textproduct: Great Falls

KEY MESSAGES

- There is a chance for scattered showers and thunderstorms through the evening hours across Southwest Montana.

- Cooler and wetter conditions return Monday and Tuesday with a chance for lower elevation rain and light mountain snow.

- Warmer temperatures return starting Wednesday and lasting through the rest of the week.

UPDATE

/Issued 509 PM MDT Sun May 3 2026/

Late afternoon update has been published, mainly to re-run diurnals to account for areas where high temperatures overachieved today. Otherwise the remainder of the forecast remains on track, with a backdoor cold front moving southwest from the late evening through the remainder of the overnight hours tonight. This front will bring the chance for lower elevation rain and mountain rain/snow to areas along and north of the US Hwy 12 corridor tonight; however, precipitation amounts will generally be light and less than 0.10". - Moldan

DISCUSSION

/Issued 509 PM MDT Sun May 3 2026/

- Meteorological Overview:

Dry northwesterly flow aloft will bring one more day of mild and generally dry condtions before a stronger trough and attendant cold front dive southward tonight into Monday. The primary concern will be dry and breezy conditions over the plains and isolated shower and thunder activity over southwest MT.

The cold front will cross the Canadian border this evening, clear much of central MT by dawn, and then move into the southwest Monday morning. Winds will shift northerly behind the front and showers and higher mountain snow will increase in a north to south fashion. Colder air aloft moves in on Monday and will support widely scattered rain, snow, and graupel showers at all elevations, especially over central/north-central MT. A secondary shortwave dives southward on Tuesday and drops H700/H500 temperatures as low as -15C/-30C over the eastern portions of the forecast area. This will reinforce the well below average temperatures and offer additional snow shower activity.

This system moves out by the mid-week period with northwesterly flow aloft returning for much of the remainder of the week. Overall, this will bring drier and milder conditions; however, weak troughs will periodically pass through and bring scattered shower and thunderstorm activity, especially on Thursday. Ensembles remain in agreement with a broader trough moving in next weekend for cooling temperatures and increased rain/mountain snow. Similar to some of the previous storms this spring, lesser defined and smaller scale forcing within this trough add forecast uncertainty in terms of precipitation amounts and timing. - RCG

- Forecast Confidence & Scenarios:

There is still a 20-30% chance for scattered thunderstorms across southwest Montana through the evening. Widespread moisture is not expected from these showers but there is a chance for some gusty winds and small hail (generally pea-sized) out of the stronger storms that develop.

With the approaching cold front, expect another round of scattered showers primarily across central and north-central Montana. Lower elevations will generally see rain during the day on Monday with a chance for mixed precipitation starting late Monday and lasting through Tuesday morning. Snowfall accumulations at lower elevations is generally expected to be minimal with less than half an inch possible at best. The main concern will be impacts to roadways which may become slushy and slippery at times, especially Tuesday morning.

Light mountain snow will be possible Monday through Tuesday with snowfall accumulations generally expected to remain less than an inch for pass level and below. Up to 2 inches is possible at the highest elevations but significant impacts outside of winter driving conditions along mountain passes are not expected.

Starting on Wednesday temperatures will quickly rebound back into the 60s to low 70s. This pattern of warmer temperatures is expected to persist through at least Friday as upper level ridging persists over the western CONUS. With northwesterly flow aloft there will be daily chances for isolated to scattered thunderstorms across the region. In general, the region will stay dry through the second half of the week except for localized areas of precipitation that hinge completely on where convective initiation occurs. There is a chance for more widespread precipitation this weekend as the next trough is expected to move through the region. But with the amount of model disagreement remaining there is not enough confidence to determine how widespread the precipitation will be at this time. -thor

AVIATION

04/00Z TAF Period

A cold front will move through central/north-central MT between 03/03 and 03/09Z before continuing southward into southwest MT Monday morning. Northerly winds gusting up to 40 kts at times will be the initial concern, followed by increased showers, scattered to broken MVFR/IFR clouds, and mountain obscuration. Scattered shower and isolated thunder activity will maintain periodic degraded flight categories during the second half of the TAF period. Winds will begin to decrease in a north to south fashion Monday afternoon, but will continue to gust up to around 40 kts over the narrow north to south oriented valleys of central and southwest MT. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 43 56 34 54 / 30 20 10 20 CTB 37 55 30 54 / 20 10 0 10 HLN 42 58 33 54 / 20 20 10 20 BZN 38 58 29 52 / 10 20 10 20 WYS 31 59 27 49 / 20 20 10 20 DLN 39 63 31 57 / 10 10 10 0 HVR 41 57 28 54 / 40 10 0 10 LWT 38 52 28 48 / 40 30 10 40

TFX WATCHES/WARNINGS/ADVISORIES

None.