749 
fxus65 kbyz 202111 
afdbyz 


Area forecast discussion 
National Weather Service Billings Montana 
311 PM MDT Sat Mar 20 2010 


Short term...valid for sun and Monday... 


Main issue for tonight is wind. Lee side troffing should intensify 
tonight as flow aloft backs/increases with energy moving into 
western Canada. Warming middle level temperatures...to near 0c at 700mb... 
will add to the stability. With this in mind and fact that models 
are underdoing pressures in Yellowstone Park...have opted to issue 
a Wind Advisory for the usual spots Livingston and Nye. Prime time 
for strongest winds should be from roughly 04-18z. Winds will 
remain gusty but should begin to diminish thereafter with mixing. 


Otherwise a period of dry weather is a certainty tonight through 
Sunday due to strong ridging aloft. Temperatures Sunday will climb 
another notch. 700mb temperatures warming to near 00c will allow for 
highs well into the 60s and perhaps near 70f in spots. Overnight 
lows will moderate each of the next two nights after a chilly one 
this morning. 


Next system to affect US will move into south central Montana by 
late Sunday night. Models have trended faster with this wave and 
associated cold front...as cold advection looks to begin as early 
as 12z Monday. Abundant instability along with shortwave dynamics 
should bring a period of healthy snowfall for our mountains from 
early Monday through Monday night...with focus of heavier snow 
shifting from southwest slopes early on to the northwest or north 
by Monday night. As energy drives toward the central rockies and 
cooler air advects from the north...we could be looking at another 
foothills snow event by Monday night into Tuesday. Moisture 
availability and duration of event will depend largely on track of 
upper level energy...which is still uncertain. Nonetheless have 
raised probability of precipitation and snow amounts in these areas Monday and Monday 
night...and will highlight potential snow accumulation in our 
hazardous weather outlook. Otherwise scattered rain/snow showers 
should be in store for our plains...again per the instability... 
but the most significant precipitation will be orographic. 


After a very mild Sunday Monday will trend cooler with highs in 
the upper 40s to middle 50s or so. Should be breezy as well on Monday 
with steady cold advection. 


Jkl 


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 by early Sunday morning. Expect 
sustained winds around 30-40 kts with gusts around 50 kts during 
this time. Winds are expected to weaken slightly by Sunday 
afternoon. Schuknecht 




&& 


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