Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 310052 CCA
AFDREV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
452 PM PST FRI JAN 30 2015

.SYNOPSIS...
LOW PRESSURE OVER THE SOUTHWEST WILL SLOWLY MOVE EAST THROUGH
SATURDAY AS HIGH PRESSURE BUILDS INTO NORTHERN CALIFORNIA AND
NEVADA. GUSTY NORTHEAST WINDS ARE EXPECTED TONIGHT AND SATURDAY,
ESPECIALLY OVER RIDGES AND ON LAKE TAHOE. HIGH PRESSURE WILL
BRING MAINLY DRY AND MILD CONDITIONS THROUGH THE MIDDLE OF NEXT
WEEK.

&&

.SHORT TERM...
AN UPPER LOW CENTERED NEAR LAS VEGAS WILL REMAIN NEARLY STATIONARY
TONIGHT AS AN UPPER RIDGE BEGINS TO NOSE INTO NORTHERN CALIFORNIA
FROM THE PACIFIC. AN INCREASING UPPER GRADIENT BETWEEN THE RIDGE
AND TROUGH, ALONG WITH AN INCREASING SURFACE GRADIENT (WITH HIGH
PRESSURE BUILDING INTO THE BASIN), WILL ENHANCE THE NORTH AND
NORTHEAST FLOW ALOFT. THIS WILL KEEP RIDGE WINDS ELEVATED INTO
SATURDAY MORNING, WITH THE STRONGEST WINDS ON THE IMMEDIATE SIERRA
CREST. ALSO, AS THE SURFACE HIGH INTENSIFIES THE SURFACE GRADIENT
ACROSS THE SIERRA SOME OF THIS WIND IS EXPECTED TO MIX DOWN ONTO
LAKE TAHOE OVERNIGHT. HOWEVER, WITH MODELS SHOWING AN INVERSION
SMASHING DOWN TO BELOW THE PEAKS OF THE CARSON RANGE I WOULD EXPECT
THE STRONGEST WINDS ON THE LAKE TO BE WEST OF SPOONER SUMMIT WHERE
WINDS CAN SQUEEZE THROUGH THE GAP IN THE RANGE. ELSEWHERE ON LAKE
TAHOE LATE TONIGHT AND SATURDAY MORNING, WINDS SHOULD BE A BIT TAMER.

FOR THE WEEKEND, HIGH PRESSURE WILL SETTLE OVER THE SIERRA, NORTHEAST
CALIFORNIA AND WESTERN NEVADA. WITH NO INFLUX OF COLDER AIR AFTERNOON
TEMPERATURES WILL REMAIN MILD/ABOVE AVERAGE DESPITE INCREASING MID
AND HIGH CLOUDS ON SUNDAY.

SUNDAY NIGHT AND ESPECIALLY MONDAY, A PERIOD OF WARM AIR ADVECTION
COULD BRING LIGHT RAIN AND HIGH ELEVATION SNOW TO FAR NORTHEAST
CALIFORNIA AND FAR NORTHERN NEVADA. AT THIS TIME, I HAVE LEFT THE
SHOWERS AT A SLIGHT CHANCE. HOWEVER, POP MAY NEED TO BE INCREASED
SOME NORTH OF A PORTOLA TO GERLACH LINE ON MONDAY-MONDAY NIGHT BASED
ON THE 18Z GFS/NAM AND THE 15Z SREF WHICH SHOW PLENTY OF MOISTURE
AND LIGHT WARM AIR ADVECTION TO SQUEEZE OUT LIGHT PRECIPITATION.
FARTHER SOUTH, IT STILL JUST LOOKS LIKE A LOT OF MID AND/OR HIGH
CLOUDS. THIS COULD WIND UP TEMPERING HIGHS A FEW DEGREES FROM OUR
CURRENT FORECAST. STILL, THE SURFACE HIGH IS WEAK AND THERE IS SOME
MODERATE 700 MB FLOW WHICH COULD SERVE TO MIX THE LOWER ATMOSPHERE
SO I HAVE NOT LOWERED HIGHS ON MONDAY WITH THIS FORECAST. SNYDER

.LONG TERM...TUESDAY THROUGH FRIDAY...
FOR TUESDAY-TUESDAY NIGHT, THE GFS MODEL ENSEMBLE SYSTEM HAS
CONTINUED TO TREND A BIT SOUTH WITH THE STORM TRACK AS A WEAK
SHORTWAVE TRACKS ACROSS THE PACIFIC NORTHWEST. THE ECMWF MODEL, ON
THE OTHER HAND, HAS BEEN CONSISTENT RUN-TO-RUN WITH KEEPING THE
STORM TRACK NORTH OF THE OREGON BORDER. GIVEN THE UNCERTAINTY, WE
INTRODUCED A SLIGHT CHANCE FOR PRECIPITATION FOR NORTHEAST CA AND
FAR NORTHWEST NV FOR TUESDAY AND TUESDAY NIGHT. SNOW LEVELS ARE
EXPECTED TO BE ABOVE 7000 FEET.

FOR WEDNESDAY-THURSDAY, THE THICKNESS OF THE CLOUDS DURING THE
AFTERNOON WILL DETERMINE HOW WARM IT WILL GET. INVERSIONS SHOULD BE
WEAK SO UNLESS A THICK OVERCAST PREVAILS ALL DAY, HIGHS EACH DAY
SHOULD CLIMB ABOVE 60 DEGREES FOR LOWER ELEVATIONS, WITH MID-UPPER
50S FOR SIERRA VALLEYS.

CONFIDENCE IS INCREASING FOR AN ATMOSPHERIC RIVER TO REACH THE WEST
COAST BY FRIDAY. HOWEVER, THE NORTH-SOUTH LOCATION OF THE
ATMOSPHERIC RIVER AS IT REACHES THE WEST COAST REMAINS UNCERTAIN (IT
IS A 7-DAY FORECAST). FURTHERMORE, A VERY STRONG RIDGE OVER THE
SOUTHERN TIER OF STATES IS LIKELY TO INTERACT AND STEER THIS
ATMOSPHERIC RIVER TO THE NORTHEAST AS THE TROUGH MOVES ONSHORE. THE
CURRENT CONSENSUS OF MODEL GUIDANCE SUGGESTS PRECIPITATION COULD
SPREAD NORTHEAST ACROSS PLUMAS-LASSEN-MODOC COUNTIES FRIDAY WITH
LOCATIONS TO THE SOUTH IN THE LEE OF THE SIERRA STAYING MOSTLY DRY.
AT THIS TIME, THE MOISTURE APPEARS TO BE PRIMARILY SUBTROPICAL, SO
EVEN IF PRECIP DOES REACH THE SIERRA IT WOULD MORE LIKELY BE RAIN
WITH SNOW LEVELS REMAINING ON THE HIGH SIDE. JCM/MJD

&&

.AVIATION...
VFR CONDITIONS EXPECTED THROUGH THE WEEKEND AS HIGH PRESSURE BUILDS
ACROSS NORTHERN CALIFORNIA AND NEVADA. AHEAD OF THE RIDGE, WINDS
ALOFT WILL INCREASE AS AN EASTERLY JET DROPS SOUTH ACROSS THE
SIERRA. AREAS OF TURBULENCE ARE POSSIBLE ALONG AND WEST OF THE
SIERRA RIDGES WITH GUSTS NEAR 65 KNOTS POSSIBLE AT RIDGE LEVEL
(~10,000 FT). RIDGE WINDS WILL INCREASE THROUGH THIS EVENING WITH
PEAK GUSTS BETWEEN 03-18Z SATURDAY. EASTERLY FLOW, LESS THAN 15 KTS
IS EXPECTED AT THE SURFACE ACROSS SIERRA TERMINALS INTO SATURDAY
MORNING WITH LIGHT WINDS AT KRNO AND KCXP.

CLOUD COVER WILL CONTINUE TO DECREASE ACROSS ALL TERMINALS INTO
SATURDAY AS A LARGE SWATH OF DRY AIR FILTERS INTO THE REGION WITH
THE HIGH PRESSURE RIDGE. LOWER CONFIDENCE FOR FOG FORMATION AT KTRK
MAINLY IF WINDS CAN KEEP MARTIS VALLEY MIXED OVERNIGHT. MAY STILL
EXPERIENCE PATCHY AREAS OF FOG DEVELOPMENT WITH CLEARING SKIES IN
AREAS OF LIGHT WINDS. FUENTES

&&


.REV WATCHES/WARNINGS/ADVISORIES...
NV...NONE.
CA...NONE.
&&

$$

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








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