textproduct: Great Falls

KEY MESSAGES

- Today through Wednesday there will be isolated snow/rain showers in the afternoon and evening.

- Thursday and Friday it will be warm and dry with precipitation returning for the weekend.

DISCUSSION

- Meteorological Overview:

Today northwest flow aloft remains over North-central, Central, and Southwestern Montana. This will allow temperatures to warm up to near seasonal averages with mountain snow showers and isolated snow/rain showers in lower-elevation areas. Warming temperatures will allow instability to build this afternoon. This will lead to a few rumbles of thunder Tuesday afternoon in Central Montana. On Wednesday an upper-level ridge begins to approach Montana with northwest flow aloft over North-central, Central, and Southwestern Montana. This will keep temperatures around seasonal averages. There will be another day of mountain showers with isolated lower- elevations seeing rain/snow showers. Warming temperatures will allow instability to build this afternoon. This will lead to a few rumbles of thunder Tuesday afternoon in Central Montana.

Thursday through Friday an upper-level ridge gradually moves over North-central, Central, and Southwestern Montana. This will allow temperatures to gradually warm up with mostly dry weather. Saturday through Sunday an upper-level trough begins to move over California with northwest flow over Montana. This will bring slightly cooler temperatures and more widespread precipitation to North-central, Central, and Southwestern Montana. On Monday an upper-level ridge begins to build in over North-central, Central, and Southwestern Montana. This will allow temperatures to warm up with mostly dry weather. -IG

- Forecast Confidence & Scenarios:

Today there is a 15 - 20% for thunder in Central Montana. On Wednesday there is a 15 - 25% chance for thunder in Central and Southwestern Montana. Deterministic models and ensemble clusters are in good agreement that this weekend there will be an upper-level low off the coast of California with northwest flow over Montana. However, there remains some uncertainty with the over all track of the upper-level pattern. This leads to uncertainty in how much cooling will occur and how much/widespread precipitation occurs/is this weekend. -IG

AVIATION

28/06Z TAF Period

An unstable northwesterly flow aloft will reside over the CWA through the period. With cold air aloft, there will be a chance for scattered rain showers across the CWA. The most likely time at the terminals will be late morning through the afternoon. Since most of the showers will be brief, for now, I confined pops to just the afternoon hours at the terminal sites. But know that showers will be possible across the CWA through the period. A lightning strike is also possible, but with the probability of thunder only around 15 percent, I kept it out of the terminal sites as well. Mountains/passes will be obscured at times across the CWA by showers/clouds. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 47 27 56 33 / 10 10 30 20 CTB 45 23 55 30 / 10 10 20 10 HLN 50 29 56 33 / 20 10 30 20 BZN 48 24 54 30 / 60 10 30 20 WYS 44 17 46 22 / 70 40 30 10 DLN 49 25 54 31 / 30 10 20 0 HVR 46 24 59 29 / 0 0 10 0 LWT 42 24 52 29 / 20 10 30 10

TFX WATCHES/WARNINGS/ADVISORIES

None.