textproduct: Great Falls

KEY MESSAGES

- Cold temperatures tonight, with a frost likely across Southwest Montana.

- Dry and seasonably warm conditions Monday will be followed by another period of unsettled and cooler weather Tuesday through Thursday.

DISCUSSION

/Issued 1243 PM MDT Sun Jun 7 2026/

- Meteorological Overview:

Partial clearing tonight and lighter winds across southwest MT will allow for efficient cooling and overnight low temps are likely to reach the lower 30s there and mid 30s to around 40 across the plains where breezy winds will persist tonight.

Monday will be mainly dry with temperatures returning to seasonal levels. An unseasonably strong upper level jet across the North Pacific sends a series of shortwaves into the NW US within a broad upper level trough that shifts across the Northern Rockies and MT Tuesday through Thursday. This will bring daily chances for showers and possibly some thunderstorms with temperatures again trending below seasonal averages. Hoenisch

- Forecast Confidence & Scenarios:

Cold Temperatures Tonight...

Breezy winds over the plains of Central and North Central Montana are likely to help keep the boundary layer coupled to prevent temperatures from falling too low tonight; however, there is a 30- 70% chance for temperatures to fall below 36 degrees (frost) along and southwest of a Lewistown, to Great Falls, to Shelby line. Additionally, there is a 5-15% chance that these areas could see temperatures fall below 32 degrees. Further south within the valleys of Southwest and Central Montana light winds throughout the night and partial clearing will allow temperatures to fall lower than over the plains. Here within the valleys there is generally a 30-80% chance for lows to fall below 32 degrees and non-zero (i.e. less than 5%) chance for lows to fall below 28 degrees with the exception of the Big Hole Valley and West Yellowstone Area where there is a 30- 90% chance of a hard freeze (i.e. 28 degrees or colder). Those with sensitive vegetation should take preventative measure to prevent damage.

Strong Winds on Wednesday...

Climate anomaly indicators are pointing towards a potential wind event during the middle of the upcoming work week, with ECMWF EFIs supporting a climatologically unusual to very unusual wind event. This is particularly true for areas along and north of the I-90 corridor where EFIs are in excess of 0.6, with values up to 0.75 along and west of the I-15 corridor and along the Montana Hwy 200/US Hwy 87 corridor in Central Montana. NBM 5.0 probabilities for areas north of the i-90 corridor have a 50% or greater chance for wind gusts in excess of 40 mph, with a 20-50% chance for wind gusts in excess of 50 mph across most locations. The exception for wind gusts in excess of 50 mph are along and west of the I-15 corridor over the plains and along the Montana Hwy 200/US Hwy 87 corridor in Central Montana where probabilities are between a 70-80%, with a 20-30% chance for gusts to exceed 60 mph in these areas. - Moldan

AVIATION

08/00Z TAF Period

Lingering shower activity diminishes and ends by around 08/03Z followed by partial taking place later in the evening and overnight hours. Gusty winds slowly decrease tonight, with seasonably breezy conditions returning on Monday. General VFR conditions prevail once the showers and clouds depart this evening, although there will be some patchy fog development over some wind protected valleys between 08/09 and 08/15Z. Left the mention of fog out of the TAFs for now, but will be monitoring the KBZN and KWYS. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 36 71 48 69 / 10 0 0 30 CTB 35 67 44 65 / 10 0 0 20 HLN 34 71 49 68 / 10 0 10 80 BZN 30 71 47 67 / 30 0 20 90 WYS 26 64 37 54 / 0 0 50 100 DLN 31 70 46 65 / 10 0 20 90 HVR 37 73 47 74 / 20 0 0 20 LWT 32 69 45 68 / 20 0 0 70

TFX WATCHES/WARNINGS/ADVISORIES

None.