textproduct: Great Falls

KEY MESSAGES

- Abnormally warm, dry and breezy today and tomorrow.

- Temperatures begin to cool down this weekend, and precipitation chances increase across Southwest MT on Saturday. - Potential for a pattern change next week, bringing much cooler temperatures and increased chances of precipitation.

DISCUSSION

- Meteorological Overview:

The weather remains fairly benign today and tomorrow, as a strong upper level ridge continues to dominate over Montana. This ridge will allow temperatures to remain abnormally warm and for little to no chance of precipitation. Occasional general breeziness can be expected across the CWA today. Winds will strengthen tomorrow as a potent upper level trough begins to dig inland from the Pacific Coast, creating increased southwesterly flow aloft. A tightening surface pressure gradient over Southwest MT will favor the stronger winds occurring south of I-90, particularly in the North-South oriented valleys.

On Saturday, the trough continues to move eastward over the Great Basin, breaking down the ridge and putting us in more southerly flow aloft. Increased moisture aloft will be caught up in and transported north along this southerly flow, leading to increased chances of precipitation over Southwest MT. The ridge breakdown will also allow for temperatures to decrease, creating a cooling trend that we will see throughout the remainder of this forecast period. This trough is fast moving, however, quickly moving towards the southern US plains by Sunday and allowing for weak ridging to build back in by Sunday afternoon. This will create a day of little to no precipitation chances and partly sunny skies, although due to the weak nature of the ridge temperatures will remain closer to seasonally average.

On Monday, a very deep upper level trough begins to move inland through Southern California, creating strong southwesterly flow aloft. From here is where the uncertainty begins. At this time, models are showing more agreement in the trough weakening as it moves northeast through the rest of the work week, followed by a strong closed upper level low moving inland off the Pacific Coast. However, some models are showing the initial trough weakening so much it begins to completely break down, whereas others show it remaining a weak closed low. Some models show the second, stronger closed low moving through Montana, whereas others show it remaining south of Montana. How these different tracks will impact our weather is outlined in the Forecast Confidence & Scenarios section below. -Dzomba

- Forecast Confidence & Scenarios:

High confidence surrounds the unseasonable warmth through Friday, as well as the transition toward ridge breakdown and cooler temperatures this weekend. Confidence is medium to high (50-60%) that Saturday into Sunday will feature low-impact light precipitation largely across SW Montana and the Rockies. Snow levels will remain well above pass levels, and the scattered nature of the precipitation indicates most lower-elevation locations will remain dry.

Confidence has lowered regarding any significant or high-impact storm system early next week. While there is moderate confidence in a return toward seasonable temperatures, model spread is substantial regarding how individual waves track and interact:

Scenario 1 (Active, Chaotic Pattern): A split-flow regime keeps the primary moisture tap and strongest dynamics displaced to the south, while a series of weaker northern-branch shortwaves cross the Northern Rockies. This brings periodic light precipitation and minor pass-level snow chances, but overall impacts remain minimal.

Scenario 2 (More Amplified or Consolidated Wave): A shortwave digs more aggressively or consolidates into a broader trough over the Plains. This would allow a stronger push of Canadian cold air and wrap-around moisture into Central Montana, potentially introducing a brief window for more organized precipitation, though confidence in this evolution remains low. -JR

AVIATION

12/12Z TAF Period

Expect mid/high level clouds across much of the CWA through the period. The clouds could obscure mountains/passes at times. Otherwise, no significant weather impacts are expected across the CWA at this time through 18z Fri. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 68 40 66 41 / 0 0 0 0 CTB 65 32 55 30 / 0 0 0 0 HLN 58 32 60 35 / 0 0 0 0 BZN 60 31 61 34 / 0 0 0 0 WYS 55 25 51 27 / 0 0 0 10 DLN 58 32 57 35 / 0 0 0 0 HVR 64 31 57 32 / 0 0 0 0 LWT 71 39 68 39 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.