Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 300517
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1115 PM MDT Thu Sep 29 2016

UPDATED AVIATION SECTION

.DISCUSSION...

Tonight...A weak upper level shortwave is moving east of the region.
Convective activity has diminished although some showery activity
continues. Freshened POPs, WX, and QPF. Current forecast looks on
track. Zelzer

&&

.AVIATION...
Updated 0515Z.

VFR conditions are generally expected through at least the next 24
hours over the forecast area with a slightly moist and unstable
southwest flow aloft. A disturbance in the flow will exit the area
through 09Z, diminishing the lingering showers over Southwest (KHLN
KEKS KBZN) and Central Montana (east of a KGTF-KHVR line, which
includes KLWT). Patchy fog with periods of MVFR/IFR conditions may
develop again in the Milk River valley (including the KHVR area)
between 09Z and 15Z. Another disturbance in the flow may bring
isolated showers and thunderstorms to the area again after 18Z, but
the focus will shift to along and west of a KBZN-KCTB line.
Coulston

&&

.PREV DISCUSSION...
/ISSUED 516 PM MDT Thu Sep 29 2016/

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

&&

.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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