Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
997 FXUS65 KGGW 262150 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 350 PM MDT Wed Jun 26 2024 .DISCUSSION... KEY MESSAGES: 1) Severe thunderstorms are increasingly likely on Thursday beginning late morning over central Montana and tracking east into the Dakotas during the evening hours. 2) Breezy conditions are likely on Friday behind the cold front, with Lake Wind criteria expected. 3) Cooler temperatures are also expected Friday and Saturday with chances for showers and thunderstorms on Friday. WEATHER PATTERN OVERVIEW: Surface low pressure looks to develop over central Montana tonight as existing ridge axis moves east turning the flow aloft to the SW which will allow for a chance of showers and thunderstorms. An upper low moves in from the west on Thursday. The surface low will shift east across eastern Montana during the day on Thursday along with a surface cold front. SE winds ahead of the cold front will bring dew points into the 60s east of Glasgow and Jordan on Thursday and approaching 70 near Sidney. The mean surface based CAPE over eastern portions of the CWA looks to reach 2000 J/KG or better by Thursday afternoon and evening while forecast soundings show 40-50 kts of 0-6 km shear present. This will all set the stage for the return of active severe weather across NE Montana. Latest HREF maximum updraft helicity shows storms reaching SW zones around 10am and spilling into the area during the late morning hours. Meanwhile, storm coverage looks to increase along the MT/ND border during the late afternoon and evening hours. Initial supercells may congeal into line segments during the evening as storms shift into the Dakotas. All hazards are favored including up to 2 inch diameter hail, wind gusts to 75 mph, an isolated tornado, and locally heavy rainfall. The SPC has eastern portions of the CWA under an enhanced risk for severe storms. Fast progression of the storms to the east should limit the flooding threat, but conditions will continue to be monitored. The upper trough will push into eastern Montana on Friday with additional lingering general thunderstorms along with gusty west winds (sustained 20, gust 30), and cooler temperatures. These conditions may be sufficient for the Lake Wind Advisory issuance at some future point. Upper ridging will guide warm and dry weather on Saturday before more ensembles hint at more active weather early next week. FORECAST CONFIDENCE & DEVIATIONS: The forecast was trended toward the NBM but edits were made to include severe wording into the weather grids and heavy rainfall. Confidence of high that there will be thunderstorms on Thursday. Confidence is low on rainfall amounts as there will be widely varying precipitation depending on exactly where storms track: ranging from a trace to upwards of an inch. Forecast soundings show precipitable water values exceeding an inch as WPC has the area under a Marginal risk for excessive rainfall. Widespread hydrology concerns are not expected as the storms will move fairly steadily eastward, but locally heavy rainfall may result in some of the storms. && .AVIATION... Mainly VFR conditions are expected tonight but MVFR/IFR conditions may result between 18Z and 02Z Thursday as strong to severe thunderstorms track from west to east across NE Montana. Expect low ceilings and visibilities if a storm tracks directly over a storm. Some of the storms may produce large hail, gusty and shifting winds, and heavy rainfall. && .GGW WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/glasgow