Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 240141
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
641 PM PDT THU OCT 23 2014

.UPDATE...
JUST A MINOR UPDATE THIS EVENING TO ACCOUNT FOR CLOUDS DECREASING
A BIT FASTER THAN FORECAST OVER THE TAHOE BASIN BUT A BIT MORE
CLOUD COVER EARLY INTO THE WRN NV BASIN AND RANGE. CLOUDS OVER THE
SRN 2/3RDS OF THE CWA SHOULD DECREASE OVERNIGHT AS MOISTURE PLUME
OVER THE NRN CWA LIFTS TO THE NORTH. LESSENING POPS THROUGH THE
NIGHT IS HANDLED WELL IN THE CURRENT FORECAST FOR THE FAR NRN CWA. 20

&&

.PREVIOUS DISCUSSION... /ISSUED 325 PM PDT THU OCT 23 2014/

SYNOPSIS...

LIGHT RAIN OVER NORTHEAST CALIFORNIA AND FAR NORTHWEST NEVADA WILL
DIMINISH TONIGHT WITH CLOUDS ALSO DECREASING. AFTER A WARM AND
SUNNY FRIDAY, LOW PRESSURE OFF THE WEST COAST WILL MOVE INLAND ON
SATURDAY, BRINGING A PERIOD OF STRONG GUSTY WINDS ALONG WITH LIGHT
RAIN AND MOUNTAIN SNOW. COOLER CONDITIONS WITH LINGERING SHOWERS
ARE EXPECTED SUNDAY, WITH MILD AND DRIER CONDITIONS FOR NEXT WEEK.

SHORT TERM...

LIGHT RAIN CONTINUES TO STREAM ACROSS NORTHEAST CA AND FAR
NORTHWEST NV WITH RAINFALL RATES LESS THAN 0.05 INCH PER HOUR.
THIS RAIN BAND WILL RETREAT FARTHER NORTH DURING THE EVENING AND
PUSH FARTHER NORTH. FOR THE REMAINDER OF THE REGION, CLOUD COVER
WILL DIMINISH FROM SOUTH TO NORTH OVERNIGHT.

ON FRIDAY, WITH FULL SUN AND MODERATE SOUTH WIND GUSTS OF 20-30
MPH IN THE AFTERNOON, HIGH ARE LIKELY TO REACH 80 DEGREES ACROSS
MUCH OF WESTERN NV, WITH THE WARMEST TEMPS ALONG AND EAST OF
HIGHWAY 95 FROM FALLON SOUTHWARD. RIDGE LEVEL WINDS WILL CONTINUE
INCREASING FRIDAY NIGHT, WITH SOME GUSTS UP TO 40 MPH MIXING DOWN
TO LAKE TAHOE SO THE LAKE WIND ADVISORY WILL GO IN EFFECT STARTING
LATE FRIDAY EVENING.

ON SATURDAY, THE PRIMARY WEATHER CONCERN WILL BE GUSTY WINDS AS
PRESSURE AND THERMAL GRADIENT TIGHTENS AHEAD OF THE APPROACHING
TROUGH AND COLD FRONT. WE ISSUED A WIND ADVISORY ALONG THE HIGHWAY
395 CORRIDOR FROM LASSEN SOUTHWARD TO MONO COUNTY, AND ALSO FOR
NORTHWEST NV. AREAS PRONE TO STRONGER SOUTH WINDS INCLUDING THE
RENO AIRPORT COULD RECEIVE THEIR STRONGEST GUSTS DURING THE MID-
LATE MORNING HOURS, BUT THE TIGHT GRADIENT WILL KEEP SUSTAINED
WINDS IN THE 20-30 MPH RANGE GOING THROUGH THE AFTERNOON, BEFORE
DIMINISHING IN THE EVENING. ALTHOUGH WIND GUSTS ARE LESS LIKELY TO
REACH ADVISORY CRITERIA IN WEST CENTRAL NV, AREAS OF BLOWING DUST
WILL BE POSSIBLE DURING THE AFTERNOON AND EARLY EVENING.

PRECIPITATION IS NOT EXPECTED TO BE SIGNIFICANT WITH THIS SYSTEM
AS FEED OF PACIFIC MOISTURE WEAKENS WHEN IT REACHES THE SIERRA. AS
HAS BEEN THE CASE FOR OTHER RECENT TROUGH PASSAGES, THE BEST
CHANCE FOR STEADY RAIN WILL BE IN WESTERN LASSEN AND CENTRAL
PLUMAS COUNTIES, WITH UP TO 0.50 INCH POSSIBLE. LESSER RAINFALL
AMOUNTS ARE EXPECTED FOR TAHOE AND NORTHWEST NEVADA, WITH LITTLE
TO NO MEASURABLE RAIN RAIN EAST AND SOUTH OF THE RENO-CARSON CITY
AREA.

AS THE 500 MB TROUGH AXIS SWINGS ACROSS THE REGION SATURDAY
EVENING, A SECOND ROUND OF SHOWERS WILL OCCUR MAINLY NORTH OF
SUSANVILLE AND GERLACH, WITH ISOLATED THUNDER POSSIBLE. BY THE
TIME SNOW LEVELS DROP BELOW 8000 FEET SATURDAY NIGHT, MOST OF THE
PRECIPITATION WILL HAVE DIMINISHED. AN INCH OR TWO OF SNOW MAY
ACCUMULATE ON SOME OF THE HIGHER PEAKS SATURDAY NIGHT IN THE
NORTHERN SIERRA BUT ARE UNLIKELY TO IMPACT MOUNTAIN PASSES. MJD

LONG TERM...SUNDAY THROUGH THURSDAY...

THE FIRST PORTION OF THE FORECAST REMAINS NEARLY UNCHANGED WITH ONLY
MINOR ADJUSTMENTS BASED ON LATEST MODEL TRENDS. LOW PRESSURE EXITS
SUNDAY WITH CONDITIONS IMPROVING ACROSS THE AREA. PRECIPITATION WILL
LINGER INTO THE EARLY AFTERNOON BEFORE LIFTING RAPIDLY INTO EASTERN
OREGON AND IDAHO. ELEVATIONS ABOVE 6000 FEET COULD SEE A MIX OF RAIN
AND SNOW WHEREAS THE HIGHER ELEVATIONS GENERALLY OVER 7000 FEET
WOULD BE MOSTLY SNOW. ACCUMULATIONS ABOVE 7000 FEET WILL BE MINIMAL
AND PREVIOUS RAINS SHOULD SEVERELY LIMIT IMPACTS OVER AREA PASSES.
RIDGING BUILDS IN BY MONDAY WITH A SLIGHT WARMING TREND.

LATER IN THE PERIOD, FORECASTER CONFIDENCE REMAINS ON THE LOWER END
OF THE SPECTRUM AS RUN-TO-RUN CONSISTENCY HAS DEGRADED OVER THE LAST
24 HOURS. DUE TO RUN-TO-RUN DISCREPANCIES, HAVE ONLY MARGINALLY
TRENDED TOWARDS CURRENT SOLUTIONS. PREVIOUS RUNS GENERALLY DEPICTED
A MORE UNSETTLED PATTERN WITH THE NEXT SYSTEM MOVING INTO THE
NORTHERN SIERRA BY MID WEEK. CURRENT SOLUTIONS ARE TRENDING TOWARDS
THE ECMWF WHERE RIDGING IS MORE PRONOUNCED. HAVE BEGUN TO SHUNT
PRECIPITATION MAINLY NORTH OF INTERSTATE 80 TUESDAY THROUGH THURSDAY
IN THE SIERRA WHILE WARMING TEMPERATURES A BIT ACROSS THE ENTIRE
FORECAST AREA. WILL WAIT ANOTHER RUN OR SO BEFORE MAKING MORE
WHOLESALE CHANGES. BOYD

AVIATION...

PRECIPITATION WILL REMAIN LIMITED TO NORTHEASTERN CALIFORNIA AND
EXTREME NORTHWEST NEVADA TONIGHT. SOUTH TO SOUTHWEST FLOW BEGINS
TO INCREASE FRIDAY PUSHING PRECIPITATION AND ASSOCIATED CLOUD
COVER NORTH INTO OREGON AS LOW PRESSURE APPROACHES THE PACIFIC
COAST. SURFACE GUSTS IN THE SIERRA AND ALONG THE SIERRA FRONT WILL
GENERALLY BE IN THE 20-25 KT RANGE WHILE RIDGE GUSTS INCREASE TO
50 KTS.

LOW PRESSURE MOVES ONSHORE EARLY SATURDAY MORNING TIGHTENING THE
PRESSURE GRADIENT FURTHER. EXPECT STRONG MECHANICAL TURBULENCE OVER
THE SIERRA AS RIDGE GUSTS EXCEED 80 KNOTS INDUCING TRAPPED LEE
WAVES. SOUTHWEST TO WEST SURFACE GUSTS WILL BE SOLIDLY IN THE
35-45 KT RANGE THROUGH SATURDAY AFTERNOON BEFORE BEGINNING TO
DIMINISH SATURDAY EVENING INTO SUNDAY. EARLY SATURDAY AFTERNOON,
MOUNTAIN WAVES WILL SET UP AS THE FRONT PUSHES THROUGH. WITH GUSTS
THIS STRONG OUT OF THE SOUTHWEST, THE CROSSWIND COMPONENT ON NORTH
TO SOUTH ORIENTED RUNWAYS WILL BECOME SIGNIFICANT.

PRECIPITATION MOVES IN SATURDAY EVENING MAINLY IN THE FORM OF RAIN
SINCE SNOW LEVELS WILL HANG ABOVE 8000 FEET UNTIL AROUND MIDNIGHT
SATURDAY NIGHT. EXPECT PERIODS OF MVFR/IFR BY SATURDAY EVENING.
SIERRA TERMINALS FROM THE TAHOE BASIN NORTHWARD COULD SEE SOME LIGHT
MIXED PRECIPITATION WITH MVFR/IFR CEILINGS SUNDAY BEFORE NOON AS
SNOW LEVELS DROP. FLYING CONDITIONS BECOME MUCH MORE IDEAL BY MONDAY
AS WINDS LESSEN WITH HIGH PRESSURE BUILDING OVER THE REGION. BOYD

FIRE WEATHER...

WINDS WILL BE GUSTING BETWEEN 20-30 MPH AGAIN ON FRIDAY AFTERNOON
FOR VALLEYS/MID SLOPES WITH LOWER HUMIDITIES THAN TODAY. ALSO, RIDGE
WINDS WILL REMAIN ELEVATED FOR WORSENING HUMIDITIES THERE TONIGHT
AND FRIDAY.

THE MAIN PERIOD OF CONCERN FOR WINDS COMBINED WITH LOWERED HUMIDITIES
WILL BE LATE FRIDAY NIGHT AND SATURDAY MORNING AHEAD OF A STRONG COLD
FRONT. WITH DRIER AIR WORKING INTO THE SIERRA AND WESTERN NEVADA
TONIGHT AND FRIDAY AND WINDS ALOFT REMAINING ELEVATED, MID SLOPE
RECOVERIES LOOK TO BE POOR TO LOW END MODERATE IN SOME AREAS
(ESPECIALLY SIERRA FRONT DOWN INTO MONO COUNTY) FRIDAY NIGHT. THIS
WILL SET UP A SHORT PERIOD OF LOWERED HUMIDITY COMBINED WITH STRONG
WINDS LATE FRIDAY NIGHT FOR MID SLOPES (AND SOME NORTH-SOUTH FACING
VALLEYS NEAR THE SIERRA FRONT), WHICH WILL MIX INTO THE VALLEYS
SATURDAY MORNING JUST AHEAD OF A STRONG COLD FRONT. HOWEVER,
HUMIDITIES SHOULD RISE WITH THE COLD FRONT, SO CRITICALLY LOW
HUMIDITIES ARE NOT EXPECTED TO LAST VERY LONG. THEREFORE, PLAN ON
JUST HIGHLIGHTING IN THE PLANNING FORECAST AND DISCUSSIONS FOR
NOW. SNYDER

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WIND ADVISORY FROM 8 AM TO 11 PM PDT SATURDAY NVZ003-005.

     LAKE WIND ADVISORY FROM 11 PM FRIDAY TO 11 PM PDT SATURDAY FOR
     LAKE TAHOE IN NVZ002.

     LAKE WIND ADVISORY FROM 11 AM TO 11 PM PDT SATURDAY FOR PYRAMID
     LAKE IN NVZ004.

CA...WIND ADVISORY FROM 8 AM TO 11 PM PDT SATURDAY CAZ070-071.

     WIND ADVISORY FROM 11 AM TO 11 PM PDT SATURDAY CAZ073.

     LAKE WIND ADVISORY FROM 11 PM FRIDAY TO 11 PM PDT SATURDAY FOR
     LAKE TAHOE IN CAZ072.

&&

$$

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






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