295 
fxus65 kboi 211547 
afdboi 


Area forecast discussion 
National Weather Service Boise Idaho 
947 am MDT sun Mar 21 2010 


Discussion...thick high clouds continue to move east across the 
area in advance of our next Pacific storm system. Morning sounding 
at kboi indicates that highs in the Treasure valley could be near 
70 if not for the clouds. It all depends on how many breaks occur 
this afternoon. Current expectations match those of the previous 
forecast...meaning highs in the lower 60s in the Treasure 
valley... and no changes will be made at this time. 


&& 


Aviation...clouds increasing and lowering from the west ahead of 
the next Pacific storm. The cold front should move across Burns near 
00z then move east over all the area by 09z tonight. Expect mountain 
obscurations along and behind the front spreading east. Valleys in 
the northern portion of the area will become MVFR/IFR in clouds and 
precipitation tonight while southern valleys should remain VFR with only 
isolated MVFR clouds and precipitation. Southeast surface winds increasing 10 to 
20 kts today turning northwest 10-20 kts behind the front tonight. 


&& 


Previous discussion... 
short term...Pacific cold front approaching today...no significant 
forecast changes on time of arrival...around 02z this evening at bke 
and bno...08z at boi...12z Monday at twf/jer. Front will bring 
widespread light precipitation to northern half of County Warning Area...less in southern half. No 
significant change in forecast maximum temperatures for today...warmest area 
will be western Magic Valley...areas further west and north will be 
cloudier and not quite as warm as yesterday...especially in Oregon 
zones. Based on 850-700 mb thickness drop behind the front min 
temperatures tonight would be 3f colder than MOS...similar to what happened 
last time a cold front moved through. Rain may mix with snow down 
to 2800 feet mean sea level around 12z Monday in the Treasure valley...not low 
enough to accumulate snow there. Using quantitative precipitation forecast values several inches of 
snow will fall in the higher parts of the west central Idaho 
mountains and Boise Mountains...but precipitation will initially fall as rain 
and the larger snow accumulations will be above 6k feet mean sea level...so now 
Winter Weather Advisory for snow will be issued. Precipitation will decrease from 
west to east early Monday with partial clearing...except rain and 
snow showers will continue in the eastern parts of the west central 
Idaho mountains and Boise Mountains. Post-frontal west or northwest 
winds will increase to 15 to 25 miles per hour in the snake basin Monday 
afternoon...not enough for a Wind Advisory. Maximum temperatures Monday 8 to 
12f lower than today in all areas. 


Long term...Monday night through Sunday...drying in northerly flow 
behind the trough on Monday night and Tuesday. Then warmer with 
ridge moving overhead on Wednesday. Then a weak trough knocks down 
the ridge a bit on Thursday for a chance of mountain showers and 
temperatures back down toward normal. A bit stronger trough comes through 
on Friday for a better chance of showers. Then on Saturday the ridge 
rebuilds in strongly...with warmer and drier conditions...as a large 
trough develops off the Pacific coast. Some models indicate that 
first pieces of this trough might be moving into the forecast area 
on Sunday for a major pattern change...but will wait for a few more 
runs of consistency before really jumping on that scenario in the 
forecast grids. For now...staying near climatology. 


&& 


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


$$ 


Weather.Gov/Boise 


Discussion...snow pellets 
aviation.....Pf 
previous short term...lc 
previous long term....tb/dd