920 
fxus65 kggw 182109 
afdggw 


Area forecast discussion 
National Weather Service Glasgow Montana 
309 PM MDT Friday Jul 18 2008 


Short term...for northeast Montana...tonight through Sunday... 
airmass unstable in increasing low level moisture in southeast flow below 
10k feet mal. Not a large amount of moisture..but this will 
continue through the night on forward side of slow moving surface low 
center in central Montana. Upper level support provided by shortwave 
activity in west-southwest flow aloft associated with slow moving upper low 
over SW ab. Surface front is weak 


Isolated convection so far is just slowly ramping up in coverage 
and intensity...slowed by too early of a start...only a couple in 
our area severe as of 2 PM. Expect this trend to continue though as 
models show increasingly unstable airmass...with forecast sounding lifted 
indexes reaching to -10 and convective available potential energy to 3000 j/kg late tonight. There 
is lower level directional shear...but now that much speed shear low. 
Much better higher level speed shear with 80 knots jet. Models 
indicate most favorable moisture and shortwave activity to be in 
our southeast. Dew points likely rising to the lower 60s southeast. This will 
create a favorable dew point gradient across our County Warning Area this evening. 


The surface low does not exit our east until noon Sat...this will 
keep scattered thunderstorms in our area...along with the upper trough 
passage. Minor change in the airmass temperatures as drier air starts 
moving in from the west in the afternoon evening. By Sat evening...skies 
become clear. 


Upper high over Colorado by sun expanding and riding north. This will bring 
sunny and warmer weather sun. Models show weak 
disturbances...channels vorticity though with little impact. 
Simonsen 


Long term...Sunday night through Friday... 
the upper level pattern will transition to one more typical of 
middle-Summer as an upper ridge steadily builds over the central United 
States through next week. Therefore...the extended period should 
trend toward drier conditions and warmer than normal temperatures. 
The 00z suite of models agree fairly well on the longwave 
features...with some differences on placement and handling of fine 
scale features. European model (ecmwf) is initially less amplified...which is 
similar to the GFS ensembles...which depart from the more 
amplified operational GFS and Canadian. The feature that brings 
the best chance for thunderstorms will be a closed low initially 
off the California coast Monday night. This closed circulation 
becomes an open wave and lifts northeast on the back side of the 
ridge. Models struggle with how quickly or slowly to bring this 
wave toward northeast Montana. Currently Tuesday night/Wednesday 
seems to be the best timing...although confidence is low. Trended 
higher with temperatures toward the end of the period as 
confidence is fairly high. Ajz 


&& 


Aviation... 
a strong upper level system will bring scattered thunderstorms to 
the region today and tonight. VFR conditions will prevail 
the majority of the time with MVFR conditions or lower along with 
large hail and strong wind gusts possible in any thunderstorms. 
The prevailing wind will be out of the southeast around 10 to 15kt 
with stronger gusts of variable direction in and around 
thunderstorms. Ajz 


&& 


Glasgow watches/warnings/advisories...none. 


&& 


$$ 


Weather.Gov/Glasgow