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.

DISCUSSION

- 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

15/18Z TAF Period

Patchy low cloud cover near the KHVR and KLWT terminals will continue to dissipate through the early afternoon hours, with otherwise VFR conditions expected through the remainder of the 1518/1618 TAF period here and at the remaining terminals of Southwest through North Central Montana. Showers and thunderstorms, isolated to widely scattered in nature, will be present through 00-06z Friday and lead to mountain obscuration at times. Main threat from any thunderstorms impacting a given terminal will be gusty and erratic winds, along with reductions to MVFR/low-VFR.

PRELIMINARY POINT TEMPS/POPS

GTF 59 89 60 94 / 20 20 30 20 CTB 56 84 58 89 / 20 20 30 20 HLN 62 90 63 93 / 10 30 40 50 BZN 56 90 58 93 / 20 20 30 50 WYS 48 87 50 87 / 20 20 30 50 DLN 55 88 56 89 / 20 20 20 40 HVR 58 89 61 95 / 30 0 20 10 LWT 54 84 55 89 / 40 30 30 10

TFX WATCHES/WARNINGS/ADVISORIES

None.