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Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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100 FXUS63 KMQT 292018 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 418 PM EDT Sat Jun 29 2024 .KEY MESSAGES... - Thunderstorms continue across the far eastern UP through the early evening; some storms may be strong to severe with large hail and gusty, damaging winds. - Rip currents and dangerous swimming conditions will be possible at Lake Superior beaches of Alger and Marquette counties through this evening. - Dry weather Sunday morning through Monday evening under high pressure. - Next rounds of showers and thunderstorms arrive Monday night through Tuesday night. - Warm and wet pattern expected to continue well into July. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 418 PM EDT Sat Jun 29 2024 Thunderstorms continue across the far eastern UP this afternoon, with a cold front not far behind in the central UP. These storms have a history of producing large hail, and with MUCAPE still up to 2000 j/kg and sufficient shear to sustain updrafts, will not rule out additional strong convection from eastern Luce county southwest through Green Bay. Meanwhile, outflow from earlier storms in northern Marquette and Alger counties is quite apparent on radar, and has touched off additional weak showers. That said, most convection apart from clusters currently working through Luce, southern Schoolcraft, and Mackinac counties have struggled to climb high enough even to produce lightning - not surprising, given modest capping indicated in model soundings and the afternoon NUCAPs profiles. Upstream, additional spotty shower activity has become apparent. Given cooler post-frontal flow as winds turn over to the NNW, moist lower levels, and another shortwave dropping from northern MN through the UP tonight, expect spotty shower activity to continue at least through the first half of the night. This would be most likely across portions of the UP where NNW flow is upsloping (so, much of the higher terrain of the western UP, portions of the north-central UP, and across Alger and northern Luce counties). Skies gradually clear out the rest of the night, with temperatures largely bottoming out in the lower to mid 40s. However, some cooler spots in the western and north-central UP may fall even further into the upper 30s. Strong post frontal northwesterly winds are expected to create dangerous swimming conditions for Marquette and Alger counties through this evening. A Beach Hazards statement is in effect. && .LONG TERM /TONIGHT THROUGH FRIDAY/... Issued at 312 AM EDT Sat Jun 29 2024 Tonight, as the main axis of the 500mb trough passes east beyond the UP, a backdoor impulse in the northwesterly flow combined with upslope flow creates just enough lift for the 00Z HREF to show an orographic pattern of light rain showers overnight. Efficient mixing will also allow for some gusty winds over the eastern UP to 20-30 mph overnight. Any lingering showers will not survive to 12Z Sunday morning however as advancing 500mb ridging aloft will support a surface high pressure of near 1028 mb to traverse from Minnesota Sunday morning to southern Ontario by Monday night. This high will usher in a period of dry weather and mainly clear skies Sunday through Monday afternoon. With the near-surface flow being mainly northwesterly on Sunday with the high still to the west, temperatures near Lake Superior may struggle to break out of the 50s, but otherwise temperatures across the UP will only be slightly below normal. Efficient radiational cooling overnight into Monday will help low temperatures to fall to near or just below 40 in some interior locations per some MOS guidance and the NBM 25th percentile and below. There is also some potential for some patchy fog in the south- central, with Euro ensemble meteograms showing a 25-30% chance of lowered visibility in Menominee Monday morning, though similar signals were not found in Iron Mountain to the northwest or Rapid River to the northeast. However, despite the relatively low probabilities, every Euro ensemble member that shows fog, the fog is below 1/2 mile, so the fog forecast bears some watching. Attention then turns upstream to 500mb troughing lifting out of the northern CONUS Rockies Monday evening. This will form a 990s mb surface low that will pass from southern Saskatchewan Monday afternoon to far-northern Ontario Tuesday night. Ahead of the low, building southerly surface flow will cause warm advection and isentropic upglide which in turn will create showers well ahead of the fronts associated with the low pressure. Ensembles still lack consensus on whether there will be enough separation in the initial wave of showers and the frontal showers to create a period of dry weather, but the NBM is leaning towards keeping PoPs in the 60-80 range all through Monday night through Tuesday night. Despite nearly 24 hours of elevated PoPs, the probabilities of flooding rainfall are below 10%. With the strongest dynamics of the system well to the north, severe weather is not expected, though the Euro ensemble shows up to a 50% chance of 500-1000 J/kg of CAPE by Tuesday night, so thunderstorms will remain a possibility with this system. After this system exits by Wednesday morning, model guidance really begins to diverge. A dry period is expected to follow, but how long that period lasts is still uncertain. Generally a wetter pattern continues into through the first half of July. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 129 PM EDT Sat Jun 29 2024 IFR ceilings prevail at CMX this afternoon, while IWD and SAW continue to come in at VFR so far with just some thickening lower to midlevel cumulus. Meanwhile, cold front is moving through the region this afternoon, which should drop ceilings to MVFR at IWD over the next couple of hours, the SAW follows by the early evening. Showers and thunderstorms are already developing near SAW, and vcts will be possible the rest of the afternoon before the front finally clears the area. Post frontal upslope flow should enable additional showers at KCMX and KIWD this evening before all terminals improve to MVFR and finally VFR overnight. && .MARINE... Issued at 312 AM EDT Sat Jun 29 2024 Westerly wind gusts below 20 knots are ongoing this morning, though as winds veer northeasterly this afternoon, increased mixing and a tighter pressure gradient allowing for gusts up to 25-30 kts over the eastern half of the lake. A few gusts may (~25% chance) reach gale force strength around 8PM EDT tonight between Stannard Rock and the Pictured Rocks National Lakeshore. North to northeast winds Saturday night gradually fall back below 20 kts by Sunday morning as high pressure builds in from the west. Winds are then expected to remain below 20 kts through much of the day Monday as this high pressure moves east over the lake. With the next passing system early next week, southeast winds increase Monday night to 20-25 kts, veering south-southeast on Tuesday as the low pressure system passes well to the north of Lake Superior. Besides a brief period Wednesday of southwesterlies gusting to 20-25 kts, winds Tuesday night onward look to remain below 20 kts through the remainder of the forecast period. Stronger northwest winds behind the cold front this evening will result in waves building up to 6-9 ft waves over the eastern half of the lake Saturday night, falling below 4 feet by Sunday morning. Sustained southeasterlies Tuesday will allow waves to grow to 4-6 feet along the US/Canada border on Lake Superior through Tuesday night. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Beach Hazards Statement until 10 PM EDT this evening for MIZ005-006. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...LC LONG TERM...GS AVIATION...LC MARINE...GS