260 
fxus65 kbyz 210349 
afdbyz 


Area forecast discussion...updated 
National Weather Service Billings Montana 
849 PM MST Friday Nov 20 2009 


Evening update... 


Forecast on track and have only made a few minor adjustments. 
Satellite showing a large trough currently moving across the 
Pacific northwest coast and into the northern rockies area. Deep 
southwest flow aloft ahead of this trough is bringing abundant 
middle and high level clouds across the forecast area this evening. 
As a result...have increased sky cover across the area especially 
the eastern zones. Models have slowed the progression of this 
trough just a bit with precipitation not making it much into our western 
zones until very late toward 12z Saturday. Area radars not 
showing any activity approaching as well. Have therefore trimmed 
back probability of precipitation in the northwest and western lower elevation zones. Did 
also lower pop chances just a bit as well for the Southwest 
Mountains. Winds have also decreased quite a bit in the 
Livingston area so have lowered these for the remainder of the 
night. Temperatures across portions of the central and west 
remain in the 40s this evening. Still expect mixing to continue 
throughout the night and latest guidance coming in a bit warmer as 
well. So have bumped up readings in a few locations. Update out 
shortly. Hooley 


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


While the fairly benign weather pattern continues into the 
extended the models are not in real strong agreement. On Monday 
European model (ecmwf) and GFS are very different in the track of an upper low 
through the area with the European model (ecmwf) the preferred solution. GFS tracks 
an upper trough across the area while the European model (ecmwf) dives a system 
south through Wyoming. GFS hints at some wrap around precipitation 
as the system and GFS has been trending upward with probability of precipitation so have 
kept some probability of precipitation in southeast Montana as a hedge...but generally 
prefer European model (ecmwf) solution. Will continue cool under northerly flow 
aloft the remainder of the day. Tuesday models continue to 
disagree with a another wave coming through the northwest flow 
and amplifying it on the GFS while the European model (ecmwf) has a lighter zonal 
flow. Since the European model (ecmwf) is doing a better job of cutting off the 
system over the plains which has been the trend as of late. Looks 
dry either way and do not strengthen winds as much as GFS would 
indicate. Both models bring an upper level ridge into the area for 
Wednesday and Thursday for temperatures 10 to 15 degrees above 
normal and a downsloping wind pattern. Ridge breaks down on both 
models for Friday and the weekend but again models disagree on 
tracks of system through the region. Definitely cooler as the 
transition occurs but not really sure about precipitation at this 
point. Borsum 


&& 


Aviation... 


Rain and snow showers are expected in and around klvm and in the 
high terrain by around midnight...as a cold front pushes from west 
to east across the region overnight. Mainly VFR flight conditions 
can be expected to prevail over the plains. Expect increasing 
cloudiness over the mountains and foothill region...with ceilings 
dropping to MVFR levels after Midnight. Mountain obscurations and 
lower ceilings will continue through tomorrow afternoon. Gilstad 




&& 


Preliminary point temp/pops... 


Sat sun Monday Tuesday Wednesday Thursday Friday 
----------------------------------------------------------- 
bil 034/046 024/041 026/041 025/044 026/050 031/052 031/053 
03/west 02/o 22/S 11/north 10/b 00/b 01/north 
lvm 031/041 022/037 018/037 024/041 025/048 030/051 029/047 
24/j 04/S 31/b 12/S 10/b 00/north 02/r 
hdn 028/051 024/043 024/045 023/048 023/051 023/052 024/053 
02/west 02/o 22/S 12/S 20/b 00/b 01/b 
mls 026/050 024/046 024/044 021/045 022/048 025/052 027/052 
02/west 02/o 21/b 12/S 20/b 00/b 01/b 
4bq 027/051 023/042 021/041 021/046 021/044 025/049 025/050 
02/west 22/o 22/S 12/S 21/b 00/b 01/b 
bhk 026/054 024/044 021/040 018/041 020/042 023/051 024/051 
02/west 20/b 22/S 12/S 21/b 00/b 01/b 
shr 029/047 019/043 020/040 018/047 019/047 022/050 021/049 
03/west 22/o 22/S 12/S 20/b 00/b 01/b 


&& 


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


&& 


$$ 
Weather.Gov/Billings