FXUS65 KPIH 250350
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
850 PM MST THU DEC 24 2009

.UPDATE...BASED ON SATELLITE AND OBSERVED TRENDS WE HAVE INCREASED
THE AMOUNT OF STRATUS AND PATCHY DENSE FREEZING FOG ACROSS THE
SNAKE PLAIN AND EASTERN MAGIC VALLEY. FOR NOW LEFT THE PLACES LIKE
RAFT RIVER AND BURLEY OUT OF IT...BUT WILL NEED TO MONITOR THINGS
AND MAY NEED ANOTHER UPDATE BEFORE THE MID SHIFTS COMES ABOARD. WE
ALSO UPPED VALLEY TEMPS A FEW DEGREES IN THESE SAME AREA AND ALSO
SOME OF THE MORE SOUTHERN VALLEYS. OCCASIONAL LIGHT SNOW/FLURRIES
WILL CONTINUE ACROSS MORE EASTERN AREAS AS A WAVE DROPS DOWN IN
THE FLOW ACROSS THE REGION.  KEYES

&&

.PREV DISCUSSION... /ISSUED 200 PM MST THU DEC 24 2009/ 

SHORT TERM...TONIGHT THROUGH SUNDAY. LATEST SATELLITE IMAGERY 
CONTINUES TO SHOW WIDESPREAD LOW CLOUDS EXTENDING FROM SHOSHONE NE 
INTO ISLAND PARK AND SOUTH TO PRESTON. A RIDGE OF HIGH PRESSURE 
REMAINED POSITIONED ALONG THE COAST WITH SOME MID AND UPPER LEVEL 
MOISTURE ROLLING OVER THE TOP AND DIGGING SE THROUGH THE CANADIAN 
ROCKIES. THE MODELS SUGGEST THAT THE ADDITION OF THIS MOISTURE ALONG 
WITH THE TRAPPED LOW CLOUDS WILL BE ENOUGH TO PRODUCE SOME LIGHT 
FLURRIES OVERNIGHT AND THUS HAVE ADDED THIS TO THE FORECAST (NOT 
REALLY EXPECTING ANY REAL ACCUMULATION). THE FLOW ALOFT TURNS MORE 
N-NE FRIDAY WHICH IS TYPICALLY A DESICCATING FLOW FOR THE REGION AND 
WILL LIKELY CAUSE THE LOW CLOUDS TO DISSIPATE ACROSS THE AREA. 
CHANGING LOW CLOUD COVER COUPLED WITH VALLEY INVERSIONS WILL MAKE 
FOR A DIFFICULT TEMPERATURE FORECAST THROUGH THE PERIOD WITH HIGHER 
ELEVATIONS GENERALLY WARMING THROUGH THE PERIOD AND VALLEYS 
REMAINING MOSTLY COLD. HUSTON

LONG TERM...SUNDAY NIGHT THROUGH THURSDAY. UPPER RIDGE OVER THE 
NORTHERN ROCKIES EXPECTED TO CREATE A BLOCKING PATTERN FOR THE FIRST 
HALF OF THE LONG RANGE. MODELS ARE TRENDING TOWARDS SPLITTING 
PACIFIC SYSTEMS APPROACHING THE AREA...DEFLECTING THEM WELL NORTH 
AND SOUTH OF THE AREA.  BY TUESDAY NIGHT HOWEVER...FLOW TURNS MORE 
WEST-NORTHWESTERLY AND SEVERAL WEAK WAVES ARE EXPECTED TO TRACK INTO 
THE AREA. ISOLATED TO SCATTERED SNOW SHOWERS REMAIN IN THE FORECAST 
FOR MIDWEEK. TEMPERATURES WILL REMAIN GENERALLY BELOW NORMALS. HANKO 

AVIATION...LOW STRATUS AND FOG WILL CONTINUE TO BE PROBLEMATIC 
ACROSS THE SNAKE PLAIN THIS AFTERNOON THROUGH AT LEAST FRIDAY 
MORNING. EXPECT MVFR AND LOWER CONDITIONS AT ALL TAF SITES EXCEPT 
KSUN WHERE NORTHERLY WINDS WILL HOLD OFF THE LOW CLOUDS. MODELS DO 
NOT SHOW THIS MOISTURE BREAKING UP UNTIL SATURDAY AT THE EARLIEST. 

AIR STAGNATION...LITTLE IN THE FORECAST AS A BLOCKING RIDGE OF HIGH 
PRESSURE REMAINS POSITIONED ACROSS THE WRN STATES THROUGH SUNDAY. BY 
MONDAY...PAC SYSTEMS ARE EXPECTED TO BEGIN TO UNDER-CUT THE RIDGE 
AND BY AS EARLY AS TUESDAY THE SURFACE BASED INVERSION MAY BREAK 
ACROSS SE IDAHO. HUSTON

&&

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

$$