Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
367 FXUS65 KGGW 142009 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 209 PM MDT Fri Jun 14 2024 .DISCUSSION... KEY MESSAGES: - Showers and thunderstorms already popping up in far northeast Montana. Later tonight, highest severe risk will be south of the Missouri River. - Another round of thunderstorms Saturday, with eastern zones seeing the greatest risk of a mixed severe hail/wind threat. - Pattern change starting Sunday with well below average temperatures and more widespread rain by Monday. WEATHER PATTERN OVERVIEW: Warmest day of the year likely today with some locations potentially seeing their first 90 deg reading of the summer. Upper ridge begins moving east today with southwesterly flow moving into the area. A few upper level disturbances along with some unstable air moving into the region with a surface Low moving up from Wyoming is already generating isolated thunderstorms in far northeast Montana. On Saturday 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 set off another round of afternoon and evening thunderstorms. SPC has the eastern half of our CWA in a slight risk for severe weather so this will have to be monitored closely. Highs Sunday behind the aforementioned front will be much cooler than Saturday`s readings. 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. Weak ridging begins building on Wednesday starting a warming trend with temperatures heading back toward seasonal averages by the end of the week. FORECAST CONFIDENCE and DEVIATIONS: Given this morning`s base reflectivities from GGW over the western half of the CWA, I investigated the HREF members to determine which one had a better grasp of this morning`s nuisance showers. The best representation had been the 14 June 00Z initialization of the NAM Nest. It nailed the convective strengthening of an isolated thunderstorm near Daniels County. Though it is one model, the NAM Nest has also hinted at convection developing near the Prairie/Wibaux/Fallon County area and moving toward the south, ahead of southeast MT`s main convective event this evening. This individual storm has the possibility of producing a quick 50-60 mph gust. The 12Z initialization of the NAM Nest, doesn`t have this northern storm in its guidance, but it is showing the convection to the west of Billings already moving into the city, which may modify the dynamics of any storm developing near Wibaux. There is a moderate to high (60-90%) probability for a wetting rain (0.10") across much of the region with the weekend system with the highest chances in the northeast corner of the state. Moderate probability (30-60%) of 0.25". For the Monday/Wednesday AM system, QPF amounts are higher, with a probability around 70-80% for at least 0.25", 50-60% for 0.50", and 20-40% for 1". ** Update: the QPF dropped in areas along and south of the Yellowstone River Valley. Otherwise, amounts came down for the Monday-Wed AM range for most of northeast Montana by about a 0.25 inches. ** -Bernhart/Enriquez && .AVIATION... LAST UPDATE: 2000Z FLIGHT CAT RANGE: VFR DISCUSSION: Thunderstorm over far northeast Montana continues moving east, producing brief gusty outflows, reducing flight categories down to MVFR. WIND: SE at 15-25 kt for KGDV and KSDY. Otherwise, winds will become light and variable overnight, outside of a shower/thunderstorm. -Bernhart/Enriquez && .GGW WATCHES/WARNINGS/ADVISORIES... None. && $$ weather.gov/glasgow