Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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641 FXUS63 KMQT 171849 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 249 PM EDT Mon Jun 17 2024 .KEY MESSAGES... - Continued showers and thunderstorms this afternoon with some potential for isoalted strong or severe storms. - Multiple rounds of showers and thunderstorms expected this week. Strong to severe storms possible Tuesday night into Wednesday. - Hot and humid Tuesday, followed by very muggy rest of the week. - Potential heavy rain event this weekend. && .SHORT TERM /THROUGH TONIGHT/... Issued at 159 PM EDT Mon Jun 17 2024 A line of showers and thunderstorms moved through Upper Michigan today along of a warm frontal boundary, with what appeared to be a mix of strong to severe storms embedded within the complex. As of now, some pea sized hail has been reported and a wind gust at KIMT measured 53 mph. Ahead of the line, dewpoints surged into the upper 60s to near 70F. Behind the line, temps in the 60s were observed ahead of another line of showers draped northeast from northwest WI and western Upper Michigan into western Lake Superior. At the time of this writing, no lightning was being observed with this second line. To the south, isolated thunderstorms are developing across northeast WI within an environment characterized by 2000-2500 j/kg MLCAPE, per SPC mesoanalysis just south of or along the warm frontal boundary. Effective bulk shear from the same source generally ranges from 40-50 kts. As we progress through the remainder of the afternoon, ongoing thunderstorms currently across the central will continue its eastward progression. Additional shower and thunderstorm development will be possible as the warm front begins lifting north. Main focus area will be across central and eastern Upper Michigan given the mean flow and proximity to the warm front as it continues lifting north. There is some potential for strong to severe thunderstorms within this, but the risk is low (<25%). && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 248 PM EDT Mon Jun 17 2024 The overall consensus of both ensemble and deterministic guidance packages suggests the pattern across CONUS will continue to include a stout mid-upper level ridge over the eastern third of CONUS while deep and broad troughing holds fast over the western third. This places Upper Michigan in a predominate south to southwest flow regime and open to both Gulf of Mexico moisture and a warm/hot airmass, and on the path for any shortwave, impulse, or MCS developing across the Plains, at least until the weekend when a more zonal pattern begins to emerge. In terms of sensible weather, Upper Michigan can expect at least one hot day, multiple humid days, multiple rounds of showers and thunderstorms, and flooding and severe weather concerns in this forecast period. Beginning this evening into tonight, showers and thunderstorms should be ongoing initially thanks to surface low organizing and beginning to lift north-northeast through the Central Plains. Initially, showers/storms should be most prevalent across the central/east but with the warm front lifting north, coverage should shift north through the night. There is some potential for training thunderstorms along the boundary. Severe weather threat should be minimal this afternoon and overnight given the thoroughly worked over environment, but some hail, stronger winds, and frequent lightning can`t be completely ruled out. The main hazard will be the rain, but it should be noted that the HRRR continues to back off on some of the training risk. At this point, the WPC slight risk for excessive rain seems reasonable given the training potential and PWATS upwards of 2 inches, in addition to the 0.5"-2 inches of rain estimated from today`s event. Through the night, the warm front will lift north into Lake Superior/Ontario, which will allow rain to end from south to north through the night. Overnight lows should only dip into the 60s or upper 50s and some fog may develop, particularly after the rain lifts north. Tuesday looks to be mostly dry with Upper Michigan positioned squarely within the low`s warm sector as it lifts into Minnesota. With a slightly more dry airmass in place, effective mixing under mainly high clouds or clear skies should support a hot, humid, and breezy day. Daytime temps climbing into the 80s to low 90s is expected while dewpoints approach 70F. This could support heat index values in the low to mid 90s, with perhaps near 100F in downsloping areas in the interior. Steep low level lapse rates should also be able to mix down strong winds aloft. Current thinking is wind gusts near 25 mph, but potential effective mixing may support winds exceeding 30 mph in many locations in the afternoon, particularly in downslope areas near Lake Superior. EFI continues to highlight this unusually high wind potential with values of 0.6-0.8 across large portions of the forecast area. The low will lift into Ontario by Tuesday night while it pulls its cold front through Upper Michigan. This will bring us another round of showers and thunderstorms into Wednesday. There is some severe thunderstorm potential, mainly across the west half Tuesday night, but instability should be waning as they move into the area, so the risk appears limited. However, the risk for heavy rain will return as PWATS look to climb above 2 inches. The front should clear the region by Wednesday afternoon/evening, with high pressure building in after. There may be some daytime re-invigoration of the showers and thunderstorms across the east half and south. Thursday looks to be mostly dry as the pattern begins to shift into something more zonal, but there is some uncertainty in where upstream impulses will line up and how far east they`ll extend. This, while a couple different shortwaves embedded within the near-zonal flow beings across the Northern Plains and exiting out of the northern Rockies. Another warm front will lift into the Upper Great Lakes Thursday night/Friday, potentially supporting showers/storms by Thursday afternoon. The boundary appears to stall out Friday over the Upper Great Lakes as a surface low deepens and lifts out of the Central Plains. The low will press through the region Saturday night and Sunday while the shortwave aloft takes on a negative tilt. For a few days now, guidance has been suggesting this setup, which could lead to a potential heavy rain/flooding event in some areas in Upper Michigan. Of course, this will be dependent on preceding rain, but this system warrants monitoring. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 122 PM EDT Mon Jun 17 2024 Showers and thunderstorms moving through Upper Michigan will continue pressing east, trailed by periods of light rain. Some additional thunderstorms may develop near KSAW this afternoon, but overall, thunderstorm activity is expected to be minimal for the remainder of the afternoon. Another wave of showers, potentially mixed with some thunderstorms, moves in to mainly western Upper Michigan this evening and tonight, impacting KIWD and KCMX. By morning, rain showers and thunderstorm activity activity is expected to be over. With the increased moisture from rain, ceilings should trend to MVFR this afternoon/evening at all sites and then to IFR at KCMX/KSAW. Additionally, fog/mist should develop overnight after the showers/storms end. Expect fog to lift in Tuesday morning, followed by gusty winds developing. && .MARINE... Issued at 248 PM EDT Mon Jun 17 2024 Thunderstorm activity should be confined to eastern Lake Superior this afternoon while showers will be possible mainly central and east. In addition to this, mainly light synoptic winds will help fog development, and its possible some that develops may be dense. Warm front will lift north into the lake tonight and north of it by Tuesday morning, supporting additional showers, possibly some thunderstorms through morning. Some stronger storms should be expected, but severe storms are not expected at this time. South of the warm front on Tuesday, a strong low level jet will move over Lake Superior ahead of a cold front moving eastward through Minnesota. This low level jet will support southerly winds upwards of 30kts across eastern Lake Superior, possibly some low end gales for higher reporting platforms or where topography plays a local influence on winds near the lakeshores between Marquette and Whitefish Pt. Cold front will press through the lake Tuesday night into Wednesday, potentially supporting another round of strong to severe storms across western Lake Superior and thunderstorms and showers lake-wide. High pressure appears to try to work in Thursday but will be dependent on upstream systems. Another front moves into the lake Friday/Saturday as a low pressure approaches from the west, bringing with it another round of showers/storms. Current thinking is for light winds in this system outside of thunderstorms. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JTP LONG TERM...JTP AVIATION...JTP MARINE...JTP