FXUS65 KBOI 271029
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
329 AM MST FRI NOV 27 2009

.SHORT TERM...TODAY THROUGH SATURDAY...SLOW MOVING UPPER TROUGH
ALONG THE WA/OREGON COASTAL RANGE HAS ALREADY SPREAD A LARGE CLOUD
SHIELD THROUGH SE OREGON AND SW IDAHO. ALONG WITH LIGHT TREASURE
VALLEY WINDS UNTIL THE FROPA IN THE MID AFTERNOON TEMPERATURES
WILL STRUGGLE TO GET OUT OF THE 30S. SO HAVE TRIMMED HIGHS A BIT.
PRECIP AMOUNTS HAVE BEEN LIGHT WITH 0.01-0.04 IN THE COLUMBIA
BASIN BUT MORE SO IN THE BLUES /MEACHAM PICKED UP 0.12 INCHES
6-9Z WITH 35F AND STILL GOOD VSBY ON WEB CAMS INDICATING RAIN.
SNOW LEVELS RANGING FROM 4500 FEET IN OREGON TO AROUND 6K FT IN
IDAHO MOUNTAINS. THE UPPER TROUGH LOOKS TO WEAKEN AND SPLIT
WITH THE MAIN ENERGY SINKING TOWARDS THE FOUR CORNERS AND THE
NORTHERN BRANCH SHIFTING EAST THROUGH THE NORTHERN ROCKIES. THIS
MAKES QPF AND SNOW LIGHT...UP TO 0.15 IN THE MOUNTAINS AND A FEW
HUNDREDTHS IN THE VALLEYS. HAVE TRIMMED BACK SNOWAMTS AS A
RESULT. SUBSIDENCE INVERSION STARTS TO REBUILD OVER THE AREA LATE
TONIGHT AND STRENGTHENS SATURDAY. SO PATCHY LATE NIGHT AND EARLY
MORNING FOG WAS LEFT IN THE FORECAST. FOG/HAZE WITH THE INVERSION
LOOKS TO LAST OR WORSEN THIS WEEKEND.

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...UPPER RIDGE AND 
ACCOMPANYING INVERSION REDEVELOPS OVER THE INTERMOUNTAIN WEST FOR 
SUNDAY AND MONDAY. MOISTURE FROM RECENT PRECIP EVENT AND LIGHT 
SURFACE WINDS WILL FAVOR FOG/STRATUS DEVELOPMENT ON SUNDAY MORNING 
IN BOTH MTN AND LOWER ELEVATION VALLEYS. WITH LITTLE CHANGE IN 
AIRMASS WOULD EXPECT THE SIMILAR CONDITIONS AGAIN MONDAY MORNING. 
HIGH TEMPS IN THE VALLEYS ARE STAGNANT FOR SUN/MON WITH SOME WARMING 
IN THE MTNS. ECMWF MODEL IS FAVORED IN THE EXTENDED PERIOD WHICH 
BRINGS A SHARP SHORTWAVE ACROSS THE FORECAST AREA ON TUESDAY. 
CURRENT FORECAST TRACK AND AMPLITUDE OF THIS FEATURE WOULD BRING 
ENOUGH COOLING/MIXING TO BREAK DOWN THE INVERSION FOR THE REMAINDER 
OF THE EXTENDED PERIOD. MOISTURE IS LIMITED SO BEST CHANCE OF PRECIP 
WOULD BE ACROSS THE WEST CENTRAL AND BOISE MTNS ON TUESDAY. A DRY NW 
FLOW SETS FOR WED/THUR.

&&

.AVIATION...WIDESPREAD IFR CONDITIONS IN SNOW DEVELOPING OVER SE 
OREGON THIS MORNING AND THE MTNS OF SW IDAHO THIS AFTERNOON. 
TREASURE AND WESTERN MAGIC VALLEY WILL REMAIN VFR WITH CEILINGS DOWN 
TO 4K FEET AGL. CEILINGS LIFT THIS EVENING OVER SE OREGON AND BY 
MIDNIGHT OVER SW IDAHO. WITH CLEARING SKIES WILL SEE LOCAL IFR 
CONDITIONS IN FOG DEVELOP IN SHELTERED VALLEYS. EXPECT FOG/STRATUS 
TO BECOME MORE WIDESPREAD SUNDAY MORNING.

&&

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

$$

WEATHER.GOV/BOISE

SHORT TERM...VM
LONG TERM....DG
AVIATION.....DG