Heavy Snow in Nevada, January 25 to 26, 2002

WESTERN NEVADA AND EASTERN CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
305 AM PST FRI JAN 25 2002

COMPLEX WX SYSTEM IN THE GULF OF AK CONTS TO DROP SOUTH TONIGHT.
SOME SUBTLE TRENDS IN THE MODELS TONIGHT AFFECTING THE FCST.  TREND
OF LESS WIND TODAY LEADS ONE TO THE CONCLUSION THAT HIGH WINDS MAY
NOT DEVELOP IN THE LEE OF THE SIERRA THIS AFTERNOON.  WILL CONTINUE
THE WATCH BASED ON THAT UNCERTAINTY AND NOT CONVERT TO A WARNING
ATTM.  ALSO WITH MORE CLOUDINESS FORECAST AND MAYBE SLIGHTLY LESS
MIXING OF THE ATMS WILL LOWER FCST HIGHS JUST A BIT IN THE WESTERN
NV ZONES.  THE QPF OF THE MODELS IS ALSO LOWER THAN PREVIOUS RUNS.
THIS LOWER QPF MAY ALSO BE THE RESULT OF THE SUBTROPICAL MOISTURE
BEING CUT OFF AT SOME POINT DURING THIS SYSTEMS TRACK SOUTH.
COMPLEXITY OF SYSTEM ALSO A FCST CHALLENGE.  MODELS HAVE A DOUBLE
FRONT STRUCTURE IN THE THICKNESS PACKING.  THE FIRST FRONT TODAY AND
TONIGHT WILL CAUSE STRONG WINDS WHILE THE SECOND FRONT WHICH PRECEED
MUCH COLDER AIR WILL LIKELY PASS THROUGH THE CWA SATURDAY AND MAY
HAVE STRONGER WINDS ASSOCIATED WITH IT.  THIS DOUBLE FRONT STRUCTURE
MAY ALSO CAUSE SOME BREAKS IN THE PRECIP.  ALL THIS VERY DIFFICULT
TO DISCRIBE IN WORDS.  BASICALLY PRECIP BEGINS IN THE NORTH LATE
THIS AFTERNOON AND CONTS INTO SAT MORNING.  ACROSS THE TAHOE AREA
MAIN PRECIP IS TONIGHT AND SATURDAY MORNING.  IN MONO COUNTY IT WILL
BE SATURDAY INTO SATURDAY NIGHT.  AS THE COLD AIR BEGINS TO MOVE IN LATE
SATURDAY TEMPS LIKELY TO DROP DRAMATICALLY WITH SNOW SHOWERS
BECOMING WIDESPREAD ON SUNDAY.  WINDS IN SOME AREAS WILL REAMIN
GUSTY THROUGH THE WEEKEND WHILE IN OTHER AREAS THE STRONG WINDS WILL
BE MORE INTERMITENT.  SNOW AMOUNTS LIKELY TO BE NEAR WINTER STORM
CRITERA SO WITH THE ADDED HAZARD OF STRONG WINDS WILL CONVERT THE
WINTER STORM WATCH TO A WARNING.  ANOTHER NON METEOROLOGICAL REASON
FOR CONVERTING THE WATCH IS THAT I CAN ONLY MAKE UNCERTAINTY OR
NEGATIVE ARGUMENTS FOR CONTINUING THE WATCH SO WILL UPGRADE TO BE
CONSISTENT ACROSS THE SIERRA .

.EXTENDED...LAST NIGHTS MEDIUM RANGE MODELS WERE IN CLOSE AGREEMENT
BUT TONIGHT ITS A DIFFERENT STORY. SO NOW THE EXTENDED FORECAST
BECOMES A LITTLE MORE COMPLICATED. SINCE THE GULF OF ALASKA TROF IS
SUCH A LARGE SYSTEM PROGS ARE NOW TRENDING TOWARDS MOVING IT SLOWER
AND IN PARTICULAR THIS TAKES ITS TOLL ON THE SYSTEM THAT WAS
SUPPOSSED TO BE DROPPING SOUTHWARD IN THE NORTHERLY FLOW ON MONDAY.
A COMPROMISE IN THE PROGS RESULTS IN THE MAIN TROF STILL IN THE
PROCESS OF WEAKENING AND MOVING THROUGH THE CWA ON MONDAY. AND ON
TUESDAY IT MOVES OUT TO THE SOUTHEAST WITH THE UPSTREAM RIDGE MOVING
TO 130 WEST AND GIVING NORTHERLY FLOW TO OUR AREA. BASED ON SYSTEMS
SIMILIAR TO THIS THERE HAS ALWAYS BEEN A FEATURE IN THIS NORTHERLY
FLOW SO WILL GO THIS WAY AGAIN AND THUS KEEP IN A CHANCE OF SHOWERS
ON TUESDAY. NEW MRF HINTS AT A VERY WEAK RIDGE OVER THE AREA ON
WEDNESDAY AND THURSDAY TO FIT THE CURRENT DRY FORECAST.

.REV...HIGH WIND WATCH FRIDAY ZONES 1..2/72...3...5 AND 71
    WINTER STORM WARNING TONIGHT-SATURDAY ZONES 2/72...71
    WINTER STORM WATCH SATURDAY-SATURDAY NIGHT ZONE 73.