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Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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541 FXUS63 KMQT 141854 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 254 PM EDT Wed Aug 14 2024 .KEY MESSAGES... - Light rain showers possible over the north central this afternoon via the lake breeze. - Low pressure system to bring showers and thunderstorms Thursday through early Saturday. - Generally more dry pattern for the back part of the weekend and beyond, though minor disturbances may bring the occasional shower. && .SHORT TERM /THROUGH TONIGHT/... Issued at 140 PM EDT Wed Aug 14 2024 Upper air pattern consists of a 500 mb trough off the west coast and a ridge over the Mississippi River valley and a trough over the eastern U.S. A shortwave over the northern Rockies will get organized over the northern plains by 12z Thu. Will continue with some slight chance pops for this afternoon for lake breeze convergence showers as there is some signal that a few could develop along the boundaries. Otherwise, did not make too many changes to the going forecast and kept pcpn chances out until really late tonight in the far west as next system approaches. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Issued at 253 PM EDT Wed Aug 14 2024 The weather for the remainder of the week will be driven by a 500mb trough centered over the Dakotas by 12Z Thursday. The resulting surface low will be around 1005mb over the Dakotas/MN border Thursday morning, and isentropic ascent ahead of the low will bring showers to the MI/WI state line Thursday morning per HREF guidance. While a soaking rainfall is expected, flooding should not be a concern given the dry pattern the past few weeks. Virtually all of western Upper Michigan has had 50% or less of the normal precipitation for the past 30 days, with the eastern half being around normal to slightly below normal. HREF mean 6-hourly QPF rates are a quarter inch to a half inch with this system. Temperatures around 70 Thursday will lead to not much surface instability until late, so thunder will be unlikely until the late evening hours, and with only around 10 kt of 0-6km shear to work with, thunderstorms will be too disorganized to be severe. Showers continue through Friday as the center of the low pressure passes close to the UP. PWAT values approaching 1.5 inches on Friday are up to a half inch above normal for this time of year, so some heavy downpours are to be expected with the stronger storms, but with cloud cover keeping temperatures from breaking much above the lower 70s, surface instability will be somewhat lacking and 6-hourly QPF rates will only be around a quarter inch broadly on Friday per LREF guidance. The last 24 hours of guidance have somewhat slowed the departure of showers in the east as the pattern which once had three distinct troughs over the US/Canada border will become more broad as ridging builds over the central CONUS. While this does support slowing the movement of the trough to the east, it will also mean a surface high of around 1020mb will build over the Upper Great Lakes by the end of the weekend, ushering in a more dry period. Ensembles greatly vary on exact solutions into next week, but the general pattern of northwesterly flow is one that is often subject to the shortwaves that rotate around the central CONUS ridge, which means that there will be at least some slight chances (15-25%) of precipitation in the forecast through the middle of next week, though the impacts of said precip chances will be lesser. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1219 PM EDT Wed Aug 14 2024 VFR conditions dominate through tonight as high pressure ridging slowly gives way to an incoming shortwave low currently over the Northern Plains. Rain will move into IWD towards the end of the forecast period with conditions dropping to MVFR. && .MARINE... Issued at 253 PM EDT Wed Aug 14 2024 Wind gusts will remain below 20 kt through Thursday morning. By Thursday afternoon, a low pressure system will approach the Upper Great Lakes, causing easterly and southeasterly wind gusts to around 25 kt Thursday afternoon through Friday morning. Wind gusts will fall to around 20 kt as winds become northerly with the low pressure passing to the south of Upper Michigan. The arrival of high pressure by the end of the weekend will result in wind gusts below 20 kt Saturday evening through the remainder of the forecast. During the period of easterlies late Thursday into Friday, waves will pick up to 4-6 feet. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...07 LONG TERM...GS AVIATION...07 MARINE...GS