textproduct: Great Falls

KEY MESSAGES

- Strong winds along the Northern Rocky Mountain Front later this evening into Saturday morning.

- Seasonally warm temperatures today through the rest of the forecast period.

- Widespread breezy conditions Sunday, along with strong winds returning to the Northern Rocky Mountain Front.

DISCUSSION

- Meteorological Overview:

As a mild trough moves to the east, weak ridging aloft builds to the west today, eventually encapturing Montana by the evening. This will allow temperatures to be seasonally warm and skies to remain mostly sunny. Breezy conditions will develop over Central/North-Central Montana, with higher winds occurring along the Northern Rocky Mountain Front. 700 mb winds increase in the afternoon to around 60- 70 kts, which due to peak diurnal heating and terrain-induced turbulent mixing, are expected to mix down to the surface. This will result in winds gusting up to 65 mph along the Northern Rocky Mountain Front, prompting the continuation of today's High Wind Watch. However, sounding and cross section analysis support the stronger winds mixing down to the surface later in the afternoon, hence the watch start time being pushed back to 4 PM. The strongest winds are expected late this evening.

Entering the weekend, the ridging aloft continues to build, allowing lower elevation high temperatures to climb into the upper 50s to mid 60s. Winds will be milder Saturday afternoon, as the stronger winds aloft move much higher in the atmosphere and do not have the opportunity to mix down to the surface. The break in the winds is short lived, as upper level troughing moves north of the Idaho Panhandle on Sunday, tightening the pressure gradient. Strong 700 mb winds, around 70-80 kts, will once again mix down to the surface across the Northern Rocky Mountain Front, prompting the continuation of Sunday's High Wind Watch. While the strongest winds will be confined to the Northern Rocky Mountain Front, generally windy conditions will be more widespread across the CWA due to the tightening pressure gradient.

Monday morning brings a brief period of zonal flow aloft as the upper level troughing moves to the east. This is followed by a general pattern of building ridging with embedded shortwaves throughout next week, creating on-and-off increased precipitation chances over the higher elevations of the western portion of the CWA. Models are showing signs of a more potent upper level trough digging south through Central MT mid next week, indicating the potential of a return of stronger winds. -Dzomba

- Forecast Confidence & Scenarios:

As of writing this AFD (~3 AM), the high wind watch was kept as a watch and not upgraded to a warning. This is because of uncertainty remaining in how strong the winds will be. Model guidance shows confidence in surface winds gusting up to 65 mph. However, there remains a 50-60% chance of winds gusting greater than 75 mph; enough to keep the watch, but not quite enough to upgrade to a warning.

There is more confidence in the strongest winds occurring on Sunday. BUFKIT analysis indicates increasing, unidirectional cross barrier flow, which is likely to support momentum transfer to the surface solely through diurnal mixing processes. Additionally, within BUFKIT exists ideal thermal profiles to support mountain wave activity, which combined with a moderately strong surface pressure gradient will further enhance winds speeds during the day on Sunday. - Moldan/Dzomba

AVIATION

06/12Z TAF Period

Main concern early this morning will be the dense fog around West Yellowstone. The fog should thin a bit by late morning in this area. Otherwise, strong winds will develop this afternoon along the Rocky Mountain front and in the Cut Bank area. These strong winds will continue through most of tonight. Mountains/passes will be obscured at times this morning around West Yellowstone and by this afternoon along the Rocky Mountain Front. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 56 45 62 44 / 0 0 0 0 CTB 51 40 59 38 / 0 0 0 0 HLN 52 34 56 35 / 0 0 0 0 BZN 48 29 54 31 / 0 0 0 0 WYS 39 21 47 22 / 0 0 0 0 DLN 48 28 52 30 / 0 0 0 0 HVR 54 39 62 38 / 0 0 0 0 LWT 54 39 60 41 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

High Wind Watch from 4 PM MST this afternoon through Saturday morning for East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera-Northern High Plains-Southern High Plains.

High Wind Watch from Sunday morning through Sunday evening for East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera-Northern High Plains-Southern High Plains.