textproduct: Great Falls

KEY MESSAGES

- Periods of rain and mountain snow to continue through Monday.

- Below normal temperatures early this week will warm back up to seasonal normals by midweek.

- Showers and thunderstorms most days Tue thru Fri, with some strong storms possible.

DISCUSSION

- Meteorological Overview: Overall the summer storm is on track and continues to affect a good portion of the CWA this morning. Precipitation has been a bit below what was forecasted along the Hi-line from Glacier Park eastward to Harlem, otherwise, the storm seems to be on track. Rainfall reports of 1 to 2 inches are common over Southwest MT, with the rain changing to snow for elevations mostly above 7000 feet over Southwest MT. About 0.25 to 0.75 inches of rain has fallen over Central MT, in the Helena, Great Falls, and Lewistown areas so far. The upper level low will slowly transition from Southwest MT to North Central MT later today. As this occurs, the heavier precipitation will also shift from the Southwest to North Central MT later today and into tonight. Overall, expect periods of precipitation today with Southwest MT harder hit this morning and North Central MT harder hit this afternoon and into the day on Monday. There will be some breaks in the precip and thunderstorms mixed in from time to time as well. At this time, no severe storms are expected through Monday.

The upper level low pulls away on Tue, ending the widespread precipitation and allowing temperatures to return to near normal fairly quickly.

For Wed through Fri...and new upper level low will develop to our west, resulting in a moist/unstable southwesterly flow aloft over our CWA. This will result in daily chances for showers/thunderstorms over a good portion of the CWA. Some of these storms could be severe later in the week, along with produce some heavy rainfall.

For next weekend, drier air is forecast to move into the area starting on the 4th of July and continuing into Sun. A few showers linger on Saturday, mostly over the eastern portions of the CWA, otherwise it is looking mostly dry, with afternoon temperatures near normal.

- Forecast Confidence & Scenarios: The current winter statements will remain in place. Snotel sites this morning are not reporting much snow accumulation, most likely because of melting. That being said, impactful snowfall is still expected throughout the day today and into tonight for higher elevations of Southwest MT.

The flood watch will continue for Glacier Park for now. The forecast models continue to prog heavier precipitation tonight into Monday for Glacier Park, with some areas getting over 3 inches of rainfall. Should the rainfall amounts decrease, the flood watch might be cancelled early.

Looking ahead to Wed thru Fri...there is the potential that a few severe storms could occur, along with some storms producing heavy rainfall. It is possible excessive rainfall for flash flooding over severe risks could be introduced into the forecast later this week. Brusda

AVIATION

28/12Z TAF Period

Periods of widespread rain will affect North Central MT through the period, with a mix of rain and snow over Southwest MT through the period. Precipitation could be heavy at times. Any thunderstorms should be isolated. Mountains/passes will be obscured across the CWA through the period. Brusda

HYDROLOGY

Periods of rain will continue to affect the CWA from today through Monday. Widespread rainfall amounts of 1 to 3 inches are still expected by Monday.

In the Glacier Park region, rainfall is expected to be a bit heavier, possibly up to 4 inches. Additionally, with some high elevation snow still left, the combination of rainfall/snowmelt could lead to some flooding on the east side of Glacier National Park. Thus a flood watch has been issued for this region starting on Sunday. Should later forecast today decrease the projected rainfall amounts, the flood watch might be cancelled.

Additional flood statement might be needed if rainfall amounts start to exceed 3 inches elsewhere across the CWA. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 58 46 59 48 / 90 90 90 90 CTB 62 47 62 48 / 90 100 100 80 HLN 54 45 57 47 / 100 100 100 80 BZN 51 39 54 41 / 100 90 100 80 WYS 48 29 47 32 / 90 80 100 70 DLN 49 36 54 39 / 100 100 90 40 HVR 66 47 66 48 / 80 90 90 80 LWT 56 41 57 43 / 100 80 70 80

TFX WATCHES/WARNINGS/ADVISORIES

Flood Watch from this evening through Tuesday morning for East Glacier Park Region.

Winter Weather Advisory until noon MDT Monday for Elkhorn and Boulder Mountains-Gallatin and Madison County Mountains and Centennial Mountains-Ruby Mountains and Southern Beaverhead Mountains.

Winter Storm Warning until noon MDT Monday for Northwest Beaverhead County.