FXUS63 KBIS 191135 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 635 AM CDT Thu Sep 19 2024 .KEY MESSAGES... - It will be windy through this evening with sustained west winds up to 30 mph at times. Gusts to 50 mph will be possible across the far southwest and far south central. - Expect medium to high chances (40 to 70 percent) for rain showers today, mainly across the north. An isolated thunderstorm or two (20 percent chance) will be possible here as well. - A cooling trend is forecast for the end of the week, with highs in the 60s by the weekend. && .UPDATE... Issued at 622 AM CDT Thu Sep 19 2024 The stacked low is now approaching the southern Saskatchewan/Manitoba border as showers are rotating into the northwest part of the state out of northeastern Montana and the southern Canadian Prairies. Chances for rain will increase through the morning across the northwest, shifting into the north central by late morning or early afternoon. There may be enough instability floating around for some thunder after 15z or so. No major changes were needed for this update. && .DISCUSSION... Issued at 330 AM CDT Thu Sep 19 2024 A stacked low is currently centered over the southeastern corner of Saskatchewan and will slowly creep east northeast into Manitoba by later this afternoon. While most of the large scale forcing will remain north of the International border, there should be enough lift to maintain medium to high chances (40 to 70 percent) of wrap around rain showers across much of the northwest and north central. While instability will be weak, RAP forecast soundings suggest the potential for 100 to 500 J/kg MUCAPE through much of the afternoon across the north. Thus a few thunderstorms are also possible (20 percent chance north). A tight pressure gradient and steepening lapse rates will lead to more breezy/windy conditions through the late afternoon hours. The strongest winds (out of the west or west northwest) should be across the south, with sustained values up to 30 mph and gusts to 50 mph. We did expand the Wind Advisory east a tier, and it now includes Sioux and Grant counties. A few other areas across the west could flirt with advisory criteria at times through the morning and afternoon. Precipitation should move out to the northeast by this evening and winds will continue to decrease, giving way to a mostly clear sky overnight. Lows will drop into the lower 40s to the lower 50s. With light winds and a clear sky overhead, a few upper 30s may not be out of the question across portions of the west. A low amplitude ridge axis will cross the state on Friday, which should help to briefly bump up temperatures. NBM highs are forecast to range from the lower 70s to the lower 80s. A reinforcing cold front will then cross the state Friday night into Saturday morning as the next trough moves through. These features will bring the next low chance (20 to 30 percent) of rain showers (maybe a thunderstorm or two) to the area Friday evening through Saturday morning. Lows Saturday morning will range from the lower 40s to the lower 50s. Saturday should be rather blustery behind the cold front with breezy northwest winds and highs only in the 60s. We will see some clouds hanging around through the first part of the day on Saturday, but surface high pressure will start to nudge in from the west late afternoon and into the evening, which should lead to diminishing clouds. As winds calm and the sky clears Saturday night, it may become rather chilly, especially across portions of the west where we will likely dip into the mid to upper 30s. Expect lows in the low to mid 40s mainly east of the Missouri River. Thus, some frost is certainly looking like a possibility across the west Sunday morning. However, if we trend more towards the NBM 25th percentile, lows at or below freezing are not out of the question across the southwest. Low amplitude progressive flow will be the pattern driver into the middle of next week with highs expected to mainly be in the lower 60s to lower 70s and only low chances of showers (15 percent) Monday night into Tuesday. Lows should mainly be in the 40s. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 622 AM CDT Thu Sep 19 2024 MVFR ceilings will remain possible this morning across much of the west and south central. KJMS and KMOT should generally remain in VFR categories but KMOT could see brief MVFR visibilities if any heavier showers move overhead today. KXWA will be the other site that may see some showers move through today. An isolated thunderstorm also cannot be ruled out across the northwest and north central through the afternoon. MVFR ceilings will hang around until mid to late morning at KDIK/KBIS/KXWA before lifting. Breezy west northwest winds will be possible for most of today, diminishing towards the late afternoon. Areas across the far south will see the strongest winds, with sustained values up to 30 mph and gusts to 50 mph. && .BIS WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 4 PM CDT /3 PM MDT/ this afternoon for NDZ040>045. && $$ UPDATE...ZH DISCUSSION...ZH AVIATION...ZH