Weather

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Area forecast discussion 
National Weather Service Great Falls Montana 
1113 am MDT Thursday Aug 28 2008 


Updated aviation discussion 


Update... 


Today...update to zones planned by 10...the main problem of the 
day will be high winds across the northern rockies and adjacent 
plains. We currently have a High Wind Warning valid from 
1100-1900. A weak shortwave will move through the area from noon 
to middle afternoon and the highest surface winds are expected during 
this time...and current wind observation from Logan Pass are gusting to 57 
kts. Other support for the high winds is weak. Current wind forecasts 
show the strongest winds staying at upper levels and expected 
mixing downward from afternoon heating is not a sure thing. Will 
leave current warning in place and update mainly to freshen first 
period sky and weather grids. Zelzer 


&& 


Aviation... 
updated 1713z. 
Strong westerly flow aloft will continue though this afternoon then 
gradually diminish through Friday as weak ridging aloft moves over 
the area. Main impact to aviation will be gusty winds this afternoon 
and evening...especially over western portions of southwest Montana. 
Otherwise...expect scattered to broken high clouds at times through 
tonight with generally clear skies on Friday. VFR conditions will 
prevail through the next 24 hours. Hoenisch 


&& 


Previous discussion... 
/issued 545 am MDT Thursday Aug 28 2008/ 
today through Saturday...a weak upper level ridge will build over 
the region through Friday with a strong west to northwest flow 
aloft...especially today with near 60kt winds at 700 mb level 
over the northern rockies at 00z Friday. Thus...plan to issue 
a High Wind Warning for the northern rockies and adjacent plains 
for late this morning through the afternoon hours. Temperatures 
will continue to warm to above seasonal average by Friday with 
a dry westerly flow aloft. The flow aloft becomes more 
southwesterly...but remain dry Friday night and Saturday with 
some low and middle level moisture moving into the northern 
rockies for isolated showers by Saturday afternoon. Temperatures 
remain Summer like. Williamson District of Columbia 


Saturday night through Tuesday night...the extended forecast period 
will be characterized by a great deal of moisture and temperatures 
that are well below the seasonal average. A deepening Pacific storm 
system is anticipated to arrive in the forecast area Sunday... 
preceded by a surface cold front Saturday night. This surface front 
will likely clear the eastern and southern portions of the area by 
Sunday evening. Chances of precipitation will increase dramatically 
Sunday as a closed upper level low pressure circulation develops 
south over eastern Idaho. The presence of this closed upper level 
feature will contribute to temperatures that are well below the 
seasonal average and widespread precipitation. Snow levels will be 
sufficiently low for snowfall over the High Mountain peaks 
throughout the forecast area between Sunday evening and Tuesday 
morning. Mostly dry conditions return to the area on Tuesday...with 
weak high pressure present. Temperatures will remain below the 
seasonal average throughout much of the extended forecast period. 
Zumpfe 


Wednesday through Thursday...models are in basic agreement during 
this period...with some differences in timing and amplitude of 
features. A weak upper level ridge moves across the forecast area 
Wednesday. Behind this system...the upper level flow backs to the 
southwest ahead of an upper level trough swinging southeast out of 
British Columbia...moving into western Montana Thursday. This 
results in increasing clouds with isolated showers and a few 
thunderstorms developing over the western mountains Wednesday 
afternoon...spreading east to much of the region during the evening. 
Most of the energy with this system will stay north of southwest 
Montana where it will remain partly cloudy and dry...except for a 
possible shower or thunderstorm over the mountains. Temperatures 
will warm a few degrees Wednesday...but will remain a little below 
seasonal averages. Ek 


&& 


Preliminary point temps/pops... 
gtf 76 51 85 53 / 0 0 0 0 
ctb 69 47 78 48 / 0 0 0 0 
hln 78 53 88 53 / 0 0 0 0 
bzn 82 47 89 46 / 0 0 0 0 
wey 72 41 78 42 / 0 0 0 0 
dln 75 45 83 46 / 0 0 0 0 
hvr 77 46 83 47 / 0 0 0 0 
lwt 75 47 82 47 / 0 0 0 0 


&& 


Tfx watches/warnings/advisories... 
High Wind Warning until 7 PM MDT this evening for mtz009-010-048. 


&& 


$$ 


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