940 FXUS65 KTFX 131138 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 535 AM MDT Tue Sep 13 2022 Updated Aviation Discussion .SYNOPSIS... An increasingly moist southwest flow across the region with embedded weather disturbances will bring a chance for showers and isolated thunderstorms through the next several days. Temperatures remain above seasonal averages today then cool back to seasonal averages Wednesday through Saturday with some additional cooling possible late this weekend. && .DISCUSSION... The upper level ridge has shifted east of the Rockies and will continue east today as broad troughing with several embedded shortwave features moves inland across the Western US through the next several days. Southwest flow aloft is importing deeper moisture into the region, initially in the mid-upper levels, with showers expected to develop and track northeast into areas near the Continental Divide and Southwest MT this afternoon with an embedded shortwave disturbance lifting out of the Great Basin. These showers look to move into areas along the I-15 corridor early this evening before shifting east overnight. Instability will be limited by extensive high cloud-cover and still dry lower levels, but cannot rule out some isolated lightning late this afternoon and evening with some of the showers. An upper level low embedded within the broader trough slowly moves inland across WA by Wednesday afternoon before lifting out across BC/AB Wednesday night and Thursday, while another embedded shortwave lifting out of Great Basin reaches SW MT late Thursday. Unseasonably deep moisture content remains across the region through at least Thursday night with better chances for diurnally driven showers and thunderstorms Wednesday and Thursday across the area, with greatest coverage across Western and Southwest MT. Another round of more widespread spread showers may lift across North-central MT Thursday night and Friday as the disturbance from the SW lifts through the area. While lower level smoke impacts to visibility and air quality has improved some in the last 24 hrs, extensive smoke aloft will likely continue across the area through the next 48hrs. Lower level smoke may increase again this afternoon before gradually improving with increases in precipitation chances both here and upstream in the vicinity of the wildfires. Looking ahead, medium range model guidance has come into better agreement on continued upper level troughing across the western US this weekend with a trend toward a sharper trough late this weekend into early next week. This is supported by ensembles means and cluster analysis with main differences related to the degree of splitting and timing of the trough. Despite the uncertainty with details, this would bring cooler temperatures (highs in the 60s) and additional chances for precipitation with some potential for snow at higher elevations in the mountains. Hoenisch && .AVIATION... 535 AM MDT Tue Sep 13 2022 (13/12Z TAF period) Mid to high level clouds continue to increase today under an increasingly moist southwest flow aloft. Showers develop over western areas this afternoon and track north and northeast across central and eastern areas tonight. Smoke will likely continue to reduce slant range visibility with some periods of surface visibility reduction to around 5-6SM possible this afternoon. MVFR conditions become more likely tonight in areas of showers. Easterly surface winds with 15- 20kt gusts are possible through the morning across eastern portions of north-central MT, including KHVR with winds decreasing this afternoon. Generally light winds elsewhere with some brief erratic winds possible near showers this afternoon. Hoenisch Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 81 53 76 47 / 20 40 30 10 CTB 76 50 72 45 / 30 30 40 20 HLN 82 55 79 50 / 30 60 30 20 BZN 81 52 75 47 / 20 50 40 20 WYS 73 42 64 38 / 20 80 70 30 DLN 75 47 72 45 / 60 60 20 20 HVR 81 55 73 46 / 10 40 30 0 LWT 81 50 72 46 / 10 40 30 10 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls