textproduct: Great Falls

KEY MESSAGES

- Near to slightly above normal temperatures through the work week, with the warmest day occurring on Tuesday.

- Gusty winds on Wednesday and Thursday, especially along the Rocky Mountain Front and in the north-south orientated valleys of Southwest Montana.

- Shower and thunderstorm chances return on Tuesday and Wednesday.

DISCUSSION

/Issued 1204 AM MDT Mon Aug 31 2026/

- Meteorological Overview:

As the upper level trough moves northeast out of the state, upper level ridging begins to build to the west. This building ridge of high pressure will allow for temperatures to warm back up, with highs today in the mid 70s to mid 80s. On Tuesday, the ridge will begin to propagate eastward with a negative tilt, creating southwesterly flow aloft. Embedded shortwaves within this flow will create enough instability for the development of afternoon/evening thunderstorms, mainly in Southwest MT. Increased moisture aloft will result in chances for some showers in the afternoon/evening hours in Southwest MT as well.

On Wednesday, the upper level ridge exits the region, and an upper level trough swing northeastward from Northern California into the Northern Rockies. This will allow for shower and thunderstorm chances to become more widespread, as well as strong southwesterly winds to form. On Thursday, this smaller upper level trough will give way to a much larger upper level trough forming over the Olympic Peninsula, allowing once again for widespread shower and thunderstorm chances and strong southwesterly winds.

Looking into Friday and beyond, conditions will depend of what this larger upper level trough does. There remains inconsistency in what the models are predicting for the path of this trough, as outlined in the Forecast Confidence and Scenarios section below. -Dzomba

Forecast Confidence and Scenarios:

Winds Wednesday and Thursday: as a series of upper level troughs embedded in persistent upper level southwesterly flow moves overhead, winds will increase, primarily across Southwestern Montana Wednesday and Thursday. While the wind increase looks likely, the magnitude, extent, and duration of the winds are likely to be quite sensitive to the exact track of these disturbances. As of Sunday, the NBM probabilities seem to indicate that there are roughly similar probabilities for wind gusts over 45 mph, with chances around 50% generally confined to some of the North/South oriented valleys of Southwestern Montana near and south of Interstate 15.

Next Weekend: There are a few ways next weekend could pan out, largely driven by how strong an upper level trough gets over the west coast and whether or not it cuts off from the flow and becomes a closed upper level low. There does seem to be a little more support for the latter scenario (around 75% of the ensemble members), but its strength and location will play a large role in the details of our weather, and models seem to be in quite a bit of disagreement with these particulars. Should the low/trough wind up staying offshore, next weekend is likely to be a bit on the warmer side of the forecast, with upper level ridging building in overhead. However, a more eastward placement of this low/trough, which is around 60% of the ensemble members would result in a cooler, more unsettled result for next weekends weather. Ludwig

AVIATION

31/12Z TAF Period

VFR conditions will prevail throughout the duration of the 3112/0112 TAF period, with mountain obscuration along the Continental Divide improving through 15-18z today.

For KGTF: Winds will remain predominately out of the southwest through 21z Monday, with the probability for crosswinds being exceeded below a 5% chance. Beyond 21z Monday winds will become light and variable. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 78 48 84 55 / 0 0 0 20 CTB 75 45 81 50 / 0 0 0 0 HLN 79 47 84 52 / 0 0 0 60 BZN 77 45 80 48 / 0 0 0 70 WYS 71 35 70 36 / 0 20 50 70 DLN 80 44 81 44 / 0 0 0 80 HVR 77 46 87 54 / 0 0 0 0 LWT 74 46 82 52 / 0 0 0 10

TFX WATCHES/WARNINGS/ADVISORIES

None.