-- Discussion containing changed information from previous version are highlighted. --
477
FXUS65 KTFX 201643
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1043 AM MDT Thu Jun 20 2024

...Aviation Section Updated...

.SYNOPSIS...

There`s a chance for some isolated showers/thunderstorms this
afternoon. Better chances for precipitation across Central and
North Central MT arrive Friday. There`s a potential for a few
strong to severe storms Friday afternoon. Drier and warmer
conditions arrive for the weekend and beginning of next week,
with well above average temperatures.

&&

.UPDATE...

West-southwesterly flow aloft today will allow for another chance
of showers and thunderstorms, primarily across Central and North-
central Montana this afternoon and evening. A corridor of greater
instability, generally peaking around 500-750 m2/s2, looks to
develop along and adjacent to the 87 corridor between Great Falls
and Grass Range. Given shear in place, any thunderstorm that
forms in this environment will have a marginal chance to become
strong to perhaps severe. The main concern will be for hail,
highlighted by the marginal risk for severe thunderstorms from SPC
in this area.

Small tweaks to PoPs were made to account for latest guidance,
otherwise no major changes this morning. -AM

&&

.AVIATION...
-- Changed Discussion --
20/18Z TAF Period

VFR conditions prevail this TAF period. Scattered showers and
thunderstorms will be around this afternoon and early evening, but
the probability for these to impact terminals is too low to warrant
a mention in TAFs (Aside from KLWT) at this time. Concerns for any
patchy fog tonight in areas that see precipitation this afternoon
will be mitigated by mid and upper level cloudiness tonight across
the region. Additional showers and thunderstorms will develop late
tomorrow morning into the afternoon, mainly across Central and North-
central Montana. -AM

Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.
-- End Changed Discussion --

&&

.PREV DISCUSSION...
/ISSUED 445 AM MDT Thu Jun 20 2024/

Today...With clear skies and calm winds, there may be some patchy
fog development this morning for portions of Central/North
Central MT where locations received rain yesterday evening. 500mb
height rises along with southwest flow aloft will continue to
bring warmer temperatures to the region. Lower elevations will
reach into the 70s this afternoon. Another small shortwave moving
through this afternoon will also produce some isolated
showers/storms across Central/North Central MT. Precipitation
looks to be light overall, with most places seeing 0.10" or less
of moisture (could see locally higher amounts if a heavier
shower/storm sets up).

Friday...Better forcing for precipitation arrives on Friday as a
compact shortwave trough moves through the region. Model guidance
shows some higher instability (1,000-1,500 J/kg of CAPE with
localized areas up to 2,000 J/kg of CAPE) and better shear(~40kts
of bulk shear) setting up to have the potential of a few strong
to severe storms during the afternoon (best chances along
Central/North Central MT). The primary threats will be hail and
strong wind gusts. The Storm Prediction Center has a "General
Thunderstorm" risk for Friday, however I can not rule out the
potential for an isolated supercell. We will continue to monitor
these chances for some stronger to severe storms with future
shifts. Best chances for precipitation looks to set up in
Central/North Central MT. Showers/storms can produce localized
areas of heavy rainfall, with model guidance targeting the Bear`s
Paw region for highest amounts of rain accumulations. There`s a
40-60% of Chouteau, Fergus, Hill, and Blaine counties receiving a
half inch or more of precipitation. For higher end amounts, the
75th percentile NBM has the Bear`s Paw region receiving up to
1-1.25" of precipitation if they get a heavier shower/storm.

Saturday and Beyond...Dry conditions return Saturday as upper
level ridging returns. Temperatures will go well above normal,
with lower elevations possibly reaching the 90s for the first
time this year on Sunday afternoon. Ensemble clusters indicate the
ridging to last for the first half of next week which will lead
to drier and warmer conditions. Ensemble clusters diverge by
Wednesday with the strength of amplitude of the ridge. This
suggests either the drier and warmer weather sticks around, or
cooler and wetter weather returns. -Wilson

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  75  50  75  49 /  20  20  60  20
CTB  72  45  72  44 /  20  10  70  20
HLN  79  53  83  52 /  20  20  40  10
BZN  75  47  80  49 /   0   0  30  10
WYS  71  40  74  41 /   0   0  20  10
DLN  73  45  81  47 /   0   0  10   0
HVR  76  51  75  50 /  20  20  90  50
LWT  72  47  72  48 /  30  20  80  40

&&

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

$$

http://www.weather.gov/greatfalls