textproduct: Great Falls

KEY MESSAGES

- The remainder of this weekend will be warm and mostly dry.

- Chances for showers and thunderstorms increase Monday and continue through the week.

- It will be warm today through Tuesday, with temperatures decreasing Wednesday and Thursday.

DISCUSSION

/Issued 114 PM MDT Sat May 23 2026/

- Meteorological Overview:

Zonal flow aloft continues today over Montana, allowing for warm temperatures and mostly dry weather. A weak disturbance moves in from the west along the flow, providing enough forcing for isolated light showers across the region this afternoon into the evening. Tomorrow will see weak ridging building aloft, causing temperatures to continue to warm and precipitation chances to decrease. However, there is a weak shortwave embedded in the ridging which will allow for low chances for weak and isolated showers to persist tomorrow afternoon.

The ridging is short lived as it is quickly forced eastward due to a large upper level trough moving inward from the west coast. This trough will cause a shift to unstable southwesterly flow aloft. Warm air advection from the southwesterly flow aloft will bring the warmest temperatures of the week, with highs in the 80s and low 90s across the region. Increased instability and warm air will result in isolated showers and thunderstorms in the evening. On Tuesday, the upper level trough deepens into the Great Basin and becomes a closed low, causing a more steep southerly flow. This, combined with an approaching Pacific cold front, will create more instability, and allow for widespread showers and thunderstorms to form in the afternoon/evening across Southwestern, Central and North-Central Montana. Some of these storms could be stronger in nature. The Pacific cold front will move through the region Tuesday evening, bringing gusty winds to Southwestern Montana and decreasing temperatures.

The closed low continues to spin over the Great Basin region on Wednesday and Thursday, keeping temperatures around seasonal averages and bringing daily chances for showers and thunderstorms in the afternoon and evening. On Friday the upper level low begins to move eastward, creating more steep southerly flow that will support the formation of showers and thunderstorms in the afternoon and evening. Warm air advection from this steep southerly flow will cause temperatures to warm up again on Friday. - Dzomba

- Forecast Confidence & Scenarios:

Next week brings daily chances for showers and thunderstorms in the afternoon and evening hours. On Monday, there is a 10-25% chance of thunderstorms in Central and Southwestern Montana, with chances decreasing to only 5-10% in North-Central Montana. On Tuesday, there are widespread 25-40% chances of thunderstorms across the region. On Wednesday, there is a 40-60% chance of thunderstorms in Southwestern and Central Montana and east of US Highway 87 in North-Central Montana. West of US Highway 87, chances for thunderstorms decrease to 10-30%. On Thursday and Friday, there are widespread 20-40% chances of thunderstorms across the region. The biggest uncertainties with the thunderstorms next week lies with the track of the upper level low and the timing of the cold front. Each day, the position of the upper level low and the subsequent flow aloft associated with it will play a large role in determining the strength and severity of the thunderstorms. On Tuesday, the timing of the cold front creates added complexity. At this time, the greatest risk for severe thunderstorms are on Tuesday and Wednesday, with some extended models showing conditions for stronger storms on Friday as well. - Dzomba

AVIATION

24/00Z TAF Period

Isolated showers associated with a subtle weather disturbance moving through westerly flow aloft will track across portions of north-cental and far SW MT through early this evening, bringing a 10-20% probability of a shower with some brief wind gusts as high as 30kts to areas near KCTB, KHVR, KLWT and KWYS through 04z. Otherwise VFR conditions prevail with decreasing cumulus across the area later this evening. Breezy west winds develop at most terminals Sunday afternoon with mainly mid-high level cloud- cover. Hoenisch

PRELIMINARY POINT TEMPS/POPS

GTF 46 81 49 88 / 0 0 0 0 CTB 44 76 45 84 / 0 0 0 0 HLN 45 81 47 85 / 0 0 0 10 BZN 41 80 44 85 / 0 0 0 0 WYS 33 74 36 78 / 20 0 0 0 DLN 41 79 43 81 / 0 0 0 10 HVR 47 85 49 91 / 10 0 0 0 LWT 43 78 46 84 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.