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Area forecast discussion 
National Weather Service Glasgow Montana 
323 am MDT Tuesday Oct 7 2008 


Short term...for northeast Montana...today through Thursday... 
an upper ridge axis will ride east over the area this morning 
pushed along by an approaching upper trough trekking across 
southwest Canada today. The day will begin dry with thickness 
heights increasing to around 560dm for very pleasant maximum 
temperatures in the 70s. However a Lee side surface trough will 
stretch south into eastern Montana resulting in a southwesterly 
surface breeze that could be enhanced by moderate mixing of 850mb 
winds in the same direction. Strongest winds will be over western 
zones today...but not quite strong enough to sustain an advisory 
over Fort Peck Lake. Wind strength could be of some concern for 
fire weather since relative humidity values will fall to around 
20-25 percent in the afternoon. See fire weather discussion. 


Latest guidance brings the cold front...associated with the fast 
moving shortwave...across the western zones late this afternoon. 
Could see some isolated light showers near the front before 
evening. Front will travel across the zones this evening 
generating a better chance for showers...which should be mostly 
over by midnight. Westerly winds will remain moderately strong 
overnight as the surface trough moves east. There remains the 
possibility that evening winds over the lake could reach advisory 
strength. This can be looked at closer by the day shift. Winds 
will help offset rather chilly temperatures aloft which will be 
around 1c to 3c at 850mb. 


Upper zonal flow will take over on Wednesday with a stationary 
boundary well to the south of the area. The result will be maximum 
temperatures slightly below normal. With a persistent surface 
gradient the westerly winds will add a chill to the cooler 
temperatures. The Canadian low will move near Hudson Bay Wednesday 
night. The result will be continued cold dry air flowing over the 
local region for clear skies and a cold night. Guidance is now 
suggesting most lows somewhere in the middle to upper 20s. 


The next upper trough will dig into the northwest Thursday 
continuing to push the stationary front farther south. With colder air 
continuing to move into the region Thursday...tmax will struggle 
to reach 60f. Scattered 




Long term...Thursday night through Tuesday... 
models are coming into better agreement for the extended period. 
Upper trough dives into the Pacific northwest Wednesday night and 
Thursday. A closed upper low forms near Boise Idaho by 12z Friday 
with a surface low over Colorado. Thursday and Thursday night some 
overrunning precipitation develops over Wyoming and South Dakota with the 
help of some frontogenetic forcing. This band of precipitation 
lifts north into southern Montana and North Dakota Thursday night 
and Friday as the upper low drops south into Nevada. Then that 
area of precipitation will move to the east as more precipitation develops over 
Wyoming Friday night and Saturday with the upper low rotating into 
Utah. Temperatures will be borderline for rain and snow Thursday 
night and Friday and then cool enough for all snow Friday night. 
Most of the precipitation will stay south of the forecast area with this 
system through Saturday as high pressure in Alberta and 
Saskatchewan suppresses the northward extent of the precipitation. Will 
limit probability of precipitation to slight chance of rain and/or snow in most areas and 
chance on Friday in the southeast. 


The upper low lifts northeast Sunday and Monday through eastern 
Montana. Models disagree on the extent of the precipitation that will 
cover eastern Montana. Will lean towards the smaller areal 
coverage of the GFS for now and focus the precipitation chances over the 
eastern half of the forecast area. 850 mb temperatures are 
forecasted to be cold enough for all snow but temperatures near 
the surface may be warm enough during the day Sunday for a mix of 
rain. The system exits Monday morning with drier air and somewhat 
warmer temperatures with a upper ridge through Tuesday. Forrester 


&& 


Aviation... 
VFR conditions through tonight. Some middle and high clouds will 
move into the region during the afternoon. Light winds early will 
become south/southeast around 13-16kts this morning and gradually 
shift southwest during the afternoon and west this evening. 


&& 


Fire weather... 
warm temperatures and gusty southwest winds ahead of a strong cold 
front will develop this afternoon mainly over fire weather zone 121 and 
southern areas of zone 119. Wind strength will be around 15 to 25 
knots through the evening. Afternoon relative humidities are 
expected to fall to between 20 and 25 percent primarily over the 
western half of fire weather zone 121 and southwest portions of 
zone 119. The combination of winds and low relative humidities 
will result in at least marginal critical fire weather conditions 
in these areas with a few locations possibly exceeding this 
criteria late this afternoon and into early evening. Conditions 
will continue to be monitored today to determine if a red flag 
warning will be necessary. Scattered 






&& 


Glasgow watches/warnings/advisories...none. 


&& 


$$ 


Weather.Gov/Glasgow