Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 291953
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
153 PM MDT Thu Sep 29 2016

.DISCUSSION...

Tonight through Saturday...Water vapor satellite imagery reveals
mid- to upper-level moisture moving north into portions of central
and southwest Montana. Short term guidance consistently introduces a
subtle shortwave trough that produces scattered showers and
isolated thunderstorms over southwest Montana this evening.
Forecast soundings indicate a dry boundary layer, so expect little
if any precipitation reaching the ground, but small hail and brief
heavy rain cannot be ruled out in a few isolated cells. Any
convective activity dissipates overnight. Remnants of a low- level
temperature inversion remain in place over north- central MT where
areas of fog are possible once again along the Milk River valley.
Height falls over the PacNW on Friday along with downslope
southwesterly surface winds will introduce greater instability.
Hence, scattered showers and thunderstorms are expected over the
western and southwest mountains Friday evening. This recent period
of warmer weather ends on Saturday afternoon as a cold front
crosses the Continental Divide. Widespread precipitation is
expected across much of central MT as the front moves through.
Total rainfall amounts Saturday afternoon and evening will be
limited to around 0.1 to 0.25 inches as the system moves through
rather quickly. PN

Saturday night through Thursday...Weather in the medium range period
continues to be dominated by the movement and subsequent development
of an upper level trough. This feature starts out as a closed low
off the Washington coast. Both medium range models have trended
toward developing this system into an open trough over the western
USA with bulk of energy associated with the system moving as far
south as the Four Corners region. As a result, models continue to
trend toward warmer (but still chilly) temperatures with the bulk of
expected precipitation trending towards Eastern Montana. There still
appears to be a good chance for showers through North Central and
Southwest Montana for much of the forecast period; but, if models
continue to trend this way, it is quite possible that any chances
for significant wetting rains may need to be dropped from the
forecast in the coming days. mpj

&&

.AVIATION...
Updated 1726Z.

Predominantly VFR expected through 18Z/Fri. A weather disturbance
over northern Nevada and northwestern Utah as of 1720Z/Thu will move
northeastward and reach southwestern Montana by around 06Z/Fri. This
disturbance will then move eastward to southeastern Montana and
northeastern WY by 18Z/Fri. Thus, scattered showers and TSRA may
develop south of a KHLN to KLWT line this afternoon and early
evening before dissipating around or soon after 00Z/Friday. Brief
MVFR and surface gusts of 30-40 knots are possible with any storm.
Patchy fog may develop around 12Z/Fri over north-central Montana,
but confidence in fog formation is low at this time. Jaszka

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  49  80  51  74 /  10  10  20  60
CTB  45  75  49  64 /  10  20  30  50
HLN  51  79  49  72 /  20  20  30  60
BZN  49  78  49  75 /  10  10  20  30
WEY  41  67  40  63 /  30  20  10  40
DLN  48  76  46  68 /  30  20  30  50
HVR  49  78  52  80 /   0   0  10  30
LWT  53  77  53  76 /  10  10  10  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

weather.gov/greatfalls



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