FXUS65 KPIH 152121
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
221 PM MST TUE DEC 15 2009

.SHORT TERM...TONIGHT THROUGH THURSDAY. COMPLICATED UPPER PATTERN
AFFECTING EASTERN IDAHO TODAY. CONSOLIDATED AREA OF MOISTURE MOVING
INTO THE REGION PER SAT IMAGERY. RADAR MOSAIC SHOWING LARGE AREA
OF STEADY PRECIP STRETCHING NORTHWEST FROM BURLEY THROUGH BOISE
INTO OREGON. TEMPERATURE DIFFERENCES WITHIN AND NEAR THIS AREA DUE
TO A COMBINATION OF DOWNSLOPE WARMING AND WEAK WARM ADVECTION
PRODUCING A RANGE OF CONDITIONS FROM RAIN TO WET SNOW. AREA
WEBCAMS INDICATING NOT MUCH IMPACT TO ROADS IN SOUTHERN FRINGES OF
SNAKE PLAIN. NORTHERN EDGE OF SNAKE PLAIN WHERE COLDER
TEMPERATURES PERSISTED THIS MORNING HAVE SEEN OCCASIONAL SNOW
SHOWERS WITH LIGHT ACCUMULATIONS ON ROADWAYS. SOME WEBCAMS ALSO
SHOWING INDICATIONS OF GUSTY WINDS WHICH MATCHES FAIRLY WELL WITH
MESOWEST OBS. HIGHER ELEVATIONS SEEING GREATER ACCUMULATIONS...TO
BE EXPECTED. MOST OF THE HEAVY SNOWFALL IN THE MOUNTAINS REMAINS
WEST OF FCST AREA AT THIS TIME. RUC SEEMS TO HAVE BEST HANDLE ON
THE PRECIPITATION EXTENT AS IT DEVELOPS THIS AFTERNOON. SNOW AND
GUSTY WINDS CONTINUE TO AFFECT HEADLINED AREAS...SO WILL LEAVE
HEADLINES IN PLACE. NOT AS CONFIDENT ABOUT OVERALL SNOW TOTALS SO
HAVE DECREASED OVERALL SNOW FORECAST SLIGHTLY. FORECAST AMTS NOW
GENERALLY 1 TO 3 IN THE UPPER AND LOWER SNAKE PLAIN...2 TO 4 IN
THE EASTERN MAGIC VALLEY AND LOWER ELEVATIONS OF THE MOUNTAIN
ZONES...AND 6 TO 10 AT THE HIGHER ELEVATIONS. STILL ENOUGH SNOW
FORECAST THROUGH HEADLINE TIME FRAME TO KEEP HEADLINES IN PLACE.
FINAL SHORTWAVE ASSOCIATED WITH THIS SURGE OF MOISTURE CURRENTLY
PROGGED TO MOVE THROUGH FCST AREA ON THURSDAY. OROGRAPHICS WILL
KEEP SHOWERS PINNED TO HIGHER ELEVATIONS...PARTICULARLY ALONG THE
WYOMING BORDER. THUS HAVE KEPT POPS HIGH THERE WITH RELATIVELY LOW
QPF AMOUNTS AND OVERALL LOW BUT STEADY SLOW ACCUMULATIONS. TEMPS
WILL CONTINUE TO BE A PROBLEM IN THE SHORT TERM. BOTH GFS AND NAM
GUIDANCE INDICATE SNAKE PLAIN TEMPS RISING WELL ABOVE FREEZING
THROUGH THURSDAY. GIVEN TODAYS TEMPS THESE VALUES SEEM REASONABLE
AND WENT WITH AN OVERALL TREND. DMH

.LONG TERM...THU NIGHT THROUGH NEXT TUE NIGHT.  LESS CONFIDENCE IN A 
DRY FORECAST AS THE 15/12Z HAS BECOME WETTER...COMING AROUND TO THE 
MUCH WETTER GFS SOLUTION.  HAVE TRIED TO SPLIT THE DIFFERENCE IN THE 
CLOUD COVER AND POP DEPARTMENT...AND WENT MOSTLY WITH THE GENERALLY 
BETTER VERIFYING ECMWF BIAS CORRECTED TEMPERATURE FORECAST.  THE 
UPPER LEVEL RIDGE REMAINS CENTERED OVER THE COAST...ALLOWING 
SHORTWAVES TO DIG SOUTHWARD OUT OF CANADA AND INTO THE GEM STATE.  
AT FIRST..THERE IS A BREAK FROM THE REALLY WET WEATHER WITH ONLY 
WEAK WAVE ACTIVITY FOR FRI AND SAT.  AND STILL...CHANCES FOR 
PRECIPITATION IS NOT LARGE.  ALSO...LITTLE TO NO WIND DEVELOPED IN 
THIS REGIME...THUS EXPECT LIGHT TO MODERATE SNOW WITH THE SHORTWAVES 
AND SEE NO SIGNIFICANT STORMS HEADED FOR THE FORECAST AREA AT THIS 
TIME.  MESSICK

&&

.AVIATION...SLOW MOVING WARM FRONT HAS FINALLY MOVED INTO KBYI AND 
KSUN THIS AFTERNOON.  DOWNSLOPE WINDS AT KPIH HAVE KEPT CEILING UP.  
HEAVY PRECIPITATION HAS A HARD TIME SPREADING EAST OF KBYI...SO NOT 
AS SURE THAT SNOW WILL AFFECT THE EASTERN AIRPORTS.  SOME LIGHT RAIN 
EXPECTED DURING THE LATE AFTERNOON AND EARLY EVENING WITH THE MAIN 
BAND...BUT OTHERWISE DO NOT SEE MUCH ACTIVITY IN THE WARM 
OVERRUNNING EXPECTED.  VERY WEAK UPPER LEVEL FORCING IN THE WARM 
SECTOR...THUS MAIN PROBLEM MAY BE JUST LOW CEILING AND POTENTIALLY 
SOME FOG WITH ALL THE MELTING.  THUS...STILL EXPECT SOME IMPACT ON 
THE AIRPORTS...BUT SNOW REMOVAL MAY NOT BE THE MAIN PROBLEM.  
MESSICK 

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 5 PM MST WEDNESDAY FOR IDZ019.

WINTER WEATHER ADVISORY UNTIL 11 AM MST WEDNESDAY FOR IDZ017-022.

WINTER STORM WARNING UNTIL 11 AM MST WEDNESDAY FOR IDZ018-031.

&&

$$