Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 272304
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
500 PM MDT Thu Jul 27 2017

...UPDATED AVIATION SECTION...

.SYNOPSIS...
A weak disturbance will bring a chance of showers and
thunderstorms through this evening. Some of the stronger storms
could produce frequent lightning and strong wind gusts. A chance
for showers and thunderstorms will continue into Friday though
thunderstorms will not be as widespread. High pressure rebuilds on
Saturday. Temperatures will remain above average.

&&

.DISCUSSION...

Tonight through Saturday...Scattered showers and thunderstorms
will continue through this evening as an upper-level shortwave
moves across the state. Thunderstorms with gusty and erratic
winds as well as frequent lightning are the primary threats. Most
of the thunderstorm activity will develop over higher terrain
initially and then move into the plains and valleys. On Friday,
the chance for thunderstorms will persist but will mainly be
confined to southwest Montana and the island mountain ranges
across central Montana, but activity over the plains can also not
be ruled out. The upper-level ridge of high pressure will re-
build on Saturday with dry and very warm conditions anticipated
statewide. An isolated thunderstorm is possible in the mountains
across southwest Montana, however the threat is low. Temperatures
will remain above average with highs ranging from the upper 80s
across southwest Montana to low 90s over north-central Montana.
MLS/Cassell

Saturday night through Thursday...Unusually-strong high pressure
ridging aloft will reside over the CWA during this period.
Simultaneously, weather disturbances will traverse the ridge from
west to east, particularly on Monday and Tuesday. As a result, a
few showers and thunderstorms are possible each day. This is
especially the case during the afternoon/evening hours and
over/near higher terrain. A dry environment will allow new fire
starts from lightning strikes to remain a concern. In addition,
significant evaporation of rain should yield strong wind gusts
in/near any shower or storm. Near-normal lows are expected during
the period, while daytime highs will be about 5-10 degrees above-
normal and easily reach the 90`s for most locations. Jaszka

&&

.AVIATION...
Updated 2300Z.

VFR conditions will generally continue at least through the day on
Friday. A weak disturbance moving over the unstable airmass will
continue to generate thunderstorms with gusty winds and frequent
lightning through 03Z east of a KHVR-KSMN line. Storms will be
scattered over Southwest Montana (including KEKS KBZN), where brief
heavy rain with MVFR conditions will also be possible. Storms will
be more isolated farther north (including KLWT). Clouds and storms
will diminish after 02Z as the airmass stabilizes. Westerly winds
should become a bit more breezy Friday afternoon over the plains,
while the main chance for additional thunderstorms stays over
Southwest Montana.
Coulston

&&

.FIRE WEATHER...
Scattered showers/thunderstorms will slowly wind down over our
southern and eastern districts through this evening, ending from
west to east as the upper-level trough axis passes through. The
main threat from any storms will be gusty erratic winds and
frequent lightning. Behind this system, gusty west to northwest
winds and continued warm and dry conditions will yield a highly
elevated (bordering critical) fire weather threat over the
plains Friday afternoon into early evening, while isolated
thunderstorms will be possible over the southern districts.
Cassell

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  62  90  59  93 /  20  10  10   0
CTB  57  87  53  90 /  10  10   0   0
HLN  62  89  61  93 /  30  20  20  10
BZN  55  86  54  90 /  30  20  20  10
WEY  46  76  43  80 /  30  20  20  10
DLN  54  82  52  87 /  50  20  10   0
HVR  65  92  60  95 /  20  10   0   0
LWT  61  87  58  90 /  20  10  20  20

&&

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

$$

weather.gov/greatfalls


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