Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
234 FXUS65 KGGW 202017 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 217 PM MDT Thu Jun 20 2024 .DISCUSSION... KEY MESSAGES: - Shower and thunderstorm chances increase through Friday, when stronger storms and a more widespread wetting rain is expected. - A few isolated severe cells Friday late afternoon and evening are possible, with wind and hail the primary threats. - A slow warm up is expected through Sunday when some 90s for highs likely appear. WEATHER PATTERN OVERVIEW: Scattered rain showers and isolated thunderstorms are increasing in coverage this afternoon and looking to be mainly south of the Missouri River. SPC`s HREF is pointing toward some gusty winds with these cells upward of 50 mph by 6pm this evening amidst increased updraft helicity, but isolated and focused to the southwest over higher terrain. However, a shortwave arriving Friday afternoon does look like it has the chance for a isolated severe cell or two with about 1000 J/kg CAPE, bulk shear around 40-50 kts, and precipitable water over 1 inch. The one problem with this environment appearing in forecast soundings and that is a cooler than average surface layer with cloud cover, which will keep most convection elevated rather than surface based. This may prevent strong winds initially. That being said, CAMs point towards strong cells embedded in light shower activity which could form their own environments and CAMs also point towards a couple 50-65 mph gusts that could occur with the strongest cells. The chance of at least one case of severe weather in the GGW CWA Friday late afternoon and early evening is about 60%, with the chance of a single point getting hit by it less than 10%. Rain totals with this passage vary from a tenth to a half inch over the CWA, with locally higher amounts where storms train. Afterward, a ridging pattern will favor seasonably warm and drier conditions from Sunday into the middle of next week. FORECAST CONFIDENCE and DEVIATIONS: There is high confidence (60-80%) in general thunder with minimal chances (10%) for severe weather at a particular point Friday afternoon and evening. Confidence is medium to high for the general conditions remaining slightly warmer and drier than normal through much of next week. -Zanker/GAH && .AVIATION... LAST UPDATE: 2000Z FLIGHT CAT RANGE: VFR - MVFR DISCUSSION: SCT/BKN mid level cumulus is developing into scattered showers and isolated thunderstorms late this afternoon and evening, especially south of the Missouri River. Mainly KSDY and KGDV will be impacted with medium (40%) confidence for brief MVFR conditions. More widespread shower activity with embedded stronger storms arrive after 18Z Friday. SFC WIND: Calming to less than 10 kts tonight, then east around 10 kts Friday afternoon. Expect gusty and erratic winds near any thunderstorm. && .GGW WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/glasgow