Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 211107
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
307 AM PST FRI NOV 21 2014

.SYNOPSIS...

A STORM SYSTEM WILL BRING STRONGER WINDS LATE TONIGHT AND
SATURDAY, WITH PERIODS OF RAIN AND HIGH ELEVATION SNOW MAINLY NEAR
THE SIERRA CREST, AND NEAR THE OREGON BORDER. COOLER AND DRIER
CONDITIONS ARE EXPECTED FOR SUNDAY, FOLLOWED BY A GRADUAL WARMING
TREND THROUGH THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...

LIGHT RAIN YESTERDAY EVENING COMBINED WITH A SHORT PERIOD OF
CLEARING HAS LED TO FORMATION OF FOG AROUND TRUCKEE, PORTIONS OF
THE TAHOE BASIN AND WESTERN LASSEN COUNTY. AS HIGH CLOUDS INCREASE
TODAY AHEAD OF THE NEXT STORM SYSTEM, THIS FOG SHOULD DISPERSE BY
MID MORNING.

THE MAIN IMPACT OF THIS STORM WILL BE STRONG WINDS DEVELOPING LATE
TONIGHT AND SATURDAY IN THE TAHOE BASIN AND ALONG THE SIERRA
FRONT OF WESTERN NEVADA AND EASTERN CALIFORNIA. THE HIGH WIND
WATCHES WILL REMAIN IN PLACE WITH 700 MB FLOW STILL EXPECTED TO
INCREASE TO 55-65 KT, AND A DOWNSLOPE SIGNATURE INDICATED ON THE
NAM MODEL SOUNDING FOR RENO ESPECIALLY BETWEEN 09-15Z. IN THE
WATCH AREAS, WE WILL MENTION POTENTIAL FOR GUSTS UP TO 65 MPH,
EXCEPT UP TO 75 MPH IN WIND PRONE AREAS AND 100 MPH FOR SIERRA
RIDGES. EVEN AFTER THE DOWNSLOPE COMPONENT WEAKENS WITH THE
DAYTIME COLD FRONT PASSAGE, THE PRESSURE GRADIENT WILL REMAIN
TIGHT WITH GUSTY WINDS CONTINUING THROUGH THE AFTERNOON. SOUTH OF
HIGHWAY 50, SOME GUSTS OF 50 MPH OR HIGHER MAY CONTINUE INTO PART
OF THE EVENING. WE WILL CONTINUE TO MENTION AREAS OF BLOWING DUST
OVER MUCH OF WESTERN NV AND EASTERN MONO COUNTY ON SATURDAY, SINCE
LITTLE OR NO PRECIPITATION IS EXPECTED IN THESE AREAS. BEFORE THE
COLD FRONT PASSAGE, TEMPERATURES IN WESTERN NV COULD BRIEFLY WARM
UP TO NEAR 60 DEGREES AROUND MIDDAY NEAR THE I-80 CORRIDOR, WITH
MID 60S POSSIBLE BY EARLY AFTERNOON FOR THE WEST CENTRAL BASIN AND
MINERAL COUNTY. HOWEVER, THIS WARMUP WILL BE SHORT LIVED AS A COLDER
AIR MASS SPREADS SOUTH LATER IN THE DAY.

PRECIPITATION IS STILL LIKELY TO BE SPARSE ACROSS MOST OF THE
REGION AS 130+ KT UPPER LEVEL JET AXIS REMAINS ORIENTED FROM
NORTHERN CA TO EXTREME NORTHWEST NV. AREAS SOUTH OF THIS AXIS WILL
BE ON THE UNFAVORABLE REGION FOR UPPER LEVEL FORCING, ALTHOUGH
PACIFIC MOISTURE STREAMING INTO THE SIERRA WILL BRING PERIODS OF
RAIN AND HIGH ELEVATION SNOW IN CLOSE PROXIMITY TO THE CREST. LOCAL
ACCUMULATIONS UP TO 6 INCHES WILL BE POSSIBLE ABOVE 8000 FEET.

FOR THE TAHOE BASIN, THERE WAS SOME UNCERTAINTY WITH SNOW LEVELS
DUE TO A DEEP ISOTHERMAL LAYER ALOFT, BUT LATEST GUIDANCE
INDICATES THAT SNOW LEVELS IN THE SIERRA WILL RISE RAPIDLY TO
ABOVE 8000 FEET FOR THE MAJORITY OF THIS EVENT. BY THE TIME COLDER
AIR WORKS DOWN TO LAKE LEVEL SATURDAY AFTERNOON, MOST OF THE
PRECIP WILL BE OVER.

ONE OTHER AREA THAT WILL BEAR WATCHING FOR PRECIPITATION WILL BE
NEAR THE OREGON BORDER, WHICH WILL BE UNDER THE MORE FAVORABLE
REGION FOR UPPER LEVEL JET DYNAMICS, AND ALSO IN THE COLD SECTOR
SOONER. MOST OF THE MODEL GUIDANCE INDICATES QPF AROUND 0.25 INCH
FROM CEDARVILLE NORTHWARD, WITH LOCALLY UP TO 0.50 INCH POSSIBLE.
WHILE THE DAYTIME OCCURRENCE OF THIS RAIN AND SNOW WILL LIMIT
ACCUMULATION ON ROADS IN THE SURPRISE VALLEY AND EXTREME NORTHWEST
NV, A FEW INCHES OF SNOW COULD OCCUR ON UNPAVED SURFACES AND AFFECT
HIGHER ELEVATION ROADS SUCH AS CEDAR PASS.

ON SUNDAY, NORTHWEST FLOW ALOFT AND LIGHT SURFACE WINDS WILL LEAD
TO COOLER TEMPERATURES IN THE MID-UPPER 40S FOR MOST LOWER
ELEVATIONS. UNLIKE RECENT SHALLOW COLD FRONT PASSAGES, INVERSIONS
ARE LIKELY TO BE WEAKER SO HIGHS IN THE SIERRA VALLEYS SHOULD BE
A FEW DEGREES COOLER THAN THE WESTERN NV VALLEYS. MJD

.LONG TERM...MONDAY THROUGH THANKSGIVING DAY...

THE ECMWF HAS TRENDED STRONGLY TOWARD THE GFS AND NOW IT APPEARS
THAT ABOVE NORMAL HEIGHTS WILL RULE WITH NAEFS HEIGHTS PEAKING
AROUND TUE-WED. LIGHT WINDS AND INVERSIONS WILL KEEP TEMPS FROM
WARMING GREATLY, BUT HIGHS COULD START APPROACHING 60 DEGREES FOR
LOWER ELEVATIONS BY THANKSGIVING DAY, AS THE RIDGE AXIS SHIFTS
EASTWARD AND ALLOWS SOME INCREASE IN SOUTHWEST FLOW AND BETTER
MIXING. UPPER ELEVATIONS WILL WARM THE MOST EARLY NEXT WEEK WITH
THE SIERRA VALLEYS SLIGHTLY WARMER THAN MANY LOWER ELEVATIONS
TUE-WED, WHEN HIGHS MAY REACH 60 DEGREES AROUND TRUCKEE.

WHILE CERTAINTY IN THE RIDGE AND DRIER WEATHER IS HIGHER THIS
MORNING, THAT CERTAINTY DECREASES BY THE END OF THE WEEK. SOME
MODELS WANT TO BRING A WEAK SHORTWAVE THROUGH THE AREA FRI-SAT,
BUT OTHERS ARE DRY. IN EITHER CASE, THERE ARE NO BIG STORMS
SHOWING UP THROUGH THE NEXT 10 DAYS. THE MAIN CHANGE THIS MORNING
WAS THE REMOVAL OF A MENTION OF WEATHER WEDNESDAY. HOHMANN

&&

.AVIATION...

PATCHY FOG/FREEZING FOG IN THE SIERRA VALLEYS WILL BURN OFF BY MID
MORNING AS HIGH CLOUDS BEGIN TO INCREASE AHEAD OF OUR NEXT STORM
TODAY.

BIGGEST IMPACTS TO AVIATION LOOK TO BE TONIGHT AND SATURDAY AS A
130 KT JET PUSHES INTO NORTHERN CALIFORNIA. HIGH CONFIDENCE
EXISTS FOR A MODERATE TO STRONG WIND EVENT ACROSS AND EAST OF THE
SIERRA WHERE A HIGH WIND WATCH IS IN EFFECT. MOUNTAIN WAVES AND
TURBULENCE WILL START AFTER 00Z SATURDAY WITH POTENTIAL FOR GUSTS
OF 40-60 KT IN THE LOWER ELEVATIONS 06Z-21Z SATURDAY. AREAS OF
BLOWING DUST MAY ACCOMPANY THE WINDS ACROSS THE BASIN AND RANGE
SATURDAY. THE SATURDAY SYSTEM WILL ALSO BRING A PERIOD OF RAIN AND
SNOW TO THE SIERRA WHICH COULD LEAD TO MVFR CONDITIONS AT KTVL-
KTRK. FUENTES/HOHMANN

&&


.REV WATCHES/WARNINGS/ADVISORIES...
NV...HIGH WIND WATCH FROM THIS EVENING THROUGH SATURDAY AFTERNOON
     NVZ002-003.

CA...HIGH WIND WATCH FROM THIS EVENING THROUGH SATURDAY AFTERNOON
     CAZ071>073.

&&

$$

FOR MORE INFORMATION FROM THE NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/RENO (ALL LOWER CASE)









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