323
FXUS65 KTFX 170534
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1134 PM MDT Fri Aug 16 2024

UPDATED AVIATION SECTION

.SYNOPSIS...

There will be isolated showers and thunderstorms across North-
central, Central, and Southwestern Montana today. Sunday through at
least the middle of next week there will be isolated showers and
thunderstorms. Saturday it begins to warm up and it will be hot for
Sunday through at least the middle of next week.

&&

.UPDATE...

Given the showers that have moved through the area and clearing
skies expected overnight, there is an increased chance for fog
development along the hi-line tonight. Widespread dense fog is not
expected but patchy fog is possible along river valleys and
coulees.

Otherwise no major changes were made to the going forecast. -thor

&&

.AVIATION...
17/06Z TAF Period

VFR conditions are mostly expected to continue through at least
18/06Z across North Central (KCTB, KHVR), Central (KLWT, KGTF,
KHLN), and Southwest (KBZN, KEKS, KWYS) Montana, unless otherwise
mentioned.

A disturbance exiting the area in a southwest flow aloft may still
bring a few showers and thunderstorms to the eastern TFX plains
areas through 08Z, including KLWT, where brief periods of MVFR
conditions and erratic wind gusts to 40 kt are possible. Otherwise,
weak high pressure aloft should bring clearing and light winds to
the area through the remainder of the period. However, this may
allow at least patchy fog to form between 09Z and 15Z in low-lying
areas and areas that received precipitation late this afternoon or
this evening. Have mentioned the potential for MVFR/IFR conditions
at terminals that received measurable precipitation. -Coulston

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

&&

.PREV DISCUSSION...
/ISSUED 137 PM MDT Fri Aug 16 2024/

This afternoon through Sunday... This afternoon an upper-level ridge
is over North-central, Central, and Southwestern Montana. However,
an upper-level shortwave moving through the upper-level flow has
brought and will bring showers and thunderstorms to the area.
This afternoon through tonight in North-central and Central
Montana there is a 10 - 40% chance for a tenth of an inch of rain
or greater. This afternoon through tonight along the Rocky
Mountain Front and adjacent plains there is a 40% chance for a
quarter inch of rain or greater. This afternoon in Northern
Beaverhead, Gallatin, and Madison Counties there will be isolated
showers and thunderstorms. The thunderstorms will produce frequent
lightning, gusty erratic winds, and brief heavy downpours(only in
North-central Montana). Saturday morning in isolated locations
that receive rain this afternoon/evening and where there are clear
skies patchy fog will form. On Saturday the upper-level ridge
remains over North-central, Central, and Southwestern Montana. On
Saturday temperatures warm up to about seasonal averages. On
Saturday it will be dry across North-central, Central, and
Southwestern Montana. 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 isolated showers and thunderstorms to the area. On Sunday
temperatures will warm up to above seasonal averages. On Sunday
there is 50 - 90% chance for the lower-elevations of North-
central, Central, and Southwestern Montana north of I-90 having a
high temperature of 90 degrees or greater. On Sunday there is a
10% chance for greater than a tenth of an inch of rain across
North-central, Central, and Southwestern Montana.

Monday through next Friday... On Monday the upper-level ridge
remains over North-central, Central, and Southwestern Montana.
This will keep hot temperatures across the area. However, an
upper-level shortwave moves through the upper-level flow and will
bring isolated showers and thunderstorms to North-central,
Central, and Southwestern Montana. On Monday there is a 10 - 30%
chance for greater than a tenth of an inch of rain across North-
central, Central, and Southwestern Montana. On Tuesday the upper-
level ridge remains over North-central, Central, and Southwestern
Montana. This will keep hot temperatures across the area. However,
an upper-level shortwave moves through the upper-level flow and
will bring isolated showers and thunderstorms to North-central,
Central, and Southwestern Montana. On Wednesday two clusters (48%
of ensemble members) show the upper-level ridge remaining over
North-central, Central, and Southwestern Montana. The other two
clusters (52% of ensemble members) show an upper-level trough
moving over the area. This indicates that the weather pattern has
a 50% to change or remain the same as on Tuesday across North-
central, Central, and Southwestern Montana. On Thursday continuing
through next Friday clusters, ensembles, and deterministic models
begin to diverge. One scenario is for an upper-level ridge to stay
over North-central, Central, and Southwestern Montana. Another
scenario is for an upper- level trough to move over the area. A
third scenario is for the upper- level flow to be zonal (west to
east). This will continue to be monitored for details. -IG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  53  87  56  90 /  20   0   0  10
CTB  47  82  52  86 /  30   0  10  10
HLN  54  89  58  94 /  30   0   0  10
BZN  47  88  55  93 /  50   0   0  10
WYS  38  80  45  79 /  10   0  20  20
DLN  46  83  52  85 /  20   0   0  10
HVR  55  88  58  96 /  60   0   0   0
LWT  50  85  56  91 /  40   0   0  20

&&

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

$$

http://www.weather.gov/greatfalls