Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 311019
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
319 AM PDT FRI OCT 31 2014

.SYNOPSIS...
THE FIRST WINTER STORM OF THE SEASON WILL MOVE INTO THE REGION
FRIDAY AND SATURDAY. MODERATE TO HEAVY SNOW WILL OCCUR IN THE SIERRA
FRIDAY EVENING THROUGH SATURDAY MORNING. RAIN WILL SPREAD ACROSS
WESTERN NEVADA FRIDAY NIGHT, WITH ACTIVITY TAPERING TO SHOWERS BY
SATURDAY AFTERNOON. WARM AND DRY CONDITIONS WILL RETURN BY THE
MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...
NUDGED UP QPF FURTHER NEAR THE MONO COUNTY CREST LATE TONIGHT AND
SATURDAY MORNING, OTHERWISE NO NOTABLE CHANGE TO THE SHORT TERM
FORECAST THIS MORNING AS THE FORECAST REMAINS ON TRACK.

A COLD FRONT CURRENTLY NEAR THE CALIFORNIA AND OREGON COASTS WILL
ADVANCE TO NEAR THE SIERRA THIS EVENING AS AN UPPER TROUGH
APPROACHES THE COAST. BY LATE THIS EVENING, A FAIRLY DYNAMIC
DISTURBANCE/JET STREAK WILL ROUND THE BASE OF THE TROUGH AND
PROVIDE FORCING FOR INTENSIFYING RAIN AND SNOW ALONG THE FRONTAL
BOUNDARY. WITH THE GOOD FORCING ALOFT, THE FRONT IS PROGGED TO
HOLD TOGETHER WELL ALL THE WAY THROUGH WESTERN NEVADA WITH
WIDESPREAD SOAKING RAINS EXPECTED.

AS FAR AS OROGRAPHICS IN THE SIERRA, SOUTHERLY FLOW ALOFT FRIDAY
EVENING WILL NOT BE FAVORABLE FOR ENHANCEMENT IN THE NORTHERN
SIERRA ALTHOUGH FORCING WILL STILL BRING A PERIOD OF MODERATE TO
LOCALLY (ESPECIALLY NEAR CREST) HEAVY SNOW. HOWEVER, OVERNIGHT
INTO SATURDAY MORNING FLOW WILL TURN MORE WESTERLY FOR BETTER
OROGRAPHIC FORCING AND CONTINUED SNOW SHOWERS IN THE SIERRA.
FARTHER SOUTH INTO ALPINE AND MONO COUNTY, THE COMBINATION OF
UPPER FORCING AND MORE FAVORABLY ALIGNED OROGRAPHICS WITH THE
SOUTHERLY FLOW ALOFT IS EXPECTED TO BRING THE HEAVIEST PRECIPITATION
TO THAT AREA TONIGHT AND EARLY SATURDAY. MODELS TEND TO UNDER-DO
PRECIPITATION IN THE MAMMOTH AREA, THEREFORE I HAD TO MANUALLY
ADJUST QPF UPWARD NEAR THE MONO AND SOUTHERN ALPINE COUNTY CREST.

AS FAR AS SNOW LEVELS, THEY REMAIN A BIT ELEVATED WELL INTO THIS
EVENING WITH SOUTHERLY FLOW ALOFT. THEREFORE, ROAD TROUBLES OVER
THE LOWER NORTHERN SIERRA PASSES SUCH AS I-80 AND US-50 MAY HOLD
OFF UNTIL MID EVENING (~8-9 PM) OR SO. HOWEVER, AS THE UPPER
DISTURBANCE APPROACHES OVERNIGHT SNOW LEVELS WILL FALL QUICKLY
WITH A PERIOD OF MODERATE TO HEAVY SNOW LATE IN THE EVENING
CAUSING ALL SIERRA PASSES TO EXPERIENCE WINTRY DRIVING CONDITIONS.

SATURDAY MORNING, THE DYNAMIC UPPER DISTURBANCE WILL MOVE OFF INTO
NORTHERN/NORTHEASTERN NEVADA. HOWEVER, THE SIERRA AND WESTERN
NEVADA WILL REMAIN UNDER THE TROUGH`S COLD POOL WITH MODELS STILL
HINTING AT A WRAP-AROUND BAND OF SNOW SHOWERS AND LOWER VALLEY
RAIN/SNOW SHOWERS NORTH OF HIGHWAY 50. WITH UNCERTAINTY AS TO
EXACTLY WHERE A BAND OF SHOWERS COULD DEVELOP SATURDAY MORNING, I
HAVE KEPT THE BROAD-BRUSH LIKELY POP FOR THE SIERRA AND WESTERN
NEVADA NORTH OF ABOUT HIGHWAY 50. TEMPERATURES WILL REMAIN CHILLY
WITH MID 40S TO LOW 50S FOR THE LOWER VALLEYS SATURDAY AFTERNOON.

SUNDAY, THE REGION DRIES OUT AS AN UPPER RIDGE BEGINS TO BUILD
INTO THE WEST. TEMPERATURE-WISE, IT WILL STILL REMAIN WELL BELOW
AVERAGE AS COOL HIGH PRESSURE BUILDS IN AT THE SURFACE. SNYDER

.LONG TERM...MONDAY THROUGH THURSDAY...
MINIMAL CHANGES MADE TO MOST OF THE EXTENDED FORECAST AS MEDIUM
RANGE MODELS ARE IN FAIRLY GOOD AGREEMENT THIS CYCLE. NORTHWEST FLOW
ALOFT TRANSITIONS TO MORE WESTERLY FLOW MONDAY AS A FLAT RIDGE
DEVELOPS OVER THE REGION. THE MAIN IMPACT FROM THIS FEATURE SHOULD
BE COPIOUS CLOUD COVER OVER THE FAR NORTHERN CWA...BUT THE BEST FORCING
STAYS NORTH SO WE HAVE LEFT PCPN OUT OF THE FORECAST FOR NOW.

THE RIDGE REMAINS FAIRLY FLAT THROUGH TUESDAY THEN BEGINS TO AMPLIFY
ON WEDNESDAY. THIS MEANS CONTINUED CLOUD COVER FOR THE FAR NORTHERN
CWA TUESDAY GIVING WAY TO DECREASED CLOUD COVER BY WEDNESDAY. BELOW
NORMAL HIGH TEMPERATURES MONDAY WILL MODERATE THROUGH THE WEEK
REACHING ABOVE NORMAL BY WEDNESDAY.

UNCERTAINTIES BEGIN TO CREEP INTO THE FORECAST BY THURSDAY. MOST
OPERATIONAL MODELS SHOW A TROUGH BEGINNING TO AFFECT THE WESTERN
U.S. BY THIS TIME BUT THERE DIFFERENCES IN THE TIMING AND STRENGTH
OF THE PART OF THE SYSTEM THAT AFFECTS OUR AREA. GEFS ENSEMBLE
MEMBERS ARE FAR LESS ENTHUSIASTIC WITH THIS SYSTEM BRINGING ANY
CHANCE OF PCPN TO THE AREA. ECMWF IS THE MOST AGGRESSIVE OF THE
OPERATIONAL MODELS AND BRINGS PCPN TO THE FAR NORTHERN CWA BY
THURSDAY AFTERNOON. THE GEM AND GFS KEEP THE AREA DRIER...WITH THE
GFS THE DRIEST. DUE TO INCONSISTENCIES IN THE MODEL SOLUTIONS...WE
HAVE OPTED TO KEEP THURSDAY DRY...BUT WILL SHOW A SLIGHT DECREASE IN
THE HIGH TEMPS OVER THE FAR NORTHERN CWA. 20

&&

.AVIATION...
PRIMARY AVIATION CONCERNS TODAY AND TONIGHT CENTER AROUND IMPACTS
FROM THE INCOMING STORM. WINDS SHOULD INCREASE TODAY WITH GUSTS IN
THE 25-30 KT BY AFTERNOON. OVER THE SIERRA RIDGES GUSTS COULD REACH
UP TO 65 KTS. WHILE THIS SYSTEM WILL NOT BE A HUGE WIND PRODUCER
THERE SHOULD STILL BE POCKETS OF TURBULENCE OVER AND DOWNSTREAM OF
THE SIERRA THIS AFTERNOON AND TONIGHT.

CIGS LOWER LATER TODAY AS PCPN STARTS TO MOVE INTO THE SIERRA. SNOW
LEVELS START NEAR THE PEAKS THEN LOWER THROUGH THE EVENING AND
OVERNIGHT HOURS. MVFR/IFR CONDITIONS ARE LIKELY BY 1/02 UTC FOR
SIERRA TERMINALS WITH OBSCURED MOUNTAINS. ACCUMULATIONS ON SIERRA
RUNWAYS SHOULD BE LIMITED EARLY IN THE EVENING...BUT SLUSHY
ACCUMULATIONS ARE LIKELY FOR KTRK AND KTVL BY LATE EVENING AND KMMH
AFTER MIDNIGHT. A FEW INCHES ARE NOT OUT OF THE QUESTION FOR KMMH BY
MORNING...WITH LESSER AMOUNTS FOR KTRK AND KTVL.

EAST OF THE SIERRA CIGS AND VSBYS WILL STAY AT OR ABOVE VFR THROUGH
THE EVENING...BUT SHOULD DROP OVERNIGHT. MVFR CONDITIONS ARE POSSIBLE
AT THE TERMINALS BELOW 5500 FEET BY SATURDAY MORNING. WHILE SNOW
IS NOT EXPECTED AT THESE TERMINALS...IT IS POSSIBLE ABOVE ROUGHLY
5500-6000 FEET BY SATURDAY MORNING SO ICING ON APPROACH AND DEPARTURE
IS A GOOD POSSIBILITY.

CONDITIONS BEGIN TO IMPROVE LATE SATURDAY WITH RAIN/SNOW SHOWERS
TAPERING BY THE EVENING. 20

&&


.REV WATCHES/WARNINGS/ADVISORIES...
NV...LAKE WIND ADVISORY FROM 5 AM EARLY THIS MORNING TO 5 PM PDT THIS
     AFTERNOON FOR LAKE TAHOE IN NVZ002.

     WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 11 AM PDT
     SATURDAY NVZ002.

CA...WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 11 AM PDT
     SATURDAY CAZ073.

     LAKE WIND ADVISORY FROM 5 AM EARLY THIS MORNING TO 5 PM PDT THIS
     AFTERNOON FOR LAKE TAHOE IN CAZ072.

     WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 11 AM PDT
     SATURDAY CAZ072.

&&

$$

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






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