867 FXUS65 KTFX 290442 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1040 PM MDT Sun May 28 2017 Updated Aviation Discussion .UPDATE... Main update this evening is to significantly trend down the isolated shower and thunderstorm activity along the east slopes of the Rockies and into Southwest Montana. The main area of activity currently is in the vicinity of Great Falls, and it should diminish after sunset as it loses daytime heating and moves into the area of the Big/Little Belt Mountains. Any lingering showers and thunderstorms should be done by midnight. The rest of the forecast remains in good shape. Coulston && .SYNOPSIS... An upper-level ridge of high pressure currently over the Pacific Northwest will slowly move eastward over the next few days. As a result, scattered showers and thunderstorms over our area today will become more isolated for Monday through Wednesday. Temperatures trend gradually warmer through Wednesday. Chances for showers and thunderstorms increase again late in the week. && .AVIATION... Updated 0440z. With upper level ridging exerting its influence on the area, tranquil conditions with VFR cigs and visibility should predominate all terminals through the next 24 hours. Enough instability remains over the mountains after 18z Monday to trigger a few showers/storms. However, with light winds aloft any shower/storm activity will remain confined to the mountainous terrain. Cassell && .HYDROLOGY... The Big Hole River near Melrose is forecasted to go above flood stage later this week. The rate the river rises this week is greatly dependent on how fast the higher elevation snow pack melts. Thus we will continue to monitor for possible flood highlights later this week. Brusda && .PREV DISCUSSION... /ISSUED 500 PM MDT Sun May 28 2017/ Tonight through Tuesday...Scattered rain showers and thunderstorms have been most concentrated today over Fergus County and along central portions of the Rocky Mountain Front. Satellite imagery reveals boundary layer cumulus marking a convergence line running from near Cut Bank to Havre to Lewistown. This is providing a source of initiation for the observed showers. Short-term model guidance suggest that a minor short wave feature aloft, combined with northeasterly upslope is responsible for the showers along the Rocky Mountain Front. All of this activity will continue to drift slowly SSE into central Montana through this evening. Gusty winds may be possible in the vicinity of some of the stronger showers or thunderstorms. The large scale upper level ridge axis drifts over the forecast area Monday and Tuesday, providing mainly dry and warmer conditions, except for isolated mountain showers. PN Tuesday Night through Sunday...An upper-level ridge of high pressure will be over the region Tuesday night into Wednesday, resulting in fair weather for most. Just a few showers and thunderstorms are possible over and near higher terrain Tuesday evening and again Wednesday afternoon/evening. The EC and GFS are in good agreement that a Pacific disturbance will then overspread our area Thursday into Friday, resulting in a somewhat higher potential for scattered showers and thunderstorms. The aforementioned models then disagree on the timing of additional shortwaves for the upcoming weekend. However, the potential of scattered showers and thunderstorms should persist. Temperatures look to be above normal through the extended period, with Wednesday likely being the warmest day. Brusda/Jaszka && .PRELIMINARY POINT TEMPS/POPS... GTF 45 71 46 79 / 20 0 0 0 CTB 44 71 43 77 / 10 0 0 0 HLN 48 75 49 82 / 20 0 0 0 BZN 43 72 43 79 / 20 0 0 0 WEY 36 63 34 70 / 30 10 10 20 DLN 44 72 45 78 / 10 0 0 10 HVR 41 71 41 79 / 0 0 0 0 LWT 41 67 41 73 / 0 0 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/greatfalls