textproduct: Great Falls

KEY MESSAGES

- Warm and windy on Tuesday ahead of a cold front, which will bring scattered showers and thunderstorms Tuesday afternoon into Wednesday morning.

- Seasonable temperatures return for the end of the week, though shower and thunderstorm chances increase towards the weekend.

DISCUSSION

/Issued 1243 PM MDT Mon Jun 15 2026/

- Meteorological Overview:

Overall, tranquil conditions should persist across the area until this ridge begins to flatten later this evening as our next weather system approaches from the northwest. As this system approaches, a few showers and thunderstorms are likely to develop along the Hi- Line and gradually slide southward through the overnight hours, bringing some light rain before decaying around midnight or so.

Winds will be the main story on Tuesday as our system arrives into the area, bringing gusty winds to all of North Central and Southwestern Montana. While winds are expected to remain below our High Wind Warning criteria (58 mph gusts) for the most part, the winds will still be somewhat impactful as they will pose some difficulty for high profile vehicles and any fires that manage to get started could be somewhat difficult to contain. Winds should be a bit limited in duration, however, as a cold front coming in from the north should undercut the strongest winds by the evening hours, though thunderstorms along the front could help cause some localized stronger gusts.

Beyond Tuesday, our weather will remain slightly active as the jet stream remains overhead through Thursday, bringing a few afternoon showers and thunderstorms to the area each day. Our next chance for widespread precipitation will arrive Friday night and Saturday, with multiple upper level troughs and lows coming ashore the West Coast, bringing increased chances for showers and thunderstorms. Ludwig

- Forecast Confidence & Scenarios:

High wind potential on Tuesday...

H700 flow of 40-55kts, which is 2 to 3 standard deviations above normal per NAEFS analysis, will overspread Southwest through North Central Montana between 18z Tuesday and 06z Wednesday (in reality this window will likely be more compressed to a 3 to 6 hour timeframe like 21z Tue to 03z Wednesday) as an embedded shortwave within northwest flow aloft begins to dive southeast and over the Northern Rockies; with the core of strongest winds still expected to reside north of the I-90 corridor and south of the US Hwy 2 corridor. At the surface a cold front across Alberta will begin to surge south and across North Central by the late afternoon/early evening hours, with this front progressing south and across Central and Southwest Montana through the remainder of the evening and overnight hours. The exact timing of this front will be critical with respect to how long of an opportunity there will be for high winds on Tuesday across areas, with a faster/earlier front limiting the window for high winds while a slower/later front would support a 3-6 hour window. Given the time of year and limited amount of (prog'd) cool air in wake of the front a slower/later front is more likely vs a fast/earlier; however, residual cold pools from convection tonight would also be in play.

Latest NBM5.0 probabilities for wind gusts in excess of 50kts largely range from a 20-50% chance across most lower elevations across the aforementioned areas (between the I-90 and US Hwy 2 corridors), with the exception of the Rocky Mountain Front where probabilities range from a 60-75%. While these higher probabilities for the Rocky Mountain Front, specifically the Cut Bank and Mission Lake areas where High Wind criteria is 50kts vs further west where it is 65kts, would suggest the need for a High Wind Warning a deeper dive into BUFKIT soundings only supports a 1-2 hour window for these winds. Given the brevity for the threat of high winds here we will continue to hold off on any High Wind Watches or Warnings and address the winds with a Special Weather Statement with future shifts; however, should high winds develop earlier and persist longer than expected then a short lead time warning would be needed.

Strong thunderstorms Tuesday afternoon/evening...

Showers and thunderstorms are expected to develop along the southward advancing cold front on Tuesday, with ample shear and sufficient instability (especially within the hail growth zone) supporting the potential for a few strong thunderstorms along and northwest of a Lewistown, to Great Falls, to Browning line. Within this area latest HREF guidance support the best opportunity for an isolated severe thunderstorm across Hill, Blaine, and Fergus counties, most notably across Northern Blaine county. - Moldan

AVIATION

16/00Z TAF Period

VFR conditions will prevail through the period. West winds start to increase after 16/06Z along the Rocky Mountain Front and the western portion of the Northern Plains, after 16/12Z for the rest of North-Central and Central Montana, and after 16/16Z for Southwest Montana. The peak gusts are expected Tuesday afternoon into the evening with gusts in the 40-50kt range possible for KCTB, KGTF, and KEKS. Isolated higher gusts about 50kts are possible, especially at KCTB. The strongest winds are expected to start tapering off after 17/06Z although some lingering higher gusts are possible. LLWS may be a concern at times Tuesday morning before peak mixing occurs. -thor

PRELIMINARY POINT TEMPS/POPS

GTF 58 86 49 69 / 10 0 50 20 CTB 58 81 45 66 / 20 10 70 20 HLN 56 86 49 73 / 10 10 0 10 BZN 49 88 47 74 / 0 0 0 0 WYS 38 81 37 72 / 0 0 0 0 DLN 48 86 46 75 / 0 0 0 0 HVR 56 86 47 67 / 30 20 60 40 LWT 51 82 45 64 / 10 0 80 30

TFX WATCHES/WARNINGS/ADVISORIES

None.