Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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200 FXUS65 KTFX 272256 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 456 PM MDT Thu Jun 27 2024 ...Aviation Section Updated... .SYNOPSIS... Showers and thunderstorms diminish later this afternoon and evening, but showery, windy, and much cooler conditions are expected tonight into Friday, with most precipitation falling over North-central Montana. Drier and milder weather is expected for the first half of the weekend, followed by a return of more active weather Sunday into early next week. && .DISCUSSION... Showers and embedded thunderstorms continue to move through the eastern portions of Central/North-central Montana this afternoon while a much more isolated brand of activity is situated farther to the west. Instability never really sufficiently recovered for any widespread stronger to severe thunderstorm development, but there were a a few instances of wind gusts over 40 mph and some small hail along the Hi-Line and the southwest. This trend should continue, with only isolated small hail and or wind gusts, if any, for the remainder of the afternooon. Post frontal westerly winds have already begun to increase and westerly flow aloft will become stronger this evening and tonight while the mid- level low moves along the Canadian border. This will maintain breezy to windy conditions along the Rocky Mountain Front and the plains during the overnight hours. Wind speeds should generally stay in the 20 to 35 mph, except along the Rocky Mountain Front and adjacent high plains where there is around a 60 to 80% chance for wind gusts exceeding 55 mph this evening into the overnight hours. Given the higher criteria (75 mph) for high winds along the Rocky Mountain Front and the lower wind exceedance probabilities over the high plains, I opted for a Special Weather Statement and weather stories to address the expected impacts. Precipitation chances remain on the low side this evening before wrap around moisture brings showers and stratiform rains southward over northern areas as the night progresses. There will be sufficient cold air aloft for some higher mountain snow over the higher terrain of Glacier National Park, though accumulations look to be negligible and impacts are expected to be limited to cool and wet outback conditions. Showers and perhaps a few thunderstorm will move deeper into Central and North-central Montana on Friday while cool northwesterly winds keep temperatures a good 10 to 20 degrees below average for this time of year. H700 to H500 flow in the 40 to 45 kt range combined with cold air advection and lower end shower/thunder activity may result in a few surface wind gusts over 50 mph, mostly along the Hi- Line and Fergus/Judith Basin Counties. There are no plans for high wind products on Friday either with the expected isolated nature of higher end wind gusts and NBM probabilities for criteria winds remaining well under 80% at this time. Transient ridging brings a period of lighter winds and drier conditions Friday night and much of Saturday before a more unstable southwesterly flow aloft develops ahead of the next approaching Pacific weather system by Sunday and brings a return of shower thunderstorm chances. Most ensembles favor a northwesterly flow aloft for the first half of next week with passing disturbances maintaining daily chances for showers and thunderstorms and near to slightly below average temperatures. - RCG && .AVIATION... 28/00Z TAF Period Showers and thunderstorms have largely pushed east of Southwest through North Central Montana; however, and isolated shower/storm will remain possible over the plains through approximately 03z Friday, primarily over eastern portions of Central and North Central Montana. Additionally, rain showers and an isolated thunderstorm or two will continue along the Continental Divide north of the Montana Hwy 200 corridor through much of the overnight hours. Biggest impact to terminal operations over the next 9-12 hours will be strong and gusty west winds, especially at the KCTB terminal where frequent gusts of between 35-45kts will occur over this timeframe. A southward advancing cold front beyond 09z Friday will then bring a wind shift to more of the north, in addition to lowering CIGS and additional chances for showers and an isolated thunderstorms. These lowering CIGS, which are expected to fall as low as LIFR/IFR/MVFR, will predominately impact the KCTB, KHVR, KGTF, and KHLN terminals through Friday afternoon. Isolated mountain obscuration through the overnight hours will become more widespread in wake of the aforementioned cold front on Friday. - Moldan Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 49 61 43 74 / 10 80 10 0 CTB 48 61 42 70 / 50 90 0 0 HLN 50 68 45 84 / 0 30 0 0 BZN 42 68 40 81 / 10 10 0 0 WYS 36 65 34 80 / 10 0 0 0 DLN 41 69 40 82 / 0 0 0 0 HVR 50 63 43 74 / 30 70 10 0 LWT 45 59 38 71 / 10 50 10 0 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls