Lewistown, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

194
FXUS65 KTFX 152345
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
545 PM MDT Thu May 15 2025

Aviation Section Updated.

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms continue this
  afternoon and evening.

- Daily chances for rain showers/higher elevation snow continues
  into mid next week.

- Widespread rain and mountain snow Sunday and Monday.

&&

.DISCUSSION...
/Issued 241 PM MDT Thu May 15 2025/

 - Meteorological Overview:

An active weather pattern continues through the forecast period. For
the rest of today, northwest flow aloft will continue to bring
scattered showers across the region today. Weak instability in the
area will produce isolated, brief thunderstorms this afternoon.
Friday is looking to play out the same, with scattered showers and
isolated thunderstorms. For Saturday, we begin to transition to
southwest flow aloft with an upper level trough starting to move
across the Western CONUS. This will bring another round of
isolated to scattered showers and isolated thunderstorms to the
region.

As the trough axis moves farther east and begins to occlude
Sunday, better moisture will move in. A pacific system will bring
widespread rain to the region Sunday and Monday. There still
remains uncertainty where the main axis of moisture/precipitation
will set up, but where it sets up will bring good wetting rain to
the area. After Monday, zonal flow aloft will bring slight chances
for precipitation for the middle of next week, but currently
precipitation doesn`t look to be as robust as this next system.

 - Forecast Confidence & Scenarios:

This Weekend`s System:

There is still a bit uncertainty in where the main precipitation
axis will be. Within the past 24 hours, there has been an
increasing signal for a northern shift for the higher amounts of
precipitation. Some of the newer model guidance suggest the Fergus
and Judith County/Little Belts corridor get the bulk of
. However, there still is a slight chance for a more southern
track across the Southwest Montana. There`s currently a 50% chance
for 1" of precipitation extending from the Big Belts to the
Little Belts and Lewistown area. If the axis of precipitation sets
up more towards the Central/North-Central plains then that will
reduce flooding concerns with most rivers running at a lower bank
flow (the exception will be Belt Creek, as they are running higher
currently). If things shift towards the Southwest, that can
increase the potential for river flooding with higher bank flow
there currently. Though, another thing to monitor there as well
would be snow levels. If snow levels remain towards pass level,
then the risk of flooding will remain low.

That`s where the next uncertainty lies with this system: snow
levels. Current forecasted snow levels are between 6,000-7,000ft
Sunday night through Monday morning. Some ensemble members show
snow levels dropping lower towards the lower elevations like the
the Helena/Bozeman Valley and Lewistown area. Although this is a
low chance of happening at this time, it`s something to monitor as
it increase the impacts of this system. -Wilson

&&

.AVIATION...
16/00Z TAF Period

A few -SHRA and -TSRA continue to track across portions of North
Central and Southwestern Montana this evening, particularly along
lines extending from KHVR to KLWT and KHLN to KBZN, with
additional activity south and west of the KHLN/KBZN line. Expect
these showers and storms to continue to move in a southwestward
motion, more or less training along the lines in their position as
of 0z for the most part before dying out around 6z. After an
overnight with MVFR ceilings for the most part with a few embedded
IFR ceilings, a few showers will develop once again on Friday,
mainly across SW MT, with a few across the plains as well. Ludwig

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  39  61  40 / 100  40  50  50
CTB  51  33  59  37 /  70  10  50  40
HLN  55  40  62  41 /  80  40  60  40
BZN  54  36  59  39 /  70  30  50  70
WYS  50  28  52  31 /  80  60  70  80
DLN  53  35  54  37 /  50  30  60  40
HVR  60  40  64  41 /  40  30  30  50
LWT  50  36  57  38 /  80  40  60  60

&&

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

$$
http://www.weather.gov/greatfalls