Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 271711 AAA
AFDREV

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RENO NV
911 AM PST FRI FEB 27 2015

.UPDATE...
MAIN FOCUS FOR THE UPDATE IS TO ISSUE A WINTER WEATHER ADVISORY
FOR THE SIERRA FRONT TONIGHT INTO SATURDAY. AS FOR THE REST OF
TODAY, DID MAKE SOME MINOR CHANGES TO ADD THE THREAT OF
THUNDERSTORMS NORTH OF I-80 THIS AFTERNOON AND REDUCE SOME CLOUD
COVER TO MAKE IT MORE MOSTLY CLOUDY AS THERE WILL BE BREAKS OF
SUN. REGARDING THE CONVECTION, MODERATE SHOWERS ARE ALREADY
POPPING NORTH OF HIGHWAY 50 AND THESE SHOULD INTENSIFY WITH
HEATING. MODELS ALL SHOWING ENOUGH INSTABILITY FOR SOME ISOLATED
THUNDERSTORMS AS WELL.

TONIGHT INTO SATURDAY MORNING, THE GFS AND EC CONTINUE TO SHOW A
BAND OF MODERATE SNOW TO AFFECT PORTIONS OF THE TAHOE BASIN AND
SIERRA FRONT. HIGH CONFIDENCE NOW IN THIS BAND DEVELOPING AS THE
LATEST HRRR IS SHOWING IT AT THE END OF ITS RUN. LATEST RUNS HAVE
ALSO SHIFTED IT SOUTH AGAIN OVER DOUGLAS COUNTY AND SOUTH LAKE.
ADVISORY ALREADY ISSUED FOR TAHOE AND WILL ADD THE SIERRA FRONT TO
RUN FROM 8 PM TONIGHT UNTIL 10 AM TOMORROW MORNING. OUTSIDE OF
THIS BAND LIGHTER AMOUNTS NEAR 2 INCHES FOR THE SIERRA FRONT AND
UP TO 4 INCHES FOR THE TAHOE BASIN ARE LIKELY. HOWEVER, IN THIS
BAND EXPECT HEAVIER AMOUNTS AS MODEL QPF IS NEAR 1/2 TO 3/4 INCH
IN PLACES. WITH A GOOD DENTRITIC SNOW GROWTH LAYER PRESENT, IT
COULD ADD UP. WILL GO WITH 3-6 INCHES IN THIS BAND FOR THE SIERRA
FRONT AND 4-8 FOR THE TAHOE BASIN WITH 12+ INCHES POSSIBLE ABOVE
7K.

WILL MENTION THE MOST LIKELY PLACES (OR OUR BEST GUESS) FOR
THE HEAVIER BAND. HOWEVER, THE EXACT LOCATION REMAINS LOW
CONFIDENCE. IT IS STILL POSSIBLE IT COULD BE CENTERED OVER CARSON
CITY OR EVEN TRUCKEE/RENO (LOWEST PROBABILITY FOR THE LATTER).
HOPE TO HAVE ALL UPDATES OUT BY 10 AM. WALLMANN

&&

.PREVIOUS DISCUSSION... /ISSUED 324 AM PST FRI FEB 27 2015/

SYNOPSIS...

WINTER SYSTEM IS ON TRACK TO IMPACT THE SIERRA AND NORTHWEST
NEVADA TODAY AND SATURDAY. ACCUMULATING SNOW AND DIFFICULT TRAVEL
CONDITIONS ARE LIKELY IN THE SIERRA WITH LIGHTER ACCUMULATIONS
POSSIBLE IN WESTERN NEVADA. THIS SYSTEM WILL SLOWLY EXIT SUNDAY
WITH ANOTHER CHANCE AT PRECIPITATION POSSIBLE LATE MONDAY INTO
TUESDAY.

SHORT TERM...

THE UPPER LEVEL LOW RESPONSIBLE FOR THE THE WINTER WEATHER THIS
WEEKEND IS CURRENTLY DROPPING SOUTH ALONG THE PACIFIC NORTHWEST
COAST. AHEAD OF THIS FEATURE, WEAK WARM AIR ADVECTION IS GENERATING
LIGHT PRECIPITATION EARLY THIS MORNING.

THE LOW WILL CONTINUE SOUTH TODAY, PUSHING A DIFFUSE COLD FRONT
THROUGH THE EASTERN SIERRA AND WESTERN NEVADA AND BRINGING GUSTY
WEST TO NORTHWEST WINDS TO THE REGION THIS AFTERNOON. THE FRONT
WILL RAPIDLY DROP SNOW LEVELS TO AROUND 4000-5000 FEET FRIDAY
NIGHT, POSSIBLY REACHING AS LOW AS 3500 FEET BY SATURDAY MORNING.
MOST OF THE MOISTURE IS ALONG AND BEHIND THE FRONT WITH SHOWERS
EXPECTED TO INCREASE IN COVERAGE THIS AFTERNOON AND EVENING.

SHOWER ACTIVITY IS RATHER DISORGANIZED, OUTSIDE OF A DEFORMATION
BAND EXPECTED TO FORM LATE TONIGHT INTO SATURDAY. THESE BANDS ARE
NOTORIOUSLY HARD TO PINPOINT LOCATIONS, BUT MODEL TRENDS OVER THE
PAST COUPLE DAYS ARE SHOWING THIS BAND DEVELOPING BETWEEN THE I-80
AND HIGHWAY 50 CORRIDOR. CONFIDENCE IS HIGH THAT THERE WILL BE
SNOW SHOWERS BOTH IN THE SIERRA AND WESTERN NEVADA, BUT MUCH
LOWER IN THE TOTALS. THE SHOWERY NATURE OF THIS SYSTEM MEANS THAT
SNOW TOTALS WILL BE HIGHLY VARIABLE.

THE GREATEST CONFIDENCE IN ACCUMULATING SNOWS IS THROUGH THE TAHOE
BASIN WHERE A WINTER WEATHER ADVISORY IS IN EFFECT LATE FRIDAY
AFTERNOON THROUGH SATURDAY AFTERNOON. 6 TO 12 INCHES OF SNOW IS
POSSIBLE ALONG THE CREST, WITH 3 TO 7 INCHES AT LAKE LEVEL. THOSE
LOCATIONS UNDER ANY ORGANIZED BANDS WILL BE ON THE HIGHER END OF
THE TOTALS, WHILE LOCATIONS WITH JUST GENERAL SHOWERS WILL BE ON
THE LOWER END. FOR WESTERN NEVADA AND THE SIERRA FRONT, CONFIDENCE
IS INCREASING IN SOME AREAS SEEING SEVERAL INCHES OF ACCUMULATION,
BUT CONFIDENCE REMAINS LOW IN EXACTLY WHERE...AND SOME AREAS MAY
STILL SEE NOTHING. MONO COUNTY IS LIKELY TO SEE ACCUMULATING SNOWS
SATURDAY AFTERNOON INTO SUNDAY AS THE UPPER LEVEL FLOW TURNS
NORTHEAST, AIDING IN UPSLOPE ENHANCEMENT. CURRENT FORECAST WOULD
YIELD 6 TO 10 INCHES OF SNOW IN THE HIGH SIERRA WITH 2 TO 4 INCHES
IN THE REST OF MONO COUNTY. THE BIGGEST THING TO TAKE AWAY IS THAT
TRAVEL WILL LIKELY BE IMPACTED FRIDAY AFTERNOON THROUGH SUNDAY
THROUGH PORTIONS OF THE SIERRA AND WESTERN NEVADA. BE PREPARED FOR
WINTER DRIVING CONDITIONS AND CHECK BOTH WEATHER AND ROAD CONDITIONS
BEFORE TRAVEL.

THERE IS PLENTY OF INSTABILITY WITHIN THE CORE OF THE LOW AND THERE
IS A SLIGHT CHANCE OF THUNDERSTORMS NORTH OF I-80 LATE THIS AFTERNOON
AND THEN FROM I-80 SOUTH SATURDAY. PELLET SHOWERS AND/OR A WINTRY
MIX IS POSSIBLE THROUGH THE DAY SATURDAY IN THE COLD CORE. THE LOW
IS SLOWER TO EXIT THE AREA THAN PREVIOUSLY PROGGED, WITH SHOWERS
POSSIBLY LINGERING IN MONO COUNTY THROUGH SUNDAY AFTERNOON IN THE
MOIST AND UNSTABLE NORTHEAST FLOW. TEMPERATURES WILL BE BELOW
NORMAL THROUGH THE PERIOD WITH THE BREEZY WINDS MAKING IT FEEL
EVEN COLDER. DJ

LONG TERM...MONDAY THROUGH THURSDAY...

NO MAJOR CHANGES TO THE LONG TERM FORECAST, WITH THE MAIN WEATHER
CONSIDERATION MONDAY INTO TUESDAY ANY ADDITIONAL SLIDER ENERGY (AND
ASSOCIATED SNOW SHOWERS) THAT MIGHT MOVE OVER EASTERN CALIFORNIA AND
WESTERN NEVADA BEHIND THIS WEEKEND`S SYSTEM.

MONDAY AND MONDAY NIGHT, THE ECMWF, GFS AND GEM ENSEMBLES STILL SHOW
VARYING SOLUTIONS REGARDING A SLIDER-TYPE DISTURBANCE TO MOVE
OVER/NEAR THE REGION. IN FACT, IN THE LAST FEW OPERATIONAL RUNS THE
GFS AND ECMWF HAVE GONE THE OPPOSITE WAY WITH THE GFS LEANING
FARTHER EAST AND MORE PROGRESSIVE WITH THE ECMWF GETTING SLOWER AND
FARTHER WEST (OVER NORTHERN CALIFORNIA) WITH THE SLIDER. MEANWHILE,
THE GEM SEEMS TO BE IN BETWEEN WITH MANY ENSEMBLE RUNS SHOWING THE
DISTURBANCE OVER WESTERN NEVADA OR FAR EASTERN CALIFORNIA.

THE POSITION OF THE SLIDER IS KEY FOR THE COVERAGE/INTENSITY OF SNOW
SHOWERS FOR THE SIERRA AND WESTERN NEVADA, WITH A TRACK NEAR OR WEST
OF THE CREST (BUT STILL EAST OF I-5) IDEAL FOR AN ORGANIZED BAND OF
SNOW. WITH LARGE UNCERTAINTY AS TO THE EXACT TRACK OF THE DISTURBANCE
MONDAY-TUESDAY, I HAVE KEPT THE RUNNING SLIGHT CHANCE TO CHANCE OF
SHOWERS IN PLACE. IN ANY CASE, WELL BELOW AVERAGE TEMPERATURES ARE ON
TAP FOR MONDAY AND TUESDAY WITH NORTHERLY FLOW KEEPING COLDER AIR
INTACT.

WEDNESDAY AND THURSDAY STILL LOOK DRY AS ENSEMBLES ARE IN GOOD
AGREEMENT WITH BUILDING A RIDGE OVERHEAD. TEMPERATURES WILL BEGIN TO
REBOUND TOWARDS NORMAL FOR THE SECOND HALF OF THE WEEK. SNYDER

AVIATION...

FOR THIS MORNING IN NORTHEAST CALIFORNIA AND WESTERN NEVADA,
SCATTERED SHOWERS WILL BRING OCCASIONAL MVFR CIGS TO THE NORTHERN
SIERRA WITH OCCASIONAL HIGHER TERRAIN OBSCUREMENT TO WESTERN NEVADA
NORTH OF HIGHWAY 50. NORTH OF KSVE-GERLACH, CIGS LOOK WORSE WITH
WIDESPREAD MVFR CIGS WITH -SHSN ABV 5-5.5 KFT MSL (AND -SHRASN BLO).

THIS AFTERNOON AND TONIGHT, CIGS/VIS WORSEN AS LOW PRESSURE DROPS
INTO NORTHERN CALIFORNIA AND NEVADA AND WIDESPREAD SNOW AND
RAIN/SNOW BELOW 5,000 FT MSL DEVELOPS. WIDESPREAD IFR CIGS AND ICING
ARE EXPECTED IN THE SIERRA, WITH MVFR (LOCALLY IFR) CIGS INTO
WESTERN NEVADA NORTH OF HIGHWAY 50. ACCUMULATING SNOW IS LIKELY FOR
KTRK/KTVL WITH EVEN SOME ACCUMULATIONS POSSIBLE AT KRNO/KCXP (60%
CHANCE) BETWEEN LATE FRIDAY EVENING AND SATURDAY MORNING.

FOR KMMH, THE WORSE CONDITIONS ARE LIKELY TO BE ON SATURDAY. SNYDER

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM PST
     SATURDAY NVZ002.

     WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 10 AM PST
     SATURDAY NVZ003.

CA...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 PM PST
     SATURDAY CAZ072.

&&

$$

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





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