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fxus65 ktfx 220319 
afdtfx 


Area forecast discussion 
National Weather Service Great Falls Montana 
919 PM MDT Thursday Aug 21 2008 


Update... 
upper level trough axis movies across the region tonight with 
upper low center tracking southeast across southern ab/sk. Secondary frontal 
feature moved across the forecast area this evening with strong 
gradient winds behind the front bringing gusty west to northwest 
winds to the area...especially SW and central zones closest to the 
boundary. Winds should gradually diminish as the gradient weakens 
and surface high builds in from the west...however cold advection 
in middle levels will keep boundary layer well mixed enough to 
support breezy winds through the overnight hours. Main band of 
precipitation associated with the shortwave moving through the 
trough axis and strong upper level jet support is weakening/moving 
east of the forecast area with just some lingering isolated 
showers over central Montana behind this feature. Most of the forecast 
area should see some drying and partial clearing after 06z. 
Exception will be areas near the Alberta border where wrap-around 
moisture will work south...brining another round of showers to 
areas from Cut Bank to Havre later tonight. Have made some 
modifications to probability of precipitation...weather...sky and wind grids based on 
latest trends. Hoenisch 


&& 


Aviation... 
updated 2345z. Bulk of broad upper level trough crossing through 
west-central Montana at the present time. Accompanying surface cold 
front is currently located from Big Sky to Glendive and moving 
slowly southeastward. Instability and strong 100+ knots jet stream with the 
main trough is also generating wide area of mostly light rain with a 
few short-lived embedded thunderstorms along and west of line from 
khvr to khln to kmso. Conditions should remain generally VFR 
tonight...although patchy MVFR is possible near some of the precipitation. 
Strong jet stream will push the trough axis across Montana tonight with 
rain and cloud cover decreasing from the west beginning about 03z. 
Residual moisture moving south from Alberta behind the trough axis 
will keep ceilings at fl050-080...with a slight chance of an isolated 
rainshower...across north central Montana on Friday morning. As trough 
moves further downstream...skies in will become clear to scattered at all 
local airfields on Friday afternoon. Waranauskas 


&& 


Previous discussion... 
/issued 545 PM MDT Thursday Aug 21 2008/ 


Tonight through Saturday...a cool and moist Pacific storm system 
will continue to affect the forecast area through Friday morning. 
Anticipate precipitation to be most concentrated along the 
Continental Divide and across the Central Mountain ranges. Surface 
winds from the west and southwest will remain strong along The East 
Slope of The Rockies and adjacent north Central Plains through 
Friday morning...with gusts to 40 miles per hour at times. Precipitation 
chances will diminish from west to east throughout the overnight 
tonight...with clearing taking place during the morning and early 
afternoon on Friday. Temperatures will remain below the seasonal 
average during Friday as the upper level low pressure trough moves 
across central Montana. By Saturday morning...temperatures will 
drop well below the seasonal average throughout the region...with 
some valley locations in southwest Montana dropping below freezing. 
High pressure will the dominant feature from Friday afternoon through 
the end of the short term forecast period...with dry 
conditions...warming temperatures...and mostly clear skies 
present. Zumpfe 


Saturday night through Tuesday night...the biggest changes to the 
previous forecast were to slightly warm the lows on Sunday night 
and the maxes on Monday. Also dried out the probability of precipitation on Monday. The 
upper ridge remains in place through Monday with very warm 
temperatures. A weak weather system moving across the area will 
trigger some thunderstorms into the early evening hours on Monday. 
The upper ridge moves eastward on Tuesday and Wednesday as an 
upper trough develops over the West Coast and cooler air filters 
in across the area. This cooler air will bring a seasonal chance 
of precipitation with low probability of precipitation across the area Tuesday and 
Wednesday. Db 


Wednesday and Thursday...long range models indicate an upper 
level low pressure system moving into the Pacific northwest. 
During this period used climatology for precipitation due to 
timing of disturbances flowing through the northwest flow aloft 
and the position of the jet stream. Temperatures are expected to 
be near normal for much of west and central Montana. Saucier 


&& 


Preliminary point temps/pops... 
gtf 48 75 43 84 / 40 0 0 0 
ctb 45 69 41 81 / 30 10 0 0 
hln 51 77 47 87 / 40 10 0 0 
bzn 43 75 40 87 / 50 0 0 0 
wey 36 72 38 81 / 30 0 0 0 
dln 40 74 40 84 / 20 0 0 0 
hvr 49 73 38 85 / 30 20 0 0 
lwt 45 69 40 82 / 70 0 0 0 


&& 


Tfx watches/warnings/advisories... 
none. 
&& 


$$ 


Short term...zumpfe 
long term...db 
aviation...waranauskas 


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