FXUS65 KTFX 290552 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1152 PM MDT Thu May 28 2026 Aviation Section Updated. .KEY MESSAGES... - Daily rounds of showers and thunderstorms continue for the next few days, some storms will be strong to severe. - Widespread rain, gusty winds, and some high mountain snow move in for the weekend. - Additional scattered showers and thunderstorms and slowly warming temperatures are in the forecast for next week. && .DISCUSSION... /Issued 545 PM MDT Thu May 28 2026/ - Meteorological Overview: A closed mid- level circulation over the Great Basin area will continue to bring difluent south to southeasterly flow aloft over the Northern Rockies for the next few days. This will result in daily rounds of showers and thunderstorms. Similar to yesterday, storm coverage will be most widespread over areas of higher terrain with bulk shear generally remaining less than 25 kts; however, this does not mean that some storms will break away from the terrain and bring localized strong wind gusts, hail, and heavy downpours. Lower elevations will be most susceptible to storm activity later this evening during a shortwave passage. Also, with the combination of slow storm motion and PWATS approaching the one inch mark, areas of higher terrain may observe some training of storms and localized rainfall rates up to an inch per hour. The omega block over the central CONUS begins to migrate northeastward into Canada this weekend. This will encourage the mid- level to slowly move northward towards the Northern Rockies. On Friday shortwave energy will increase bulk shear levels above 35 kts while ML CAPE remains steady around 1000 J/kg and PWATS stay above three quarters of an inch for the most part. This will increase storm coverage and intensity, especially over central and north- central MT. Dry sub- cloud layers and elevated CAPE/PWATS will be supportive of localized strong, gusty convective winds, large hail, and heavy downpours. The moisture laden closed low moves into the Northern Rockies later Saturday through Monday. Initially this will bring another round of strong to severe storms to the eastern portions of the forecast area, mainly for plains locations east of I15; however, the latest suite of ensembles have largely decreased the CAPE from earlier runs. This will be followed by widespread rain moving northward through southwest, central and north-central MT later Saturday through Monday. Deep easterly flow ahead of this system will maintain PWATS close to an inch while cooling temperatures aloft support convective enhanced rainfall within the main precipitation shield, especially early in the event. H700 temperatures are progged to fall to as low as -5C on the backside of the low by late Sunday and early Monday, which will add some mountain snow for elevations above 6000 ft. Ensembles are steadily increasing precipitation amounts and now support a widespread rainfall generally between one and three inches between Saturday and Monday, with some higher amounts along the Continental Divide. This system will have strong wrap around winds with H700/H850 flow approaching the 40 to 50 kt range. At least some of these winds will mix to the surface for central and northern areas, especially along the Hi-Line and over the high plains west of I15. This system looks to lift north of the forecast area by Monday night, but cooler, showery conditions will continue through at least early Tuesday. Note the omega block moving into central Canada may result in a slower exit than what may otherwise be expected. Ensembles then favor a continued unsettled conditions heading deeper into next week via shortwave passages within a west to southwesterly flow aloft. - RCG - Forecast Confidence & Scenarios: Showers and thunderstorms though Saturday followed by widespread precipitation, gusty winds, and even some higher mountain snow this weekend... Widely scattered showers and thunderstorms over areas of higher terrain may move northward onto the plains this evening into tonight in response to a passing shortwave. Severe weather is generally not expected with this activity, although some localized wind gusts over 50 mph and brief heavy downpours can't be ruled out. More shortwaves will pass through on Friday and will increase effective shear rates above 35 kts, helping support more widespread shower and thunderstorm activity, especially over central and northern areas. Once again, strong, gusty convective winds, large hail, and localized heavy downpours will be the primary concerns. On Saturday, showers and thunderstorms will gradually transition to widespread stratiform rains and embedded thunderstorms. Model guidance continues to trend down the CAPE Saturday afternoon, which may reduce the overall severe threat; however, even CAPE in the lower 100s will be still be supportive of localized convective enhanced rainfall and flooding to the more susceptible problem areas, including burn scars and areas of poor drainage. By Saturday evening, the moderate to heavy precipitation shield will be lifting northward through southwest, central, and north- central MT. A more defined low pressure system and slower motion is encouraging ensembles to become more aggressive with rainfall totals. This trend is corroborated by climate anomaly indices, including the ECMWF Extreme Forecast Index showing rainfall totals up to the 90th percentile of climatology. The latest probabilistic guidance highlights over an 80% chance for one inch or more of rainfall for virtually the entire forecast area with only a few exceptions. The probability for two inches of rain or more are impressive as well with 60% chances for most central and north- central locations roughly along and west of a Helena to Havre line. Southwestern areas east of I15 also have similar probabilities for two or more inch rainfall totals. Note that these probabilities only cover the 48 hour period ending 6 am Monday morning and there will be additional rainfall on either side of this timeframe. The dry ground and low water levels on area rivers should be able to take much of this moisture, but there will be instances of water rises and localized flooding, particularly over higher prone locations, including burn scars and areas of poor drainage. It's been quite a while since a rainfall of this coverage and magnitude, so there may also be some ponding of water due to temporary hydrophobic surfaces and there may also be rock falls in some areas. If the rain wasn't enough, there will also be mountain snow and wind concerns with this system. Snow levels will drop to the 6000 to 7000 ft range Sunday morning, lowest along the Continental Divide. Accumulating snow will generally be above pass level, but impacts to outdoor recreation will be significant to those not properly dressed or prepared for the conditions. Stronger H700/H850 north-to northwesterly winds will wrap around the low pressure system as it moves over central and north-central MT Saturday night into Sunday. Many places will see gusts over 40 mph while the rain is falling and areas from the Sweetgrass Hills westward to the Northern Rocky Mountain Front will see at least some gusts over 50 mph. Areas along the highway 87/200 corridor in Fergus and Judith Basin counties may also join in with higher gusts. These aforementioned areas already have probabilities over 50% for wind gusts exceeding 50 mph. The combination of the winds and wet conditions may result in some isolated instances of property damage and power outages, particularly for the Sweetgrass Hills, Shelby, and Cut Bank areas. - RCG && .AVIATION... 29/06Z TAF Period Scattered thunderstorms will continue over Central and North- Central MT through the beginning of this TAF period, before dissipating around 09-011Z. Thunderstorms will reignite across Central and North-Central MT around 21Z, and remain scattered through the rest of this TAF period. Lightning and gusty, erratic winds are the main concerns with these storms. VFR conditions are expected to prevail throughout the TAF period, with MVFR conditions possible with a passing thunderstorm. -Dzomba && .HYDROLOGY... A moisture laden mid- level low pressure system will bring waves of showers and thunderstorms for the next couple of days followed by widespread moderate to heavy rainfall late Saturday through Monday. There is increasing confidence for widespread rainfall between one and three inches over southwest, central, and north- central MT, highest for central and north-central locations roughly along and west of a Helena to Havre line and then southwestern areas east of I15. The dry ground and low water levels on area rivers should be able to take much of this moisture, but there will be instances of water rises and localized flooding, particularly over higher prone locations, including burn scars and areas of poor drainage. It's been quite a while since a rainfall of this coverage and magnitude, so there may also be some ponding of water due to temporary hydrophobic surfaces and there may also be rock falls in some areas. - RCG && .PRELIMINARY POINT TEMPS/POPS... GTF 56 88 55 70 / 20 30 60 60 CTB 53 84 51 68 / 40 40 40 70 HLN 54 85 52 65 / 20 30 50 90 BZN 47 85 46 63 / 30 20 40 100 WYS 39 78 39 55 / 20 10 40 100 DLN 46 80 46 58 / 10 10 40 100 HVR 55 94 53 82 / 30 30 40 60 LWT 51 86 49 70 / 40 30 50 80 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls