445
FXUS65 KTFX 290539
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1145 PM MDT Fri Jun 28 2024

Aviation Section Updated

.SYNOPSIS...
Rain showers will continue across North-central and Central Montana
through this evening. Winds and wind gusts will gradually diminish
through the rest of this afternoon into the evening. Saturday will
be dry with about seasonal averages for temperatures. Sunday through
at least the middle of next week will have about seasonal averages
for temperatures with showers and thunderstorms each day.

&&

.UPDATE...
For the most part, the going forecast remains on track. The one
debate is whether or not fog will develop along portions of central
and north-central Montana tonight. The winds are light and air is
moist for places that received rainfall today. But the cloud cover
has been a bit iffy at times. When looking for clearing skies
overnight, the latest run of the NBM does clear things out sooner
than previous runs which increases confidence a little. But longer-
duration clearing is not expected with the next cloud bank arriving
approximately 2 hours later. So if fog is able to get set up and
settled in that small window, that would be the thing to watch. But
if conditions end up being a little off at the time the cloud
clearing occurs, it is likely fog may not develop at all.

Regarding impacts, the fog is not likely to be widespread and
unlikely to be dense except for isolated locations. Folks living
in coulees, river valleys, and other low-lying areas have the
greatest potential to see fog develop overnight. Otherwise, not
too much is expected in the way of impacts.

-thor

&&

.AVIATION...
29/06Z TAF Period

Generally VFR conditions are expected to prevail over the CWA
through the period. There are some slow clouds around Lewistown
currently, that should thin out by 08z. Also, there is a small
potential for fog early Saturday morning, but to low of a
probability to have it at a TAF site right now. The next chance for
thunderstorms generally develop after 06z Sunday over Central MT.
Brusda

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

&&

.PREV DISCUSSION...
/ISSUED 538 PM MDT Fri Jun 28 2024/

This afternoon through Saturday... This afternoon an upper-level
trough is over North-central, Central, and Southwestern Montana.
This will keep temperatures cool this afternoon. Isolated showers
will continue to affect North-central and Central Montana through
this evening. From a line east of Havre to Great Falls there is a 20
- 40% chance for a tenth of an inch of rain through midnight
tonight. The winds and wind gusts across North-central, Central, and
Southwestern Montana will gradually die down this afternoon and
evening. There is a High Wind Warning for the lower-elevations of
Fergus and Judith Basin until 6 pm tonight. However, it appears most
of the stronger wind gusts have moved out of the area and the High
Wind Warning has the potential (80% chance) to be cancelled
early. In areas of North-central and Central Montana where skies
clear patchy fog will likely (70%) form Saturday morning due to
the recent moisture and high dewpoints/relative humidity. However,
there is low confidence that the skies will clear overnight and
allow fog to form. On Saturday an upper-level ridge moves over
North-central, Central, and Southwestern Montana which will dry
out the area and warm temperatures back up to about seasonal
averages.

Sunday through Tuesday... The upper-level ridge remains in place
over North-central, Central, and Southwestern Montana until about
midday when an upper-level trough begins to move over the area. The
upper-level trough is associated with a weak surface cold front.
This will produce an environment conducive for severe weather. On
Sunday the Storm Prediction Center (SPC) has from Havre to Great
Falls to Beaverhead County south and east in a Marginal Risk for
severe weather (5% chance of severe wind and/or hail within 25 miles
of a point). This will need to continue to be monitored for details.
On Sunday locations across Southwestern Montana have 25 -50% chance
for receiving a tenth of an inch of rain or greater. On Sunday North-
central and Central Montana have a 15 - 40% chance for receiving a
tenth of an inch of rain or greater. Temperatures will be at about
seasonal averages on Sunday. On Monday the upper-level trough will
remain over North-central, Central, and Southwestern Montana. A weak
upper-level disturbance will move through the upper-level flow. This
will bring showers and thunderstorms to North-central, Central, and
Southwestern Montana. The thunderstorms at this time have a low
chance of being severe. On Monday locations across Southwestern
Montana have a 40 - 80% chance for receiving a tenth of an inch of
rain or greater. On Monday across North-central and Central Montana
there is a 20 - 50% chance for receiving a tenth of an inch of rain
or greater. Temperatures across North-central, Central, and
Southwestern Montana will stay about the same as Sunday.

Tuesday through next Friday... On Tuesday the upper-level trough
remains over North-central, Central, and Southwestern Montana until
Tuesday late evening when it transitions to move zonal flow. A
surface cold front will move through Southwestern Montana on Tuesday
and bring thunderstorms to the area. For North-central and Central
Montana the trough will bring showers and possibly a rumble of
thunder or two. Temperatures across North-central and Central
Montana will remain about the same as on Monday. On Wednesday two of
the clusters (70% of ensemble members) have an upper-level trough
over North-central, Central, and Southwestern Montana. The other two
clusters (30% of ensemble members) have an upper-level ridge over
the area. On Thursday one of the clusters (11% of ensemble members)
has an upper-level ridge over North-central, Central, and
Southwestern Montana. The other three clusters (89% of ensemble
members) have an upper-level trough over the area. On Friday one
of the clusters (25% of ensemble members) has an upper-level ridge
over North-central, Central, and Southwestern Montana. The other
three clusters (75% of ensemble members) have an upper-level
trough over the area. This indicates that cool, showery, and
stormy weather could continue for Southwestern, Central, and
North-central Montana or it could warm up and dry out across the
area for Wednesday through next Friday. -IG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  41  75  52  77 /  10   0  10  40
CTB  41  70  50  74 /  10   0  10  40
HLN  46  83  56  82 /  10  10  10  50
BZN  41  79  50  81 /   0   0   0  50
WYS  35  77  44  78 /   0   0  10  30
DLN  39  81  49  80 /   0  10   0  50
HVR  41  74  53  80 /  10   0   0  30
LWT  37  71  47  76 /  20   0  10  40

&&

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

&&

$$

http://www.weather.gov/greatfalls