AREA FORECAST DISCUSSION

 
 FXUS65 KPIH 242109 CCA
 AFDPIH
 
 AREA FORECAST DISCUSSION...CORRECTED 
 NATIONAL WEATHER SERVICE POCATELLO ID
 208 PM MST TUE NOV 24 2009
 
 .SHORT TERM...TONIGHT THROUGH FRIDAY. THE UPPER RIDGE POSITIONED 
 OVER THE REGION WILL DOMINATE THE PATTERN THROUGH THURSDAY 
 REINFORCING VALLEY INVERSIONS.  DAYTIME HIGHS WILL REMAIN BELOW 
 NORMAL STRUGGLING TO BREAK THROUGH THE INVERSIONS. ALSO...LOW LEVEL 
 STRATUS CLOUDS AND FOG WILL CONTINUE TO IMPACT THE UPPER SNAKE PLAIN 
 AND HIGHLANDS THROUGH AT LEAST THURSDAY MORNING. THE NEXT PACIFIC 
 STORM SYSTEM IS EXPECTED TO MOVE INLAND FRIDAY. THERE IS SOME ROUGH 
 AGREEMENT AMONG THE MODELS AS THE UPPER WAVE MOVES INLAND FRIDAY 
 AFTERNOON. HOWEVER...THE DETAILS ARE STILL RATHER MURKY. FOR 
 NOW...WE FAVOR THE ECMWF SOLUTION WHICH BRINGS THE PRECIPITATION 
 SHIELD TO OUR WRN DOOR STEP FRIDAY AFTERNOON WITH A MODEST 
 SPLIT-LOOKING UPPER TROUGH. GENERALLY SPEAKING...UNDER SPLIT FLOW 
 REGIMES...WE TEND TO GET LESS PRECIPITATION THAN THE MODELS 
 INITIALLY INDICATE. THUS WE WILL MAINTAIN CHANCE PRECIPITATION 
 WORDING IN THE FORECAST FOR THE WRN MOUNTAINS UNTIL DETAILS COME 
 INTO FOCUS AS EVENT APPROACHES. MODEL TEMPERATURE GUIDANCE IS 
 DEPLORABLE (IT DOES NOT APPEAR TO BE HANDLING THE INVERSIONS WELL) 
 AND WE HAVE TRIED TO STAY CLOSE OR COLDER THAN THE STATISTICAL 
 GUIDANCE THROUGH THURSDAY ALLOWING CONDITIONS TO WARM FRIDAY AS THE 
 SW FLOW INTENSIFIES ACROSS THE REGION AHEAD OF THE ADVANCING TROUGH. 
 HUSTON
 
 .LONG TERM...FRIDAY NIGHT THROUGH TUESDAY. THE MODELS ARE STILL 
 STRUGGLING WITH HOW TO PUSH A TROF THROUGH THE REGION HEADING INTO 
 THE END OF THE THANKSGIVING WEEKEND. THE MAIN PROBLEM HERE IS HOW 
 THE MODELS HANDLE THE DEVELOPING SPLIT OF THE TROF. THE ECMWF IS 
 TRYING TO SPLIT THE SYSTEM AS IT MOVES INTO IDAHO WITH A NORTHERN 
 LOW CLOSING OFF BY SATURDAY OVER SASKATCHEWAN AND THE SOUTHERN 
 SYSTEM CLOSING OFF IN EASTERN OREGON AND DROPPING INTO NEVADA. THE 
 GFS SHOW SOME SPLITTING BUT NOT AS STRONG AND SHOWS THE DIGGING OF 
 THE SOUTHERN BRANCH SEVERAL HUNDRED MILES TO THE EAST IN THE PLAINS. 
 WE HAVE DECIDED TO NOT BY OFF ON ANY ONE SOLUTION AS OF YET. 
 HOWEVER...THE MODELS ARE SHOWING SIMILAR PRECIPITATION PATTERNS FOR 
 EASTERN IDAHO SO GO FIGURE. THAT WOULD MEAN A CONTINUED CHANCE OF 
 SNOW OVER THE MOUNTAINS WITH SOME HELP FROM UPSLOPE OVER WESTERN 
 PART OF THE CENTRAL MOUNTAINS AND INTO THE EASTERN/SOUTHEASTERN 
 MOUNTAINS. THERE IS ALSO A LITTLE BETTER CHANCE OF SNOW ACROSS THE 
 EASTERN FRINGE OF THE SNAKE PLAIN. AS WE HEAD INTO SUNDAY...BOTH THE 
 GFS AND ECMWF SHOW A LITTLE MORE RIDGING SO SOME DECREASE IN POPS IS 
 WARRANTED WITH LOW CHANCE/SLIGHT CHANCE FOR THE MOUNTAINS. 
 OVERALL...SNOW AMOUNTS FOR THE WEEKEND ITSELF SHOULD NOT BE THAT 
 HIGH...BUT COULD PROVIDE TO BE A NUISANCE FOR THOSE TRAVELING OVER 
 THE PASSES.  IT SHOULD EVEN BE DRIER ON MONDAY. THE MODELS ARE 
 CONTINUING TO BRING DRIER AIR INTO THE REGION AND HAVE TRENDED THE 
 FORECAST IN THAT DIRECTION BUT STILL NOT READY TO DRY US OUT 
 COMPLETELY. THEN...BOTH MODELS TRY TO SWING A SYSTEM TOWARD EASTERN 
 IDAHO BY MONDAY NIGHT AND TUESDAY. THE GRIDS DO SHOW A SLIGHT 
 INCREASE IN MOUNTAIN SNOW ACROSS THE NORTH TO ACCOUNT FOR THIS 
 POSSIBILITY. FOR THE ENTIRE EXTENDED PERIOD...IT WILL BE COLD ONCE 
 AGAIN WITH HIGHS IN THE 20S AND 30S. THERE SHOULD BE SOME WARMING AT 
 MID AND UPPER SLOPE WITH THE RIDGE...AND LITTLE WARMING IN THE 
 VALLEYS DUE TO THE INVERSION.  KEYES 
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 .AVIATION...MID AND HIGH CLOUDS ARE CURRENTLY SPREADING INTO EASTERN 
 IDAHO FROM THE NORTH AS A SYSTEM DROPS DOWN EAST OF THE DIVIDE THIS 
 AFTERNOON. THIS CLOUD COVER SHOULD BE THINNING OUT OVERNIGHT WITH 
 SOME RESIDUAL HIGH CLOUDINESS. THE QUESTION OF THE DAY...AND 
 NIGHT...IS STRATUS AND FOG GOING TO DEVELOP AGAIN IN PARTS OF THE 
 SNAKE PLAIN. THIS SHOULD BE A PROBLEM FROM ABOUT KPIH NORTHWARD. 
 WHILE NOTHING DEVELOPED AS FAR SOUTH AS KPIH LAST NIGHT...THE MODEL 
 CROSS SECTIONS SHOW SOME MOISTURE TRYING TO POOL AROUND THE AREA 
 AGAIN TONIGHT. WHILE IT IS NOT CLEAR CUT THAT STRATUS OR FOG WILL 
 DEVELOP...WE HAVE DECIDED TO LEAVE IT IN FOR KIDA/KPIH OVERNIGHT AND 
 WEDNESDAY MORNING PER THE MIDNIGHT FORECAST.  KIDA STANDS A MUCH 
 BETTER CHANCE OF SEEING A REPEAT OF STRATUS AND FOG AS CONDITIONS 
 ARE NOT CHANGING THAT MUCH. THE CURRENT FORECAST SHOWS LOW STRATUS 
 REDEVELOPING BEFORE MIDNIGHT WITH FOG FORMING CLOSER TO 3AM...THEN 
 IMPROVING CONDITIONS BY MID MORNING TOMORROW. KEYES
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 .PIH WATCHES/WARNINGS/ADVISORIES...NONE.
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