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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 66 °
• Low: 41 °
• Partly Cloudy

• Thursday
• 
• High: 61 °
• Low: 34 °
• Chance of Rain

• Friday
• 
• High: 57 °
• Low: 32 °
• Partly Cloudy

• Saturday
• 
• High: 43 °
• Low: 36 °
• Chance of Snow

• Sunday
• 
• High: 57 °
• Low: 39 °
• Chance of Rain

Area forecast discussion 
National Weather Service Glasgow Montana 
315 PM MDT Tuesday may 22 2012 


Short term...for northeast Montana...tonight through Thursday... 
the cold front will move east across eastern Montana this 
morning and into North Dakota this afternoon. Scattered showers 
and thunderstorms are developing right behind the cold front as it 
moves into North Dakota. The front is being push by a jet streak 
over southern Montana and we are still in the left front quadrant. 
Instability behind the front with a lifted index of somewhere 
between -2 and -4*c with cape values of 800 to 1200 j/kg. These 
scattered showers and thunderstorms will come to an end quickly 
this evening around sunset but a few could become strong enough to 
produce dime sized hail and brief gusty winds before then. 


The westerly winds will also die down around sunset so we will be 
able to let the lake winds advisory expire this evening. Probably 
could have expired it with the afternoon package but decided to 
let it ride. The conditions are very marginal but we are still 
seeing occasional gusts up to 30 miles per hour with sustain wind speed of 
around 15 to 20 miles per hour. 


Upper trough becomes an upper low over Saskatchewan tonight into 
Wednesday and this feature will linger over that area through 
Thursday. Southern part of the County Warning Area will be dry slotted but the 
area along the international border will see some scattered 
showers and thunderstorms. The western zones may see a few 
scattered showers and thunderstorm especially in the afternoon as 
wrap around moisture drops south into central Montana.In both of 
these areas lifted index of around -2*c with cape values of around 
350 j/kg. The winds will remain westerly for most of the day in 
the 15 to 25 miles per hour range so another lake Wind Advisory might be 
needed for the afternoon hours. Will let the night shift take a 
look at that. That moisture moves into northeast Montana on 
Thursday with a cold front that will bring unseasonably cold air 
into the area. Will maintain a chance of showers for now. Rsmith 


Long term...Thursday night through Tuesday... 
a very wet-looking period...in what is typically the wettest time 
of the year. A strong upper trough that originates from the Gulf 
of Alaska...moves into the SW states. All models then turn it NE 
toward Montana. Although they vary on the exact path...this system is 
large and moist enough that all models have significant precipitation 
for our area this weekend...and over several periods. Latest GFS 
raises confidence in that...since previous runs had kept the 
precipitation S of our area. Ensembles still show some variation...but in 
line with other model variation though. Will raise probability of precipitation to likely 
and go with steady rain rather than showers. With this mind have 
lowered highs also. 


Coldest 850 mb temperatures are Friday with part of our area below 0c at 850 mb. 
Thicknesses indicate that this to be a cold rain with the main 
part of the system. The coolest layer is fairly shallow at lower levels. 
Therefore any snow chances remain possible...but is a 
Longshot...not enough to mention in the forecast. Simonsen 


Previous long term...Thursday night through Tuesday...the extended 
period begins Thursday night with a broad upper level trough 
covering the western states. The closed low center will be located 
upstream over the Pacific-northwest coast. This low will slide south into 
central California on Friday...then round the corner and begin to 
lift northeast Friday night. The low center will continue north 
until it is centered over northeast Montana on Sunday... then 
continue moving north or east out of the area around Sunday night. 


Thursday night...an upper disturbance over southern Saskatchewan 
drops 850mb temperatures to around 0c to -2c. Raw mex guidance 
suggest freezing lows along the international border. So departing 
light showers have the potential to become mixed with snow. 


Friday/Friday night...the West Coast storm system will be picking in 
Pacific moisture and ejecting it northeast into the central and 
northern rockies...but not quite reaching nemont. Yet the models 
put the moisture close enough to the lingering cold boundary to 
maintain probability of precipitation. Timing differences between GFS and the European model (ecmwf) show 
up at thi spoint with the ec out ahead of the GFS. 


Saturday through Sunday night...while the 12z ec keeps the low 
together and ejects a large amount of moisture north into 
northeast Montana...the 00z GFS opens the low and ejects moisture 
to the northeast...tending to miss nemont with most of the quantitative precipitation forecast. So 
confidence decreases that nemont will see significant rain. With 
the models still bouncing around...will tend to make few 
significant changes to probability of precipitation for the weekend. 


Monday/Monday night...models can agree with a narrow upper ridge 
following the departing trough. So expect a dry and mild Memorial 
Day. 


The picture for temperatures is also somewhat muddled because of 
the differences in how the models treat the upper trough. But both 
the ec and GFS trend cooler than normal through the period... 
returning to normal around Monday and beyond. Scattered 




&& 


Aviation... 
mainly VFR. There will be scattered showers and isolated 
thunderstorms which will lower visibilities at times to 4 to 6 
miles...along with broken ceilings as low as 5k feet above ground level until 
sunset. 20 to 30 knots northwest winds also diminish at sunset. Simonsen 


&& 


Glasgow watches/warnings/advisories... 
lake Wind Advisory until 9 PM MDT this evening for Fort Peck 
Lake. 


&& 


$$ 


Weather.Gov/Glasgow