666
FXUS65 KTFX 150159
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
759 PM MDT Wed Aug 14 2024

.SYNOPSIS...

Showers and thunderstorms will continue across North-central,
Central, and Southwestern Montana through Friday with the greatest
coverage and precipitation amounts on Friday. Thursday morning
the West Yellowstone area will see patchy fog. Sunday through the
middle of next week it will be about seasonal averages for high
temperatures with isolated showers and thunderstorms Monday
through Wednesday.

&&

.UPDATE...

Showers and thunderstorms are slowly waning across the region
with loss of daytime heating. Radar imagery shows a few outflow
boundaries across North-central Montana, which will maintain
chances for showers and thunderstorms over the next few hours
across portions of the plains. Otherwise, activity across much of
Central and Southwest Montana has either fully dissipated or is
weakening significantly.

Looking toward the rest of the night, a brief, weak period of
upper level ridging will build in. This will promote mostly, if
not entirely clear skies across most areas tonight. Given a few
areas saw heavy rain today, the clearing skies will raise concerns
for fog, especially in elevated valleys such as the West
Yellowstone area.

Minor tweaks were made to the forecast to account for latest
trends, otherwise no significant update was needed this evening.
-AM

&&

.AVIATION...
15/00Z TAF Period

The initial concern this TAF period will be for lingering showers
and thunderstorms, primarily in and near terrain through sunset.
Clearing skies will lend to opportunities for fog overnight where
precipitation fell today, most notably at KWYS. Given heavy rain has
fallen here, clear skies forecast tonight, and the tendency for KWYS
to fog up the morning after rain, I went ahead and prevailed 1/4SM
late tonight through mid-morning tomorrow. Otherwise the next
concerns will be for additional afternoon and evening showers and
thunderstorms tomorrow afternoon, along with a bit of wildfire smoke
near the Canadian border (KCTB and KHVR). Mention of both of these
was largely omitted at this time due to lack of confidence in
impacts directly at terminals. -AM

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PREV DISCUSSION...
/ISSUED 529 PM MDT Wed Aug 14 2024/

This afternoon through Thursday... This afternoon an upper-level
trough is over North-central, Central, and Southwestern Montana.
This will allow for isolated showers and thunderstorms in the
afternoon and evening across the area. Due to the cold front that
moved through yesterday temperatures will be 5 to 10 degrees below
seasonal averages across the lower-elevation`s of North-central,
Central, and Southwestern Montana this afternoon. This afternoon
locations across southern Beaverhead, Madison, and Gallatin Counties
have a 40 - 70% chance for receiving a tenth of an inch of rain or
greater. North-central and Central Montana have 15 - 40% chance for
a tenth of an inch of rain. This afternoon and evening isolated
thunderstorms in the West Yellowstone area will produce strong to
severe wind gusts. Due to the rain this afternoon and evening and
clearing skies tonight, Thursday morning patchy fog is likely
(60% chance) in the West Yellowstone area. On Thursday an upper-
level ridge moves back over North-central, Central, and
Southwestern Montana. However, an upper-level shortwave moves
through the upper-level flow and will bring showers and
thunderstorms to the area. On Thursday Southwestern Montana has a
30 - 60% chance for a tenth of an inch of rain or greater.
Thursday along the Rocky Mountain Front and adjacent plains there
is 20 - 50% chance for a tenth of an inch of rain or greater.

Friday through Sunday... On Friday the upper-level ridge remains
over North-central, Central, and Southwestern Montana. However, an
upper-level shortwave moves through the upper-level flow and will
bring showers and thunderstorms to the area. On Friday there is a
25 - 40% chance for a quarter inch of rain or greater. On Friday
along the Rocky Mountain Front and adjacent plains there is a 50 -
75% chance for a quarter inch of rain or greater. On Saturday the
upper-level ridge remains over North-central, Central, and
Southwestern Montana. However, an upper-level shortwave moves
through the upper-level flow and will bring very isolated showers
and thunderstorms to the area. On Sunday the upper-level ridge
remains over North-central, Central, and Southwestern Montana.
However, an upper-level shortwave moves through the upper-level
flow and will bring very isolated showers and thunderstorms to the
area. On Saturday and Sunday it will warm back up to about
seasonal averages.

Monday through Next Wednesday... On Monday and Tuesday clusters show
that an upper-level ridge remains over North-central, Central, and
Southwestern Montana. This will keep warm and mostly dry conditions
across the area on Monday and Tuesday (isolated showers and
thunderstorms will occur). On Wednesday two of the clusters (67% of
ensemble members) keep the upper-level ridge over North-central,
Central, and Southwestern Montana. On Wednesday one cluster (29% of
ensemble members) has a trough moving over the area. On Wednesday
the other cluster (4% of ensemble members) has a strong ridge
beginning to move over North-central, Central, and Southwestern
Montana with northwest flow aloft. This indicates that isolated
showers and thunderstorms are likely to continue across the area
on Wednesday. -IG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  85  57  81 /   0  10  50  60
CTB  52  83  54  75 /  20  20  60  80
HLN  54  87  56  83 /  20  20  60  50
BZN  48  86  49  83 /  20  20  50  30
WYS  36  76  38  73 /  30  20  60  20
DLN  46  80  46  79 /  20  40  50  20
HVR  58  89  60  85 /   0  10  20  60
LWT  51  82  55  80 /  20  10  30  70

&&

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

$$

http://www.weather.gov/greatfalls