Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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327 FXUS63 KMQT 241743 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 143 PM EDT Mon Jun 24 2024 .KEY MESSAGES... - Line of thunderstorms moves through the forecast area tonight, some storms could be strong to severe and produce damaging winds and large hail. - Tuesday will be the warmest day of the week with highs in the mid 70s to mid 80s. Gusty winds to 30 mph also expected, especially over the Keweenaw. - Next round of precipitation expected Thursday night into the weekend. && .SHORT TERM /THROUGH TONIGHT/... Issued at 143 PM EDT Mon Jun 24 2024 Current mesoanalysis across the region places an upstream shortwave moving through northern Minnesota and a cold front tied to a surface low moving through Lake Winnipeg not far behind. Precip associated with this is trending down per DLH radar and GOES IR. To the south, mid-level ridging extends across the Plains with subtle shortwaves perturbations embedded atop. At the surface, a surface low was observed moving across eastern South Dakota along with a southeastward draped warm front and several surface troughs tied to the mid-level perturbations. Across our forecast area, surface high has allowed for clear skies to largely dominate; at the time of this publishing though, high clouds streaming eastward into the region associated with the shortwave pressing through Minnesota was observed on GOES Vis imagery. With these mostly clear skies and predominately southerly flow, daytime temps have warmed into the 70s while dewpoints in the 50s have been observed. As we progress through the remainder of the afternoon and overnight tonight, upstream weakening showers in Minnesota will continue to weaken as it presses into Lake Superior/western Upper Michigan. HRRR and other CAMS suggest it may hold together enough to support some showers in our forecast area late this afternoon/early evening. Otherwise, expect temps to continue climbing into the upper 70s to low 80s and increasing cloud cover. Impressive instability will continue building on the south side of the decaying shower activity over Minnesota. As this area of instability grows and southwesterly low level winds strengthen this evening, a line of thunderstorms will develop over central Minnesota. These will grow upscale and evolve into a bowing MCS as they stream southeast along the instability gradient. CAMS appear to be coming into better agreement that the strongest storms will stay south of our forecast area, but storms capable of mostly damaging winds can`t be ruled out early in the event. Some large hail will also be possible. The main risk area will be in the counties bordering Wisconsin. North of this bowing segment, the HRRR and to some degree, the FV3 and NAMNEST resolve a secondary line of showers and thunderstorms across the Arrowhead into Ontario, then press these into Lake Superior and Upper Michigan. Some large hail and maybe strong winds will be possible with these storms if the materialize, but confidence in these developing is low to medium (25- 50%) given their proximity to the main bowing segment and the lack of a consensus among the various CAMS solutions. If this develop, these and the northern fringes of the MCS pressing southeast, will press eastward through Upper Michigan, likely clearing the east just after sunrise. While confidence in the evolution is lacking somewhat, consistent temporal signatures in the various CAMS suggest the main period of thunderstorms to be between 5z and 11z with the most likely period for strong to severe being early in the event. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 411 AM EDT Mon Jun 24 2024 Tuesday morning, a cold front draped from a 989mb low over far northern Ontario and its parent 500mb trough will push through the UP. While some thunderstorms will likely remain over some portions of the UP, the extent that thundershowers remain is uncertain. Among the 00Z HREF run, only the HRRR shows widespread thunderstorms present by 12Z Tuesday with the other members showing only isolated to scattered showers remaining. Attempted to somewhat split the gap in these solutions with this forecast, but confidence is somewhat low given the spread in the ensemble solutions. Any lingering storms are unlikely to be severe as the better instability will be to the south while better forcing will be to the north with probably less than 1,000 J/kg of MUCAPE to work with over the UP. MOS guidance suggests high temperatures in the central UP climbing to the mid 80s with the 75th percentile of the NBM still hinting that 90s could be possible in some typical warm spots in the south. Mixing behind the front will allow for dew points to not be as high as originally forecast. The other thing that mixing will do is create some gusty conditions especially in the west and over the Keweenaw. This forecast will reflect gusts in the 30-35 mph range, but the ceiling for gusts over the Keweenaw could be higher as the HREF suggests locally over 50% chances for 40 mph gusts Tuesday evening. A dry period then is expected into Thursday night as a ~1015 mb high pressure descends southeast through the Great Lakes from the Canadian Prairie Provinces. While a shortwave trough will pass over the UP Wednesday morning and both the Euro ensemble and GEFS show a 20-30% chance of precipitation, this forecast will reflect dry weather with the subsidence associated with the dry weather. Cool northerly surface flow on Wednesday will cause highs to only reach the 60s, and potentially only the high 50s along the eastern Lake Superior shores. Attention then turns upstream as a trough over the Pacific NW makes landfall Wednesday night, then continues east along the U.S./Canada border and reaches the Upper Great Lakes by Saturday. This will support cyclogenesis in the northern Rockies Thursday night/Friday with the low ejecting east-northeast to just north of Lake Superior for Friday night/Saturday. While spread is still high on the details of this system, the general trend is for this low pressure to weaken as it approaches the Upper Great Lakes, so hazardous weather seems unlikely at this forecast issuance. Drier weather looks to return the rest of the weekend as a stronger high pressure near 1025 mb settles over the UP by Sunday evening. As the high shifts east to start next week, PoPs increase as another low is expected somewhere in the Plains, but spread is high on the track of said low. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 143 PM EDT Mon Jun 24 2024 VFR conditions will prevail this afternoon and evening, followed by a rapid deterioration as a line of thunderstorms moves into Upper Michigan. Expecting most activity between 5 and 11z, with the greatest potential for severe winds, maybe some large hail, at KIWD early on in the event. Expect ceilings to fall to MVFR/IFR after the line moves through with some brief fog/mist developing before the sunrise. Tuesday, gusty winds are expected to develop as ceilings improve. Initial thoughts are KCMX could gust near 30kts from the west, but some models indicate higher being possible. && .MARINE... Issued at 411 AM EDT Mon Jun 24 2024 Expect winds below 20 kts through the day as high pressure ridging passes over Lake Superior. South winds increase to around 20 kts tonight ahead of a passing cold front. Tuesday, gusty westerly to northwesterly winds will increase to around 25 knots over the western and central portions of the lake and to near 30 knots between Isle Royale and the Keweenaw, with a 10% chance of a few gale force gusts. Winds taper off Wednesday morning as they veer north, remaining below 20 kts under high pressure through Thursday. A weakening low pressure approaching the region will allow for gusts near 20 kt, but given the uncertainty in the track of the low, the timing and direction of these gusts is difficult to determine with this forecast package. High pressure returns Sunday and ushers in light winds. Strong to severe storms are possible in the west tonight into Tuesday with the passing cold front. Waves will be strongest north of the Keweenaw Peninsula Tuesday afternoon and evening (4-6 feet). && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JTP LONG TERM...GS AVIATION...JTP MARINE...GS