865 FXUS65 KTFX 150002 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 559 PM MDT SUN AUG 14 2016 .UPDATE AVIATION... .DISCUSSION... Tonight through Tuesday...Flow aloft over Montana will vary from westerly this evening to northwesterly on Monday then back to westerly again on Tuesday. A weak disturbance in the flow aloft has already triggered scattered showers and thunderstorms over northern portions of the forecast area this afternoon. These storms will persist into this evening with additional storms also developing in southwest Montana over the next few hours. Convection will die out in most locations around midnight, although a few showers may persist near Glacier Park into the early morning hours. Warm temperatures and slightly more stable conditions will prevail on Monday. Isolated/possibly scattered storms may develop during the afternoon and early evening hours but coverage is expected to be mainly over the mountains and eastern portions of the forecast area. As another ridge of high pressure aloft builds over the region on Tuesday, temperatures will rise to near or possibly above 90 for many locations. Isolated storms will be possible over far southwest Montana during the afternoon but the remainder of the forecast area should remain dry. Synoptic level winds are expected to remain light through the short term period, but any storms that develop could produce locally strong gusts. mpj Tuesday night through Sunday...An upper level low pressure trof will move through the Pacific Northwest and approach the Rockies Wednesday and again cause the air mass to become unstable. Greatest instability will remain north of the Canadian border while, to the south, extreme Southwest Montana will become slightly unstable. Timing of the cold front Thursday will largely determine thunderstorm activity. As colder air moves aloft, the air mass will become increasingly unstable, especially Southwest Montana, but northern portions of the CWA behind the front will be cooler and stable. Current timing indicates winds will switch north along the border by midnight Wednesday night with colder air moving across the border by sunrise. The 500mb pattern of the GFS and ECMWF are now quite similar...evolving more towards the earlier ECMWF solutions. Thus, the GFS has strengthened its cold front and drives it deeper into the CWA. However, the GEM has changed to a sharper trof very similar to the earlier runs of the ECMWF and brings the colder air into the region nearly a day later. With the consistency of the ECMWF, will use a GFS/ECMWF blend this period. Mostly stable conditions will return Saturday and Sunday although unsettled northwest flow will keep some chance of showers in the forecast Saturday. Zelzer Long Term Afternoon Update: Models continue to come in alignment on the strong cold front for later this week. Front looks to come through Wednesday night through Thursday. This will bring widespread showers and a few thunderstorms. Increased pops to get some areas into likely with the latest model agreement. Cold air behind the front on Thursday will cause temperatures to struggle...and highs in the low to mid 60s across the lower elevations is looking more and more likely. Lowered temps slightly on Thursday...then tweaked them into the weekend...as looks like temps may rebound back into the 80s by late next weekend. 700 mb temps near to slightly below zero will also promote some chances for snow...mainly around 8000 feet and higher on Thursday night into Friday morning. GFS still dries things out quicker than the Euro for Friday. Continued at least slight pops to account for the Euro. Next weekend is starting to trend dry as northwest flow is replaced by a weak ridge of high pressure. Anglin && .AVIATION...UPDATED 0000Z. Primarily VFR expected over next 24-hours as westerly flow aloft persists. Isolated showers and thunderstorms are currently developing across northern, central, and far southern portions. Expect this thunderstorm threat to linger through the evening hours. Brief gusty winds of 30 to 35 Knots will be possible, along with brief MVFR conditions mainly along and north of a line from KGTF to KLWT and south of KBZN. Thunderstorms will diminish shortly after sunset tonight, with some isolated showers possible until around 12z. VFR conditions with only a few cumulus clouds is expected for Monday. Anglin && .PRELIMINARY POINT TEMPS/POPS... GTF 54 88 54 91 / 10 10 0 0 CTB 52 84 53 88 / 20 10 0 10 HLN 58 90 58 93 / 0 0 10 0 BZN 52 88 51 91 / 10 10 10 0 WEY 41 77 43 79 / 20 20 20 10 DLN 51 86 50 87 / 10 0 0 0 HVR 56 87 57 90 / 10 10 10 0 LWT 55 85 56 88 / 10 20 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/greatfalls