Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
865 FXUS65 KGGW 152009 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 209 PM MDT Sat Jun 15 2024 .DISCUSSION... KEY MESSAGES: - Pattern change starts today as a cold front brings showers and thunderstorms with eastern zones seeing the greatest risk of a mixed severe hail/wind threat. - Cooler temperatures begin Sunday, with the coldest readings occurring on Monday and Tuesday. - More widespread rain moves in during Monday and Tuesday. - Warming trend later this week, but things remain unsettled with daily shower and thunderstorm chances. WEATHER PATTERN OVERVIEW: Today the first Pacific Northwest Trough will begin to settle into the area driving a cold front ahead of it. This will not only be the beginning of a pattern change to below average and wetter conditions, but this front will be the focusing mechanism for another round of afternoon and evening thunderstorms. SPC has the eastern half of our CWA, roughly east of a line from Glentana to Winnett in a slight risk for severe weather with large hail and damaging winds the main threat. The supportive dynamics for any rotation within a supercell looks to increase eastward, with the primary focus of a tornadic concern in North Dakota. An isolated tornado cannot be ruled out before crossing the North Dakota border late this afternoon/evening. Sunday will be cooler behind the front with a little break in the action overall before a stronger Pacific trough moves in Monday bringing widespread rain and even cooler temperatures at 10-20 degrees below mid June averages for both Monday and Tuesday. A warming trend begins Wednesday with temperatures warming close to late June averages by the end of the week. Still unsettled with afternoon showers and thunderstorms continuing to be a possibility. FORECAST CONFIDENCE and DEVIATIONS: ++ Discussion regarding this afternoon ++ This morning`s shower/thunderstorm activity has stabilized the lower atmosphere across many places north of the Missouri River. Since those showers have passed, ample sunshine has return for most locations south of the Missouri. This will help recharge southern zones with the sufficient instability to support stronger updrafts, with sufficient shear to sustain upscale growth and organized convection. At 20Z, a special upper air launch will give us and the SPC a better idea of how the instability has evolved since the return of sunshine, and consequently, whether the threat for significant hail/severe winds remains as discussed from this morning and/or increased/decreased. ++++ There is a moderate to high (50-90%) probability for a wetting rain (0.10") across much of the region with today`s system with the highest chances in the northeast corner of the state. Low to moderate probability (25-60%) of 0.25". QPF`s have trended downward some, especially in the southeastern zones. For the Monday/Wednesday AM system, QPF amounts have trended downward but are higher than today`s system, with a probability around 70-80% for at least 0.25", 40-60% for 0.50", and 10-35% for 1". Confidence is lower Wednesday onward on shower and thunderstorm chances and timing as models start diverging in that time period. -Bernhart/Enriquez && .AVIATION... LAST UPDATE: 2000Z FLIGHT CAT RANGE: VFR, Brief MVFR possible near storms. DISCUSSION: A round of showers and thunderstorms moves through the region this afternoon and into tonight. Main threat will be squally conditions in and near organized storms, including severe outflows and large hail. WIND: After the passage of storms, winds will be more northwesterly at 15-25 kts. Sunday morning, winds will be more westerly at 20-30 kts gusting up to 40 kts. -Bernhart/Enriquez && .GGW WATCHES/WARNINGS/ADVISORIES... Lake Wind Advisory from 6 PM this evening to 9 PM MDT Sunday for Central and Southeast Phillips-Central and Southern Valley- Garfield-McCone-Petroleum. && $$ weather.gov/glasgow