Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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622 FXUS63 KMQT 032005 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 405 PM EDT Mon Jun 3 2024 .KEY MESSAGES... - Showers and a few thunderstorms progress eastward across west and central Upper MI today. Greatest coverage will be over the west. Severe storms not expected. - Frequent opportunities for showers and thunderstorms over the next 7 days, with a break on Tuesday. - Above normal temperatures through Wednesday, then turning cooler for the second half of the week. && .SHORT TERM /THROUGH TODAY/... Issued at 141 PM EDT Mon Jun 3 2024 RAP analysis shows a 500mb shortwave over Minnesota generally flattening with time this morning and early afternoon. This correlates with the decrease in rain shower intensity with a broad line of showers over the central UP at 15Z per KMQT radar reflectivity and METAR obs. CAMs consistently show this deteriorating trend continuing as forcing continues to decrease and precipitation battles dry air. However, a break in the showers altogether will be brief at most as a shortwave over Iowa will progress northeast throughout the day today and force another round of showers through central to northern Wisconsin by 20Z today. The main source of uncertainty is the northern extent of the showers and thunderstorms, as cloudy conditions associated with the current shortwave are limiting the ability of the atmosphere over Upper Michigan to destabilize. The 12Z HREF shows some SBCAPE recovery in the west, but with forcing being limited to the south and central UP, where even HREF max SBCAPE struggles to reach 250 J/kg, severe weather is not expected, and thunder chances are limited to below 33%. As far as high temperatures go, clearing behind the showers in the west and the persisting dry air over the east will make the west and the east ends warm into the low 70s today while the central UP stays in the 60s. Overnight, as heating decreases, so too will shower coverage, with HREF probabilities of hourly QPF > 0.01" not exceeding 40% after 03Z tonight. Persistent cloud cover and a more moist surface airmass will limit radiational cooling, with lows around the mid 50s and low 60s tonight. In the wake of showers, marine dense fog over Lake Superior is 60%+ likely per the HREF, with the central UP seeing 30-60% chances to see patchy dense fog overnight. With the wide range of probabilities, no land-based dense fog advisories are going to be issued with this forecast package until a bit more certainty is gained in regards to the moistening of the atmosphere by the showers. && .LONG TERM /TUESDAY THROUGH MONDAY/... Issued at 404 PM EDT Mon Jun 3 2024 Another subtle shortwave moving through the Great Lakes will keep a potential for a few sprinkles, light rain showers, and a few rumbles of thunder across the eastern UP into Tuesday morning. Otherwise, with plenty of lower level moisture behind today`s rain showers and partially clearing skies behind the front, much of hte UP should be starting off with some patchy fog. This mixes out soon after sunrise with our high sun angles, then a brief dry period is expected until late afternoon over the far west at the very earliest as a second, stronger cold front approaches from the Northern Plains. With warm air advection continuing ahead of the cold front, expect the warmest temperatures of the week to occur Tuesday, with highs getting into the 80s across some of the interior areas, particularly over the west and downslope areas near Lake Superior where the increasing southerly downslope winds throughout the day could locally increase temperatures by at least a few degrees; the warmest temperatures will likely be around Ontonagon to the Porcupine Mountains. In addition to the warm temperatures, Tuesday may also feel pretty muggy, with much of the guidance showing dewpoints in the lower to mid 60s across the UP. The cold front looks to begin bringing showers and thunderstorms to the western UP Tuesday evening, though guidance is hinting at some earlier convection during hte late afternoon courtesy of a pre- frontal trough rippling through. With quite an unstable airmass (SBCAPE in excess of 1000j/kg) and an inverted-v type sounding, any stronger cells that can get going could bring down some marginally- severe winds or hail. That said, bulk shear remains lackluster even as the cold front approaches, with values generally less than 30 knots likely not enough to sustain a severe threat much further eastward into the UP. What may be more of a concern is the threat for heavy rainfall, with ensembles generally showing PWATS around and even in excess of 1.5in. Soundings show plenty of deep moisture and impressive warm cloud depths, with storm motion largely parallel to the cold front. Training could be a problem, particularly throughout the western UP where we were able to pick up on widespread rainfall amounts around and in excess of half an inch over the past day. For its part, HREF ensemble mean rainfall totals show a widespread 0.5- 0.75in across the western half of the UP, but higher totals in excess of an inch are possible with some members even as high as 1.5in. The cold front continues through the eastern half of the U.P. Wednesday as a secondary shortwave drops down from Canada and brings light rain showers and maybe a thunderstorm or two back across the western half of the U.P. Wednesday afternoon behind the front. Behind the cold front, expect cooler temperatures to dominate the rest of the extended forecast period as a synoptic troughing set-up settles over Canada and rotates multiple shortwaves across our region throughout the rest of this week and upcoming weekend. This will bring multiple light rain shower chances across our area for the rest of the extended period, and maybe a thunderstorm or two during the afternoon hours when daytime heating becomes maximized. With cooler and a somewhat drier airmass working in, it is not out of the question that RH falls into the 30s at times throughout the extended period...but will note that this isn`t very certain given hit and miss rain chances, rather a cloudy period, and lackluster mixing in soundings. Winds may be elevated at times throughout the period, particularly Thursday and Friday with a tighter pressure gradient over the area, which could enhance drying at the surface. This would all point to a concern for fire weather into the extended period, but mitigating this will be the early-week rainfall. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 141 PM EDT Mon Jun 3 2024 VFR conditions briefly prevail at all three TAF sites this afternoon following the first passage of showers today. A secondary wave of showers will push over Upper Michigan from the southwest later this afternoon, though will probably miss CMX and IWD altogether, leaving only -SHRA at SAW. With a much more moist air mass trapped at the surface following the passage of the second wave of showers, all three TAF sites are expected to experience low cigs and vis tonight, though uncertainty on timing and extent of lowered flight categories does exist. Each site is over 50% likely to have IFR cigs and MVFR vis overnight with around 25% chances of LIFR or lower cigs and IFR or lower vis, so a TEMPO group was put in at each site overnight to cover for those low-probability but high-impact scenarios. Improvement is expected with the sunrise as skies scatter out and fog dissipates during the morning hours of Tuesday. && .MARINE... Issued at 404 PM EDT Mon Jun 3 2024 Winds generally out of the SE remain elevated across the eastern half of the lake, gusting to around 20-25 knots for the most part. However, especially around the Keweenaw where downsloping comes into play, higher gusts around and even in excess of 30 knots remain possible into the earl evening hours. Winds fall back below 20 knots overnight while a high pressure ridge briefly builds into the region. This tranquil period will be short-lived as winds pick up again later in the day Tuesday ahead of our next approaching frontal system. SSE winds gust to around 20 knots across most of the lake Tuesday evening through Tuesday night, with some higher gusts of 25- 30 knots north of the Keweenaw. After winds briefly fall back behind the passing cold front Wednesday morning, we could see southwest to westerly winds pick up to around 20 knots over the west half of the lake Wednesday afternoon as a secondary shortwave moves through. As additional shortwaves rotate through our area the rest of this week through this weekend, expect winds to increase from the west and northwest at times; we could see westerly winds gust up to 20 to 30 knots Thursday and again to 20 to 25 knots from the northwest Friday as shortwave lows impact the Upper Great Lakes. As for other marine concerns this week, expect lingering patchy fog, dense at times, across most of the lake tonight through Tuesday in the wake of our rounds of rain today. This patchy fog looks to persist until the second, stronger cold front moves through Tuesday night and Wednesday, when the cooler air behind the front could allow the moisture to mix out. Thunderstorms return late Tuesday afternoon as the second cold front moves into the far western lake; some severe weather could be seen over the far west Tuesday afternoon and evening near Duluth, although the chance for severe weather is still rather low (~5%); severe hail and winds are the primary concerns. The thunderstorm activity continues across Lake Superior from west to east Wednesday until leaving into northern Ontario late in the day. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Dense Fog Advisory until 5 PM EDT /4 PM CDT/ this afternoon for LSZ162. Lake Michigan... None. && $$ SHORT TERM...GS LONG TERM...LC AVIATION...GS MARINE...LC