High Wind in Nevada, December 11, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
314 AM PST THU DEC 11 2014

.SYNOPSIS...

A SIGNIFICANT WINTER STORM WILL PRODUCE VERY WINDY CONDITIONS OVER
THE REGION TODAY AND TONIGHT. HEAVY RAIN AND SNOW WILL MAINLY
AFFECT NORTHEAST CALIFORNIA TODAY, THEN SPREAD ACROSS THE SIERRA
AND WESTERN NEVADA TONIGHT AND FRIDAY. MAINLY DRY AND COOL
CONDITIONS ARE EXPECTED THIS WEEKEND AS HIGH PRESSURE RETURNS TO
CALIFORNIA AND NEVADA.

&&

.SHORT TERM...

WINDS HAVE BEGUN TO PICK UP IN THE TAHOE BASIN AND FAR WESTERN
NEVADA, WITH GUSTS TO 50 MPH AROUND TRUCKEE, AND 35-45 MPH
BETWEEN RENO AND CARSON CITY. RIDGE GUSTS ALONG THE SIERRA CREST
WEST OF TAHOE HAVE INCREASED TO NEAR 100 MPH. THIS IS JUST THE
START OF THE HIGH WIND EVENT WHICH HAS BEEN ADVERTISED FOR THE
PAST FEW DAYS, AND ALL WARNINGS AND ADVISORIES WILL REMAIN INTACT.
AREAS OF BLOWING DUST HAVE BEEN INCLUDED FOR MUCH OF WESTERN
NEVADA AND EASTERN MONO COUNTY FROM LATE MORNING THROUGH THIS
EVENING, AS MEANINGFUL PRECIPITATION IS NOT EXPECTED TO ARRIVE IN
THESE AREAS UNTIL LATER TONIGHT.

PRECIPITATION SO FAR HAS GENERALLY BEEN CONFINED TO NORTHEAST
CALIFORNIA WHERE RAINFALL BETWEEN 0.50 AND 1 INCH HAS BEEN
MEASURED IN CENTRAL PLUMAS COUNTY AND WESTERN LASSEN COUNTY. THESE
AREAS ARE EXPECTED TO RECEIVE THE LION'S SHARE OF THE RAIN AND
HIGH ELEVATION SNOW FOR MUCH OF TODAY AS MODEL GUIDANCE PULLS THE
MAIN MOISTURE FEED NORTH OF INTERSTATE 80 FOR MUCH OF TODAY.
RECENT RUNS OF THE HRRR MODEL ARE SIMILAR TO THE OPERATIONAL
MODELS, ALTHOUGH A SHORT PERIOD OF RAIN MAY BRUSH ACROSS THE
TRUCKEE-TAHOE VICINITY EARLY THIS MORNING. SNOW LEVELS FROM
PROFILER DATA WEST OF THE SIERRA CREST HAVE GENERALLY HOVERED
AROUND 8500 FEET, EXCEPT DIPPING BELOW 8000 FEET WITHIN HEAVIER
PRECIP BANDS. WE RAISED SNOW LEVELS ABOVE 8000 FEET FOR TAHOE AND
DELAYED DROPPING THE SNOW LEVEL BELOW 7000 FEET UNTIL MID-LATE
AFTERNOON.

FOR NORTHEAST CALIFORNIA, PRECIPITATION WILL GENERALLY FALL AS
RAIN EXCEPT FOR THE HIGHER MOUNTAINS OF WESTERN LASSEN COUNTY
THROUGH TODAY. TRAVEL IMPACTS ARE MORE LIKELY FOR HIGHER ELEVATION
ROADS HIGHWAY 44 WEST OF SUSANVILLE, FREDONYER SUMMIT AND YUBA
PASS BY LATE AFTERNOON OR EARLY EVENING.

FOR TONIGHT, THE MAIN IMPACTS TRANSITION FROM STRONG WINDS TO
HEAVY SIERRA SNOW AND VALLEY RAIN. A RAPID WORSENING OF TRAVEL
CONDITIONS IS EXPECTED EARLY THIS EVENING FOR THE MAIN PASSES
ALONG THE CREST INCLUDING I-80 AND HIGHWAY 50, THEN SPREADING
SOUTH ACROSS ALPINE AND MONO COUNTY LATER THIS EVENING. SNOW
AMOUNTS MAY NOT BE QUITE AS HIGH DUE TO A SHORTER DURATION OF
HEAVY SNOW. HOWEVER, SNOWFALL RATES COULD BE AS HIGH AS 3 INCHES
PER HOUR ABOVE 7000 FEET AND UP TO 2 INCHES PER HOUR IN THE TAHOE
BASIN AFTER THE COLD FRONT PASSES THROUGH DURING THE EVENING.
STEADY SNOW SHOULD CONTINUE THROUGH MID MORNING FRIDAY AROUND
TAHOE, AND INTO THE EARLY AFTERNOON FOR MONO COUNTY BEFORE
TAPERING TO SNOW SHOWERS. MORE INFORMATION ON SNOW AMOUNTS ARE
INCLUDED IN OUR WINTER STORM STATEMENTS.

FOR WESTERN NV, THE BEST CHANCES FOR RAIN WILL ARRIVE AFTER
MIDNIGHT AND CONTINUE THROUGH FRIDAY MORNING. THE GFS AND ECMWF
ARE PROJECTING AROUND 0.50 INCH AROUND RENO-SPARKS, WITH LOCALLY
HIGHER AMOUNTS UP TO 1 INCH POSSIBLE SOUTH OF CARSON CITY. IN
CONTRAST, THE NAM SHOWS MORE SHADOWING WITH PRECIP TOTALS OF 0.25
INCH OR LESS FOR RENO-CARSON-DOUGLAS. DUE TO THE DEEP MOISTURE
AND STRONG FORCING ALONG AND BEHIND THE FRONT, WE ARE FAVORING
THE HIGHER RAIN TOTALS AT THIS TIME. BY FRIDAY, SNOW LEVELS DROP
TO 5000-5500 FEET AS PRECIP WINDS DOWN WITH POSSIBLE LIGHT
ACCUMULATIONS ABOVE 5500 FEET, BUT LITTLE TO NO ACCUMULATION IS
EXPECTED FOR THE HEAVILY POPULATED AREAS OF WESTERN NEVADA.

SNOW SHOWERS WILL CONTINUE DIMINISHING FRIDAY NIGHT AND END BY
SATURDAY MORNING FROM WEST CENTRAL NV TO MONO COUNTY, WITH LITTLE
TO NO ADDITIONAL ACCUMULATIONS EXPECTED. DAYTIME TEMPS WILL BE
NOTABLY COOLER ON SATURDAY BUT NEAR MID DECEMBER NORMALS WITH
HIGHS MAINLY IN THE 40S FOR LOWER ELEVATIONS AND AROUND 40 FOR
SIERRA VALLEYS. MJD

.LONG TERM...SUNDAY THROUGH WEDNESDAY...

LIMITED CHANGES WERE MADE TO THE EXTENDED FORECAST AS MODELS
REMAIN AT ODDS WITH EACH OVER ON THE DETAILS...BUT THE INDIVIDUAL
MODELS ARE CONSISTENT WITH THEMSELVES.

SHORT WAVE RIDGE OVERHEAD SUNDAY SHOULD BRING DRY WEATHER WITH LIGHT
WINDS. BUT A LACK OF MIXING WILL KEEP HIGH TEMPS IN THE VALLEYS FROM
CLIMBING ABOVE AVERAGE.

OPERATIONAL MODELS CONTINUE TO BRING THE NEXT SYSTEM INTO THE REGION
ANYWHERE FROM LATE SUNDAY EVENING...GEM...TO MONDAY AFTERNOON...
ECMWF. GFS IS BETWEEN THOSE TWO. THIS TROUGH IS COMING IN AS AN
ELONGATED SYSTEM WITH A HINT THAT A JET STREAK ROUNDING THE BASE OF
THE TROUGH WILL EITHER FORM A SECONDARY LOW SOUTH OF THE BAY AREA OR
PRODUCE A WEAKLY NEGATIVELY TILTED TROUGH. EITHER SOLUTION WOULD
TEND TO SLOW THE APPROACH OF THE MAIN TROUGH AND PCPN. FOR NOW HAVE
EDGED CLOSER TO ECMWF SOLUTION WITH THIS FEATURE.

OPERATIONAL MODELS ALSO SHOW A SECONDARY SHORT WAVE MOVING THROUGH
THE MAIN LONG WAVE TUESDAY. ECMWF KEEPS THE PATTERN STORMY THROUGH
WEDNESDAY IN WEAK WNW FLOW WHILE THE 00Z GFS SHOWED A BREAK IN THE
SERIES OF SHORT WAVES FOR WEDNESDAY. NOW THE 06Z GFS IS TRENDED MORE
TOWARD THE ECMWF.

BOTTOM LINE. WE SHOULD SEE AT LEAST LOW END POPS IN THE EXTENDED
EVERY DAY STARTING MONDAY. BECAUSE THESE SYSTEMS START
COOLER...SNOW LEVELS WILL BE LOW ENOUGH TO PRODUCE SOME SNOW AT
THE VALLEY FLOORS OF WESTERN NEVADA IF THESE SOLUTIONS HOLD. NONE
OF THESE SYSTEMS HAVE IMPRESSIVE AMOUNTS OF QPF...BUT AT LEAST THE
SIERRA SHOULD ADD A LITTLE TO THE HIGH ELEVATION SNOW PACK.

HIGH TEMPS EACH DAY SHOULD BE AT OR BELOW AVERAGE DUE TO PCPN AND
CLOUD COVER. 20

&&

.AVIATION...

SOUTHERLY GRADIENT WINDS STARTING TO INCREASE QUICKLY THROUGH THE
SIERRA...FAR NORTHEAST CALIFORNIA AND WESTERN NEVADA THIS MORNING.
GUSTS OVER THE SIERRA RIDGES HAVE ALREADY TOPPED 90 KTS WHILE SOME
SIERRA VALLEYS AND AREAS EAST OF THE SIERRA ARE SEEING GUSTS IN THE
45-50 KT RANGE. THIS SHOULD CONTINUE THROUGH THE MORNING HOURS AND
WILL LIKELY SPREAD A BIT FARTHER EAST...ALTHOUGH EAST OF HIGHWAY 95
THE STRONGEST GUSTS MAY NOT TOP 40-45 KT.

GUSTS UPWARDS OF 60-65 KTS ARE POSSIBLE THROUGH THIS EVENING BEFORE
THEY BEGIN TO DECREASE A BIT OVERNIGHT FOR FAR WESTERN NEVADA AND
THE SIERRA. UNIDIRECTIONAL FLOW FROM THE SFC UP TO ABOUT 5000 FT SHOULD
LIMIT DIRECTIONAL SHEAR...BUT THERE IS STILL LIKELY TO BE SOME SPEED
SHEAR THROUGH THE FIRST 4000-5000 FT. TURBULENCE SHOULD BE
WIDESPREAD TODAY AND WILL LIKELY BECOME QUITE ROUGH ON APPROACH AND
AT LOWER TO MID FLIGHT LEVELS OVER THE SIERRA AND TO THE EAST TODAY.

RAIN AND VERY HIGH ELEVATION SNOW HAS MOVED INTO NORTHERN AND FAR
NORTHEAST CALIFORNIA THIS MORNING. THE SHIELD OF PCPN SHOULD DRIFT
SOUTHEAST LATER TODAY AND TONIGHT...DRIVING CIGS TO IFR/MVFR
CONDITIONS AS IT MOVES. LATER THIS EVENING SNOW LEVELS BEGIN TO
DROP IN THE SIERRA FROM HIGHWAY 50 NORTH WITH ACCUMULATING SNOWS
ON SIERRA RUNWAYS. SNOW LEVELS FALL THROUGH MONO COUNTY OVERNIGHT.
BY FRIDAY MORNING WE COULD HAVE 4 TO 12 INCHES ON RUNWAYS IN THE
SIERRA...HIGHER AMOUNTS IF SNOW LEVELS FALL FASTER THROUGH THE
EVENING.

BOTTOM LINE...VERY STRONG WINDS AT THE SFC AND ALOFT TODAY WITH
WIDESPREAD TURBULENCE. DETERIORATING CIGS/VSBYS THROUGH THE
AFTERNOON AND EVENING. MOUNTAIN OBSCURATIONS DEVELOPING ALONG WITH
IFR CONDITIONS IN SNOW OVERNIGHT THROUGH THE SIERRA. LOWERED CIGS
AND RAIN IN WESTERN NEVADA VALLEYS. SNOW ACCUMULATIONS OF 4 TO 12
INCHES LIKELY FOR SIERRA RUNWAYS BY FRIDAY MORNING. 20

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...HIGH WIND WARNING UNTIL 4 AM PST FRIDAY NVZ003-005.

     HIGH WIND WARNING UNTIL 1 PM PST THIS AFTERNOON NVZ002.

     WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 1 PM PST FRIDAY
     NVZ002.

     WIND ADVISORY UNTIL 4 AM PST FRIDAY NVZ001-004.

CA...HIGH WIND WARNING UNTIL 4 AM PST FRIDAY CAZ070-071.

     WINTER STORM WARNING FROM 10 AM THIS MORNING TO 10 AM PST FRIDAY
     ABOVE 5000 FEET FOR CAZ071.

     HIGH WIND WARNING UNTIL 7 PM PST THIS EVENING CAZ073.

     WINTER STORM WARNING FROM 7 PM THIS EVENING TO 4 PM PST FRIDAY
     CAZ073.

     HIGH WIND WARNING UNTIL 1 PM PST THIS AFTERNOON CAZ072.

     WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 1 PM PST FRIDAY
     CAZ072.

&&

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