187 FXUS65 KTFX 272027 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 227 PM MDT Thu Jul 27 2017 .SYNOPSIS... A weak disturbance will bring a chance of showers and thunderstorms through this evening. Some of the stronger storms could produce frequent lightning and strong wind gusts. A chance for showers and thunderstorms will continue into Friday though thunderstorms will not be as widespread. High pressure rebuilds on Saturday. Temperatures will remain above average. && .DISCUSSION... Tonight through Saturday...Scattered showers and thunderstorms will continue through this evening as an upper-level shortwave moves across the state. Thunderstorms with gusty and erratic winds as well as frequent lightning are the primary threats. Most of the thunderstorm activity will develop over higher terrain initially and then move into the plains and valleys. On Friday, the chance for thunderstorms will persist but will mainly be confined to southwest Montana and the island mountain ranges across central Montana, but activity over the plains can also not be ruled out. The upper-level ridge of high pressure will re- build on Saturday with dry and very warm conditions anticipated statewide. An isolated thunderstorm is possible in the mountains across southwest Montana, however the threat is low. Temperatures will remain above average with highs ranging from the upper 80s across southwest Montana to low 90s over north-central Montana. MLS/Cassell Saturday night through Thursday...Unusually-strong high pressure ridging aloft will reside over the CWA during this period. Simultaneously, weather disturbances will traverse the ridge from west to east, particularly on Monday and Tuesday. As a result, a few showers and thunderstorms are possible each day. This is especially the case during the afternoon/evening hours and over/near higher terrain. A dry environment will allow new fire starts from lightning strikes to remain a concern. In addition, significant evaporation of rain should yield strong wind gusts in/near any shower or storm. Near-normal lows are expected during the period, while daytime highs will be about 5-10 degrees above- normal and easily reach the 90's for most locations. Jaszka && .AVIATION... Updated 1730Z. Scattered cumulus clouds having bases around FL080 and mid-level ceilings will increase in coverage this afternoon as an upper-level disturbance approaches the area. Scattered showers and thunderstorms are expected mainly over southwest Montana affecting KEKS and KBZN, possibly extending toward KLWT this evening. Isolated showers and thunderstorms further north into central MT are less likely, but cannot be ruled out. VFR conditions prevail except for local MVFR ceilings near thunderstorms. && .FIRE WEATHER... Scattered showers/thunderstorms will slowly wind down over our southern and eastern districts through this evening, ending from west to east as the upper-level trough axis passes through. The main threat from any storms will be gusty erratic winds and frequent lightning. Behind this system, gusty west to northwest winds and continued warm and dry conditions will yield a highly elevated (bordering critical) fire weather threat over the plains Friday afternoon into early evening, while isolated thunderstorms will be possible over the southern districts. Cassell && .PRELIMINARY POINT TEMPS/POPS... GTF 62 90 59 93 / 20 10 10 0 CTB 57 87 53 90 / 10 10 0 0 HLN 62 89 61 93 / 30 20 20 10 BZN 55 86 54 90 / 30 20 20 10 WEY 46 76 43 80 / 30 20 20 10 DLN 54 82 52 87 / 50 20 10 0 HVR 65 92 60 95 / 20 10 0 0 LWT 61 87 58 90 / 20 10 20 20 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/greatfalls