Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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591 FXUS65 KTFX 100257 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 857 PM MDT Sun Jun 9 2024 .SYNOPSIS... Showers and thunderstorms will continue to lift northeast from Idaho and across Southwest and into Central Montana through the afternoon and early evening hours. A few of the thunderstorms this afternoon could be severe and produce damaging wind gusts. Additional showers and thunderstorms are then expected to slide east across the remainder of Central and North Central Montana overnight and into the morning on Monday. Drier and breezy conditions are expected through the first half of the work week, especially on Tuesday and Wednesday. && .UPDATE... Main update for this evening was to bring showers into Central Montana a bit sooner than previously forecast. Radar echoes are spreading northeast out onto the plains as of this evening, so have moved mention of showers there from around midnight to this evening. Otherwise, the forecast is generally on track, as the Pacific cold front continues to move into the area. The scattered showers and thunderstorms have moved northeast out of Southwest Montana, but another round of showers and storms may still move into that area from Idaho around and after midnight. && .AVIATION... 10/00Z TAF Period VFR conditions are mostly expected through at least 11/00Z across North Central (KCTB KHVR), Central (KLWT, KGTF, KHLN), and Southwest (KBZN, KEKS, KWYS), unless otherwise specified. A Pacific disturbance with an associated cold front will move scattered showers and thunderstorms over the area through at least 09Z, with the main threat being wind gusts of up to 40 kt. The greatest threat for thunderstorms will mostly be along and south of a KHLN-KLWT line, where periods of mountain-obscuring MVFR conditions are possible with heavier downpours. As the disturbance pushes the cold front east through the area between 09Z and 15Z, the breezy southerly to easterly winds will shift more westerly, and the westerly winds aloft will cause some mountain wave turbulence. Clouds and showers should also decrease from the east after 12Z with this shift to more of a downslope wind. Gusts of 20 to 30 kt over the plains could exceed 35 kt along the Rocky Mountain Front. -Coulston Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 615 PM MDT Sun Jun 9 2024/ Rest of today through tonight...primary forecast concern throughout the period will be the threat for thunderstorms, some of which could become severe and produce damaging wind gusts. Thunderstorms have initiated over Northeast Idaho early this afternoon and were beginning to lift northeast over the Idaho/Montana border into Southwest Montana. BUFKIT soundings across Southwest Montana, most notably in the Dillon and Bozeman Areas, in advance of these initial storms show a classic inverted-V beneath H600. Showers and thunderstorms, especially collapsing ones, moving into this environment will be capable of producing gusty/erratic winds and even a few isolated damaging wind gusts through the afternoon hours. After the initial push of showers and thunderstorms through the mid- to late afternoon the threat for damaging winds should begin to subside as the column becomes saturated and a transition to brief periods of heavy rainfall occurs. Showers and thunderstorms will continue to lift northeast and into Central Montana through the early evening hours tonight, with additional showers and an isolated thunderstorm or two sliding east from Western Montana and across Central and North Central Montana from the late evening through overnight hours tonight. - Moldan Monday through Friday...Westerly winds increase and things dry out on Monday following the passage of the shortwave, but another weak perturbation does move across the region during the afternoon hours for additional isolated to scattered showers and thunderstorms, mostly along the Hi-Line and over and near areas of higher terrain elsewhere. Ensembles remain in fairly good agreement with a zonal flow aloft settling in for the mid-week period. H700 to H500 flow will be on the stronger side for this time of time of year, mostly between 40 and 50 kts or 2 to 3 standard deviations above climatology according to the NAEFS (North American Ensemble Forecast System). Deep layer mixing should encourage breezy to windy conditions, especially over the plains and the Rocky Mountain Front on Wednesday. Wind exceedence probabilities suggest that peak wind gusts will mostly fall between the 35 and 55 mph range except along the Rocky Mountain Front and adjacent high plains where gusts up to and exceeding 60 mph will be more common. The primary impact will be to summer outdoor recreation and travel; however, afternoon temperatures in the 70s and 80s combined with the said winds and minimum relative humidity values in the teens and 20s is expected to accelerate the curing/drying of grassland fuels. While no fire products are anticipated this time around, this may set up fire weather concerns in the future. Saturday through next Sunday...Uncertainty remains in terms of forecast details for the upcoming weekend, but ensembles continue to highlight a Pacific trough exerting an influence over the Northern Rockies. At this time, there is an expectation for breezy conditions, isolate to scattered shower and thunderstorm activity, and a slight cool down for Saturday and Sunday. - RCG && .PRELIMINARY POINT TEMPS/POPS... GTF 56 80 50 84 / 60 20 0 0 CTB 51 77 49 81 / 50 20 10 0 HLN 59 84 51 86 / 80 10 0 0 BZN 55 78 45 84 / 90 60 0 0 WYS 47 71 39 74 / 80 40 10 0 DLN 51 76 45 82 / 90 20 0 0 HVR 53 77 49 84 / 70 60 30 0 LWT 54 76 46 79 / 60 60 10 0 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls