054 
fxus65 kboi 080333 
afdboi 


Area forecast discussion 
National Weather Service Boise Idaho 
930 PM MDT Tuesday Oct 7 2008 


Discussion...a dry cold front has crossed the area but cold air has 
yet to reach Idaho with front lying just south of the Snake River 
Valley in an east west orientation. However...colder air is now 
filtering into eastern Oregon where temperatures have already 
dropped in the middle 40s at both Burns and Baker City. Aligned west 
winds aloft behind the front is generating a well mixed atmosphere 
and breezy conditions. Winds finally drop off enough around sunrise 
to allow temperatures to drop to the 40 to 45 degree range in the 
Snake Valley and 30s elsewhere. Wednesday will be a sunny day with 
very dry air advecting east across the area...although it will be 
much cooler than today by almost ten degrees. Trends well handled by 
current forecast. 


&& 


Aviation...VFR conditions will prevail tonight through Wednesday. 
Surface winds will be light to moderate northwest tonight through 
Wednesday morning then moderate northwest Wednesday afternoon. Winds 
aloft will be moderate westerly. 


&& 


Previous discussion...tonight through Thursday...cold front has passed 
through Baker and Burns and will swing through the remainder of the 
forecast area this evening. Not much in the way of moisture with the 
front...with the only indication of light showers in the west 
central mountains. West to northwest winds of 15 to 25 with higher 
gusts will continue behind the front and will gradually diminish 
after sunset. A cool but dry westerly flow follows on Wednesday with 
lighter winds with most areas seeing maximum temperatures in the 50s to lower 
60s. Skies will remain generally clear and with a cool dry airmass 
in place...forecast temperatures in the upper 20s and lower 30s Thursday 
morning will call for a freeze watch in the Treasure and western 
Magic Valleys. An unseasonably cold upper low will start to take 
shape over the region on Thursday...with brisk northwest winds... 
snow levels falling to near 4500 feet...and temperatures 10 to 15 
degrees below normal. 


Long term...Thursday night through Tuesday...improved model 
consistency lends to greater confidence in cooler temperatures and 
widespread precipitation this weekend. A potent upper level trough 
will dig south along the British Columbia coast Wednesday and 
Thursday. Open wave is prognosticated to close off over the intermountain 
west early Friday...maintaining its position through Saturday. Main 
concerns include unseasonably cool temperatures and widespread 
precipitation...with snow levels dropping to valley floors Friday 
and Saturday night. Boise Mountains favored to receive the most 
overall precipitation due to persistent wrap-around moisture...with 
storm total snow amounts averaging 2 to 6 inches. Showers will 
linger through Sunday...mainly along eastern edge of the forecast 
area. Warmer and drier conditions on Monday/Tuesday as storm system 
exits and a shortwave ridge moves into the intermountain west. 


&& 


Boi watches/warnings/advisories... 
Idaho...freeze watch from late Wednesday night through Thursday morning 
for idz012-idz014-idz016. 
Or...freeze watch from late Wednesday night through Thursday morning 
for orz064. 
&& 


$$ 


Weather.Gov/Boise 


Discussion...gs 
previous discussion...bw 
long term....Mt/dd 
aviation.....Jt