997 
fxus65 kbyz 210259 
afdbyz 


Area forecast discussion...updated 
National Weather Service Billings Montana 
859 PM MDT Sat Mar 20 2010 


Evening update... 


Quiet night in store across the forecast area with the exception 
of winds in the Livingston and adjacent foothills areas. High 
pressure ridging continues to build across the northern rockies 
tonight. Satellite showing quite a bit of middle and high level 
clouds rotating over the ridge out of the Pacific northwest and 
moving southeast across our state. Have opted to remove mostly 
clear skies in the forecast and add partly cloudy wording across 
the entire forecast area. Winds have just started picking up some 
in the Livingston area with gusts near 40 miles per hour. Expect winds to 
increase throughout the night as warm air advection aloft moves 
overhead and pressure gradients tighten across the upper 
Yellowstone and Stillwater valleys. Will continue with the Wind 
Advisory for these locations through early afternoon Sunday. 
Given partly cloudy skies all areas with windy conditions central 
and west...overnight lows will be much milder than last night. 
Minor update to zones already sent. Hooley 




Long term...valid for Tuesday...Wed...Thu...Fri...Sat... 


Generally good agreement continues among the 12z model runs. The 
extended period begins Tuesday morning with an upper-level trough 
over the region. The bulk of the energy associated with this 
feature is depicted south of the County Warning Area. Kept probability of precipitation over much of the 
County Warning Area for Tuesday given the remnant vorticity/forcing for ascent 
and lingering middle-level moisture. An upper-level ridge will begin 
to build over the region for Wednesday. The surface pressure 
gradient is favorable for downslope flow. 850-mb temperatures approach 
10 c over the western zones. Increased temperature forecasts in 
response. Dry conditions will prevail through Thursday morning. 
Confined slight chance probability of precipitation to local mountain ranges as a 
shortwave trough approaches from the west. Spread probability of precipitation eastward 
through early Saturday as a secondary wave moves overhead. An 
upper-level ridge begins to build over the region on Saturday. 
Removed probability of precipitation in response. For 12z guidance...the mex and mosguide 
products have performed well for maximum temperatures. Likewise...the raw 
GFS has performed well for min temperatures. Blended inherited forecasts 
with these products with minor adjustments as needed. Schuknecht 




&& 


Aviation... 


VFR conditions will prevail across the forecast area through 
Sunday. The primary aviation concern will be very strong winds 
along the beartooth foothills west into the Livingston area. The 
strongest winds will develop within the next couple of hours and 
last through middle-day Sunday. Expect sustained winds of 30-40 kts 
with gusts around 50 kts during this time. Winds are expected to 
weaken slightly Sunday afternoon. Stc/hooley 




&& 


Preliminary point temp/pops... 


Sun Monday Tuesday Wednesday Thursday Friday Sat 
----------------------------------------------------------- 
bil 036/067 040/053 031/047 030/055 033/060 035/056 031/055 
00/north 05/west 53/j 10/b 01/b 22/west 21/b 
lvm 035/062 036/050 028/043 023/053 029/055 028/052 028/050 
00/north 26/west 65/j 11/b 11/b 23/west 21/b 
hdn 026/066 034/055 031/048 028/058 031/062 032/059 030/059 
00/b 05/west 43/j 10/b 01/b 22/west 21/b 
mls 027/063 034/054 030/045 028/055 031/057 031/052 029/050 
00/b 13/west 32/j 10/b 11/b 22/west 21/b 
4bq 025/063 032/056 030/046 027/057 030/059 032/054 030/055 
00/u 04/west 42/j 10/b 01/b 22/west 21/b 
bhk 023/058 030/052 027/040 027/052 028/053 028/045 026/047 
00/u 03/west 32/j 10/b 01/b 22/west 21/b 
shr 022/064 032/056 030/044 023/053 025/060 029/054 027/053 
00/b 05/west 54/j 11/b 01/b 22/west 21/b 


&& 


Byz watches/warnings/advisories... 
Montana...Wind Advisory in effect until 3 PM MDT Sunday for zones 
65-66. 
Wyoming...none. 


&& 


$$ 
Weather.Gov/Billings