROPPING INTO THE
20S AND 30S IN NRN ZONES...AND ONLY FAIR TO MODERATE RECOVERIES
ELSEWHERE. HUMIDITIES WILL REMAIN LOW THROUGH TOMORROW...MINUS SOME
PORTIONS OF THE SIERRA. MODELS INDICATE A PUSH OF SLIGHTLY HIGHER RH
INTO THE SIERRA WHICH MAY KEEP TAHOE AND WRN LASSEN OUT OF THE RED
FLAG FOR MONDAY...BUT NIGHT SHIFT MAY WANT TO MAKE SURE OF THAT
TONIGHT. AFTER A DAY OF SOMEWHAT LIGHTER WINDS TODAY THE WINDS WILL
PICK BACK UP AGAIN ON MONDAY AS THE STRONG LOW OFF THE WEST COAST
APPROACHES THE AREA. MODELS HAVE SLOWED DOWN THE SYSTEM WHICH MAY
HAVE AN EFFECT ON HOW FAR SOUTH THE GUSTY WINDS MAKE IT. NWRN NV AND
THE REST OF NERN CA LOOK GOOD FOR LOW END RED FLAG...WITH GUSTS
30-35 MPH AND HUMIDITIES BELOW 15%. HOWEVER THE RENO-CARSON CITY
AREA IS QUESTIONABLE. LEFT THE WATCH UP FOR THIS AREA (AS OPPOSED TO
CANCELING IT) IN CASE THE MODELS SPEED UP THE SYSTEM AGAIN...AND
UPGRADED TO A WARNING FOR NRN ZONES. AFTER TALKING TO GACC OFFICES
THE RECENT RAIN THAT FELL UP NORTH DID IMPROVE THE 100 HOUR FUELS
SLIGHTLY...HOWEVER IT DID NOT MAKE A MAJOR DIFFERENCE AND THE AREA
IS STILL TO BE CONSIDERED AS DRY.

THE MAIN CONCERN IS TUESDAY. THE 700 MB FLOW AHEAD OF THE LOW
INCREASES OVERNIGHT MONDAY TO 25-35 KTS...AND PERSISTS THROUGH
TUESDAY AND THE FRONTAL PASSAGE TUESDAY NIGHT. VALLEY GUSTS WILL
LIKELY DROP OFF LATE MONDAY EVENING...HOWEVER MIDSLOPES AND HIGHER
ELEVATIONS MAY SEE WINDS GUST ALL NIGHT LONG...ALTHOUGH HUMIDITY
SHOULD IMPROVE. THE SURFACE GRADIENT REALLY TIGHTENS ON TUESDAY
AHEAD OF FRONT AND WOULD THINK WIND GUSTS UP TO 40 MPH OR HIGHER ARE
LIKELY ACROSS THE AREA. HUMIDITY WILL BE THE MAIN QUESTION. FOR
AREAS SOUTH OF INTERSTATE 80 IN NEVADA HUMIDITY SHOULD REMAIN BELOW
15% FOR SURE. OTHER AREAS FROM MONO COUNTY NORTH THROUGH ZONE
450/458 ARE MORE QUESTIONABLE. BUT MY FEELING IS THAT THE STRONGER
WINDS WILL COUNTERACT ANY RH INCREASE EVEN TO 20% OR SO...SO
CRITICAL FIRE WEATHER IS STILL POSSIBLE...AND WATCH WAS ISSUED FOR
TUESDAY. OVER 458 THERE WILL DEFINITELY BE A SIGNIFICANT WIND SHIFT
FROM SOUTHWEST TO NORTH AS THE FRONT MOVES THROUGH TUESDAY
EVENING...SO THAT WILL ALSO ADD TO THE CRITICAL FIRE BEHAVIOR
THREAT. CONDITIONS WILL IMPROVE FROM NORTH TO SOUTH TUESDAY NIGHT AS
THE WINDS DECREASE AND COOLER TEMPERATURES QUICKLY MOVE INTO THE
AREA. BENINATO

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...LAKE WIND ADVISORY FROM 10 AM TO 8 PM PDT MONDAY FOR NVZ002.

     RED FLAG WARNING FROM 2 PM TO 11 PM PDT MONDAY FOR NVZ458.

     LAKE WIND ADVISORY FROM 1 PM TO 9 PM PDT MONDAY FOR NVZ001-004.

     FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
     FOR NVZ450-453-458-459.

     FIRE WEATHER WATCH FROM MONDAY AFTERNOON THROUGH MONDAY EVENING
     FOR NVZ450.

CA...LAKE WIND ADVISORY FROM 10 AM TO 8 PM PDT MONDAY FOR CAZ071-072.

     RED FLAG WARNING FROM 2 PM TO 11 PM PDT MONDAY FOR CAZ270-278.

     LAKE WIND ADVISORY FROM 1 PM TO 9 PM PDT MONDAY FOR CAZ073.

     FIRE WEATHER WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
     FOR CAZ273.

&&

HTTP://WEATHER.GOV/RENO