025
FXUS65 KTFX 300232
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
832 PM MDT Sat Jun 29 2024


.SYNOPSIS...

Scattered showers and thunderstorms are expected tomorrow, with a
few being on the strong side in the afternoon and evening.
Unsettled weather conditions then persist for much of the upcoming
week.


&&

.UPDATE...

Aside from some virga and isolated lighter end shower activity
along the Continental Divide and Southwest Montana, mostly dry
condtions are expected for tonight. Southwesterly flow aloft
becomes more established overnight tonight into Sunday morning for
increasing mid- and higher level clouds, with an initial wave of
isolated, lighter shower activity expected to move into Central
and North-Central Montana Sunday morning. More impactful showers
and thunderstorms arrive during the afternoon and evening hours,
with the stronger cells potentially producing gusty, erratic
winds, hail, and brief downpours in addition to lightning. The
best chance for stronger storms will mostly be for locations along
and south and east of a KHLN to KHVR line. - RCG

&&

.AVIATION...
30/00Z TAF Period

Diurnal heating will support cloud builds and perhaps even a few
light showers over the higher terrain along the Continental Divide
and Southwest Montana through 30/03Z. Otherwise, Diffluent
southwesterly flow aloft becomes more established tonight into Sunday
morning for increasing mid- and higher level clouds, with an initial
wave of isolated, lighter end shower activity and lower VFR clouds
moving into Central and North-Central Montana after 30/12Z. The more
impactful shower and thunderstorm activity arrives during the
afternoon and evening hours. The stronger cells will contain gusty,
erratic winds, hail, and brief downpours in addition to lightning,
mostly for locations south and east of a KHLN to KHVR line. - RCG

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

&&

.PREV DISCUSSION...
/ISSUED 117 PM MDT Sat Jun 29 2024/

Key Points Continued:

-Dry and comfortable temperatures today and tonight.

-Showers and thunderstorms expected during the afternoons the first
half of next week

-Temperatures will be below average through midweek, with a warming
trend for the end of the week

Rest of today through tomorrow night... Upper level ridging
continues today for our area with sunny skies and comfortable
surface temperatures in the 60s and 70s. A few passing high level
cirrus clouds continues across North Central Montana, but otherwise
a dry evening is in store and quiet weather conditions continue
tonight into tomorrow morning. Overnight lows are forecasted to be
in the 40s and 50s across North Central and Southwest Montana.

For tomorrow, upper level troughing from the Pacific Northwest is
still on track to move into our area tomorrow morning. The first
impacts of this quick shortwave trough is going to bring scattered
rain showers to Glacier, Toole, and western Pondera counties that is
forecasted to move northward across these counties through the early
afternoon hours. The second impact is an associated surface cold
front to move through, helping initiate a few stronger thunderstorms
to occur tomorrow afternoon across Southwest Montana into southern
Cascade, Judith Basin, and Fergus counties. The primary location to
watch for stronger thunderstorms tomorrow afternoon into the evening
is between Geyser and Lewistown. This is because the current high
resolution model guidance is in favor for thunderstorms to move
through here between 5 PM and 7 PM (could be early or later
depending on how fast the front moves through) and has some
favorable environmental ingredients needed for severe criteria to
occur. Such as CAPE values between 1000 and 2000 J/kg (we need
this range of cape to help kick off thunderstorm development and
become stronger), 0-3 km and 700-500 mb lapse rates are between 8
and 8.5 degrees C/km and significant hail parameter is between 1
and 1.5. These values all indicate to us that a few storms could
become stronger with hail sizes reaching warning criteria. The
primary hazard is going to be hail size between 1 and 1.5 inches
with stronger thunderstorms. Otherwise, lightning and heavy rain
can occur tomorrow with thunderstorms and accumulating small sized
hail. Have multiple ways to receive warnings tomorrow if severe
thunderstorms do develop, and remember when thunder roars, head
indoors! Scattered thunderstorms across Southwest Montana into
Central Montana could continue through the overnight hours, but
high resolution model guidances aren`t fully agreeing with each
other on end timing of thunderstorms, so continue to monitor the
latest forecasts and primary concerns would be lightning through
the overnight hours.

Quick Forecaster Note: It has been a great opportunity and rewarding
experience to serve the communities and our partners of North
Central and Southwest Montana over the last two years. I want to
thank the TFX team for their commitment to our mission and for their
guidance on forecasting for North Central and Southwest Montana. As
I head forward and onward in my career, I`ll always value the
conversations I`ve had with partners, spotters, and members of the
public to accomplish our goals and provide valuable weather
information. Thank you. Sincerely, Rosemary Webb.

Extended (Monday through next Saturday)... The first half of the
work week will be strongly influenced by a broad upper level trough
across the Northwestern US, which will keep North Central and
Southwestern Montana on the unsettled side with temperatures near to
slightly below seasonal norms. Expect highs to generally be in the
70s through the first half of the week with more or less daily
development of a few showers and thundershowers across the area,
particularly over the higher terrain of Southwestern Montana.

As we move towards the second half of the week, models are in
extremely good agreement (~90%) that upper level ridging will begin
to make its return to the Western US, which will result in us drying
out and rapidly warming up as warmth quickly builds across the
Western CONUS. With this ridging quickly building, expect
temperatures to begin to knock on the 90 degree mark as we head into
the weekend, with warmth likely to continue into the following week.
Ludwig

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  52  78  53  76 /   0  40  30  30
CTB  50  73  50  72 /  10  50  10  50
HLN  55  84  55  81 /  10  50  40  40
BZN  49  83  50  76 /   0  60  80  60
WYS  42  79  45  65 /   0  30  60  80
DLN  49  81  48  73 /  10  50  40  60
HVR  52  84  55  78 /   0  20  30  40
LWT  47  80  50  73 /   0  40  60  30

&&

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

$$

http://www.weather.gov/greatfalls