Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 232352
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
551 PM MDT Wed Aug 23 2017

...Update to Aviation...

.SYNOPSIS...
With an upper level ridge moving east tonight and a weak upper
level trof approaching the region, a few isolated thunderstorms
will be possible over Southwest MT. The storms will become a bit
more widespread and also affect areas further northward on
Thursday. Afternoon highs for Thursday and Friday will be slightly
cooler than they have been, with highs in the upper 70s to lower
80s. However, warmer temperatures and dry conditions return over
the weekend and into the first half of next week.

&&

.DISCUSSION...
Tonight through Friday...The upper level ridge is moving eastward,
as a an upper level disturbance moves into Southwest MT. Most of
the storms this evening will affect areas mainly south of
I-90...but an isolated storm could develop as far north as the
Helena area. On Thursday, an upper level trof will move through,
cooling temperatures a bit and allowing for a slightly better
chance for storms to develop over portions of Central and
Southwest MT. A few of the storms will linger on Friday over the
eastern portions of the region...but much of the area will be
dry...along with seasonable temperatures. Brusda

Friday night through Wednesday...Overall a warming and dry
pattern will be found through the long term, with elevated fire
weather danger to continue. Friday night through Saturday we will
find ourselves in the wake of Thursday/Friday`s disturbance. This
will bring weakly unstable zonal flow with a weak jet max
overhead. The result will bring some lingering chances for
showers and thunderstorms across southern and eastern portions
during this time period. A large area of high pressure will then
build across much of the western US starting Sunday and
continuing through at least the rest of the long term period. The
result will be warming temperatures and mainly dry conditions.
Afternoon RH values will continue to be low. This combined with
normal afternoon breezes may continue at least elevated fire
weather danger through the long term. A slight shift in location
of this high pressure on Tuesday and Wednesday may bring just
enough moisture and instability for isolated thunderstorms across
western and southern portions. With pwats expected to be low,
this looks to be mainly a dry thunderstorm threat, perhaps
further enhancing fire weather danger. Temperatures will start
near normal on Saturday, then start a warming trend with the
mentioned high pressure. Highs in the 90s are possible by next
week...especially Monday through Wednesday.
Anglin

&&

.AVIATION...
Updated 2351Z.
Spotty showers and possibly a thunderstorm or two will continue to
affect southwest Montana and southern portions of central Montana
through 04Z Thursday. Only sprinkles or light rain and occasional
lightning strikes are anticipated from these storms. Gusty west
winds along the east slopes of the Rocky Mountains will diminish by
mid-evening leaving scattered to broken mid and high level clouds
across the region for widespread VFR conditions. However, some areas
of reduced visibility due to wildfire smoke could cause periods of
MVFR conditions, mainly at KHLN and KGTF as well as in the valleys
of southwest Montana. Scattered showers and thunderstorms are
expected across western and southern portions of the forecast area
after 18Z Thursday. mpj

&&

.FIRE WEATHER...
Red Flag conditions continue this afternoon along the I-15
corridor from Great Falls to Cut Bank. Expect slowly improving
conditions after 9 PM, but overall humidity should only have a
poor recovery overnight. On Thursday, thunderstorms are possible
but no highlights are planned for at this time. After some
slightly cooler temperatures on Friday, it then turns mostly dry
and warm again over the weekend and through the first half of next
week. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  59  84  51  81 /   0  20  20   0
CTB  55  81  46  77 /   0  20  10   0
HLN  58  82  54  83 /   0  30  30  10
BZN  54  80  49  81 /  20  50  40  20
WEY  45  69  35  73 /  10  40  40  20
DLN  52  79  45  80 /  20  20  30  10
HVR  58  90  53  81 /   0  20  30   0
LWT  59  86  53  79 /  10  40  40  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening Eastern
Glacier/Toole/Central/Eastern Pondera/Liberty...Lewis and Clark
National Forest Rocky Mountain District-Rocky Mountain Front...
Central and Eastern Lewis and Clark National Forest Areas.

&&

$$

weather.gov/greatfalls


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