textproduct: Great Falls

KEY MESSAGES

- Widespread rain and snow today, with some of the precipitation being heavy at times.

- Temperatures will be much cooler today, with the cooler temperatures then continuing into next week.

- The next storm system arrives by the middle of next week, with much of that precipitation falling as snow.

DISCUSSION

- Meteorological Overview: Two upper level disturbances are moving toward Central MT this morning, one from the south and one from the north. There is ample amounts of precipitation coming up with the disturbance from the south this morning. This will be a quick moving system, with much of the precipitation exiting the region by early Saturday morning. Some of the precipitation could be heavy at times this afternoon. Overall, QPF is expected to range from about 1/2 inch to 3/4 of an inch over Central and Southwest MT, with lighter amounts as you go northward towards the US/Canadian border.

There are two main concerns with this event.

One, strong winds. Expect strong wind gusts later this morning and through early this evening over portions of North Central MT. Thus, no changes to the high wind warning area.

The second concern is when does the rain change to snow. The freezing level was over 11,000 feet on Thursday evening. The forecast models have this freezing level lowering very quickly this afternoon, as the heavy precipitation brings down the colder air from aloft. This is possible, but also the airmass might be so saturated at lower levels, it doesn't adiabatically cool as efficiently as the forecast models have progged. Thus, the only change to the winter weather advisory was to add a few more mountain ranges over Southwest MT. Otherwise, for most lower elevation locations, the rain should change to snow by this evening, but with the majority of the precipitation through by this time, snow accumulations at lower elevations will be on the low side for this event.

Temperatures today will be much cooler than they have been, with most areas having high temperatures this morning, and falling temperatures this afternoon.

After this event, expect rather dry conditions for Sun/Mon, with the cool temperatures continuing. For Tue/Wed, the next weather system approaches the CWA, with the best chance for precipitation over the Central and Southwest portions of the CWA. The airmass will be quite a bit colder by the middle of next week, that much of the precipitation will fall as snow, with some rain mixing in at lower elevations.

- Forecast Confidence & Scenarios: The main concern with the rain/snow today is what time does the rain change to snow? The quicker it changes to snow, the higher probability of a bit higher snow accumulations. Since this will be a quick moving system, impacts from the snowfall will short. That being said, some snowfall rates could approach 1 inch per hour this afternoon/evening...which could affect the evening commute.

Also, I can't rule out a lightning strike here/there...but the probability is to low to include thunder for most areas right now. Brusda

AVIATION

23/12z TAF Period

Main concern will be rain/snow developing over the CWA this morning and then spreading eastward this afternoon/evening. Some precip could be heavy at times late morning through this afternoon. The rain should change to snow for most areas/elevations by this evening. IFR/LIFR conditions are possible at times in areas of snow. An isolated lightning strike is possible, but the probability is too low to include at a terminal site right now. Much of the precipitation ends by 06z Sat. Some patchy fog possible on Sat morning. Mountains/passes will be obscured through 06z Sat. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 51 27 47 26 / 100 50 0 0 CTB 48 22 44 22 / 90 0 0 0 HLN 52 23 47 26 / 100 60 0 0 BZN 52 22 45 21 / 100 100 0 0 WYS 45 14 46 14 / 100 90 0 0 DLN 51 26 46 25 / 100 90 0 0 HVR 57 24 46 22 / 100 80 0 0 LWT 57 22 43 21 / 100 100 0 0

TFX WATCHES/WARNINGS/ADVISORIES

High Wind Warning from 11 AM this morning to 3 PM MDT this afternoon for Eastern Glacier, Western Toole, and Central Pondera-Eastern Toole and Liberty-Hill County.

Winter Weather Advisory from 4 PM this afternoon to 3 AM MDT Saturday for Bears Paw Mountains and Southern Blaine-Fergus County below 4500ft-Judith Basin County and Judith Gap-Snowy and Judith Mountains.

High Wind Warning from noon today to 9 PM MDT this evening for Fergus County below 4500ft.

Winter Weather Advisory from noon today to midnight MDT tonight for Big Belt, Bridger and Castle Mountains-Elkhorn and Boulder Mountains-Gallatin and Madison County Mountains and Centennial Mountains-Little Belt and Highwood Mountains-Northwest Beaverhead County-Ruby Mountains and Southern Beaverhead Mountains-Upper Blackfoot and MacDonald Pass.