Lewistown, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

960
FXUS65 KTFX 142036
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
236 PM MDT Wed May 14 2025

.KEY MESSAGES...

 - Precipitation gradually decreases in areal coverage through
   tonight across Southwest through North Central Montana;
   however, some areas will continue to see showers during the
   overnight hours.

 - Unsettled conditions persist through the remainder of the week,
   with showers and a few thunderstorms in most areas during the
   afternoon hours.

 - Although details remain murky, a more widespread precipitation
   event is looking likely late this weekend and into the upcoming
   work week across portions of the Northern Rockies.
 &&

.DISCUSSION...

 - Meteorological Overview:

Neutrally orientated H500 trough over the Western CONUS, with an
attendant closed low over Southwest Montana, will begin to lift
northeast and over the Upper Mississippi Valley through Thursday.
This will gradually lead to an areal reduction in precipitation
across Southwest through North Central Montana through the overnight
hours tonight; however, lingering showers will continue to persist
at times in northerly upslope areas and over the plains of Central
and North Central Montana as the upper level flow transitions to
northwesterly. By Thursday morning a surface cold front, which is
currently over Northern Alberta as of this (Wednesday) afternoon,
will push south and east across North Central and Central Montana
through Thursday morning; with this cold front providing additional
opportunities for showers and isolated thunderstorms through the day
on Thursday here. The heaviest precipitation associated with this
front will fall along the northern and eastern slopes of the Island
Ranges in Central Montana and Continental Divide in Central and
North Central Montana on Thursday given continued northwesterly flow
aloft. High temperatures in wake of the cold front on Thursday will
generally be 5 to 10 degrees cooler over the plains of Central and
North Central Montana, with the valleys of Southwest Montana
generally being 5 to 10 degrees warmer thanks to the fronts forward
progression being stalled until Thursday afternoon.

Northwest flow over the Northern Rockies will begin to back to the
west and become predominately zonal through Thursday night, with
zonal flow then expected to dominate over the region through
Saturday morning. This zonal flow combined with transient waves
rippling east will provide additional chances for precipitation,
especially to the Continental Divide and mountains of Southwest
Montana through the period. Temperatures moderate slightly to end
the work week, but remain below normal across all of Southwest
through North Central Montana.

By the weekend and through early next (work) week focus shifts to a
series of H500 shortwaves digging southeast from the Eastern Pacific
and Pacific Northwest towards the Great Basin, with these two
distinct shortwaves briefly phasing together, and partially
dumb-belling around one another, from Sunday and into Monday. This
developing longwave trough through the weekend and early next (work)
week over the Western CONUS will provide additional opportunities
for, potentially heavy, precipitation across Southwest through North
Central Montana. Additionally, below to well below normal
temperatures look to persist beneath this unsettled pattern. - Moldan

 - Forecast Confidence & Scenarios:

Precipitation from Sunday through Monday :

NBM probabilistic data continues to support between a 40-70% chance
for QPF amounts to reach or exceed 0.5" along and south of the
Montana Hwy 200 corridor across Central Montana, with generally a 10-
30% chance for amounts to exceed 1" south of this line and north of
the I-90 corridor in Southwest Montana. - Moldan

&&

.AVIATION...
14/18Z TAF Period

The main precipitation band across Central/North Central MT this
morning will move south this afternoon as the low pressure system
moves south. Steady rain will impact the Southwest MT terminals
(and KLWT). Across the North-Central MT plains(and later this
evening in Southwest MT), there will be scattered showers through
the rest of the TAF period. There will be a few lulls in
precipitation Thursday morning, but overall on and off showers
will be persistent through the TAF period. This will bring
periods of MVFR/IFR conditions. -Wilson

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  55  39  60 /  80  80  40  50
CTB  40  51  34  59 /  60  70  20  40
HLN  42  56  38  61 /  80  70  50  50
BZN  37  54  36  58 /  90  70  50  50
WYS  29  48  27  50 /  80  70  50  50
DLN  32  52  34  53 /  70  40  40  40
HVR  40  61  38  63 /  30  40  20  30
LWT  38  52  36  56 /  90  70  40  50

&&

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

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