Area Forecast Discussion
Issued by NWS Great Falls, MT

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547
FXUS65 KTFX 260056
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
655 PM MDT Thu May 25 2017

.UPDATE...
Issuing a quick early evening update to PoPs with a few shower
clusters moving south down the Interstate 15 corridor in the
general direction of Great Falls and the Big Belt/Little Belt
mountains. Expect to see more rapid diminishing of shower
activity after 03z this evening with total loss of daytime
heating. Cassell


&&

.SYNOPSIS...

Winds will gradually diminish this evening as low pressure in
Saskatchewan moves off to the east. A few light showers are
possible this evening and again of Friday, mainly in the vicinity
of the mountains. Drier and warmer conditions move in for the
holiday weekend with temperatures trending above seasonal
averages.

&&


.AVIATION...
Updated 2315z.

Moist upper-level northwesterly flow aloft will persist over north-
central Montana through early Friday morning which will bring
predominant VFR cigs but can`t rule out isolated MVFR cigs in
places. However, south of Interstate 90, an upper low will push
-SHRA north from Idaho to our southern terminals (KWYS, KDLN) after
06z, which will mean VFR cigs transitioning to MVFR at times
through 18z.

&&

.PREV DISCUSSION...
/ISSUED 515 PM MDT Thu May 25 2017/

Tonight through Saturday...Low pressure at the surface and aloft
over SK continues to slowly trudge east with winds aloft over
N-central MT beginning to decrease late this afternoon with a
more noticeable diminishing of surface winds expected this
evening. Cyclonic northwesterly flow aloft along with low level
moisture and weak instability has led to the development of
cumulus in all areas this afternoon with widely scattered light
showers through early this evening, becoming isolated tonight and
mainly limited to area areas near the continental divide. On
Friday, unsettled NW flow aloft continues with some warming. A
shortwave disturbance moving across southern ID will focus a
greater coverage of shower and weak thunderstorm activity over SW
MT with isolated showers and weak thunderstorms possible during
the afternoon period elsewhere. By Saturday, an upper level ridge
builds onto the west coast for more significant warming and
drying across the region with temperatures warming into the 70s
for most lower elevation locations and only a small chance for
isolated afternoon/evening convection, mostly in the vicinity of
the mountains. Hoenisch

Saturday night through Thursday...The remainder of the Holiday
Weekend will see our CWA in between high pressure to our west and a
strong upper level disturbance in the northern plains to our east.
The result will see warming temperatures Sunday through the upcoming
week. Models now showing that limited instability and weak
disturbances caught in between systems could still bring isolated to
widely scattered showers and thunderstorms...with the best chances
confined to the mountains. So overall Sunday and Monday of Memorial
Day Weekend look decent as long as those with outdoor plans keep an
eye out for briefly changing weather conditions. Tuesday the ridge
attempts to build in across the region bringing warmer temperatures
and enough instability to produce chances for mainly mountain
showers and thunderstorms. This ridge begins to flatten on
Wednesday...returning southwest flow to the region...and again
seeing only isolated chances for showers and thunderstorms...mainly
in the mountains. Thursday may be the next better chance for
Thunderstorms to our area as a trough enters into the Pacific NW and
sends unstable moist air ahead of a cold front our way. Granted this
is still a ways out...but models do indicate some stronger storms
possible. Will have to keep an eye on this setup. Each day in the
extended will be warmer than the previous. Sunday into the start of
the week will see temperatures in the 60s and 70s...with
temperatures warming into the 80s by mid week. Winds will be mainly
tame during the long term...although some afternoon breezes may be
found at times...especially across eastern portions. Anglin

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  36  64  43  72 /  20  20  10  10
CTB  36  66  42  72 /  20  20  10  10
HLN  41  67  44  73 /  20  20  10  10
BZN  37  62  38  68 /  10  30  20  20
WEY  30  55  29  60 /  30  50  30  20
DLN  39  61  38  68 /  40  40  20  10
HVR  38  69  43  74 /  10  20  20  10
LWT  34  60  40  67 /  10  20  10  20

&&

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

$$

weather.gov/greatfalls



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