FXUS65 KPIH 091024
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
324 AM MST WED DEC 9 2009

.SHORT TERM...TODAY THROUGH FRIDAY AFTERNOON. THE COLD
NORTHWESTERLY FLOW WILL HOLD THROUGH THURSDAY NIGHT. THIS WILL
KEEP US ON THE COLD SIDE...ESPECIALLY WITH SNOW ON THE GROUND OVER
MUCH OF THE AREA. 

FOR TODAY...A COUPLE OF WAVES WILL MOVE THROUGH KEEPING SOME
LIGHT SNOW IN THE FORECAST. WITH THE NORTHERLY FLOW IN
PLACE...MOST OF THIS WILL OCCUR ACROSS THE SOUTHERN/EASTERN
MOUNTAIN RANGES AND SOUTHERN/EASTERN FRINGE OF THE SNAKE PLAIN.
WITH VERY COLD TEMPS...THE SNOW RATIO WILL BE QUITE HIGH. WHERE IT
DOES SNOW TODAY...THE VALLEYS AND CENTRAL MOUNTAINS WILL SEE LESS
THAN ONE INCH WHILE THE HIGHER ELEVATIONS CLOSER TO THE WYOMING
BORDER WILL SEE 1 TO 3 INCHES OF POWDER. DURING THE AFTERNOON AND
EARLY EVENING HOURS...WINDS WILL BE INCREASING SOMEWHAT. SUSTAINED
WINDS IN THE 10 TO 20 MPH RANGE ARE FORECAST...WITH THE STRONGEST
WINDS ACROSS THE SNAKE PLAIN AND THE SOUTHERN/SOUTHEASTERN
MOUNTAINS. WITH THESE WINDS AND THE POWDERY NATURE OF THE
SNOW...AREAS OF BLOWING SNOW AND LOWER VISIBILITY ARE EXPECTED IN
THESE LOCATIONS. THEREFORE...A WINTER WEATHER ADVISORY WILL BE
ISSUED FOR THE LATE MORNING THROUGH EARLY EVENING HOURS. EVEN IF
IT IS NOT SNOWING AT TIME...SNOW ON THE GROUND WILL BE BLOWING
AROUND. WIND CHILLS WILL ALSO BE QUITE LOW THANKS TO HIGHS RANGING
FROM -10 TO 15 ABOVE TODAY IN THE WARMEST SPOTS. WITHIN THE
ADVISORY AREA...WIND CHILLS WILL BE IN THE ZERO TO -20 RANGE.
ELSEWHERE...WIND CHILLS WILL DROP TO AS LOW AS -35 BELOW HOWEVER
THESE WILL BE IN LOCATIONS WHERE IT IS MUCH COLDER - THE MUCH
HIGHER PEAKS - AND THE LIGHTEST WINDS WILL CREATE LOWER WIND
CHILLS. A WIND CHILL WARNING WILL NOT BE ISSUED BUT WILL MAKE
MENTION OF THIS IN THE VARIOUS PRODUCTS. 

BY TONIGHT AND THURSDAY...SNOW WILL BE CONFINED TO THE MOUNTAINS CLOSER
TO THE DIVIDE WHERE ANOTHER INCH OR TWO OF POWDERY SNOW WILL FALL.
WINDS WILL BEGIN TO CALM DOWN AS WELL. THE STORY FOR TONIGHT WILL
BE THE REALLY COLD LOWS AND POSSIBILITY OF STRATUS ACROSS THE
SNAKE PLAIN. TEMPERATURES TONIGHT WILL GENERALLY BE IN THE 0 TO-15
RANGE...WITH THE COLDEST SPOTS LIKE STANLEY AND NEAR YELLOWSTONE
APPROACHING -25. LOWEST ELEVATION RH DATA ALSO INDICATES STRATUS
FORMING ACROSS THE NORTHERN AND WESTERN PORTIONS OF THE SNAKE
PLAIN INTO THE VALLEYS OF THE UPPER SNAKE HIGHLANDS. HAVE PLACED
THIS IN THE SKY GRIDS FOR TONIGHT AND THURSDAY MORNING...BUT WE
ARE NOT THINKING THAT FOG WILL FORM AT THIS TIME. IT WILL BE A
LITTLE WARMER TOMORROW...AROUND 5 DEGREES IN THE VALLEYS AND UP TO
10 DEGREES AT MID AND UPPER SLOPE. THE VALLEYS WILL NEED TO BE
WATCHED AS SNOW AND THE INVERSION MAY KEEP IT COLDER THAN CURRENT
FORECASTED VALUES...WHICH ARE ALREADY BELOW MODEL GUIDANCE. 

THE FLOW THURSDAY NIGHT AND FRIDAY WILL FINALLY SWITCH TO MORE
ZONAL AND OFF THE PACIFIC. THIS WILL ALLOW FOR SOME WARMING ON
FRIDAY...BUT STILL KEEPING MOST AREAS IN THE 15 TO 25 DEGREE RANGE
AS IT WILL TAKE A LITTLE STRONGER PUSH OF WARMER AIR AND MIXING TO
REALLY WARM THINGS UP. THAT WILL COME OVER THE WEEKEND. ANY SNOW
WILL BE VERY LIGHT AND CONFINED TO THE UPPER SNAKE HIGHLANDS.
STRATUS WILL ALSO BE A PROBLEM AGAIN FOR THE UPPER SNAKE PLAIN AND
HIGHLANDS DURING THE MORNING HOURS.  KEYES

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY. MODELS REMAIN IN 
GENERAL AGREEMENT THROUGH THE PERIOD. ZONAL FLOW IN PLACE FOR THE 
WEEKEND WITH PACIFIC ENERGY BRINGING WET CONDITIONS BACK TO EASTERN 
IDAHO. HAVE KEPT CHANCE POPS ABOVE CLIMO WITH LIKELY POPS HIGHER 
ELEVATIONS THROUGH THE WEEKEND...ALONG WITH MODERATED SEASONABLE 
TEMPS. EXCELLENT AGREEMENT BETWEEN GFS ECMWF AND ENSEMBLES WITH 
RIDGE TRYING TO BUILD INTO WESTERN STATES BY MONDAY THOUGH MODELS 
CONTINUE TO SHOW LIGHT PRECIP ACCUMULATIONS. HAVE LEFT POPS AT OR 
SLIGHTLY BELOW CLIMO FOR MONDAY TUESDAY AS HEIGHTS RISE ALONG WITH 
CONTINUED SEASONABLE TEMPS. DMH

&&

.AVIATION...A MIXED BAG OF CONDITIONS CAN BE EXPECTED TODAY. MODEL 
CROSS SECTIONS CONTINUE TO SHOW THIN LAYER OF MOISTURE INDICATIVE OF 
STRATUS ACROSS THE REGION. SAT IMAGERY SHOWS THIS LAYER THROUGH MUCH 
OF THE SNAKE PLAIN. WITH SHORTWAVE DROPPING SOUTH INTO EASTERN IDAHO 
TODAY...EXPECT MID LEVEL CLOUDS TO FEED SNOW SHOWERS THROUGH STRATUS 
LAYER. MVFR CONDITIONS CAN BE EXPECTED MOST PLACES WITH IFR OR LIFR 
UNDER SHOWERS. DMH

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 11 AM THIS MORNING TO 8 PM MST THIS 
EVENING FOR IDZ017-020>025.

&&

$$