Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 140418
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1015 PM MDT Sun Aug 13 2017

...UPDATED AVIATION SECTION...

.UPDATE...
Main update tonight was to decrease shower and thunderstorm
activity across north central and central Montana overnight in the
wake of the cold front. The scattered showers and few
thunderstorms lingering over Hill/Blaine/Chouteau/Fergus Counties
will diminish overnight. However, the cold front has yet to move
completely through Blaine County, so wind gusts in excess of 40
mph are still possible there through midnight. Otherwise, winds
and clouds will continue to decrease overnight from the west.
Coulston

&&

.SYNOPSIS...

Scattered showers and isolated thunderstorms along and east of a
Havre to Lewistown line will move east out of the area overnight.
Otherwise, clouds will gradually decrease from the west
overnight, but a few showers will move through southwest Montana.
A low pressure trough will then keep the area generally dry Monday
through Tuesday, with only a slight chance of showers and
thunderstorms during the afternoon and evening hours along the
Hi-Line and in far southwest Montana.

&&

.AVIATION...
Updated 0415Z.

VFR conditions are expected over the next 24 hours. Clouds and any
lingering showers/storms in the KHVR and KLWT areas will continue to
decrease from west to east through 09Z as the cold front exits the
area. However, a weak disturbance will bring showers to far
southwest Montana (KBZN, KEKS) between 09Z and 15Z. Weak instability
will redevelop along the Hi-Line (KHVR) and in far southwest Montana
(KBZN, KEKS) after 18Z, so have continued the chance of showers
(KHVR) and thunderstorms (KBZN, KEKS) between 21Z and 03Z.
Coulston

&&

.FIRE WEATHER...

The Red Flag Warning for all of the TFX fire districts has been
allowed to expire at 9 pm MDT. The cold front and its gusty
shifting winds has all but moved east out of the area as of 9 pm.
A few showers and possible thunderstorms will linger over Hill
and Blaine Counties as the front moves east out of those counties
through midnight. Though wind gusts in excess of 35 mph are
possible still with the frontal passage and storms, humidity has
recovered into the 60 to 65 percent range where the storms have
already moved through. This has lessened and will continue to
lessen the threat for additional critical fire weather conditions
this evening.  Coulston

Beyond this weekend, drier conditions are expected along with
near normal temperatures. MARTIN

&&

.PREV DISCUSSION...
/ISSUED 555 PM MDT Sun Aug 13 2017/

Rest of today through tonight...Latest water vapor shows a potent
shortwave encroaching on the northern Rockies at this time. Ahead
of it, a band of showers continues to progress east across
northern Idaho/western MT. Ahead of this band, scattered showers
and isolated thunderstorms have begun developing across much of
central/SW MT. Instability continues to look weak, and the overall
coverage and strength of thunderstorms looks a bit lower than
originally forecast. The strength of storms looks in question as
well with the lack of better instability. To the west, several
surface obs have been reporting gusts of 20-30 mph associated with
the front and that will likely continue as the front pushes east.
The strongest winds with the front looks to be along/west of a
Chester to Great Falls line with somewhat lower gusts as it pushes
east. The front then slows down some tonight across our far
eastern counties and south through SW MT. Lingering moisture/lift
should keep showers and a few thunderstorms going there longer.
MARTIN

Monday through Tuesday...We begin to see an end to the widespread
rain coverage early Monday morning, with our area remaining in a
persistent southwesterly flow aloft. Broadscale trough and lingering
moisture will allow for chances of showers and thunderstorms to
continue for Monday, mainly be for southern and some eastern areas.
Tuesday will feature continued drying conditions with continued near-
seasonal temperatures. Lingering moisture across the south my once
again bring a few isolated to scattered showers and thunderstorms
for these areas.

Tuesday night through Sunday...We stay in a quasi-zonal upper-
level flow aloft as we get into the middle part of the week. A
passing weak disturbance may ignite some isolated showers or storms
Thursday, however, coverage will remain limited. We return to a weak
ridging pattern aloft by late week and into the weekend with the
potential for dry weather and moderating temperatures back to
slightly above-normal. Fortunately, there continues to be no sign of
any extreme heat returning in the foreseeable future.
KLG/Anglin

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  53  77  48  78 /  10  10  10  10
CTB  50  75  44  75 /  10  10  10  10
HLN  52  78  49  80 /  10  10  10  10
BZN  51  76  48  78 /  40  50  30  20
WEY  42  67  38  68 /  40  50  40  40
DLN  48  76  46  77 /  50  50  20  10
HVR  57  80  51  79 /  70  10  20  10
LWT  54  74  50  75 /  70  20  20  20

&&

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

$$

weather.gov/greatfalls



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