Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 212051
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
251 PM MDT Tue Oct 21 2014

.DISCUSSION...
Tuesday through Thursday...Showers will continue to develop
and move through the area as a low pressure system tracks across
the area this afternoon and evening. Most of the precipitation is
expected to move off to the east overnight. Higher elevation
locations especially over the Rocky Mountain Front and Southwest
Montana can expect some light snow accumulations with this system
with the biggest impacts being to area passes with roadways
becoming snow covered and slippery overnight. A weak shortwave
ridge will build into the area behind the system passage and
temperatures should rebound back above seasonal averages by
Wednesday with warm and dry conditions also extending into
Thursday. Suk

Thursday Night through Tuesday...Overall, seasonably mild weather
expected as a progressive pattern steers a series of Pacific low
pressure troughs through the area during the period. High pressure
ridge centered over the Rocky Mountain states at start of period
quickly gives way to Pacific low pressure trough during the weekend.
Models are in relatively close agreement with timing and strength of
system as it moves through with both ECMWF and GFS calling for
temperatures 10 to 15 degrees cooler and areas of rain or snow
showers, mainly over the west and southwest mountains. Downslope
winds will limit precipitation chances over the plains and valleys.
This low pressure trough starts working off to the east on Monday
with high pressure again rebuilding briefly before the next trough
begins pushing in Tuesday.

&&

.AVIATION...
UPDATED 1745Z.
Latest analysis shows surface cold front has gone thru KCTB/KHLN and
is just west of KGTF. Front will progress steadily eastward this
aftn/eve with areas of -SHRA and -RA primarily ahead and along the
front. Have also kept TEMPO groups for -TSRA from earlier TAFs for
all but KCTB, as 12Z balloon launch at KGTF showed sufficient
instability for isolated -TSRA and already have observed some small
but potent (convective gust to 40kts at KBTM) storms across
southwest MT.  Expect lowering ceilings across the region as the
front comes through with predominantly VFR conditions, but brief
periods of MVFR or IFR cig/vis possible with any heavier showers or
storms.  Weather system heads into eastern MT, with gradually
clearing skies tonight.  Winds strengthening this aftn behind the
front with widespread gusts of 25-30 kts likely, then tapering off
this evening.
Waranauskas

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  61  44  65 /  40   0  10  10
CTB  36  61  41  63 /  20   0  10  20
HLN  37  62  39  65 /  40  10  10  10
BZN  29  56  31  64 /  50  10  10  10
WEY  24  46  23  52 /  50  10  10  10
DLN  32  56  37  61 /  50   0  10  10
HVR  39  63  39  68 /  30  10   0  10
LWT  38  61  39  67 /  50  10  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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