textproduct: Great Falls

KEY MESSAGES

- Strong and gusty winds along the Rocky Mountain Front today, with strong winds shifting to the north-south orientated valleys of Southwest Montana on Wednesday.

- A potent spring storm will bring accumulating snow to the Northern Rockies from Wednesday night through Thursday night, especially to Southwest Montana.

- Below normal temperatures expected from Thursday through Friday.

DISCUSSION

/Issued 1214 AM MDT Tue Apr 14 2026/

- Meteorological Overview:

Unsettled conditions are expected across the Northern Rockies through the remainder of the work week as zonal flow (today) backs to the southwest (tonight and Wednesday) ahead of a potent upper level wave digging into the Pacific Northwest. This upper level wave will continue to dig southeast and over the Great Basin through the day on Thursday before lifting northeast and over the Central Rockies and High Plains on Friday. At the surface a Pacific front will sweep east across the Northern Rockies by Wednesday evening, with a cold front quickly plunging south during the early morning hours on Thursday. Northwest flow will settle in over the Northern Rockies from Friday night through Saturday night before upper level ridging builds back in for the second half of the weekend and start to the work week. - Moldan

- Forecast Confidence & Scenarios:

Strong Winds Today...

Lee-side surface trough along the Rocky Mountain Front will begin to sharpen through the day as low pressure develops over Southern Alberta, with the surface pressure gradient peaking at between 0.125 to 0.15 mb/km from the mid-morning through the late afternoon hours across this area. H700 flow per NAEFS analysis will increase and peak at between 40-60kts from the afternoon through evening hours, with BUFKIT soundings for areas along the immediate Rocky Mountain Front over this timeframe supporting ideal thermal profiles for mountian wave activity. With this all in mind the best opportunity for strong winds looks to be from 12-9PM today when the winds will be enhanced from both pressure gradient force, mountain wave activity and overall mixing. While it is possible that these strong winds work east of the US Hwy 89 corridor to areas like Mission Lake over this timeframe, current thinking is that the strongest winds will remain along and west of the US Hwy 89 corridor (i.e. Browning and East Glacier Areas). Latest NBM4.3 probabilities for gusts in excess of 55 mph for Browning and East Glacier are at a 70% and 95% chance respectively, 25% and 65% chance for 65 mph, and 5% and 20% chance for 75 mph. With High Wind Criteria for the Browning and East Glacier Areas being 75 mph we will not be issuing any High Wind highlights at this point in time.

High Wind Potential on Wednesday...

Climate anomaly indicators such as the ECMWF EFIs and NAEFS support a climatologically unusual to very unusual wind event, with respect to mid-April climatology, within the north-south orientated valleys of Southwest Montana (south of the I-90 corridor) from the late morning through afternoon hours on Wednesday. ECMWF EFIs with respect to sustained wind speeds generally range from 0.6 to 0.8 for these valley locations, with gusts being slightly higher at 0.7 to nearly 0.9. H700 winds per NAEFS analysis peak around 30-40kts during the afternoon hours, which is 2.5 standard deviations above normal. Most critically of all these winds will be orientated parallel with the valleys, which is likely to lead to enhanced speeds due to terrain funneling. Additionally, rain showers developing across Southwest Montana within an environment characterized by inverted-V soundings will be capable of producing strong and erratic winds. Given these factors a High Wind Watch has been issued for the Beaverhead and Madison River Valleys in Southwest Montana from 9AM to 6PM Wednesday.

Accumulating Snow from Wednesday afternoon/evening through Thursday night....

Model guidance (deterministic and ensemble) has been consistent over the last 3-4 days in bringing accumulating snow (what) to the Northern Rockies and High Plains over the timeframe (when); however, this consistency has waffled in where the heaviest snow actually falls. Over the past 48 hours the aforementioned guidance has largely settled in on a solution that places the heaviest snow over the Tobacco Root, Gravelly, Centennial, Madison, and Gallatin Ranges from Wednesday evening through Friday morning; however, even mountains and lower elevation location outside of this area across Southwest through North Central Montana will see some accumulating snow. Latest ECMWF EFIs support the potential for a very unusual snowfall for the West Yellowstone Area and southern halves of the Madison and Gallatin Ranges, with unusual snowfall for the remainder of the Southwest Montana mountains and Glacier National Park mountains. NBM4.3 probabilities for snowfall accumulations of 9" or more for the Tobacco Root, Gravelly, Centennial, Madison, and Gallatin Ranges is in excess of a 70% chance, with between a 45-55% chance for Raynolds and Targhee Passes. Given these high probabilities and run-to-run consistency over the past 48 hours a Winter Storm Watch has been issued for the Gallatin and Madison County Mountains and Centennial Mountains; including the cities of Big Sky, West Yellowstone, Targhee Pass, and Raynolds Pass from Wednesday evening through Friday morning. This watch may need to be expanded to include the East Glacier Park Region given similar probabilities; however, given that Marias Pass has only a 35% chance for 9" of snow current thinking is that this area could be covered with a Winter Weather Advisory given that the most impactful snow will occur in GNP where the park is largely still closed. Otherwise, most locations have been trending towards Winter Weather Advisory level snowfall amounts, which can be addressed as the event draws nearer. - Moldan

AVIATION

14/12Z TAF Period

Increasing southwest to west surface winds can be expected across most terminals from 15z this morning through 03z this evening, with the strongest winds occurring along the eastern slopes of the Continental Divide. Mountain wave activity is likely along and west of the I-15 corridor across Central and North Central Montana over this same timeframe. Otherwise low-VFR/VFR conditions will prevail throughout the 1412/1512 TAF period, with mountain obscuration along the Continental Divide for much of the next 24 hours. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 59 41 59 29 / 0 20 30 80 CTB 53 33 54 22 / 10 10 10 50 HLN 61 37 59 28 / 0 10 40 90 BZN 61 35 59 28 / 10 10 40 100 WYS 47 27 45 27 / 10 10 90 100 DLN 57 35 57 28 / 0 10 40 100 HVR 64 38 62 28 / 0 10 10 80 LWT 60 36 58 28 / 10 20 50 90

TFX WATCHES/WARNINGS/ADVISORIES

Winter Storm Watch from Wednesday evening through late Thursday night for Gallatin and Madison County Mountains and Centennial Mountains.

High Wind Watch from Wednesday morning through Wednesday afternoon for Beaverhead and Western Madison below 6000ft- Madison River Valley.