Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
530 FXUS65 KGGW 270825 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 210 AM MDT Thu Jun 27 2024 .DISCUSSION... KEY MESSAGES: 1) Severe thunderstorms are likely on today beginning late morning over central Montana and tracking east into the Dakotas during the evening hours. 2) Breezy west to northwest winds are expected 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 will continue to develop over south central Montana early this morning as an upper low moves in from the west. The surface low will shift east across eastern Montana during the day today along with a surface cold front. SE winds ahead of the cold front will bring dew points into the 60s over most of NE Montana today and will reach near 70 around Sidney. The mean surface based CAPE over eastern portions of the CWA looks to reach 2000 J/KG or better this afternoon and evening while forecast soundings show 40-50 kts of 0-6 km shear present. This will all set the stage for active severe weather across NE Montana. The cold front will move into the western zones of the forecast area this morning which will allow for showers and thunderstorms mainly west of Glasgow and Jordan. The storms will move east this afternoon as the cold front moves to the east. Latest HREF maximum updraft helicity shows storms reaching SW zones in the late morning and spreading east this afternoon. 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 2.5 inch diameter hail, wind gusts to 80 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 to 25, gust 30 to 40), 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 is high that there will be thunderstorms today. 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 NE corner of the state under a slight risk for excessive rainfall and the remainder of NE MT in a marginal risk. 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... LAST UPDATED: 0800Z FLIGHT CAT: VFR most of the time today and tonight. Areas of MVFR/IFR at times today and tonight in showers and thunderstorms. DISCUSSION: There will be varying amounts of clouds this morning mainly at mid and high levels. Expect a mix of low and mid level clouds with a cold front this afternoon and evening with showers and thunderstorms at all TAF sites. Some storms will become severe with erratic wind guts that could exceed 50 knots, hail and heavy rain that could bring periods of MVFR/IFR conditions. Skies will clear after 03z at KGGW and after 06z at the other TAF sites tonight. WIND: East to SE 5 to 15 knots this morning with stronger east winds 15 to 20 knots at KGGW until 12z. A cold front will turn winds to the NW 10 to 20 knots around 19z at KGGW, 20Z at KOLF and 22z at KGDV and KSDY. West to NW winds 10 to 15 knots are expected tonight. && .GGW WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/glasgow