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LMZ521 Green Bay South Of Line From Cedar River To Rock Island Passage And North Of A Line From Oconto Wi To Little Sturgeon Bay Wi- Green Bay South Of Line From Oconto Wi To Little Sturgeon Bay Wi- 400 Am Cdt Fri May 17 2024
.dense fog advisory in effect until 10 am cdt this morning - .
Early in the morning - W wind around 5 kts. Areas of dense fog. Waves 2 ft or less. Today - SW wind around 5 kts backing S in the afternoon. Areas of dense fog in the morning. Waves 2 ft or less. Tonight - SE wind 5 to 10 kts. Mostly clear. Waves 2 ft or less.Saturday - S wind 5 to 10 kts increasing to 10 to 20 kts in the afternoon. Sunny. Waves 2 ft or less. Saturday night - S wind 10 to 15 kts veering W 5 to 10 kts after midnight. Mostly clear. Waves 2 ft or less.

LMZ500
No data

FXUS63 KMQT 170756 AFDMQT

Area Forecast Discussion National Weather Service Marquette MI 356 AM EDT Fri May 17 2024

KEY MESSAGES

- There is a slight (30%) chance of thunderstorms across the western UP this afternoon and evening over the western UP, lingering across the Keweenaw into tonight.

-Breezy south winds and very warm temps in the 70s and 80s Saturday ahead of a cold front that will bring scattered afternoon/evening thunderstorms. The strongest storms may contain small hail.

-Elevated fire weather possible on Saturday then very dry with light winds on Sunday.

-More rain chances early to middle of next week as a series of disturbances moves across the area in a developing warm and moist southerly flow.

SHORT TERM /THROUGH TONIGHT/
Issued at 318 AM EDT Fri May 17 2024

Showers have come to an end in the wake of an exiting shortwave that is currently swinging into Ontario. Drier midlevel air is apparent on water vapor over the area, and skies are clearing out across the western half of the UP. Satellite shows plenty of lingering low cloud cover across the eastern UP, as well as the Keweenaw and Lake Superior, and even where skies have cleared, patchy fog is apparent in surface observations and webcams. Temperatures are dropping into the lower 40s already where skies have been able to clear, but remain in the upper 40s and lower 50s where low clouds linger.
Temperatures shouldn't fall back much further tonight.

Patchy fog mixes out into the daytime hours, though at least some patchy marine fog may linger into the morning. Expect otherwise sunny skies to start the day with weak ridging over the area as the Great Lakes look to be situated in between two systems. However, rain chances sneak into the western UP into the late afternoon with a subtle shortwave grazes the area, coincident with a warm front lifting into the Upper Midwest. Given weak forcing, would not expect much out of this, with HRRR guidance showing a few hundred j/kg of CAPE. That said, various individual models continue to show patches of 500-1000j/kg of CAPE during the afternoon, indicating a potential for some stronger cells with small hail or a good wind gust. Still, coverage of any showers looks spotty at best with a rather weak trigger for anything to develop at all. Otherwise, expect warmer temperatures ranging well into the 70s across most of the interior UP, while lake breeze development keeps areas closer to the lakeshores in the 60s to lower 70s.

Tonight, though the warm front should be lifting north over Superior, the potential for some convection lingers at least the first half of the night over the western UP as a 40kt LLJ becomes directed into the area. Will note, however, that guidance continues to favor this staying mainly over the water. Otherwise, expect partly cloudy skies, and maybe some patchy fog where any showers would have developed during the afternoon. Temperatures stay quite mild, bottoming out in the mid and upper 40s across the eastern UP while the western half of the UP falls only as far as the 50s. Some of the typically warmer, southerly downsloping areas may even stay in the upper 50s overnight.

LONG TERM /SATURDAY THROUGH THURSDAY/
Issued at 320 AM EDT Fri May 17 2024

Highlights of the extended forecast include very warm conditions this weekend with the potential for elevated fire weather conditions at times, then more opportunities for possible widespread rain next week.

Beginning Saturday, the UP will be squarely in the warm sector of a surface low near Lake Winnipeg with 850 mb temps of 14-16C spreading across the UP. This unseasonably warm air mass will support high temps most locations in the lower to mid 80s with the highest readings most likely for downsloping areas along Lake Superior west and central where breezy south winds in the tightening gradient ahead of the approaching frontal boundary could gust as high as 30- 35 mph at times per model soundings. However, south flow off Lake MI will keep the eastern UP mostly in the 70s to perhaps even 60s readings along the shorelines. ECMWF EFI highlights the unseasonably warm temps well, and like the model soundings, also hint at the possibility of unseasonably strong wind gusts across the far west.
The combination of hot temps and gusty winds suggests potential for elevated fire wx conditions, but the main limiting factor is RH values as dew points surge to around 50F.

Elevated dew points could also result in late afternoon/evening thunder chances as the system's cold front presses across the area. SPC has placed the west half of the UP in a marginal risk of severe storms on Saturday. However, believe there is some question on the degree of fcst instability across the area. The NAM soundings depict a drier airmass with limited CAPE (generally 500 j/kg or less) and more capping at mid-levels while the GFS shows MLCAPE values increasing near 1000 J/kg range in the west with almost no capping during the afternoon based on more aggressive ramp up of sfc dew points rising well into the 50s. If the more moist and unstable GFS verifies then bulk shear values forecast in the 30-40kt range could possibly generate a few stronger storms with marginally severe hail or gusty winds. Ultimately, the threat of storms or severe potential will hinge on how much sfc dew points mix out during the day on Saturday ahead of the front. Gut feeling is that the drier and more stable NAM soundings may have a better handle on the fcst instability, leading to perhaps decreased coverage for t-storms and thus a lower threat of SVR storms.

A much drier air mass and associated surface ridging follows the frontal passage for Saturday night into Sunday. Abundant sunshine and light winds will result in deep mixing into extremely dry mid- levels on Sunday. For example, the 00z NAM fcst sounding advertised a -33C dew point at 760 mb at 1 PM Sunday. Fortunately, surface dew points won't mix that low, but will still incorporate the local mixed dew point tool to cut back on Td values resulting in min RHs closer to 20% across the interior portions of the cwa. The good news is light winds less than 10 mph should ease fire wx concerns, because critically low RHs appear nearly certain across interior portions of the UP. Lake breeze activity should limit fire wx concerns along the shorelines due to cooler temps and higher RHs.
Expect max temps reaching near 80F over much of the interior west half and mid to upper 70s over the interior east half. Developing lake breezes will keep readings near the Great Lakes shores in the mid to upper 60s.

Models advertise a mid-level trough amplifying over the western CONUS early next week. Periodic shortwaves in a warm/moist sw flow developing ahead of the western CONUS trough will bring more rounds of showers into the area early to mid next week. The first shortwave moves through late Sun night into Monday bringing the initial batch of showers for early next week. It looks like the best chance for widespread and possibly heavy rainfall will be in the late Tue into Wed time frame when models indicate more substantial shortwave energy lifting across a nearly stationary frontal boundary draped across the area. Model uncertainty increases later into the week but it certainly looks possible that some scattered showers could linger at least into Thursday as temps trend cooler in the wake of the midweek low pressure system/frontal boundary pushing off to the east.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
Issued at 122 AM EDT Fri May 17 2024

VFR conditions will continue at IWD through the period. LIFR conditions at CMX will continue until later tonight when MVFR moves in and then VFR by Fri morning. SAW will have LIFR conditions overnight and then VFR conditions Fri morning.

MARINE
Issued at 320 AM EDT Fri May 17 2024

Stable conditions will lead to light winds of generally 20 knots or less continue today into early next week, except for Saturday afternoon and evening when southerly gusts of 20-25 kts are forecast ahead of an approaching cold front. Patchy dense fog is possible into early morning from last night's rainfall. Thunderstorms are possible this evening over west and north central Lake Superior as a warm front lifts across the lake. More thunderstorms are possible on Saturday into Saturday night as the same system's cold front moves across the area. These storms may contain small hail, gusty and erratic winds, and frequent lightning. More thunder chances return late Sun night into Monday and then again late Tuesday into Tuesday night as a series of disturbances track northeast across the Upper Great Lakes region.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

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