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fxus65 ktfx 231148 
afdtfx 


Area forecast discussion 
National Weather Service Great Falls Montana 
426 am MST Monday Nov 23 2009 


Discussion... 


Today through Wednesday...the upper level high pressure ridge 
currently over the Pacific coast will gradually shift east across 
the Pacific northwest into the northern rockies today and tonight. 
This will shift the flow aloft from northwesterly to 
westerly...but lingering moisture and weak energy in the flow will 
keep a slight chance of mountain showers around the area. A strong 
shortwave trough moving across southern Canada will then flatten the 
ridge later tonight through Tuesday morning...bringing strong 
westerly downslope winds to the area. This will keep showers in 
the mountains once again. However...middle level winds will increase 
to between 50 and 65 knots along the Rocky Mountain front and into 
eastern Glacier County during this period. With a strong surface 
pressure gradient also over this area...wind gusts in excess of 
60 miles per hour are possible. Have therefore issued a high wind watch for 
the Rocky Mountain front and eastern Glacier County. Winds will 
quite strong elsewhere...but widespread high winds are not 
expected. Winds will generally decrease during the day on Tuesday 
as the shortwave rapidly exits the area. The resulting 
northwesterly upslope flow in the wake of the shortwave will bring 
a chance of showers to central Montana Tuesday afternoon...mainly 
in the area of the north facing slopes of the big and Little Snowy 
Mountains...as well as the Little Belt Mountains. The ridge will 
build back into the area Tuesday night into Wednesday...with the 
only chance of precipitation in the mountains of the Rocky 
Mountain front. Temperatures will gradually warm from a few 
degrees above seasonal averages to around 10 degrees above normal 
by Wednesday. Coulston 


Wednesday night through Monday night...Wednesday night and 
Thanksgiving a strong upper ridge will be over the area. This 
will translate into dry weather with temperatures on Thanksgiving 
well above normal. Raised high temperatures over the plains into 
the upper 50s to lower 60s. The European model (ecmwf) and GFS computer model runs 
are not in as good agreement as they were yesterday with the 
timing of a weather disturbance for later this week. The European model (ecmwf) 
brings the disturbance through Friday night while the GFS brings 
it through on Saturday. Will continue with a chance of snow 
showers mainly over the western mountains for Friday should the 
faster European model (ecmwf) pan out. Will continue with the idea of slight 
chance to chance chances of precipitation for Friday night and 
Saturday accounting for the differences in forecast timing of the 
weather disturbances. Both models have the area under a 
relatively drier northwest to north flow aloft later in the 
weekend into very early next week and this was well accounted for 
in the inherited chances of precipitation which were lower than 
those of Friday night and Saturday. Monday night significant 
differences between the European model (ecmwf) and GFS model runs show up as the 
European model (ecmwf) has a strong weather disturbance approaching the area while 
the GFS has a strong upper ridge over the area. With these 
differences decided to go with chances of precipitation close to 
climatological normals. Blank 


&& 


Aviation... 
updated 1145z. 
Expect VFR conditions. Widespread ceilings between 4000 and 7000 feet 
over southwest Montana along with a few snow showers will mostly 
dissipate by 18z. There could be local mountain obscurement with the 
snow showers this morning. Otherwise expect increasing clouds above 
15000 feet above ground level later this morning through early this evening. The main 
forecast problem today through tonight will be winds over the plains 
and specifically along the east slopes of the Rocky Mountains. At 
kctb and kgtf have indicated that winds will decrease some this 
evening but would not be surprised if they do not really decrease. 
At kctb expect winds to increase near and after midnight and feel 
pretty confident that there will be occasional gusts to 45 knots per 
the taf. Also expect occasional gusts of 50 knots to possibly 60 
knots over the Rocky Mountain front near and after 06z. Blank 


&& 


Preliminary point temps/pops... 
gtf 43 35 46 29 / 0 10 10 0 
ctb 41 34 43 25 / 0 10 10 0 
hln 40 26 42 27 / 10 10 10 10 
bzn 33 11 37 20 / 10 10 10 10 
wey 26 9 29 12 / 40 20 10 10 
dln 32 15 37 20 / 10 10 10 0 
hvr 45 28 45 19 / 0 10 10 0 
lwt 41 25 43 22 / 10 10 20 10 


&& 


Tfx watches/warnings/advisories... 
high wind watch from this evening through Tuesday morning 
for mtz009-010-048. 


&& 


$$ 


Short term...coulston 
long term...blank 
aviation...brusda 


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