Lewistown, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

336
FXUS65 KTFX 141129
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
529 AM MDT Sat Jun 14 2025

Aviation Section Updated.

.KEY MESSAGES...

- Daily rounds of widely scattered showers and thunderstorms
  continue through Tuesday, with a few of the strongest storms
  capable of localized strong, gusty winds, hail, and brief
  downpours.

- Drier conditions with continued seasonable temperatures move
  in for the second half of the workweek.

&&

.DISCUSSION...
/Issued 345 AM MDT Sat Jun 14 2025/

 - Meteorological Overview:

An unstable southwesterly flow aloft will continue to send waves
of lighter end showers and thunderstorms through Central/North-
central Montana through the morning hours. There looks to be
plenty of drier hours before diurnal heating initiates additional
activity later in the afternoon and evening. Storms today and
tonight will mostly be confined to areas east/southeast of a Havre
to Great Falls line. Judith Basin, Fergus, and eastern Meagher
counties will be most susceptible to the stronger storms where the
highest CAPE values in excess of 1,000 J/kg will reside. Once
again, showers and storms won`t automatically shut off with the
loss of diurnal heating and may even increase heading into the
overnight hours tonight.

More of the same is expected for Sunday, but a nicely timed
shortwave will increase bulk shear above 40 kts while CAPE
increases above 1,500 J/kg. This will serve to increase coverage
and intensity of storms with some westward expansion to include
most central/North- central and southwestern locations east of
I15. Additional rounds of showers and storms can be expected for
Monday and Tuesday with the continuation of the southwesterly flow
aloft, but there isn`t as much of a signal for stronger activity
at this time.

The shower and thunderstorm activity looks to slow down a bit for
the second half of the workweek with more of a westerly flow
aloft. There will still shortwaves that bring opportunities for
spotty precipitation and breezy to windy conditions, but there
will be less moisture availability. Most ensembles bring the
southwesterly flow back to the Northern Rockies by next weekend as
a large trough digs into the Pacific Northwest. The NBM catches
this nicely with increased coverage of showers and thunderstorms.
- RCG

 - Forecast Confidence & Scenarios:

Patchy fog development this morning...

Fog development has been far more isolated compared to 24 hours
ago; however, current satellite imagery does show low stratus/fog
moving westward out of northern Phillips County this morning.
there`s still a 30 to 50% chance for visibility reductions down to
a half mile or less in northern Hill and Blaine counties through
9 am, but higher clouds and showers approaching from the west may
impede optimal fog development. These areas will be monitored as
the morning progresses.

Daily rounds of showers and thunderstorms through Tuesday...

Southwesterly flow aloft will continue to provide a conveyor belt
of moisture and instability for showers and storms over the next
few days. Today`s activity will be shunted farther eastward than
yesterday, with the strongest storms expected over Judith Basin,
Fergus, and eastern Meagher counties later this afternoon and
evening. Storm activity is expected to persist, and may even
increase, heading into the overnight hours tonight. The passage of
a stronger shortwave and increased instability will bring
increased storm coverage on Sunday with westward expansion to
include most locations along and east of the interstate 15
corridor. Either day, the strongest storms will be capable of
producing localized strong, gusty winds, hail, and brief
downpours. - RCG

&&

.AVIATION...
14/12Z TAF Period

An unstable southwesterly flow aloft will send waves of widely
scattered showers and thunderstorms through the Northern Rockies
over the next 24 hours and beyond. This activity will be most
prevalent over Central and North-central Montana between 14/12
and 14/18Z and then east/southeast of a KGTF to KHVR line after
14/20Z. Low stratus and patchy fog along the Milk River Valley has
struggled to proceed westward towards KHVR this morning and
higher clouds advancing from the west should continue to impede
development. The mention of fog remains in the TAF, but the MVFR
visibility reduction has been taken out for now. - RCG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  79  53  80  52 /  30  20  50  40
CTB  76  45  77  46 /  20   0  20  20
HLN  82  55  83  55 /  30  20  50  30
BZN  84  49  83  49 /  30  20  40  40
WYS  76  37  79  39 /   0   0  20  10
DLN  81  45  79  47 /  10  10  30  10
HVR  80  53  83  52 /  40  20  40  50
LWT  75  51  76  50 /  60  60  70  70

&&

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

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