Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 300339
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
939 PM MDT Mon Sep 29 2014

.UPDATE...

No significant changes made to the forecast overnight into early
Tuesday morning. As of 0330Z...area of subtle enhancement on
water vapor imagery over western/southwest Montana superimposed a
slow moving cluster of showers. This area of moisture wrapped
around the large upper-level low that has been moving through the
West over the past few days and is now positioned in central
Montana. Forecast soundings through tonight indicate that the most
saturated layer exists between 700mb-500mb. Showers will be most
likely in the mountains south of a Helena-to-White Sulphur Springs
Line. Chances are lower across the plains/valleys but again
favored areas are over the SW portion of the CWA as an area of 0-1
km convergence pushes from west to east before weakening early
Tuesday morning. Uttech

&&

.AVIATION...
UPDATED 2345Z.
An upper level trough of low pressure will continue to circulate
moisture across the region as it lifts N tonight with another upper
level trough moving in from the NW Tuesday afternoon. Areas of
broken mid-level clouds will increase tonight as one of several
disturbances embedded within the upper low moves across the region.
Showers associated with this feature will be light with a brief
period of lower ceilings and mtn obscurations possible later this
evening. A trough of low pressure at the surface, extending from SW
AB southward along the East Slopes of the Rockies will shift East
late tonight through Tuesday morning, allowing surface winds to
become predominately from the W or SW at most terminals. Hoenisch

&&

.PREV DISCUSSION...
/ISSUED 545 PM MDT Mon Sep 29 2014/

Tonight through Wednesday...The longwave upper trof that has
influenced our weather since Saturday is beginning to move
northeast, presently centered over southern Idaho. Light rain
showers associated with an embedded shortwave feature have
dissipated today while drifting northwestward. Skies have turned
partly sunny as this feature splits away from the primary trof.
Afternoon shower development is expected over the southwest with
afternoon heating. Another significant trof over the Pacific
Northwest will pass through the region tonight. This will cause
widespread rain showers but with little total rain accumulation. A
Pacific front associated with this wave will cross the Continental
divide early Tuesday. Westerly wind gusts will strengthen behind
this front on Tuesday afternoon. Cooler air moving in behind the
front will lower snow levels Tuesday night to around 6500 feet
MSL. Rain may mix with snow Tuesday night and Wednesday morning on
the higher ridges along the Continental Divide. Up to one inch of
snow may be possible over the Madison and nearby ranges in
Southwest Montana. Skies will clear as drier air and subsidence
arrives behind the trof axis on Wednesday. Nutter

Wednesday night through Monday...It will continue to remain a bit
unsettled over the region through Thursday...as an upper level
disturbance moves southward through the region. Even though showers
will accompany this disturbance...the precipitation amounts will be
light...generally less than 0.10 inches and mostly over North
Central MT. The air mass continues to look cold enough that snow
will mix in with the rain in the mountains and over the Plains in
the Cut Bank area. But since any snowfall amounts should be less
than 1/2 inch...any impacts are expected to be minimal/if at all.
After this disturbance moves through...fairly quiet and nice weather
conditions are expected for Friday thru Sunday morning. For Sunday
afternoon and Monday...an unsettled northwesterly flow aloft will
try to set up once again...allowing for weak weather disturbances to
move through the northern portion of the region. Thus there will be
a chance for showers once again...mainly over the northern Rockies
and north of Highway 2 for Sunday afternoon through Monday.
Afternoon temperatures will be in the 50s Thursday...then in the 60s
for Friday through Monday...with a few lower 70s possible on
Saturday. Normal high temperatures for this time of the year are in
the lower to mid 60s. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  50  62  42  57 /  30  20  20  20
CTB  45  60  38  55 /  40  60  50  20
HLN  47  62  41  59 /  50  20  20  20
BZN  42  59  35  55 /  40  30  20  20
WEY  31  50  24  48 /  40  50  30  20
DLN  41  56  32  54 /  50  40  20  20
HVR  46  67  42  61 /  10  30  40  30
LWT  45  63  40  57 /  10  20  20  20

&&

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

$$

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