Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
642 FXUS65 KGGW 270825 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 225 AM MDT Mon May 27 2024 .DISCUSSION... KEY MESSAGES: 1) A ridge moving in will bring a warming trend through Wednesday with 80s for highs possible Tuesday and Wednesday. 2) Breakdown of the ridge will lead to strong and severe thunderstorms Wednesday afternoon through the overnight hours. Rainfall totals could be over a quarter inch for many locations. WEATHER PATTERN OVERVIEW: Today through Tuesday night: a ridge will move into and through the region during these periods. Just out ahead of the ridge a few afternoon showers and isolated thunderstorms may be possible across the far northeast near the North Dakota border. but these storms look diurnally based and should die off rapidly near sundown. Then dry and clear conditions through Tuesday night with possible highs in the upper 70s and lower 80s Tuesday. Wednesday into Wednesday night: Ridge will begin to exit the area as a Pacific Northwest trough barrels into Montana. Afternoon showers over the central Montana mountains will tap into the mid level lift coming across on a major jet and drag themselves across the western parts of our CWA by the late afternoon hours. These showers and thunderstorms are expected to become strong to severe with bulk shear in the NAM ranging from 30 to 60 kts. Dewpoints ahead of the storm will surge through the night before and reach 55+ *F during the morning hours. CAPE during the late afternoon and evening hours is expected to range from 1000-1500 J/Kg. A CAP will be in place across the east initially which may prevent a rapid expansion eastward until the evening hours when it wears away. Currently, hail and strong gusty winds are expected though CAM timings are varying by about 3 hours for surface trough and frontal passages features. CAMs do not yet agree on a convective mode for this passage, but rainfall totals are looking to range widely depending on main hit-and-misses from three quarters of an inch to a tenth of an inch respectively. Thursday into Thursday night: Center of the entering trough will move across the area and rain showers and isolated thunderstorms will linger through these periods. Friday onward: Expect a warming trend with a large ridge developing over the western half of the CONUS. The crest of the ridge will nudge northward into Montana Saturday and herald the arrival of Montana Summer with afternoon 80s becoming more common. CONFIDENCE & DEVIATIONS: A few mesoscale difference exist in model groupings Wednesday with the storms passage. Some ensemble breakdowns occur in synoptic features beginning to set in around Thursday night into Friday as models resolve exactly how fast the trough exits and the next ridge enters. Here onwards is where confidence breaks down to moderate. && .AVIATION... LAST UPDATED: 0830Z FLIGHT CAT: VFR DISCUSSION: Dry conditions through the majority of the day. Isolated showers or thunderstorms may be possible at KOLF and KSDY from 20-01Z. But currently, these chances(15-25%) do not look high enough to even be added as a Prob30 in the TAF. Then dry conditions clear skies should continue through tonight and into Tuesday. SFC WIND: WNW at 5-10 kts this morning. Picking up to 10-15 kts this afternoon. Becoming light and variable overnight. Then SE at 5-10 kts Tuesday. && .GGW WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/glasgow