FXUS65 KTFX 021528 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 928 AM MDT Sun Jun 2 2024 .SYNOPSIS... A westerly flow across the region will maintain temperatures near seasonal averages today. The next weather system brings increasing clouds tonight with precipitation mainly near the continental divide overnight before showers and a few thunderstorms move across the area with a cold front on Monday. Strong west winds develop behind the cold front Monday night with periods of stronger winds affecting much of the area through Tuesday night. Above normal temperatures and drier conditions return for later next week. && .UPDATE... Primary concern for this afternoon will be isolated shower and thunderstorm development, mostly along the Continental Divide and Southwest MT. Impacts are expected to be limited to gusty and erratic winds with the stronger cells. Otherwise, west to northwesterly breezes may gust to around 25 mph or so over the plains this afternoon and clouds will be on the increase with light rain showers expected tonight, mostly over and near areas of higher terrain. - RCG && .AVIATION... 02/12Z TAF Period A few light showers from near KEKS to KBZN and KLWT will exit to the east after 14z with otherwise scattered to broken clouds and VFR condition prevailing across the area through this afternoon. Clouds increase from west to east tonight with VFR conditions continuing at TAF sites through Monday morning but precipitation and mountain obscuration increases tonight along the continental divide. Hoenisch Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 432 AM MDT Sun Jun 2 2024/ A few light showers continue to track east across mainly southwest MT early this morning associated with a relatively weak shortwave disturbance thats exits the area later this morning. Clouds decrease through early this afternoon before increasing again later this afternoon through tonight as a deep plume of Pacific moisture begins to move into the NW US, driven by an unseasonably strong Pacific upper level jet. There is enough moisture and weak instability in place this afternoon into this evening for some isolated shower/thunderstorm development, primarily near the continental divide and across southwest MT with the arrival of additional moisture overnight leading to more widespread precipitation developing near the continental divide. A fairly potent shortwave trough moves onshore Monday and continues east with cyclogenesis occurring in southern AB as the wave emerges east of Rockies late Monday/Monday night. This drives a Pacific cold front across the area Monday afternoon with widespread precipitation initially along the continental divide transitioning to showers and a few thunderstorms shifting east across the area in association with the cold front. The risk for thunderstorms is greatest across eastern portions of central and southwest MT Monday afternoon with strong wind gusts being the primary concern with any storms. Precipitation at higher elevations in Glacier national park (above 5500 ft) may change to snow Monday evening as colder air aloft moves in behind the cold front though most areas further south and east across the area will see precipitation diminish as the colder air arrives behind the front. The passage of the cold front late Monday afternoon/evening will mark the beginning of a very windy period for much of the area as strong westerly flow surges across the Rockies to the south of the wave ejecting east across AB Monday night with another surge of stronger westerly flow moving across the area Tuesday and Tuesday night as the upper level jet moves across the region. Wind gusts in excess of 55 mph become likely (>60% probability) initially along the Rocky Mtn Front and adjacent areas Monday evening and likely also adjacent to the the Little Belt/Highwood/Bears Paw mountain ranges later Monday night aided by favorable temperature/wind profiles for mountain wave enhancement. The second surge of stronger westerly flow on Tuesday looks to bring more widespread potential for gusts in excess of 55 mph with probabilities ranging from 40-60% across much of the north-central MT plains to 90% or higher along the Rocky Mtn Front with 20-30% probabilities for valley locations north of I90 including the Helena and Bozeman areas. No changes were made to the High Wind Watch overnight. The upper level jet lifts north Wednesday with winds aloft and at the surface gradually relaxing by Wednesday afternoon and evening as upper level ridging begins to build across the western US. longer range model ensembles continue to support amplification the the ridge late this week into the weekend with temperatures trending above seasonal averages. There continues to be some divergence however with the precise location of the ridge axis leaving some uncertainty still at this time in exactly how much above average temperatures will be and the location/origin of moisture moving into the area around/over the ridge by next weekend. Hoenisch && .PRELIMINARY POINT TEMPS/POPS... GTF 72 55 70 45 / 10 30 50 10 CTB 69 50 65 42 / 10 30 20 10 HLN 75 55 70 45 / 20 20 90 20 BZN 72 51 68 40 / 30 10 90 60 WYS 64 44 55 37 / 40 20 100 80 DLN 71 52 65 40 / 10 10 90 30 HVR 75 54 75 47 / 0 30 50 20 LWT 69 50 68 41 / 10 20 80 50 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Watch from Monday evening through Wednesday morning for East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera-Northern High Plains-Southern High Plains- Southern Rocky Mountain Front. High Wind Watch from Tuesday morning through Wednesday morning for Bears Paw Mountains and Southern Blaine-Cascade County below 5000ft-Eastern Toole and Liberty-Fergus County below 4500ft-Hill County-Judith Basin County and Judith Gap-Northern Blaine County. && $$ http://www.weather.gov/greatfalls