textproduct: Great Falls

KEY MESSAGES

- Isolated light showers possible this afternoon across Central MT.

- Drier and warmer trend continuing through mid day Tuesday.

- A cold front will bring showers and thunderstorms Tuesday along with gusty winds.

- An active period returns for towards next weekend.

DISCUSSION

- Meteorological Overview:

An upper-level ridge building in along the West Coast U.S. will continue to out the region in northwest flow aloft. Therefore, a few isolated light showers will be possible this afternoon, mainly across the Little Belts/Central MT area. The main limiting factor for this will be high pressure building in. The ridge slowly moving east across the Western U.S. will keep high pressure dominating through the beginning of next week. Therefore, drier and warmer conditons build in through then. Temperatures dropping into the mid to upper 30s across Southwest MT and parts of North- Central MT can cause some frost to develop Sunday morning.

This northwest flow aloft pattern continues through Friday. An upper level wave drops down from Canada and into MT Tuesday through Thursday. Mid level winds increase Tuesday afternoon through evening. A cold front dropping south late Tuesday through Wednesday helps mix these winds down to the surface, bringing gusty winds to the region. The front will also develop showers and thunderstorms Tuesday into Wednesday morning. Towards the end of next week, another upeer-level wave developing bring additional chances for showers and thunderstorms.

- Forecast Confidence & Scenarios:

The timing of the winds Tuesday will be key to the wind threat. So far, models have the 700mb winds ramp up between 3pm to 12am. Winds ramping up closer in the afternoon will have better diurnal mixing, and a better chance for stronger wind gusts. However, the cold front passing through the evening can also help mix down these winds to the surface. There's a 40 to 70% chance for 55 mph wind gusts Tuesday along the Rocky Mountain Front. Across Central MT from MacDonald pass through US Highway 12, there's a 30 to 70% chance for 50 mph wind gusts. Hotter temperatures Tuesday combined with the wind and RH's dropping to near critical could elevate fire weather conditions somewhat, but the recent rainfall looks to limit the severity. Places where there wasn't as much rainfall like Southwest MT will probably have to be monitored. -Wilson

AVIATION

13/18Z TAF Period

Primary concern this TAF period will be for mainly low-VFR ceilings and widely scattered showers through the evening. Confidence in coverage of these showers was too low to warrant mention in TAFs at this time, however. Lower cloud cover diminishes after sunset in most areas, leading to a benign stretch heading into Sunday. Some patchy fog cannot be completely ruled out Sunday morning. -AM

PRELIMINARY POINT TEMPS/POPS

GTF 40 70 44 79 / 0 0 0 0 CTB 36 71 45 78 / 0 0 0 0 HLN 40 73 44 81 / 0 0 0 0 BZN 36 70 39 77 / 0 0 0 0 WYS 30 68 31 75 / 0 0 0 0 DLN 36 69 40 81 / 0 0 0 0 HVR 40 73 45 78 / 0 0 0 0 LWT 37 67 41 72 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.