Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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677 FXUS63 KMQT 122329 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 729 PM EDT Wed Jun 12 2024 .KEY MESSAGES... - Showers and thunderstorms expected (80% chance) between 9 pm and 3 am EDT tonight from west to east. - There is a slight risk (category 2/5) of severe weather for the western UP, with the main threats being large hail in excess of an inch and damaging winds in excess of 60 mph. There is a marginal risk (category 1/5) elsewhere, except for the far east. - Gusty winds expected Thursday along with lingering showers and thunderstorms. - Dry Friday and early Saturday before the return of showers and thunderstorms later in the weekend. - Warmer than normal temperatures frequent the forecast, with some areas approaching 90 for highs by next week. && .SHORT TERM /THROUGH THURSDAY NIGHT/... Issued at 244 PM EDT Wed Jun 12 2024 Early afternoon water vapor shows a couple of low-amplitude shortwaves embedded in fast midlevel flow over the north-central CONUS. The first is generating lift and a couple areas of showers along the WI/MI border and western Lake Superior, while an MCS is ongoing further south into the better instability over southern MN. No lightning strikes have been noted directly upstream as of yet, and with HRRR trending a bit drier/less convective for this afternoon, convection seems to be low probability and thus potential for thunder was capped at slight chance (<25%) for the remainder of the afternoon. Of greater concern is the late evening/overnight period tonight. Convection is expected to develop rapidly over northern MN this afternoon as steep (> 8C/km) lapse rates overspread the area. A classic loaded gun sounding in this area should yield intense storms assuming that forcing from the second aforementioned low-amplitude wave and attendant low-level boundary is sufficient, which it should be. The question for our area is to what extent these storms will hold together as they cross Lake Superior. The steep midlevel lapse rates should maintain MUCAPE of 1000-1500 J/kg across the western UP as the storms arrive. Wind shear is quite impressive both in the low levels, with a low-level jet of 30-40 kt overspreading the area, and in terms of deep-layer bulk shear which will max out between 40-60 kt. CAMs vary in their depiction of the incoming convection, but the HRRR has been relatively consistent in maintaining a broken line of organized strong/severe storms across the lake. Large hail in excess of an inch is a threat given the strong shear and steep midlevel lapse rates, and damaging winds in excess of 60 mph are also a threat despite the nocturnal period given the strong low-level wind field and likely maintenance of a respectable low-level mixed layer as well. SPC slight risk (level 2/5) in effect over the western counties. Storms should weaken with eastward extent as they outrun the better midlevel lapse rates and instability, but at least isolated strong/severe storm threat exists across most of the UP as SPC Marginal Risk (level 1/5) covers all areas except the eastern quarter or so. Main timeframe for storms looks to be roughly 01-06Z from west to east (9 pm-2 am EDT). && .LONG TERM /THURSDAY THROUGH WEDNESDAY/... Issued at 335 PM EDT Wed Jun 12 2024 The active weather pattern across the CONUS continues through the long-term forecast. The main features of note at 500mb are a trough passing over Lake Superior Thursday and a deep cutoff low off the coast of the Baja California, which will be the cause of active weather over the weekend. Despite high pressure keeping a day of , the overall weather pattern through the long term is wetter than normal and warmer than normal, with some of the hottest temperatures of the year thus far forecast for Monday. Thursday, the aforementioned trough will pass over the area. 850mb cold advection and dry air behind the trough will allow for 20-30kt winds to mix down to the surface. EFI shift of tails has backed off somewhat but the Euro ensemble still calls for the potential of gusts up to 35 mph. These gusts will almost certainly (90+%) not be consistently high enough for an advisory but it will still be a gusty day. CAMs call for some diurnal showers supported by post- tropa clearing allowing for some radiational heating, but only isolated thunderstorms are expected. Highs look to be in the 70s for the most part except for the southern reaches of the UP reaching into the 80s and some of the near-Lake Superior communities only seeing highs in the 60s. Once showers move out of the UP entirely Thursday evening, dry weather will be over the UP through at least Saturday morning as ridging aloft builds in and supports a near-1020mb high pressure over the Upper Great Lakes. Friday will be a slightly cooler day with highs only in the 60s to low 70s, but highs recover to the mid 70s for Saturday. RHs look to fall into the 40s and 30s, but with very light winds, weather should be benign to end the work week and begin the weekend. Meanwhile, the deep cutoff low over the Pacific will deamplify and shift northeast through the Rockies. The GEFS shows a low pressure will develop in the Canadian Prairie, with the GEFS suggesting a central pressure potentially below 990mb and perhaps into the 970s mb over Manitoba by Sunday afternoon. With high pressure shifting to the east, predominantly southerly low level flow will allow Gulf moisture to surge north, as shown in the NAEFS vapor transport being at the 90th percentile of climatology along with PWATs of near 1.5 inches. As the weakening trough approaches the Upper Great Lakes and the cold front of the Canadian Low approaches, multiple lifting mechanisms for showers and thunderstorms will be present, with PoPs spreading west to east beginning Saturday PM. As the pattern is complex, details on the strength and timing of storms is tough to narrow down, so look for future forecast packages to gain clarity there, but with the available moisture to work with, ensembles do show about a 15% chance of daily precip totals to exceed an inch by Sunday. This is a little lower than the last 24 hours of guidance, but still enough to maintain some concern about weekend outdoor plans that would be ruined by a downpour. The gradual warmup continues into next week, with high 80s in the forecast for Monday, with widespread low to mid 90s in the 75th percentile of the NBM. PoPs remain in the rest of the long term forecast as ensembles show a continued chaotic pattern through mid- June. The general pattern looks to support ridging over the eastern CONUS with a persistent surface high off the East Coast, which should help create southerly to southwesterly flow to advect further Gulf moisture north. As a result, the CPC outlooks the 8-14 day period as being more likely to be warmer than normal and wetter than normal. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 729 PM EDT Wed Jun 12 2024 Upstream thunderstorms moving into northeastern Minnesota and western Lake Superior will continue pressing east-southeast this evening, bringing thunderstorms, potentially strong to severe, to KCMX and KIWD into tonight. Guidance suggests upscale growth and eventual storm mode becoming linear as it moves across Lake Superior, and we`re already seeing this transformation upstream. This suggests strong winds, in addition to the hail potential, should be considered. Depending on how well these handle the lake transit, these strong winds may be realized at KSAW as well. In the wake of the storms, low level moisture will support MVFR ceilings at KCMX and potentially some fog. After the sun rises, expect improving ceilings to VFR at all sites and daytime mixing to support gusty conditions. Current tafs are for 20-30kt westerlies, but some guidance does suggest mixing to support upwards of 40kts in some areas by afternoon Thursday. && .MARINE... Issued at 335 PM EDT Wed Jun 12 2024 This evening, strong to severe storms are expected to be over the western half of the lake as storms come off of the MN Arrowhead and reach the western UP. Otherwise, southerly winds will broadly remain below 20 kt. Behind a cold front driving through Thursday, cold advection will drive gusty winds aloft to the surface, with westerly to northwesterly wind gusts of around 25 knots expected on Thursday. High pressure building over the Upper Great Lakes into the weekend will keep wind gusts below 20 kt Friday through Sunday morning, when a cold front will bring a return of thunderstorm chances. Waves will largely be below 4 ft until Sunday when waves along the US/Canada border on Lake Superior will grow to 4-5 ft. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Thompson LONG TERM...GS AVIATION...JTP MARINE...GS