textproduct: Great Falls

KEY MESSAGES

- Daily chances for showers and thunderstorms continue through at least Saturday.

- Some storms can produce strong to severe wind gusts, hail, and localized flash flooding for burn scars and urban areas through the week. - Temperatures warm back to above normal for the weekend.

UPDATE

/Issued Issued by National Weather Service Missoula MT/

Not much to update this evening other than to freshen the grids. Ludwig

DISCUSSION

/Issued Issued by National Weather Service Missoula MT/

- Meteorological Overview:

A closed low stationed over the coast of the Pacific Northwest will continue to bring southwest flow aloft for the weekend. This pattern will continue to advect in a warm, moist and unstable airmass into the region through at least Saturday. As a result, daily chances for showers and thunderstorms are expected through Saturday. Strong to severe thunderstorms will be possible each day through the week with modest shear of 30-50kts and CAPE reaching 1,000 j/kg or higher. Today's severe thunderstorm threat will be isolated, and concentrated to Central MT and the Montana and Canada border. Thursday has better forcing with a more potent shortwave moving through the region. The best region for thunderstorms will be between I-90 to Highway 200 corridor. Hail will be the primary hazard due to elevated instability and mid level forcing, but severe wind gusts will be possible as well. Anomalous PWATs reaching more than an inch will also bring a threat for flash flooding for the Horse Gulch Burn Scar and urban areas due to heavy rainfall from thunderstorms. A flash flood watch has been issued for Thursday as a result from the heavy rainfall threat. Showers and thunderstorms look to start isolated before congealing into a more structured cluster/line.

On Sunday, this close low lifts north and east, which helps push the moisture off to the east. Sunday looks to be a drier day, with an isolated chance for precipitation in Central/Southwest MT. Temperatures this weekend climb back above normal with lower elevations reaching into the 90s.

Next week, this "dirty ridge" pattern looks to be persistent again, with daily chances for showers and thunderstorms developing again from shortwaves pushing through the area and monsoonal moisture returning. However, moisture doesn't look to be as high than this week. -Wilson

AVIATION

16/06Z TAF Period

While VFR conditions are expected to prevail through the overnight hours and through the morning, a few TSRA and SHRA will develop tomorrow evening, particularly across SW MT and along the Rocky Mountain Front. Primarily this will affect SW MT terminals (KBZN, KWYS, KEKS, KHLN), where MVFR to IFR conditions will be possible due to reduced visibility and ceilings. Additionally, some gusty outflow winds and downdrafts, as well as hail, will be possible with the stronger storms. Ludwig

PRELIMINARY POINT TEMPS/POPS

GTF 59 89 60 94 / 10 10 20 30 CTB 56 85 59 89 / 10 20 30 30 HLN 62 91 63 94 / 0 40 40 40 BZN 56 91 58 93 / 20 30 30 40 WYS 48 87 50 87 / 10 20 40 40 DLN 55 88 56 89 / 10 20 30 30 HVR 58 91 61 96 / 30 0 10 10 LWT 54 84 55 89 / 40 30 20 10

TFX WATCHES/WARNINGS/ADVISORIES

Flash Flood Watch from Thursday afternoon through Thursday evening for Big Belt, Bridger and Castle Mountains.