802 
fxus65 kbyz 211537 
afdbyz 


Area forecast discussion...updated 
National Weather Service Billings Montana 
837 am MST Sat Nov 21 2009 


Short term...valid for today and sun... 


Cold front moving across the region this morning with 
precipitation limited to the mountains as downslope is having a 
big impact on plains. Bigger story is winds across the region as 
they are a mix of momentum mix down...pressure rises and 
gradients...and evaportive cooling from dying showers. Have 
updated forecasts to indicate stronger winds and specifically a 
tendency for winds to be gusty in nature. Also...decreased 
precipitation chances across most of the plains to sprinkles. 
Temperatures a different challenge as probably will be cooling in 
the west while still warming a bit in the east for a couple of hours. 
Updates already sent. Winds will decrease this evening and it 
should be a much cooler night. Borsum 




Long term...valid for Monday...Tue...Wed...Thu...Fri... 


A progressive pattern develops over the forecast area for the 
extended. 3 systems will impact the area next week...but 
ridging on Thanksgiving brings warm...dry and breezy conditions to 
the area. The first system is over the area Monday...shifting 
southeast Monday night. Increased probability of precipitation over eastern areas Monday 
as well as keeping some probability of precipitation for Western Mountain and foothills 
locations. Temperatures don't look terribly cold with this system 
in the lower 40s...and could be a tad cooler in some locations 
where clouds and precipitation occur. An Alberta clipper system 
quickly moves through eastern areas on Tuesday afternoon...though 
not before temperatures climb into the low to middle 40s. If timing 
of the clipper is faster will need to cool eastern areas 5 to 10 
degrees. Ridging builds into the area Wednesday and Thursday with 
downslope wind gradient in place pushing temperatures back into 
the 50s. The final system arrives Friday or Saturday depending on 
model preference. The European model (ecmwf) digs the late week system further to 
the south and brings cooler air into the area Friday 
afternoon...while the GFS is less deep with the system keeping the 
energy over Montana and Wyoming and brings colder air in for 
Saturday. 00z ensemble data supportive of the operational GFS 
keeping trough further north...and trended forecast toward the GFS 
for the later periods...including increasing probability of precipitation and lowering 
temperatures just a tad. Chambers 


&& 


Aviation... 


Cold front will continue to move across the area this morning 
bringing gusty winds up to 40 knots. Gusty winds up to 30 knots 
will continue behind the front through early evening. MVFR 
conditions and mountain obscurations will be possible through the 
day across the western routes...including the klvm area ... 
scattered snow showers will continue. Across the other 
areas...sprinkles will be possible with VFR conditions 
prevailing. Solum 


&& 


Preliminary point temp/pops... 


Today sun Monday Tuesday Wednesday Thursday Friday 
------------------------------------------------------- 
bil 048 023/040 028/042 024/046 030/051 036/055 035/051 
1/north 02/west 21/b 11/b 00/b 00/u 02/west 
lvm 041 020/036 020/035 018/043 025/050 029/054 031/046 
4/west 04/j 32/j 12/west 10/b 00/b 03/west 
hdn 051 024/043 024/044 019/047 025/052 031/057 030/053 
1/M 02/west 22/west 12/west 00/b 00/u 02/west 
mls 053 022/045 024/043 020/047 023/046 030/056 031/051 
1/north 02/west 22/west 22/west 10/b 00/u 01/u 
4bq 051 023/042 021/042 019/045 022/046 028/056 029/051 
1/north 22/west 22/j 12/west 00/b 00/u 01/u 
bhk 053 021/045 021/040 019/043 020/040 024/054 027/051 
1/north 11/b 22/j 22/west 10/b 00/u 01/u 
shr 047 020/043 022/039 014/046 024/050 028/056 028/051 
2/west 22/west 22/j 11/b 00/b 00/u 01/b 


&& 


Byz watches/warnings/advisories... 
Montana...none. 
Wyoming...none. 


&& 


$$ 
Weather.Gov/Billings