Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 302143
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
343 PM MDT TUE AUG 30 2016

.DISCUSSION...

Tonight through Thursday...Low off the BC coast will continue to
bring southwest flow to the region tonight. There is some
monsoonal type moisture caught in this flow that will push into
western MT this evening. With the strong heating today sfc cape of
over 1000 J/Kg is currently being found across the northern half
of the CWA. The bad news for convection enthusiasts is today`s
atmosphere is fairy capped with the warm air being advected aloft.
With no strong disturbance to break the cap...mainly dry
conditions are expected tonight...with some increased cloud
cover....and only a few very isolated mountain storms possible.
Warm southwest flow continues for Wednesday...returning high temps
in the 90s across the lower elevations. Ample instability will
again be found...but the atmosphere will be capped through most of
the afternoon. Weak surface low and its associated
front...combined with falling heights...weak monsoonal moisture...and
an increasing jet...may be enough to break down the cap late
Wednesday afternoon through the evening...and possibly linger
into the early overnight hours. Widespread showers and
thunderstorms will be possible if all the right ingredients can
align. Kept mainly chance pops as confidence is moderate. With
increasing shear...a few stronger storms may be possible if the
cap can break. Hail and gusty winds will be the main threat.
Thursday looks to be sightly cooler...but still warm. A frontal
boundary and trapped monsoonal moisture could provide the focus
for a few showers and thunderstorms by Thursday afternoon...mainly
across southern and eastern portion. At least elevated fire
weather danger is also expected through the short term...as RH
values will be low...and winds will be breezy at times. See the
Fire Weather Discussion for more details below. Anglin

Thursday Night through Tuesday...Temperatures trend cooler than
seasonal averages throughout the Labor Day weekend. The transition
begins early Friday morning as the upstream longwave trough begins
to move into the Pacific Northwest. A surface cold front will
advance through the region on Friday, producing scattered showers or
thunderstorms and gusty northwest winds. Although confidence is high
regarding the pattern change for cooler temperatures, the
precipitation forecast remains low confidence amid diverging model
solutions. Once the initial system pulls away on Saturday, a series
of weaker waves will progress through a broad western CONUS trough.

Tuesday morning forecast models have begun to trend toward a
secondary push of colder air combined with an upper level wave for
Sunday night and Monday. Still not complete agreement on this but
have decided to trend toward colder temperatures and higher PoPs for
this time period.l Backcountry travelers should be aware that snow
levels could drop low enough to allow light to moderate snow
accumulations at mid to higher mountain levels for Sunday night and
Monday. mpj/PN

&&

.AVIATION...
UPDATED 1723Z.

VFR will likely prevail through 18Z/Wed. Southwesterly flow aloft
will persist as a low pressure trough over/near the Pacific Northwest
coast and a high pressure ridge over eastern MT and the Canadian
Prairies move little. A few -SHRA and -TSRA may develop over the
higher terrain of Central/Southwest MT and the Continental Divide
this afternoon and persist into the evening. Any -SHRA/-TSRA will
likely dissipate between 03Z and 06Z/Wed. Erratic wind gusts of
30-45 knots are possible with any -TSRA. Patchy smoke will likely
persist over Southwest MT through the period, but VIS should remain
within the VFR range at KBZN. Jaszka

&&

.FIRE WEATHER...

Warm temperatures...low RH...and breezy winds at times could bring
elevated fire danger at time for the next couple of days.
Monsoonal moisture will increase tonight...however...a capped
atmosphere will limit chances for thunderstorms to only a few very
isolated mountain thunderstorms. Very warm temperatures return
tomorrow...with highs expected to return in the 90s. With RH
values below 20 percent also expected...most areas will have at
least elevated fire danger. Areas across the south will have
borderline gusty winds at times. This will have to monitored for
critical fire danger...however no Fire Weather Highlights are
issued at this moment. Chances for thunderstorms then return late
Wednesday afternoon...and continue through Wednesday night.
Slightly cooler...but still warm...temperatures are expected for
Thursday. This combined with continued low RH values will
continue elevated fire danger concern...especially across the far
south where some breezy winds at times are possible. Thunderstorms
may also return Thursday afternoon...mainly across the south and
east. Anglin

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  94  56  88 /   0   0  30  20
CTB  56  89  52  82 /   0  10  30  10
HLN  58  92  57  89 /  10  20  20  20
BZN  55  92  54  88 /  10  10  20  20
WEY  47  80  47  76 /  10  10  20  20
DLN  56  88  52  85 /  10  10  20  30
HVR  59  96  59  90 /  10  10  20  10
LWT  61  93  59  88 /   0  10  20  20

&&

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

$$

weather.gov/greatfalls



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