342  
FXUS65 KPIH 202104  
AFDPIH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE POCATELLO ID  
204 PM MST MON NOV 20 2017  
   
SHORT TERM
 
TONIGHT THROUGH THURSDAY. THE AIR JUST ABOVE THE  
SURFACE IS SATURATING FROM MOIST FLOW OFF THE PACIFIC THIS  
AFTERNOON, BUT AT THE SAME TIME WARM TEMPERATURE ADVECTION IS  
BEGINNING TO RAISE THE SNOW LEVELS. THIS IS A LITTLE SUBTLE SINCE  
SURFACE TEMPERATURES ARE SHOWING VERY LITTLE CHANGE HOUR TO HOUR. AS  
WE PROGRESS INTO THE EVENING THE SNOW LEVELS WILL BE RISING T O NEAR  
7400 FEET ELEVATION AROUND CHALLIS AND CLOSE TO 9000 FEET ELEVATION  
VICINITY OF BURLEY BY TUESDAY MORNING. IT IS SNOWING NOW AT HAILEY  
AND WOOD RIVER, BUT LOWER ELEVATION WILL CHANGE OVER TO RAIN BY  
MIDNIGHT. SNOW IN THE CENTRAL MOUNTAINS WILL SLOW TO NEAR LITTLE  
ACCUMULATION AFTER MIDNIGHT. THE CURRENT WINTER WEATHER ADVISORY FOR  
ELEVATIONS ABOVE 7500 FEET WILL LIKELY END MUCH EARLIER THAN  
PREVIOUSLY FORECAST. THESE SNOW LEVELS WILL REMAIN AROUND 8000 FEET  
OR SO THROUGH THANKS GIVING DAY WITH A RIDGE OF HIGH PRESSURE OVER  
THIS AREA. WE WILL CONTINUE TO SEE SOME LIGHT RAIN/SNOW IN THE  
MOUNTAINS OFF AND ON TUESDAY AND WEDNESDAY, THEN THE RIDGE GAINS  
MORE AMPLITUDE THANKS GIVING DAY, ENOUGH TO SHIFT PRECIPITATION  
FURTHER NORTH AND EVEN PROVIDE PARTIAL CLEARING SKIES. RS  
   
LONG TERM
 
THURSDAY NIGHT THROUGH NEXT MONDAY NIGHT. A LONG-WAVE  
RIDGE REMAINS POSITIONED OVER THE WEST THROUGHOUT THE PERIOD WITH  
OCCASIONAL LIGHT PRECIPITATION WORKING OVER THE RIDGE AXIS BRUSHING  
THE CNTRL AND NE MOUNTAINS. BOTH THE GFS AND ECMWF SHOW TWO PACIFIC  
DISTURBANCE BREAKING OVER THE RIDGE AXIS DURING THE PERIOD. THE  
FIRST IS THURSDAY NIGHT WHICH BOTH MODELS SHOW VERY GOOD AGREEMENT  
ON TRACK AND TIMING AND THE SECOND IS NEXT MONDAY NIGHT WHERE THE  
MODELS SHOW DIFFERENCES BOTH IN TIMING AND STRENGTH. THUS HAVE  
BOOSTED THE PRECIPITATION POTENTIAL ACROSS THE CNTRL AND NE  
MOUNTAINS THURSDAY NIGHT AND GENERALLY ALLOWED THE REMAINDER OF THE  
FORECAST TO REMAIN RELATIVELY DRY GIVEN THE MEAN RIDGE POSITION. THE  
STATISTICAL TEMPERATURE GUIDANCE WAS RUNNING WAY ABOVE NORMAL FOR  
THIS TIME OF YEAR AND ALTHOUGH THE FORECAST WAS NOT AS BULLISH, WE  
WERE ADVERTISING WARM CONDITIONS NONETHELESS. HUSTON  

 
   
AVIATION
 
SATELLITE IMAGERY WAS SHOWING A MODEST PACIFIC SHORT-  
WAVE TROUGH ADVANCING INTO WASHINGTON TOPPING THE WEST COAST RIDGE  
WHILE ATTENDING RAIN AND SNOW WERE SPREADING INTO WRN AND CNTRL  
IDAHO EARLY THIS AFTERNOON PER RADAR IMAGERY. NUMERICAL MODELS SHOW  
THE SYSTEM SHEARING ESE THROUGH THE PANHANDLE AND MONTANA OVERNIGHT  
AS THE ASSOCIATED PRECIPITATION AND LOWER CIGS ADVANCE FROM WEST TO  
EAST ACROSS THE FORECAST AREA. THE SNAKE PLAIN TERMINALS SHOW  
DETERIORATING CONDITIONS THROUGH THE EVENING WITH MVFR CIGS  
DEVELOPING OVERNIGHT. KSUN AND KDIJ WILL LIKELY BARE THE BRUNT OF  
THE IMPACTS WITH LOW MVFR CIGS AND VISBY DEVELOPING AT KSUN THIS  
AFTERNOON AND OCCASIONAL PERIODS OF IFR CONDITIONS IN -SHRASN  
THROUGH THE EVENING FOLLOWED BY IMPROVING (LOW VFR) CIGS AFTER  
MIDNIGHT. KDIJ WILL SEE DETERIORATING CONDITIONS LATER THIS  
AFTERNOON WITH IFR CONDITIONS DEVELOPING BY SUNDOWN IN LIGHT TO  
MODERATE SHSN. KDIJ MAY SEE SOME IMPROVEMENT BY TUESDAY MORNING WITH  
CIGS RISING INTO THE MVFR LEVEL AS THE STORM PASSES EAST OF THE  
REGION AND THE RIDGE REBOUNDS ACROSS THE GREAT BASIN. HUSTON  

 
   
PIH WATCHES/WARNINGS/ADVISORIES
 
 
WINTER WEATHER ADVISORY UNTIL 3 AM MST TUESDAY FOR IDZ031.  
 

 
 

 
 
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