812 FXUS65 KTFX 281506 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 906 AM MDT Sat Aug 28 2021 .UPDATE... Scattered, very light rain showers are ongoing across a portion of N-central MT, from around Augusta to Great Falls to Loma. These showers are drifting slowly east-southeast. Satellite imagery shows clearing skies further to the northwest, and as well over Southwest Montana. The lingering showers are associated with a departing upper level trough axis located over central MT, moving away to the east. A combination of post-wave subsidence and drier air arriving from the west will help to clear skies through the afternoon. Updated the forecast to adjust for the light rain showers this morning, trending to mostly sunny in the afternoon. && .SYNOPSIS... A northwest flow aloft will help decrease clouds across the region today with continued cooler than normal temperatures through tonight. A more westerly flow aloft will then bring warming and drying conditions for Sunday into Monday. However, a Pacific weather system will likely bring a return to cooler than normal temperatures and unsettled weather for the mid-week period into next weekend. && .AVIATION... 502 AM MDT Sat Aug 28 2021 (28/12Z TAF period) VFR conditions are expected across the region for much of the next 24 hours. A weak shortwave trough will keep mid level cloudiness over the area through 18Z or so with isolated rain showers over central Montana plains (mainly over KGTF and KLWT). However, there may be enough break in the clouds over southwest Montana to allow patchy fog with periods of MVFR conditions, with the main direct impact to a terminal likely being at KBZN and KWYS. Skies will partially clear after 18Z and breezy west to northwest winds will develop. Gusts may get up to 20 kt or so over the eastern plains (KHVR KLWT). Overall, though, winds will decrease after 00Z. -Coulston && .FIRE WEATHER... As temperatures warm across north central and southwest Montana Sunday and Monday, afternoon relative humidity will generally fall into the 15 to 25 percent range, which will persist across southwest Montana into Tuesday ahead of a Pacific cold front. Overall, though, fire weather concerns will be fairly low, as winds will mostly remain light. However, afternoon winds in far southwest Montana (south of Interstate 90) will become somewhat breezy (southwest 10 to 15 mph with gusts to 25 mph) on Monday and Tuesday, which will need to be monitored, but does not pose a threat at this time. && .PREV DISCUSSION... /ISSUED 502 AM MDT Sat Aug 28 2021/ Today through Sunday...A low pressure trough over Montana will dictate the weather for the region today. Weak energy on the leading edge of the trough early this morning has helped develop some light showers and weak thunderstorms over southwest Montana along and south of a Dillon to Bozeman line. However, these showers and storms should decrease and move east out of the area with the progression of the trough. Weak energy on the back side of the trough, along with more northerly mid level upslope winds, may develop a few light rain showers over the plains adjacent to the north facing slopes of the central Montana mountains, including the Great Falls and Lewistown areas, but any rainfall should only amount to 0.05 inches or less. Otherwise, the trough axis should move east of the forecast area this afternoon, which will likely help decrease the cloudiness and any lingering showers across the area. Winds should mostly remain light, but breezy northwest winds are possible across the eastern plains (including Havre and Lewistown). These continued upsloping winds may be enough to cause a few weak thunderstorms to develop over the Little Belt and Snowy Mountains, but they should diminish into the early evening with the loss of daytime heating. Daytime temperatures will only be about 5 degrees warmer than on Friday, and clearing skies overnight will cause lows to fall well into the 40s for most areas. A broad high pressure ridge will then bring a dry and brisk westerly flow aloft to the area for Sunday. More southerly winds at the surface, an inverted surface trough, and mostly sunny skies will combine to help warm temperatures back above normal. The gradual shift from northwest to west winds aloft will also help continue to keep smoke out of the area. Monday through Tuesday...The next system to impact the area will start to move into the Pacific Northwest on Monday, shifting the flow aloft from westerly to southwesterly. The inverted surface trough will remain over the area, which will help continue the warmer than normal temperatures. The flow aloft will bring a few more clouds to the area, and possibly a period of smoke once again. A weak disturbance in the flow may also bring a few very light rain showers to the plains east of Interstate 15 Monday night. The slow eastward progression of the low pressure trough across the Pacific Northwest will help push the inverted surface trough east across the forecast area on Tuesday as a Pacific cold front, bringing a chance of showers to much of the area, as temperatures cool back below normal for much of the area. There is a slight chance for a few thunderstorms, but it is less certain that they will develop. Winds behind the front over the plains will become gusty out of the northwest, but along and ahead of the front, gusty southwest winds will be more likely in southwest Montana. Wednesday through next Saturday...Overall, forecast models indicate that the low pressure trough will dig south over the Pacific coast states. This will continue the pattern of cooler than normal temperatures with a chance of showers and thunderstorms each day. This seems to be handled well by the National Blend of Models (NBM), so will not deviate from it at this time. -Coulston && .PRELIMINARY POINT TEMPS/POPS... GTF 72 44 82 46 / 20 0 0 0 CTB 71 43 77 44 / 0 0 0 0 HLN 75 47 83 51 / 0 0 0 0 BZN 74 41 81 45 / 0 0 0 0 WYS 67 29 72 34 / 0 0 0 0 DLN 73 39 80 44 / 0 0 0 0 HVR 74 47 81 49 / 10 0 0 0 LWT 67 45 79 49 / 10 0 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls