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223
FXUS65 KPIH 252042
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
142 PM MST TUE NOV 25 2014

.SHORT TERM...TONIGHT THROUGH FRIDAY. MOIST NW FLOW CONTINUES TO
PRODUCE SNOW OVER THE CENTRAL MTNS/EASTERN HIGHLANDS WHERE THE
FLOW INTERACTS WITH THE TERRAIN. SNOW HAS BACKED OFF SOMEWHAT THIS
AFTN...BUT MORE IS EXPECTED THRU THE EVE. TWO TO FOUR ADDITIONAL
INCHES OF SNOW IS POSSIBLE MAINLY ABOVE 6500 FEET UNTIL PRECIP
TAPERS OFF TO SCT LIGHT SNOW SHOWERS LATER TONIGHT. THE SNAKE
PLAIN IS NOT EXPECTED TO SEE ANY SIGNIFICANT PRECIP DUE TO BEING
IN THE SHADOW OF THE CENTRAL MTNS. LOOKS LIKE STRONG SW WINDS IN
THE SNAKE RIVER PLAIN/EASTERN MAGIC VALLEY WILL CONTINUE WELL INTO
THE EVE HOURS...SO HAVE EXTENDED THE WIND ADVISORY UNTIL MIDNIGHT.

BY WED...THE UPPER RIDGE WILL PUSH INTO THE PAC NW/GREAT BASIN.
THIS WILL PUSH THE PRECIP OUT OF THE AREA EXCEPT FOR ISOLD SNOW
SHOWERS IN THE NE CORNER WHERE NW FLOW WILL STILL MANAGE TO
INTERACT WITH THE MTNS. THE UPPER RIDGE FLATTENS TO ZONAL FLOW ON
THU...ALLOWING PAC MSTR TO FLOW BACK INTO THE CENTRAL MTNS. SNOW
WILL SPREAD ACROSS THE CENTRAL MTNS INTO THE UPPER SNAKE HIGHLANDS
DURING THE DAY FRIDAY. TEMPS WILL BE ON THE MILD SIDE WED THU
FRI. HEDGES

.LONG TERM...FRI NIGHT THROUGH NEXT TUE NIGHT. THIS ENTIRE FORECAST
PERIOD IS QUITE WET WITH LITTLE LET-UP IN PRECIPIATION OR WIND.
CENTRAL IDAHO MOUNTAIN POPS ARE MAINLY CATEGORICAL FROM FRI NIGHT
THROUGH SAT NIGHT WITH BOTH THE GFS AND ECMWF INDICATING PROBABILITY
OF PRECIPITATION IN STANLEY AS HIGH AS 82 PERCENT. HAVE INCREASED
POPS TO MATCH NEIGHBORING OFFICES AND LATEST GUIDANCE. THUS THE
TRAVEL DAYS AFTER THE THANKSGIVING HOLIDAY WILL BE ROUGH GOING IF IT
MEANS PASSING THROUGH THE HIGH COUNTRY. THE WINTER STORM THAT
ARRIVES DURING THAT TIME COMES FROM THE MID-PACIFIC AND IS BRINGING
FAIRLY MILD AIR. SNOW LEVEL SHOULD BE SOMEWHAT HIGH...ESPECIALLY
DURING THE DAY.  EVEN TEMPERATURES AT STANLEY ARE FORECAST ABOVE
FREEZING...ALTHOUGH THE GUIDANCE HAS HAD A WARM BIAS LATELY. AT THE
LOWER ELEVATIONS...MAINLY THE SNAKE RIVER PLAIN...THE DIFFICULTY
WILL BE HEAVY RAIN AND VERY WINDY CONDITIONS. WILL ISSUE A SPECIAL
WEATHER STATEMENT HIGHLIGHTING THESE CONDITIONS. THIS IS NOW THE
THIRD DAY IN A ROW THAT THIS SAT STORM HAS BEEN IN THE FORECAST AND
SO CONFIDENCE IS HIGH.

BEYOND THIS STORM...THE SPLITTING FLOW THAT DEVELOPS BEHIND THIS
EVENT IS STILL PUMPING WARM AIR AND MOISTURE INTO THE GEM STATE ON
MON AND TUE. IT INTERACTS WITH A TROUGH DIGGING SOUTHWARD OUT OF THE
NORTHERN PART OF THE SPLIT TO MEAN ANOTHER WINTER STORM EVENT FOR
TUE. THIS NEEDS A LITTLE MORE TRACKING BUT RIGHT NOW THE GFS AND
ECMWF SOLUTIONS ARE POINTING TOWARDS THIS SCENARIO.  MESSICK

&&

.AVIATION...WIND IS REACHING EXPECTED LEVELS AT KPIH AND KIDA WITH
KBYI CLOSE BEHIND. LOCAL WIND STUDY INDICATES WIND TO STAY STRONG
THROUGH THE NIGHT...THUS HAVE EXTENDED THE WIND PERIOD. THE MORE
DIFFICULT FORECAST IS THE CIG. NAM MOS CONTINUES TO INDICATE PERIOD
OF BELOW FIELD MINIMUMS FOR KPIH AND KIDA. WITH A TURBULENT
ATMOSPHERE AT AND BELOW THE BOUNDARY LAYER...DO NOT SEE HOW THAT IS
POSSIBLE...BUT MARGINAL VFR IS POSSIBLE. HAVE COMPROMISED BETWEEN
THE OPTIMISTIC GFS-MOS AND THE NAM-MOS...WITH A LEAN TOWARDS THE
GFS. WIND-STRATIFIED CONDITIONAL CLIMATOLOGY ALSO SUGGESTS CLOSURE
CIGS HIGHLY UNLIKELY. BUT JUST HOW LOW IS SUBJECT TO QUITE A BIT OF
UNCERTAINTY AND WOULD NOT BE SURPRISED TO SEE SOME IFR CIGS DURING
THE LATE NIGHT HOURS. THUS WOULD CALL THIS A LOW-CONFIDENCE FORECAST
FOR THE THREE SNAKE RIVER PLAIN AIRDROMES. KSUN SHOULD BE FINE IN
THE CIG AND VSBY DEPARTMENT...THE BIGGER QUESTION THERE IS IF THE
STRONG WIND ALOFT WILL SURFACE. THE LIGHT AND VARIABLE HAS BEEN
OCCURING ALL DAY TODAY WITH 45KT WIND JUST 4.5KFT ABOVE THE SURFACE.
FORTUNATELY IT IS RIGHT DOWN THE RUNWAY AND THE STRONG DOWNSLOPE
EFFECT IS KEEPING CIG AND VSBY FROM BEING A PROBLEM. MESSICK

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL MIDNIGHT MST TONIGHT IDZ017-021.

WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT ABOVE 6500
FEET FOR THE IDZ019-023-025.

WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT ABOVE 7000
FEET FOR THE IDZ018-031.

&&

$$








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