textproduct: Great Falls

KEY MESSAGES

- Strong and gusty winds continue today, especially along the Rocky Mountain Front.

- Below normal temperatures through Tuesday, especially over the weekend and Monday when highs will struggle to rise into the 40s and 50s.

- Mountain snow and lower elevation rain and snow mix this weekend.

UPDATE

/Issued 417 AM MDT Fri May 15 2026/

Early morning update has been published, with the primary adjustment being to raise PoPs along the Continental Divide and spread low chance PoPs further east over the adjacent plains of Central and North Central Montana.. Otherwise the remainder of the forecast remains on track, with strong and gusty west winds expected across the Northern Rockies today. - Moldan

DISCUSSION

/Issued 417 AM MDT Fri May 15 2026/

- Meteorological Overview:

Montana will be under zonal flow today, keeping temperatures seasonable and conditions dry. Breezy conditions will continue, but will dissipate towards the evening. The gusty winds may create areas of blowing dust, reducing visibilities at times. On Saturday, an upper level trough begins to move over the Northern Rockies from the west, along with a surface cold front. This combination will bring increased chances of precipitation and cooler temperatures. The trough deepens over the Great Basin on Sunday, resulting in well- below seasonal average temperatures across North-central, Central, and Southwestern Montana. Increased moisture aloft with the trough will bring chances of precipitation on Saturday, becoming widespread across the area on Sunday. The precipitation will primarily take the form of snow in the mountains, while the cooler temperatures will result in a rain/snow mix at the lower elevations. There is enough instability on Sunday afternoon that a rumble of thunder may be heard, mainly over Southwestern Montana.

On Monday, the trough deepens eastward through the Four Corners of the Southwestern U.S., keeping North-central, Central and Southwestern Montana under its influence. This will cause precipitation chances to linger and well-below seasonal average temperatures to continue. A rumble of thunder may also be heard Monday afternoon, once again mainly in Southwestern Montana. By the middle of next week an upper level ridge begins to build in from the west, allowing temperatures to warm with mostly dry weather. -IG and Dzomba

- Forecast Confidence & Scenarios:

On Saturday there is a 10 - 20% chance for thunder across Southwestern Montana. On Sunday these chances become more widespread, with there being a 10 - 20% chance for thunder across most of North-central, Central, and Southwestern Montana, with the higher chances being in southwestern Montana.

Sunday through Monday there is a 10 - 50% chance for greater than a tenth of an inch of snow across the lower-elevations of North- central, Central, and Southwestern Montana. Across the mountains of North-central, Central, and Southwestern Montana there is a 50 - 80% chance for 4 inches of snow or greater. One area of uncertainty with this snowfall is when it falls will have drastic differences on impacts. If snow falls during daylight hours there will be minimal impacts. However, if snowfall falls overnight this has the potential to be more impactful. Another area of uncertainty with the precipitation types of this system is when the cold air moves in, as this will determine when precipitation transitions from rain to snow at at the lower-elevations.

Sunday morning across the lower-elevations of Southwestern Montana there is greater than a 40% chance for low temperatures of 28 degrees or colder. On Sunday, there is a 50 -70% chance for high temperatures of 45 degrees or colder across most of the lower- elevations of North-central, Central, and Southwestern Montana. Monday morning there is a 30 - 50% chance for low temperatures of 28 degrees or colder across the lower-elevations of North-central, Central, and Southwestern Montana. -IG and Dzomba

AVIATION

15/12Z TAF Period

Despite mid- to upper level cloudiness moving over the Northern Rockies VFR conditions are expected to prevail through the 1512/1612 TAF period; however, mountain obscuration will occur through 18-21z this afternoon, especially for peaks above 9kft. Otherwise strong and gusty west winds will be experienced with frequent gusts up to 35 kts across most terminals, with gusts even approaching 45 kts at the KCTB terminal through 21-24z this afternoon. Mountain wave turbulence will remain a concern across the Northern Rockies through 03-09z Saturday before mid-level wind gradually decrease. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 62 41 57 34 / 0 10 30 60 CTB 57 34 55 29 / 10 10 10 50 HLN 63 39 55 34 / 0 10 60 50 BZN 65 37 59 29 / 10 10 70 100 WYS 63 31 56 26 / 0 0 10 50 DLN 65 38 58 28 / 0 10 30 70 HVR 65 39 63 33 / 20 0 20 60 LWT 61 38 56 30 / 10 10 80 90

TFX WATCHES/WARNINGS/ADVISORIES