746 FXUS65 KTFX 300519 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1119 PM MDT Thu Jun 29 2023 ...Aviation Section Updated... .SYNOPSIS... An upper level ridge of high pressure will start to build over the Northern Rockies for a few days. This will result in very warm temperatures moving into Central MT for Friday and Saturday. The chances for storms will also be on the low side the next few days. Cooler temperatures and a chance for precipitation moves back in for early next week and the 4th of July. && .UPDATE... Main adjustment to the overnight forecast was to bring a slight chance of a weak shower or thunderstorm to the Hi-Line area between Cut Bank and Havre. High resolution short range models are in agreement with this, and convective cloud cover just north of the border in southern Alberta hints that something could move south of the border overnight. Also lowered temperatures a few degrees to reflect the potential for better radiational cooling than previously expected, as much of the area should remain mostly clear with light winds after a day of low relative humidity. Also matched up with idea from NWS Glasgow for an increased chance of showers and thunderstorms across North Central Montana tomorrow afternoon and evening. A weak disturbance moving through the high pressure ridge may have just enough moisture to combine with unseasonable warmth to cause a few showers or thunderstorms. -Coulston && .AVIATION... 1119 PM MDT Thu Jun 29 2023 (30/06Z TAF Period) VFR conditions prevail this TAF period. An outside chance exists for a shower or thunderstorm late Friday afternoon and early evening across terminals, but confidence was too low to even include prob30 groups at this time. Light westerly to southwesterly winds are expected across most terminals Friday afternoon. -AM Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 543 PM MDT Thu Jun 29 2023/ Tonight through Saturday...A few thunderstorms will affect the CWA this evening, with the best chance for storms mainly south of a line from Helena to White Sulphur Springs. Brief heavy rainfall and lightning will be the main impacts from any storms this evening. The thunderstorm activity will be more isolated for both Friday and Saturday. Otherwise, the warming trend will continue with slightly warmer afternoon temperatures expected each day for Friday and Saturday. Sunday through Thursday...An upper level trof of low pressure will start to move southward from Canada into North Central MT early next week. The forecast models differ a bit on the timing of when precipitation begins/ends but overall the forecast models bring in some cooler temperatures for early next week. For the 4th of July, afternoon temperatures could be close to 10 degrees below normal for this time of year. In terms of precipitation, the EC is wetter than the GFS, with the EC showing long periods of steady rain for Monday into Tuesday. The GFS is not quite as wet, and more scattered with the precipitation. Overall, I will continue with the NBM solution for this time period with some potential for pops to increase should the precipitation become more likely. Brusda && .PRELIMINARY POINT TEMPS/POPS... GTF 55 87 58 90 / 0 0 0 10 CTB 53 87 55 88 / 0 10 0 0 HLN 57 89 61 91 / 0 10 0 10 BZN 50 84 55 86 / 0 10 0 10 WYS 39 77 44 78 / 10 10 10 20 DLN 47 79 53 83 / 0 10 0 20 HVR 58 91 60 94 / 10 10 10 0 LWT 51 82 57 85 / 0 20 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls