FXUS65 KTFX 191536 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 936 AM MDT Fri Jul 19 2024 .SYNOPSIS... Persistent upper level ridging over the Western US will help to maintain well above normal temperatures and overall dry conditions across Southwest through North Central Montana through the middle of next week. && .UPDATE... Updated forecast is out. Only real change this morning was to update the temperatures towards current trends, then limit thunderstorm activity to mostly the Rocky Mountain Front area this afternoon. Otherwise, the rest of the forecast is on track. Brusda && .AVIATION... 19/12Z TAF Period VFR conditions are expected to prevail through the TAF period with generally light winds. Isolated showers and thunderstorms are possible this afternoon along the Rocky Mountain Front and in far southwestern Montana but confidence in impacts for any terminals remains too low to mention in the TAFs. With regards to haze, there is a less than 20% chance for visibility reductions at KEKS and KWYS. The difficultly in whether or not to include the mention of haze in the TAFs was there is such low confidence in the timing of any potential impacts. For the most part, visibility at the terminals is not expected to be impacted so given the low confidence in timing, haze was left out of this round of TAFs. Otherwise, density altitude concerns from hot temperatures, as well as slant range visibility concerns due to wildfire smoke will continue this TAF period. -thor Equipment Note: Due to a failure of the KEKS AWOS, no amendments are scheduled until further notice. Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 545 AM MDT Fri Jul 19 2024/ Today through Saturday...upper level ridge will amplify through the first half of the weekend, with continued well above normal temperatures and overall dry conditions expected across Southwest through North Central Montana. Surface winds beneath this amplifying ridge will remain overall light; however, infrequent wind gusts during peak mixing may approach 15 to 25 mph. While most locations will remain dry through the timeframe, isolated to scattered showers and thunderstorms will be possible during the afternoon and evening hours, most notably over the higher terrain on both days and east of a Lewistown to Havre line on Saturday. Primary threat from any shower or thunderstorm will be gusty and erratic winds given inverted-V soundings. Sunday through Wednesday...ensemble clusters continue to favor strong upper level ridging residing over much of the Western CONUS, with longwave troughing over the Pacific Northwest and western seaboard of Canada. This upper level ridge will help maintain well above normal temperatures and overall dry conditions across Southwest through North Central Montana through the period. Leading mode of uncertainty through the timeframe will be position and/or timing of the aforementioned trough over the Pacific Northwest and western seaboard of Canada, which will ultimately impact when the upper level ridge over the Northern Rockies begins to be broken down. Thursday through next Friday...ensemble clusters favor the breakdown of the upper level ridge over the Northern Rockies as a longwave trough slides east from the western seaboard. Leading mode of uncertainty through the period will be the position and/or timing of the longwave trough, which will ultimately impact how long the above normal temperatures last across Southwest through North Central Montana. None-the-less, ensemble model guidance does support a brief and slight "cool down" towards the end of the work week as upper level heights fall, but this may only result in daytime highs reaching the mid- to upper 80s vs the preceding 90s to near 100 degrees. Additionally, as the ridge breaks down, expect southwest to west winds to increase. - Moldan && .PRELIMINARY POINT TEMPS/POPS... GTF 93 60 94 59 / 0 10 10 0 CTB 92 55 94 57 / 0 10 20 10 HLN 98 60 98 60 / 0 0 10 0 BZN 95 54 95 54 / 0 0 10 10 WYS 86 42 85 42 / 0 10 20 10 DLN 90 52 90 51 / 0 0 10 0 HVR 96 61 97 60 / 0 10 20 20 LWT 88 56 88 55 / 0 10 30 20 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls