FXUS65 KPIH 260901
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
201 AM MST SAT DEC 26 2009

.SHORT TERM...TODAY THROUGH MON NIGHT. HIGH PRESSURE GIVING WAY
TO A WEAK TROUGH ROTATING IN FROM THE EAST...BUT AT THIS POINT IT
HAS NOT DONE ANYTHING TO BREAK UP THE WIDESPREAD STRATUS AND AREAS
OF FOG THAT HAVE PERSISTED IN THE EASTERN MAGIC VALLEY AND SNAKE
RIVER PLAIN FOR SEVERAL DAYS NOW. HAVE INCREASE FOG COVERAGE AS
WEB CAMERAS INDICATE FOG...ESPECIALLY SOUTH OF THE SNAKE RIVER.
EXPECT SOME THINNING...BUT THE STRATUS DID NOT BREAK IN MANY PARTS
OF THE HEAVILY POPULATED SNAKE RIVER PLAIN ON CHRISTMAS DAY. THE
PASSING OF THE TROUGH MAY HELP THIS...BUT DOUBTFUL AT THIS POINT.
FOR TONIGHT...HIGH PRESSURE STRENGTHENS AND THUS DO NOT BELIEVE
ANYTHING WILL BE ACTING TO ELIMINATE THE FOG AND STRATUS FOR SAT
NIGHT. ON SUN...A WEAK TROUGH APPROACHES WESTERN IDAHO FROM THE
WEST...BUT ITS EFFECT ON CENTRAL AND EASTERN IDAHO LOOKS AGAIN TO
BE NEGLIGIBLE. HOWEVER...IT DOES BEAR MONITORING AND COULD KEEP AT
LEAST THE EASTERN MAGIC VALLEY CLEARER. MEANWHILE...CENTRAL IDAHO
AND THE MOUNTAINS ARE GETTING STRONG TEMPERATURE SWINGS WITH BELOW
ZERO TEMPERATURES FOR LOWS IN THE NORTHWESTERLY TO NORTHERLY FLOW.
THE CLEAR SKIES MEANS THAT LOCATIONS SUCH AS SUN
VALLEY...DRIGGS...AND ISLAND PARK ARE WARMER THAN THE CLOUDED-IN
SNAKE RIVER PLAIN. WITH ALL THE HIGH PRESSURE...WIND IS NOT
AMOUNTING TO MUCH. SOMETHING OF A CHANGE DEVELOPS ON MON AFTERNOON
AS A TROUGH APPROACHES FROM THE WEST. SHOULD AT LEAST BRING SOME
CLOUDS AND PERHAPS ENOUGH WIND TO BREAK UP THE BOUNDARY LAYER
STRATUS AND FOG. ECMWF WAS STRONGER WITH THIS FEATURE AND THUS
GIVES A LITTLE MORE HOPE TO END THE MONOTONY OF STRATUS AND FOG.
HOWEVER VERY LITTLE PRECIPITATION EXPECTED WITH THIS FEATURE AND
LOW POPS ONLY DEVELOP FROM LATE SUN NIGHT THROUGH MON NIGHT.
MESSICK 

&&

.LONG TERM...TUESDAY THROUGH SATURDAY.
UPPER RIDGE BREAKS DOWN BY TUESDAY AND THIS WILL ALLOW MORE PACIFIC 
MOISTURE INTO SOUTHEAST IDAHO.  DETAILS AND HOW MUCH MOISTURE DIFFER 
BETWEEN EUROPEAN AND GFS BUT A SERIES OF WAVES WILL MOVE THROUGH 
BEGINNING WEDNESDAY AND CONTINUING INTO THE WEEKEND.  ADDED 
PRECIPITATION TUESDAY NIGHT AND HAVE A CHANCE OR SLIGHT CHANCE 
THROUGH SATURDAY ALL LOCATIONS.  EUROPEAN IS COLDER SOLUTION BUT 
BOTH THAT AND GFS KEEP TEMPERATURES SLIGHTLY BELOW NORMAL AT THE 
BEGINNING OF THE LONG TERM TO AT OR SLIGHTLY ABOVE BY NEXT WEEKEND.  
WENT CLOSER TO THE COLDER EUROPEAN.
GK

&&

.AVIATION...STRATUS AND FOG REMAINS A HUGE PROBLEM AT THE SNAKE 
PLAIN SITES FROM BURLEY TO IDAHO FALLS THIS MORNING.  IFR PERSISTS 
AT BYI AND IDA WITH MVFR AT PIH.  BURLEY HAS DROPPED BELOW A MILE 
EARLY THIS MORNING.  SO FAR DOWNSLOPE FLOW HASNT ERODED IT MUCH BUT 
IT HAS PUSHED WEST STEADILY ALL DAY AND REXBURG SCATTERED OUT AT 
LEAST BRIEFLY AT 2 AM.  FOR NOW WILL LIFT THE STRATUS BRIEFLY AT BYI 
AND PIH IN THE AFTERNOON AND BRING BACK IN OVERNIGHT.
GK

&&

AIR STAGNATION...CLOUD COVER IS PREVENTING SINGLE DIGIT
TEMPERATURES IN THE POPULATED AREAS ALONG THE SNAKE RIVER. THUS
INVERSIONS ARE NOT AS STRONG AS THEY WOULD WITH A CLEAR NIGHT.
STRATUS APPEARS TO CONTINUE INTO SUN NIGHT. INVERSIONS LIFTING OUT
TO AROUND 8700 FT ELEVATION. DO NOT SEE MUCH ABILITY TO SCOUR OUT
POLLUTION AND WOULD EXPECT THE STAGNANT AIR TO WORSEN FOR NEXT
COUPLE OF NIGHTS.  MESSICK

&&

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

$$