Heavy Snow in Nevada, November 24 to 25, 2001

NORTHERN GREAT BASIN FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ELKO NV
245 AM PST SAT NOV 24 2001

.SYNOPSIS... A LOW PRESSURE SYSTEM WILL MOVE ACROSS NORTHERN NEVADA
TODAY BRINGING SIGNIFICANT RAIN AND SNOW TO THE GREAT BASIN THIS
WEEKEND. WINDY CONDITIONS AND COOLER TEMPERATURES WILL ALSO ACCOMPANY
THIS SYSTEM. MORE LOW PRESSURE SYSTEMS WILL MOVE THROUGH NORTHERN
NEVADA NEXT WEEK KEEPING UNSETTLED WEATHER ACROSS THE REGION.

.DISCUSSION...IMPRESSIVE WX SCENARIO SHAPING UP FOR TODAY WITH UPPER
TROUGH IN EASTERN PACIFIC WITH MAIN S/W LOCATED NEAR 35N/138W ATTM.
THIS IS A MAJOR SYSTEM AND WILL UPGRADE THE WINTER STORM WATCH TO A
WARNING GIVEN THE AVAILABLE MOISTURE AND COLD AIR WHICH WILL BRING
SIGNIFICANT SNOW TO MOST...IF NOT ALL...OF THE CWFA. AVN SEEMS TO
HAVE BEST INITIALIZATION WITH THIS SYSTEM AS ETA/NGM SEEM A BIT WEAK
WITH S/W. THIS SYSTEM WILL MOVE THRU THE CWFA LATE TOMORROW BUT WILL
SEE PRECIP START ACROSS WESTERN ZONES LATE MORNING WITH MOISTURE
AHEAD OF THIS SYSTEM. PRECIP WILL MOST LIKELY START AS SNOW BEFORE
CHANGING TO RAIN IN LOWER VALLEYS BEFORE RETURNING TO ALL SNOW
TONIGHT. VERY IMPRESSIVE FEATURES WITH VERY STRONG DIVERGENCE COUPLET
AND LLVL LIFT. BEST QPF VALUES ARE ACROSS NORTH GIVEN PROGGED
POSITION OF SFC FRONT AND THIS LOOKS GOOD FOR HUMBOLDT AND NORTHERN
ELKO ZONES GIVEN CURRENT TRACK AS SEEN FROM OBS AND SATELLITE. SOME
GUIDANCE VALUES NEAR ONE INCH WHICH MAY BE A BIT OVER DONE...THOUGH
CONSENSUS IS QPF VALUES SHOULD BE OVER HALF INCH ACROSS ENTIRE CWFA
SO IN HIGHER ELEVATIONS WILL SEE SOME SIGNIFICANT SNOWFALL.

FORECAST A LITTLE MORE COMPLICATED IN THE VALLEYS REGARDING PRECIP
TYPE AS HAVE EXTREME LLVL WAA WHICH SHOULD TURN PRECIP TO RAIN IN THE
AFTERNOON AND EVENING. HOWEVER WITH IMPRESSIVE LLVL OMEGA IT WILL BE
MORE DIFFICULT TO MIX IN WARMER AIR SO WAA EFFECT MAY NOT BE AS
PRONOUNCED. FOR WINTER STORM WARNING WILL GO WITH WARNING ABOVE 5000
FT FOR HUMBOLDT COUNTY AND TO VALLEY FLOORS ELSEWHERE AS SNOW LVLS
WILL BE BTWN 5-6000 FT IN THE AFTERNOON AND EARLY EVENING. DEPENDING
ON RAIN/SNOW MIX WILL SEE VARIETY OF ACCUMULATIONS IN LOWER VALLEYS
ALONG HUMBOLDT RIVER WITH THIS SYSTEM AS STRENGTH OF WAA AND AMT OF
SNOW BEFORE RAIN BEGINS WILL VERY IMPORTANT. WITH COLD AIR AND PRECIP
ALREADY MOVING INTO NV BELIEVE 3 INCHES IS NOT OUT OF THE QUESTION
BEFORE RAIN BEGINS IN LOWER VALLEYS. SNOW LVLS WILL FALL TO THE
VALLEY FLOORS QUICKLY TONIGHT AS CAA WITH THIS SYSTEM IS NEARLY AS
IMPRESSIVE AS THE LLVL WAA AHEAD OF IT. WILL HAVE VERY TIGHT SFC
GRADIENT AS FRONT PASSES...AVN SHOWS 986 LOW OVER NW HUMBOLDT THIS
AFTERNOON...SO WILL HAVE WINDY CONDITIONS ACROSS THE ENTIRE REGION
WHICH WILL LAST INTO THE EVENING. WIND ADVISORY NOT OUT OF THE
QUESTION FOR LATE TODAY INTO TONIGHT ALONG HIGHWAY 50 CORRIDOR AND
WILL LOOK INTO MORE CLOSELY. ATTM WILL NOT ISSUE ADVISORY BUT WILL
BRIEF DAY SHIFT ACCORDINGLY TO WATCH GRADIENTS AND CLOUD COVER.

...REST OF SHORT TERM...
UPPER LVL LOW WILL MOVE OUT OF CWFA EARLY SUNDAY AND WILL RETROGRADE
INTO PAC NW SUN AFTERNOON. WILL HAVE LINGERING SHOWERS FOR MOST OF
THE DAY AND USUALLY SEE MTNS RECEIVE ADDITIONAL ACCUMULATIONS DUE TO
OROGRAPHICS. NORTHWEST FLOW WILL DEVELOP OVER CWFA ALLOWING FOR
IMPULSES IN SYNOPTIC FLOW TO MOVE INTO THE GREAT BASIN UNABATED WITH
NEXT SYSTEM MOVING INTO REGION LATE MONDAY. WITH COLD AIR AND
MOISTURE IN PLACE FOR SUNDAY WILL KEEP CHANCE POPS BUT WILL
DECREASE CHANCE AS DAY GOES ON. GIVEN TIMING ISSUES WITH THE NEXT
SYSTEM MOVING INTO GREAT BASIN IN NW FLOW WILL GO WITH SLIGHT
CHANCE ON TUESDAY AS WET PATTERN WILL CONTINUE FOR AWHILE.

...EXTENDED...
NORTHWEST FLOW ALOFT WILL PERSIST WITH EMBEDDED SHORT WAVES PASSING
THROUGH THE CWFA THROUGHOUT THE WEEK. GIVEN AVAIL MOISTURE AND COLD
AIR IN PLACE EMBEDDED VORT FEATURES WILL BE STRONG ENOUGH TO FORM
PRECIP OVER THE REGION. WITH DIFFERENCES IN EXACT TIMING PLUS MODEL
RESOLUTION ISSUES WITH SMALLER FEATURES WILL GO WITH SLIGHT CHANCE TO
CHANCE POPS THROUGH THE WEEK.  FEHRN

.EKO...WINTER STORM WARNING SATURDAY THROUGH SUNDAY MORNING
       NVZ30>34...36
       WINTER STORM WARNING SATURDAY NIGHT THROUGH THROUGH SUNDAY
       MORNING NVZ35...37