Winter Storm and Heavy Snow in Idaho, February 7 to 8, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
220 PM MST WED FEB 6 2008

.SHORT TERM...LATEST WATER VAPOR SATELLITE IMAGERY WAS CLEARLY
SHOWING THE NEXT UPSTREAM SYSTEM PUSHING ESE TOWARD VC ISLAND.
SATELLITE ESTIMATED PW/S WITH THIS SYSTEM WERE RUNNING UPWARDS OF
1.25 INCHES OF LIQUID WHILE THE UPPER JET WAS PROGGED IN EXCESS OF
160KTS INDICATING THE STRENGTH OF THE SYSTEM. MODELS CONTINUE TO
PRODUCE MODERATE TO STRONG PRECIPITATION RETURNS OVER THE FAVORED NW
UPSLOPE AREAS AS THE DISTURBANCE DIGS RAPIDLY SE INTO THE CNTRL
MOUNTAINS LATE TONIGHT AND THEN ACROSS THE FORECAST AREA DURING THE
DAY THURSDAY. SNOWFALL TOTALS WERE RUNNING UP NEAR WARNING LEVELS
(9+ INCHES) IN THE UPPER ELEVATIONS OF THE FAVORED UPSLOPE REGIONS
OF THE CNTRL AND ERN HIGHLANDS WHILE THE MOUNTAIN VALLEYS WERE
RUNNING MUCH LOWER IN THE 2-4 INCH RANGE. THE SNAKE VALLEY COULD
POTENTIALLY SEE 1 TO 3 INCHES FAVORING THE ERN BENCHES. THE
ASSOCIATED SURFACE COLD FRONT SWEEPS ACROSS THE FORECAST AREA AROUND
18-00Z WITH WINDS RAMPING UP THROUGH THE DAY AND GUSTING TO 40-50
MPH IN THE AFTERNOON WITH A 65KT 700MB AND 140KT JET ALOFT. THIS
SHOULD PROVE TO BE THE COMPLICATING FACTOR WITH LIGHT SNOWFALL
ANTICIPATED IN THE MAJORITY OF THE VALLEYS AND AT LEAST ADVISORY
LEVEL WINDS DEVELOPING BELIEVE A SNOW AND BLOWING SNOW ADVISORY FITS
THE SITUATION BEST. THUS HAVE ISSUED A WINTER STORM WARNING FOR THE
MOUNTAIN ZONES 18/31/19/23 AND 25 FOR THE COMBINATION OF SNOW AND
WIND BEGINNING LATE TONIGHT AND CONTINUING THROUGH THURSDAY. FOR THE
REMAINING ZONES HAVE POSTED A SNOW AND BLOWING SNOW ADVISORY FOR THE
DAY THURSDAY. UPPER WAVE EXITS EAST RAPIDLY THURSDAY NIGHT WITH A
DIRTY/MOIST NW FLOW REMAINING OVER THE REGION THROUGH FRIDAY. THUS
HAVE HIGH CHANCE/LOWER LIKELY PROBABILITY FAVORING THE NW UPSLOPE
AREAS OF THE CNTRL AND ERN HIGHLANDS WITH SLIGHT CHANCE TO CHANCE
MENTION FOR THE VALLEYS THURSDAY NIGHT/FRIDAY. GOOD NEWS IS
TEMPERATURES BEGIN TO MAKE A SLIGHT MOVE UPWARD THROUGH FRIDAY AND
THIS TREND APPEARS TO CONTINUE INTO THE LONG TERM PERIOD. HUSTON

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY.  LONG WAVE PROGS
CONTINUE TO INDICATE A LONG WAVE RIDGE SHIFTING EASTWARD INTO THE
GREAT BASIN...BUT AMPLITUDE STILL SMALL AND SHORTWAVES WILL BE
DETERMINING FACTOR IN WHICH DAYS HAVE PRECIPITATION.  THIS WILL MEAN
WARMER TEMPERATURES WITH 500MB HEIGHTS PEAKING ON MON AFTERNOON.  IN
THE THE DETAILS...GFS ENSEMBLE SHOW GOOD AGREEMENT THROUGH MON.  AT
THAT POINT TIMING OF SUBSEQUENT SHORTWAVES PRODUCES WIDE RANGE OF
SOLUTIONS.   UP UNTIL THAT TIME...UPPER LEVEL RIDGING MOVES THROUGH
THE AREA SAT/SAT NIGHT AND A WEAK TROUGH MOVES THROUGH SUN/SUN
NIGHT.  THEN DRY NORTHWESTERLY FLOW FOR MON.  COMPARING THE GFS TO
THE ECMWF...ECMWF IS SLOWER WITH THE WEEKEND TROUGH.  MAJOR
DIFFERENCES BETWEEN THESE TWO GUIDANCE PRODUCTS CROP UP ON TUE WITH
ECMWF BRINGING IN A VERY VIGOROUS SHORTWAVE COMPARED TO THE GFS
SOLUTION.  SO WOULD LIKELY GO SLIGHTLY HIGHER THAN GFSX MOS GUIDANCE
FOR TUE NIGHT/WED.  MESSICK
&&

.AVIATION...NEXT STORM COMING IN LATER TONIGHT IS VERY MUCH A REPEAT
OF WHAT WAS EXPECTED LAST NIGHT.  WINDS SHOULD BE STRONGER AS A
WESTERLY 130KT JET STREAK SLIDES OVER THE FORECAST AREA.  OTHER THAN
KSUN...EXPECT NEAR HIGH WIND WARNING WIND SPEEDS TO DEVELOP LATE IN
THE FORECAST PERIOD FOR TAFS.  SNOW SHOULD DEVELOP DURING THE LATE
EVENING/EARLY MORNING.  WITH SOUTHERLY FLOW AHEAD OF THIS
FRONT...KBYI AND KPIH WILL BE IN THEIR PRECIPITATION SHADOW AND IT
WILL TAKE LONGER FOR SNOW TO DEVELOP.  KSUN WILL BE THE FIRST TO GO
DOWN AND WILL LIKELY BE BELOW FIELD MINIMUMS BY THIS AFTERNOON.
MESSICK
&&

.PIH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING ZONES 18/19/23/25 AND 31 LATE TONIGHT THROUGH
THURSDAY.
SNOW AND BLOWING SNOW ADVISORY ZONES 17/20/21/22/24 AND 32 THURSDAY.
SEE STATEMENTS FOR FURTHER INFORMATION.
&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE POCATELLO ID
230 PM MST WED FEB 6 2008

IDZ017>025-031-032-071315-
EASTERN MAGIC VALLEY-SAWTOOTH MOUNTAINS-UPPER SNAKE HIGHLANDS-
UPPER SNAKE RIVER PLAIN-LOWER SNAKE RIVER PLAIN-
SOUTH CENTRAL HIGHLANDS-CARIBOU HIGHLANDS-
CACHE VALLEY/IDAHO PORTION-WASATCH MOUNTAINS/IDAHO PORTION-
BIG AND LITTLE WOOD RIVER REGION-LOST RIVER/PAHSIMEROI-
230 PM MST WED FEB 6 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN IDAHO.

.DAY ONE...TONIGHT AND THURSDAY

A STRONG PACIFIC STORM WILL PUSH RAPIDLY SOUTHEAST THROUGH THE
REGION LATE TONIGHT AND THURSDAY. WARNING LEVEL SNOWFALL IS EXPECTED
ACROSS THE UPPER ELEVATIONS OF THE CENTRAL MOUNTAINS AND THE EASTERN
HIGHLANDS THROUGH THE PERIOD.  LIGHTER SNOWFALL OF 2-4 INCHES IS
ANTICIPATED ACROSS THE REMAINING VALLEY LOCATIONS.  A COMPLICATING
FACTOR WILL BE THE DEVELOPMENT OF STRONG ADVISORY LEVEL WINDS. THUS
HAVE ISSUED A WINTER STORM WARNING FOR THE AFOREMENTIONED CENTRAL
AND EASTERN HIGHLANDS FOR MODERATE SNOW AND STRONG WINDS AND A SNOW
AND BLOWING SNOW ADVISORY FOR LIGHT TO MODERATE SNOWFALL AND STRONG
WINDS. PLEASE SEE OUR HIGHLIGHTS FOR ADDITIONAL INFORMATION.

.DAYS TWO THROUGH SEVEN...THURSDAY NIGHT THROUGH WEDNESDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.  THE NEXT
SIGNIFICANT WINTER SYSTEM APPEARS TO SPREAD ACROSS THE REGION SUNDAY
AND SUNDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

WE ASK TRAINED SPOTTERS AND CITIZENS TO REPORT SIGNIFICANT
WEATHER CONDITIONS WHEN IT IS SAFE TO DO SO. THESE CONDITIONS MAY
INCLUDE HAIL...TORNADOES...STRONG WIND...DUST STORMS...SNOWFALL...
EXTREME COLD TEMPERATURES...FREEZING RAIN OR HEAVY RAIN...DENSE
FOG...AND FLOODING OR ICE JAMS. INFORMATION ABOUT THESE HAZARDOUS
CONDITIONS SHOULD BE CALLED INTO YOUR NATIONAL WEATHER SERVICE
OFFICE IN POCATELLO USING THE 1-800 SEVERE WEATHER HOTLINE...OR
208-233-0834.