Snow Advisory 11, NWS Reno, NV

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
405 AM PST SUN JAN 27 2008

.SHORT TERM...
AN IMPRESSIVE BAROCLINIC LEAF PATTERN IS ASSOCIATED WITH THE DEEP
UPPER LOW THAT IS SPINNING NEAR 30N 130W THIS MORNING.  A 120-KT JET
MAX OVER THE SWRN CONUS CAN BE INFERRED FROM 00Z RAOB DATA.  THE
TRANSVERSE CLOUD BANDING OVER NWRN MEXICO IS ALSO INDICATIVE OF A
JET.  THIS JET WILL CONTINUE TO PULL SUBTROPICAL MOISTURE INTO THE
SRN CALIFORNIA TODAY.  LLVL MOISTURE HAS ALREADY MADE IT INTO CNTRL
CALIFORNIA.  LIGHT TO MODERATE RAINFALL IS BEING REPORTED AT MANY
LOCATIONS THROUGHOUT THE SAN JOAQUIN VALLEY THIS MORNING.

AREA RADARS ARE SHOWING PRECIP MOVING NORTH ACROSS CNTRL CALIFORNIA.
PRECIP IS NOW SPILLING OVER THE SIERRA CREST INTO MONO COUNTY AND
THE TAHOE BASIN.  THE AIR MASS HAS BEEN QUITE DRY SO IT HAS TAKEN
SOME TIME FOR SATURATION TO OCCUR TO ALLOW PRECIP TO REACH THE
GROUND.  HOWEVER THE BROAD AREA OF PRECIP THAT HAS BEEN MOVING NORTH
THROUGH CNTRL CALIFORNIA IS NOW SPREADING INTO WRN NEVADA.  THE
HEAVIEST PRECIP HAS BEEN WEST OF THE SIERRA CREST OVERNIGHT.
HOWEVER SNOWFALL IS BECOMING HEAVY IN MONO COUNTY WITH JUNE LAKE
WEBCAM SHOWING 3 TO 4 INCHES OF SNOWFALL SINCE MIDNIGHT.  THE
SNOWFALL WILL CONTINUE TO SPREAD NORTH TODAY.  THE GFS SHOWS BETWEEN
0.75 AND 1.00 INCH OF QPF ACROSS NRN WASHOE COUNTY FROM 12Z THIS
MORNING THROUGH 12Z MONDAY.  WILL ISSUE A WINTER STORM WATCH FOR
THIS AREA FOR TONIGHT AS THE FRONT PASSES THROUGH.

THE MODELS SHOW A TIGHT TEMPERATURE AND PRESSURE GRADIENT WITH THIS
COLD FRONT.  WINDS WILL INCREASE AHEAD OF THE FRONT AS IT MOVES INTO
THE NRN SIERRA.  WINDS WILL DECREASE AS THE HEAVIER PRECIP MOVES
IN.  HOWEVER PRECIP WILL NOT BE AS EXTENSIVE IN MINERAL AND SRN LYON
COUNTIES TONIGHT AND STRONG WINDS COULD BE A PROBLEM.  WILL ISSUE A
HIGH WIND WATCH FOR THIS AREA AND DAY SHIFT CAN ADJUST IF NECESSARY.

A WEAK UPPER TROUGH IS PROGGED TO MOVE INTO THE PACIFIC NW ON
TUESDAY.  THE ADDITION OF THE COLD AIR ASSOCIATED WITH THIS SYSTEM
WILL HELP TO DEEPEN THE BROAD TROUGH THAT SHOULD STILL BE OVER THE
WEST COAST.  THE GFS...ECMWF...UKMET AND CANADIAN ALL KEEP THIS
SYSTEM NORTH OF THE GREAT BASIN TUESDAY AND TUESDAY NIGHT.  WITH THE
BROAD TROUGH IN PLACE OVER THE REGION THERE WILL BE PLENTY OF COLD
AIR ALOFT TO CONTRIBUTE TO INSTABILITY.  AS A RESULT WILL KEEP SHSN
LIKELY IN THE SIERRA FROM TAHOE NORTH WITH A CHC TO SLGT CHC OF
PRECIP ACROSS THE REST OF THE KREV CWFA.  OHARA

.LONG TERM...WEDNESDAY THROUGH SATURDAY...

MEDIUM RANGE MODELS IN GOOD AGREEMENT WITH PROGRESSIVE PATTERN
THROUGH SATURDAY. TIMING VARIATIONS HAVE INCREASED BETWEEN THE GFS
AND ECMWF.  SPREAD HAS ALSO INCREASED IN THE ENSEMBLES...THUS
LOWERING ANY CONFIDENCE IN SPECIFIC DETAILS OF EACH SYSTEM IN THE
FORECAST.

STORMS SHOULD AFFECT THE AREA THURSDAY NIGHT/FRIDAY AND SATURDAY
NIGHT/SUNDAY.  SNOW LEVELS WILL REMAIN AT 5500 FEET OR LESS SO EACH
COLD AND FAST MOVING SYSTEM HAS A CHANCE TO BRING SIGNIFICANT SNOW
TO THE SIERRA AND POSSIBLY A FEW INCHES TO WESTERN NEVADA. OVERALL
AMPLITUDE OF THE PATTERN IS SLIGHTLY LOWER THAN PREVIOUS RUNS...SO
THAT WOULD FAVOR HIGHER RAIN/SNOW CHANCES NORTH OF US-50. HOWEVER
WITH AMOUNT OF UNCERTAINTY...DECIDED TO LEAVE POPS ROUGHLY THE SAME
NORTH AND SOUTH OF US-50.

AHEAD OF EACH SYSTEM WINDS WILL INCREASE AND HELP TO MIX OUT THE
VALLEYS.  DEPENDING ON TIMING AND CLOUD COVER WITH EACH SYSTEM THIS
MAY HAVE AN IMPACT ON TEMPERATURES.  OVERALL TEMPERATURES WILL BE
NEAR TO SLIGHTLY BELOW NORMAL...WHICH PUTS HIGHS IN THE 30S FOR THE
SIERRA AND UPPER 30S TO MID 40S FOR WESTERN NEVADA.  BRONG

&&

.AVIATION...

HEAVY SNOW IN THE SIERRA AND LIGHT RAIN/VIRGA ACROSS WESTERN NEVADA
WILL CONTINUE TODAY AS THE FIRST OF TWO AREAS OF LOW PRESSURE
AFFECTS THE AREA.  THIS FIRST OFF THE CALIFORNIA COAST WILL MOVE
ONSHORE AND BE ABSORBED BY THE SECOND SYSTEM TONIGHT.  EXPECT
IFR/LIFR CONDITIONS IN THE SIERRA...WITH A BRIEF PERIOD OF
IMPROVEMENT TO MVFR CONDITIONS LATE THIS AFTERNOON.

SECOND SYSTEM FOR TONIGHT AND MONDAY MORNING IS THE BIGGER CONCERN
AS IT WILL PRODUCE SNOW AND STRONG WINDS.  COLD FRONT WILL MOVE
THROUGH THE AREA FROM NORTH TO SOUTH BETWEEN 00Z-18Z MONDAY.  MOST
OF THE SNOW WILL COME ALONG THE FRONT...ESPECIALLY FOR WESTERN
NEVADA.  ABOUT 2-4 HOURS AHEAD OF THE FRONT POTENTIAL FOR SURFACE
WIND GUSTS OF 45-50 KTS AND LLWS.  OVER THE SIERRA RIDGES WINDS MAY
REACH 80-90KTS...WITH MOUNTAIN WAVES/TURBULENCE DOWNWIND OF THE
SIERRA.

FOR KRNO...BIGGEST PERIOD OF CONCERN IS TONIGHT.  LIGHT RAIN/SNOW
WILL BE NEAR THE TERMINAL THROUGH 18Z...THEN DECREASE AS THE SECOND
SYSTEM APPROACHES.  WINDS WILL INCREASE BY 00Z MONDAY...WITH
STRONGEST WINDS POSSIBLE BETWEEN 06Z-12Z DEPENDING ON THE TIMING OF
THE FRONT.  GUSTS DURING THIS TIME SHOULD EASILY GET TO 40KTS.
COULD BE AN HOUR OR TWO WHERE GUSTS NEAR 50KTS.  ESTIMATING FRONT
WILL REACH THE TERMINAL BETWEEN 10Z-14Z MONDAY...COULD SEE A
MODERATE TO HEAVY SNOW BURST WITH VISIBILITIES BELOW 2SM AND
CEILINGS BELOW 020 AGL.  AT KRNO...HIGHEST CONFIDENCE IS IN THE
WIND FORECAST WITH MODERATE CONFIDENCE IN THE SNOW/VSBY. BRONG

&&

.REV WATCHES/WARNINGS/ADVISORIES...
NV...WINTER STORM WARNING UNTIL 10 AM PST MONDAY FOR NVZ002.

     WINTER STORM WATCH FROM 4 PM THIS AFTERNOON THROUGH 4 AM
       MONDAY MORNING FOR NVZ005.

     WINTER STORM WATCH FROM 4 PM THIS AFTERNOON THROUGH 10 AM
       MONDAY MORNING FOR NVZ003-004.

     HIGH WIND WATCH FROM 10 PM TONIGHT THROUGH 10 AM MONDAY FOR
       NVZ001.

     LAKE WIND ADVISORY FROM 10 AM TO 10 PM PST TODAY FOR NVZ004.

CA...WINTER STORM WARNING FROM 4 AM THIS MORNING TO 4 AM PST MONDAY
       FOR CAZ071.

     WINTER STORM WATCH FROM 4 PM THIS AFTERNOON THROUGH 4 AM
       MONDAY MORNING FOR CAZ070.

     WINTER STORM WARNING UNTIL 10 AM PST MONDAY FOR CAZ072-073.

&&

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