textproduct: Great Falls

KEY MESSAGES

- Above average temperatures return this week. - Dry conditions aside from a stray shower or thunderstorm Tuesday afternoon and Wednesday. - Next system arrives late week with windy and wet conditions.

DISCUSSION

- Meteorological Overview:

Southwesterly upper level flow will be the predominant weather pattern this week as upper level ridging stalls out over the center of the North American Continent this week, keeping us generally warm and dry for most of this week. Expect temperatures to generally be either side of 80 along the Missouri River corridor, with temperatures not as warm in the higher terrain and along the Rocky Mountain Front. Winds will also be uncharacteristically light for much of the week, with winds generally struggling to gust over 20 mph through Thursday. Aside from a stray shower or thunderstorm across Southwestern Montana Tuesday or Wednesday afternoon, our next weather system will arrive Friday or Saturday, which will bring cooler temperatures, gusty winds, and the possibility for some widespread precipitation, though the amount of rainfall remains fairly uncertain at this point in time.

- Forecast Confidence & Scenarios:

Friday/Saturday system: an upper level trough and associated surface front embedded in the upper level flow are expected to arrive in the Northern Rockies late Friday. Current model forecasts suggest that this setup will bring some widespread precipitation, with the potential for many areas to receive over a quarter inch of liquid equivalent. The other concern will be the wind, as the strengthening trough may produce a bit of a descending jet on its southwest side, which would produce some gusty westerly winds thanks to the sinking air behind a cold front. As of Monday afternoon, probabilities for 60 mph wind gusts still appear low (generally under 20 percent). However, wind gusts over 50 mph are likely to be common, and stronger wind gusts will be heavily dependent on the timing and strength of this system. Ludwig

AVIATION

21/18Z TAF Period

VFR conditions will prevail through much of the 2118/2218 TAF period, with the exception of the KHVR terminal where fog is expected to develop once again Tuesday morning and reduce CIGS/VIS. Latest Hi-Res Ensemble Forecast (HREF) guidance supports a 50% chance that VIS falls to 5 miles between 10-16z Tuesday at the KHVR terminal, with a 25% chance that VIS falls to 1/4sm. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 79 49 80 50 / 0 0 0 0 CTB 76 45 77 48 / 0 0 0 0 HLN 75 46 78 48 / 0 0 0 20 BZN 73 41 75 45 / 0 0 0 20 WYS 67 30 66 33 / 0 0 0 50 DLN 72 41 73 42 / 0 0 10 20 HVR 79 46 80 49 / 0 0 0 0 LWT 75 45 79 49 / 0 0 0 10

TFX WATCHES/WARNINGS/ADVISORIES

None.