FXUS65 KBOI 021631
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
930 AM MST WED DEC 2 2009

.DISCUSSION...UPPER RIDGE JUST OFF THE WEST COAST WITH COLD DRY 
NORTHERLY FLOW OVER IDAHO. UPPER RIDGE WILL COLLAPSE AND MOVE EAST 
AS STORM MOVES ACROSS THE NORTHERN GULF OF ALASKA. THIS STORM WILL 
HEAD INTO THE PACIFIC NORTHWEST LATE FRIDAY TO BRING ANOTHER SHOT OF 
COLD AIR AND PRECIP TO MUCH OF THE AREA. DUE TO THE STORM COMING IN 
FROM THE NORTH IT WILL BE COLD AND NOT CARRY TOO MUCH MOISTURE. THUS 
SNOW IN THE FORECAST FOR ALL AREAS BUT AMOUNTS WILL BE VERY LIGHT. 
NEXT MAJOR CHANGE COMES LATER NEXT WEEK WHEN WESTERLIES ARE EXPECTED 
TO BREAK THROUGH UNDER THE GULF OF ALASKA HIGH. EXACT PLACEMENT OF 
PRECIP FROM NEXT WEEKS EVENT STILL UNCERTAIN BUT A CHANGE TO WETTER 
ACROSS THE AREA LOOKS PROMISING.

&&

.AVIATION...MOST TAF SITES THIS MORNING WERE REPORTING VFR UNDER 
MOSTLY CLEAR SKIES. KBNO WAS THE EXCEPTION WITH MVFR STRATUS. 
SATELLITE SHOWED ISOLATED MOUNTAIN VALLEY FOG...AND AREAS OF STRATUS 
MAINLY IN HARNEY AND MALHEUR COUNTIES IN OREGON AND EASTERN OWYHEE 
AND SOUTHERN TWIN FALLS COUNTIES IN IDAHO. FOG AND STRATUS WILL 
DISSIPATE BY 19Z...BUT EXPECT ISOLATED FOG TO FORM AGAIN AFTER 06Z.  
SURFACE WINDS WILL BE LIGHT THIS MORNING...THEN NORTHWEST 5-15 KTS 
THIS AFTERNOON. WINDS ALOFT WILL BE NORTH 25-40 KTS AT 12K FT MSL. 

&&

.PREV DISCUSSION...NEW AIR MASS WHICH CAME IN FROM THE NORTH 
WEDNESDAY AFTERNOON IS COLDER AND DRIER THAN THE AIR MASS IT 
REPLACED.  SAPIX...HOWEVER...STILL SHOW AREAS OF STRATOCUMULUS IN 
OUR SRN ZONES EARLY THIS MORNING ALTHOUGH TENDING TO SHIFT TOWARD 
THE SOUTHWEST.  UNDER THESE CLOUDS TEMPS HAVE BEEN RELATIVELY HIGHER 
THAN IN THE CLEAR AREAS.  LATER TODAY THE CLOUDS SHOULD MOVE OUT AND 
THE COMING NIGHT WILL BE QUITE COLD DUE TO OUTWARD RADIATION UNDER 
CLEAR SKIES...LIGHTER WINDS...AND LOW HUMIDITY.  TOO DRY FOR FOG 
THURSDAY MORNING EXCEPT POSSIBLY NEAR MYL...ONO...AND ALONG THE 
SNAKE RIVER.  LITTLE CHANGE IN MAX TEMPS THURSDAY.

LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...SHORTWAVE RIDGE OVER 
THE AREA ON FRIDAY WILL BRING TEMPS BACK TO NEAR NORMAL. COLD FRONT 
PUSHES THROUGH THE AREA FRIDAY NIGHT AS UPPER LOW DROPS SOUTH OUT OF 
BC. LOW SETTLES OVER ID ON SATURDAY WITH NOTICEABLY COLD TEMPS 
/AROUND 10 DEGREES BELOW NORMAL/ AND A CHANCE OF SNOW SHOWERS ACROSS 
THE FORECAST AREA. WITH CONTINENTAL SOURCE PW/S ARE LOW SO EXPECT 
PRECIP AMOUNTS TO BE LIGHT. MODELS SHOWING LOW CENTER BECOMING 
ELONGATED E-W WITH AXIS STRETCHING ACROSS SOUTHERN ID THROUGH 
MONDAY. THIS WILL LOCK IN COLD AIR WITH VALLEYS STRUGGLING TO MAKE 
IT ABOVE FREEZING. BETTER AGREEMENT IN MODELS ON TIMING INJECTION OF 
MILD AND MOIST PACIFIC AIRMASS FOR NEXT TUE/WED.   

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...PRF
AVIATION...JT