Strong cross barrier flow combined with a tightening pressure gradient allowed for a period of gusty winds along the Rocky Mountain Front Dec 26 into Dec 27. Only one sensor, a few miles east of the Rockies, ended up reaching high wind criteria.
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The episode as NWS TFX wrote it up.
Strong cross barrier flow combined with a tightening pressure gradient allowed for a period of gusty winds along the Rocky Mountain Front Dec 26 into Dec 27. Only one sensor, a few miles east of the Rockies, ended up reaching high wind criteria. Additionally, the pressure gradient resulted in sustained high winds at Norris Hill at the northern end of the Madison River Valley.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Great Falls, MT wrote its last area forecast discussion before the first event at Dec 25, 9:52 PM MST, 8 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Great Falls MT 952 PM MST Wed Dec 25 2024 Aviation Section Updated. .KEY MESSAGES... - Periods of mostly snow will move through Southwest Montana Thursday through Saturday, mostly impacting the higher terrain south of I90. - Winds will become strong and gusty at times along the Rocky Mountain Front, the high plains, and over the Madison Valley Thursday through early Friday and again on Saturday. - A more widespread snowfall is expected Sunday into Monday, particularly for mountain areas. && .UPDATE... /Issued 826 PM MST Wed Dec 25 2024/ The next wave of active weather will begin to arrive late tonight across the region. Initially westerly winds aloft will become more southwesterly as the system approaches. Combine this with an increasing pressure gradient across southwest Montana, and strong winds become a concern, mostly in north south oriented valleys like the Madison River Valley. The duration of stronger winds appears to be narrow, lasting for a few hours mid-morning Thursday, and be confined to more wind prone areas like Norris Hill. With this in mind, we will continue to hold off on a High Wind Warning. That said, sustained winds between 25 and 35 mph will become common late tonight in the Madison River Valley, with gusts up to 55 mph or so before winds gradually diminish Thursday afternoon. Mainly light, but at times moderate snow will develop over Southwest Montana terrain Thursday morning. Consideration was given toward a Winter Weather Advisory for the Chief Joseph Pass area for Thursday, but the limited areal extent of impacts swayed me to hold off at this time. The Winter Weather Advisory for Raynolds and Targhee passes and vicinity remains in effect with no changes made at this time. Another period of potentially strong winds will be around along the Rocky Mountain Front. A High Wind Watch remains in effect for this area from Thursday afternoon into Friday morning. No significant changes were made to the forecast this evening. -AM && .DISCUSSION... /Issued 826 PM MST Wed Dec 25 2024/ - Meteorological Overview: The progressive weather pattern will continue to send a parade of Pacific troughs into the Northern Rockies through early next week. There will be a short period of transient ridging before the next trough approaches the Continental Divide early Thursday and brings more mostly mountain snow to Southwest Montana. Central and northern areas look to remain on the drier side, though there will be some light mountain snow along the immediate eastern slopes of the Rocky Mountain Front and over the central ranges. There may also be a few sprinkles or even some mixed precipitation for lower elevations east of a Great Falls to Havre line. In addition to the snow, a tightening pressure gradient combined with a 50 kt + H700 westerly jet will bring breezy to windy conditions along the Rocky Mountain Front, portions of the plains, and the north-south oriented valleys of Southwest Montana Thursday afternoon through early Friday. Forecast soundings highlight prospective mountain wave activity and stronger winds transferring to the surface along the Rocky Mountain Front, adjacent high plains and even on the lee side of the central island ranges along highway 87/200. The tight surface pressure gradient will also bring stronger southerly winds to the Madison Valley late tonight and on Thursday. Another system brings another round of mountain snow on Friday, again mostly impacting Southwest Montana. This will be followed by another period of strong westerly flow moving across the region on Saturday for more breezy to windy conditions over the same areas mentioned above for Thursday night's winds. Surface pressure gradients don't look as strong, but the stronger core of 50kt H700 flow may be better timed during peak mixing for more opportunity to mix stronger gusts to the surface. Other than the ongoing wind and mountain snow potential, temperatures will run around 10 to 15 degrees above average through Sunday, thanks to milder Pacific air aloft. A potentially more impactful system moves in for the second half of the weekend into early next week. Colder air aloft and better frontogenesis look to bring an opportunity for more widespread snowfall later Sunday into Monday. Weakening westerly surface winds will encourage colder slide southward, resulting in temperatures trending closer to average and even below average for locations along the Hi-Line. - RCG - Forecast Confidence & Scenarios: The periods of snow expected Thursday through Saturday will come in two waves and look roughly similar to the one observed last night. though there will be snow a little farther north for these upcoming events. The higher end 24 hour snowfall probabilities (70% +) for 2 inches of snow or greater for each event look to be concentrated over the higher terrain along the Continental Divide and the mountains south of I90. The Centennial Mountains adjacent to the ID/WY borders do have over a 60% chance for 4 inches of snow or more, but this drops off to around 30% heading north of West Yellowstone. A longer term winter weather advisory was sent out for the Gallatin/Madison ranges to cover the impacts for the mountain passes along the Idaho/Wyoming borders. The winds with the Thursday through Saturday systems will challenge high wind criteria along the Rocky Mountain Front, portions of the plains, and even in the Madison Valley. The southerly winds over the Madison Valley increase as early as late tonight into early Thursday, with probabilities for sustained 40 mph/gusts 58 mph both approach the 60 to 70% for the Norris Hill area. No high wind products were issued due to a shorter time window for stronger winds and continued lower end exceedence probabilities. Later on Thursday, the focus for strong and gusty winds shift to the Rocky Mountain Front and the plains. The strongest winds aloft and the tightest surface pressure gradients look to occur later in the afternoon and during the nighttime hours, so there will be a dependence on mountain wave activity to reach 58/75 mph gusts. Regardless, deterministic guidance continues to trend upward and a high wind watch was issued for the Rocky Mountain Front and the high plains zones despite the probabilities not quite up to product issuance level. Roughly similar wind probabilities and meteorological conditions are expected for Saturday, though there are some trade offs. The surface pressure gradient looks weaker compared to the Thursday event and the winds aloft look a little weaker as well. However, better phasing of the stronger winds aloft with diurnal mixing increase the likelihood of stronger gusts mixing to the surface. all in all, expect a breezy to windy day on Saturday. Things get a little more interesting later Sunday into Monday as colder air begins to move in and opportunities for more widespread snowfall arrive. Current probabilistic guidance supports a general 2 to 5 inch snowfall for most mountain areas, with the exception of the Madison/Gallatin ranges where totals in the 3 to 9 inch range look more common. Lower elevation probabilistic guidance is not as impressive, generally supporting a during to around an inch or two. With that being said, the individual number of ensemble members are beginning to support higher amounts. As mentioned in the sections above, temperatures will slowly trend downward early next, particularly for northern areas. - RCG && .AVIATION... 26/06Z TAF Period VFR conditions will prevail at all terminals except for the KEKS terminal during this TAF period. However, between 26/13Z and 26/23Z at the KBZN, KHLN, and KLWT terminals there is a 20 - 40% chance for snow, rain, and/or a rain/snow mix. This precipitation is unlikely to reduce visibility or ceilings below MVFR levels. At the KEKS terminal there is a 30 - 50% chance for snow between 26/12Z and 26/14Z and between 26/19Z and the end of the TAF period. Snow will reduce visibility to MVFR levels at the KEKS terminal between 26/14Z and 26/19Z. Across all terminals during this TAF period it will be breezy with the strongest winds at the KEKS, KGTF, and KCTB terminals. There will be instances of mountain wave turbulence and low-level wind shear during this TAF period. During the beginning and middle of this TAF period there will be mountain obscuration in Southwestern Montana. -IG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 27 48 31 45 / 0 10 0 10 CTB 25 43 27 42 / 0 10 0 10 HLN 25 45 27 41 / 0 40 10 40 BZN 22 42 22 39 / 0 40 10 40 WYS 15 28 15 29 / 20 100 90 80 DLN 21 39 20 37 / 10 60 10 30 HVR 22 44 27 43 / 0 10 0 0 LWT 24 43 26 43 / 0 30 0 10 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Watch from Thursday afternoon through Friday morning for East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera-Northern High Plains-Southern High Plains- Southern Rocky Mountain Front. Winter Weather Advisory from 5 AM Thursday to 11 PM MST Friday for Gallatin and Madison County Mountains and Centennial Mountains. && http://www.weather.gov/greatfalls
Special Weather Statement National Weather Service Great Falls MT 833 PM MST Wed Dec 25 2024 MTZ301-302-260700- East Glacier Park Region-Northern High Plains- Including the cities of East Glacier Park, Kiowa, Babb, Saint Mary, Marias Pass, Logan Pass, Browning, Heart Butte, and Dupuyer 833 PM MST Wed Dec 25 2024 ...Gusty Winds This Evening... Gusty winds will continue along the immediate eastern slopes of the Rockies through the evening. Sustained winds on the order of 35 to 45 mph, with gusts between 55 and 70 mph will persist through midnight before slowly diminishing later tonight. Those operating high profile vehicles should be prepared for difficult driving conditions if traveling near the Rocky Mountain Front this evening.
The national radar mosaic for the moment the first event began.
2 high wind. Local standard time, as filed.
Mesonet sensor MTNOR Norris Hill (MT DOT) measured two separate stints of high sustained winds (Averaged over at least an hour) of 40 mph.
Montana Mesonet sensor Dog Gun Lake E (acedoggu) measured sustained winds, averaged over an hour, of 50 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2024Every state in 2024This day in weather historyWarnings in Montana, December 2024
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1224665, 1221607.