492
FXUS65 KTFX 161500
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
900 AM MDT Fri Aug 16 2024

.SYNOPSIS...

A lingering disturbance will keep scattered showers and
thunderstorms over North Central Montana today, but fewer storms
expected over Southwest Montana. High pressure aloft will bring
warmer and drier conditions for Saturday, but a southwest flow
aloft will then bring chances for showers and thunderstorms each
day next week.

&&

.UPDATE...

Dense fog in the West Yellowstone area is beginning to diminish
and will clear up over the course of the next hour. Haze from
wildfires remains along the High-Line and in Fergus county this
morning and will affect those areas through the day today. Showers
and thunderstorms will affect most of North-central, Central, and
Southwestern Montana today.

For the update high temperatures across the plains of North-
central and Central Montana were increased to better match current
observations. Sky grids were adjusted to better match current
satellite imagery trends. Pops in Hill, Blaine, Choteau, and
Fergus Counties were increased this morning to better match
current radar trends. The rest of the forecast is on track. -IG

&&

.AVIATION...
16/12Z TAF Period

Scattered showers and perhaps a rumble of thunder or two will impact
the Hi-Line terminals through 16/18Z. Patchy dense fog will continue
over some southwest valleys including KWYS through 16/16Z. Smoke and
haze from regional wildfires may compromise diurnal slantwise
visibility for many locations, with some periods of MVFR or near
MVFR visibility restrictions for KHVR and KLWT. Another disturbance
advances northeastward into the region this afternoon and evening
for more scattered showers and thunderstorms and associated brief
downpours, gusty winds, and lightning. Once again some of this
activity will persist into the overnight hours tonight. Light winds
are generally expected outside of showers and thunderstorms. - RCG

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

&&

.PREV DISCUSSION...
/ISSUED 547 AM MDT Fri Aug 16 2024/

Key Points:

- Another round of scattered showers and thunderstorms this
  afternoon and evening, some with gusty winds and heavy
  downpours

- Near to slightly above normal temperatures for much of next week
  with chances of thunderstorms each day

Today through Saturday... The most immediate concern this morning
will be the potential for areas of fog and low clouds to form in
the valleys of Southwest and Central Montana, as well as on the
Rocky Mountain Front, where showers and thunderstorms persisted
until around midnight. Am not anticipating dense fog conditions at
this time, but will monitor the situation.

Otherwise, a slow-moving shortwave trough over North Central
Montana will continue scattered showers and thunderstorms there
into this evening; farther south, isolated showers and
thunderstorms are forecast to develop over Central and Southwest
Montana this afternoon. The scattered storms to the north will
have precipitable water values of 1 to 2 standard deviations above
normal, making brief heavy downpours a possibility with wind
gusts up to 40 mph. However, the storms to the south will not have
as much moisture to draw from, and downdraft instability values
are forecast to be a bit higher there, so there is less of a
potential for heavy downpours, but gusts could reach 50 mph at
times, similar to those on Thursday. Overall, though, wind shear
should be fairly weak, so severe storms are not expected.

Weak high pressure aloft is then forecast to move in overnight
and into Saturday, which should help dry out and warm up the
forecast area. Slightly below normal temperatures today should
warm to near seasonal averages on Saturday.

Sunday through next Friday... Ensemble model forecast clusters
tend to be in agreement in developing a fairly stagnant weather
pattern for much of this period. The axis of a strong high
pressure ridge will extend from the Southern Great Plains north
into Eastern Montana, which should keep temperatures generally 5
to 10 degrees warmer than normal. However, a deep low pressure
trough off the Pacific Coast will maintain an unstable
southwesterly flow aloft with a tap into Pacific and monsoonal
moisture, keeping at least a chance of showers and thunderstorms
for each day, with some storm potentially becoming strong. As of
the latest model runs, the highest chance for showers and storms
will be on Monday. Model blend guidance indicates a lowering of
temperatures a bit late next week, with the potential for the low
pressure to start pushing the ridge slightly east. -Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  82  53  85  55 /  40  20   0   0
CTB  75  47  81  52 /  70  30   0  10
HLN  82  54  88  57 /  50  20   0   0
BZN  83  47  88  54 /  30  30   0   0
WYS  72  38  80  44 /  10  10   0  20
DLN  77  46  83  52 /  30  20   0  10
HVR  85  55  87  59 /  40  60   0   0
LWT  81  49  84  56 /  50  30   0   0

&&

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

$$

http://www.weather.gov/greatfalls