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000
FXUS65 KPIH 130945
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
245 AM MST FRI DEC 13 2013

.SHORT TERM...TODAY THROUGH SUN NIGHT. WEAK TO MODERATE TROUGH
WITH ACCOMPANYING BAROCLINIC ZONE/SURFACE FRONT EXPECTED TO MOVE
THROUGH TODAY AND TONIGHT. SNOWFALL AMOUNTS APPEAR LIMITED TO THE
NORTHWEST AND NORTHEAST CORNERS...AND MUCH LESS THAN 5 INCHES FOR
THE NEXT 24 HOURS. THUS SEE NO NEED FOR ANY WATCH OR ADVISORY AT
THIS TIME. FOR THE SNAKE RIVER PLAIN...LOOKS LIKE FLURRIES ARE
ABOUT AS MUCH THAT ARE POSSIBLE...SO ANY ACCUMULATION THERE IS
NEAR ZERO. THE MAIN FORECAST PROBLEM OCCURS AFTER THE CLOUDS CLEAR
OUT SAT MORNING...WHAT WILL BE THE FOG OR STRATUS SITUATION FOR
SAT NIGHT AND SUN MORNING. LATEST NAM INDICATES A VERY RICH
BOUNDARY LAYER HUMIDITY-WISE FOR LATE NIGHT FRI AND ACTUALLY NEARLY
ALL DAY SAT...AT LEAST FOR THE SNAKE RIVER PLAIN AND PORTIONS OF
THE MOUNTAINS ALONG THE MONTANA BORDER AND SOME OF WYOMING. SINCE
THE NAM IS THE BEST MODEL...HAVE DECIDED TO PUT IN SOME EXTENSIVE
STRATUS WITH PATCHY VALLEY FOG...AND WHERE THE GUIDANCE GENERATES
PRECIPITATION...MAKE IT AREAS OF FOG. NOT QUITE SURE IT WILL BE
DENSE. THE BOUNDARY LAYER MOISTURE IS DRIES OUT A BIT FOR SAT NIGHT/
SUN MORNING...BUT HAVE CONTINUED THE PATCHY VALLEY FOG WITH AREAS
OF FOG FOR THE AREA FROM IDAHO FALLS TO ISLAND PARK. FOR SUN
NIGHT/MON MORNING...BOUNDARY LAYER IS MUCH DRIER AND DO NOT SEE
RIGHT NOW A CONTINUANCE OF THE FOG AND STRATUS SITUATION. THE
CLOUDS SHOULD HAMPER THE WARM UP...WHICH APPEARS TO BE
INCORPORATED IN THE NAM TEMPERATURE FORECASTS FOR SAT...THEN MUCH
WARMER SUN. THE STRATUS AND FOG ALSO FIT THE SYNOPTIC SITUATION
WELL...THERE IS STRONG RIDGING BOTH ALOFT AND AT MSL. THIS WILL
PRODUCE SUBSIDENCE...ALTHOUGH IT IS NOTED THAT THERE IS A LAYER
BETWEEN THE BOUNDARY LAYER AND 600MB WHERE THERE IS ACTUALLY SOME
UPWARD VERTICAL MOTION. PROBABLY A GREATER COVERAGE OF FOG WHEN
SUBSIDENCE PEAKS ON SAT NIGHT...RATHER THAN TONIGHT. AS YOU SHOULD
FIGURE...WIND IS NOT A SIGNIFICANT FACTOR THIS PERIOD...UNLESS YOU
CONSIDER THE LACK OF IT WHICH IS HELPFUL FOR FOG FORMATION.
MESSICK

.LONG TERM...MONDAY THROUGH FRIDAY NIGHT. NW FLOW ALOFT WILL
DOMINATE THRU TUE NIGHT...WITH NO SIGNIFICANT PRECIP EXPECTED. TEMPS
WILL REMAIN ON THE MILD SIDE THRU WED. THE PATTERN BEGINS TO CHANGE
ON WED AS A DEEP UPPER TROF BEGINS TO ROTATE SOUTHWARD OUT OF BC.
SNOW WILL BEGIN TO MOVE INTO THE CENTRAL MTNS BY WED AFTN. AS THE
STORM SYSTEM MOVES SE INTO THE PAC NW...PRECIP CHANCES WILL INCREASE
WED NIGHT. THE GFS PUSHES THE COLD FRONT INTO CENTRAL ID ON THU...
INCREASING THE PRECIP CHANCES EVEN MORE. THE MAIN SURGE OF COLD AIR
COMES THU NIGHT...WITH TEMPS FRI ONLY IN THE TEENS OR LOWER 20S. BY
SAT MORN...MANY AREAS WILL BE BELOW ZERO. PRECIP TAPERS OFF TO SNOW
SHOWERS BY FRI...AND DIMINISHES MORE FRI NIGHT. TOO EARLY TO
DETERMINE SNOW AMOUNTS...BUT THIS TYPE OF SYSTEM COMMONLY PRODUCES
AT LEAST A COUPLE OF INCHES OF SNOW IN THE VALLEYS. HEDGES

&&

.AVIATION...PATCHY FOG/LOW CIGS FLOATING AROUND KPIH AGAIN THIS
MORNING...ENHANCED BY THE NEARBY INDUSTRIAL PLANT. CONDITIONS WILL
IMPROVE TO VFR BY MID MORNING. SNOW SHOWERS EXPECTED THIS AFTN IN
THE CENTRAL MTNS AND NE HIGHLANDS. KSUN AND KIDA MAY SEE SNOW
SHOWERS IN THE VCNTY...ALONG WITH LOWER CIGS. HEDGES

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$