233 
fxus65 kboi 220301 
afdboi 


Area forecast discussion 
National Weather Service Boise Idaho 
901 PM MDT sun Mar 21 2010 


Discussion...isolated thunderstorms brushed extreme far northwest 
Harney and far West Baker County this evening. With sunset the 
instability has decreased but middle level lapse rates of 7 to 7.5 
c/km persist through the wee am hours. So a stray strike is 
possible near the upper trough over NE Oregon tonight but 
confidence is low so will let the forecast ride. In the warm air 
ahead of the front wind gusts were around 30 miles per hour from the SW from 
Rome to Twin Falls with the latter area seeing minimum relative humidity values 
in the teens. Winds briefly gusted up to around 45 miles per hour with the 
front in Burns. As the front crosses SW Idaho tonight wind gusts 
briefly around 30 miles per hour are expected. The deeper cold upper trough 
axis centered from off the Queen Charlottes to Oregon coastal 
waters will shift into a ksea- kbke zone about 6 am MDT and 
through SW Idaho Monday. This will bring continued showers /snow 
in the mountians above 3500 feet in the morning 5k feet in the 
afternoon/ and breezy west to northwest winds. Highs Monday are expected 
to range from 5-8f colder in Oregon to 15-20f degrees colder in 
the Magic Valley...where Twin Falls hit the middle 60s this 
afternoon. This is on track with the current package for no 
changes. 


&& 


Aviation...a cold front will be crossing SW Idaho tonight with 
clouds and showers. Most valley areas will have VFR conditions but 
the mountains will have MVFR and local IFR conditions with snow 
above about 5000 feet. On Monday...a cold upper trough moving over southeast 
Oregon and SW Idaho will produce scattered showers for some mountain 
obscuration and MVFR mountain conditions while valleys stay VFR. 
Moderate northwest surface wind Monday. 




&& 


Previous discussion... 
short term...tonight through Wednesday...no significant 
differences in models in the short term. A strong system is 
finally poised to move into the area tonight. This will bring 
showers and a cold front with a sharp wind shift overnight to the 
region. The cold front was moving over the Cascades as of middle- 
afternoon. A second wave moves through late Monday afternoon into 
Monday night...bringing snow showers down to 4000 feet. However... 
amounts will be light. On Tuesday a strong ridge begins to move in 
from the west... bringing warming temperatures and clearing skies 
through Wednesday. Temperatures will be sharply cooler tomorrow...from 5 
to 10 degrees cooler in southeast Oregon...to 10 to 15 degrees cooler in 
SW Idaho. Tuesday will see about 5 to 10 degrees of warming 
region-wide...and another 5 to 10 degrees of warming for Wednesday. 
Overnight lows will be mild Monday morning owing to cloud cover 
and winds associated with the front. However...mins will be cooler 
Tuesday morning as skies clear and winds slacken. We will see 
conditions get a few degrees warmer in most places for Wednesday 
morning. With the ridge building in...chance for precipitation 
drop off rapidly Monday night and are near zero for Tuesday and Wednesday. 


Long term...Wednesday night through Sunday...looks like two storms 
will move across the area Wednesday night through Saturday. The 
first Wednesday night/Thursday will affect mainly northern areas. 
The next on Friday looks like it will sweep across most of the area. 
Thus an unsettled last part of the week before a strong ridge builds 
in on Sunday. Temperatures will be on the cool side with each storm 
with a warming trend this coming weekend. 


&& 


Boi watches/warnings/advisories... 
Idaho...none. 
Or...none. 
&& 


$$ 


Weather.Gov/Boise 


Discussion...vm 
aviation.....Jj 
previous short term...snow pellets 
previous long term....pf/pf