Sunrise 6:06 AM   Sunset 9:26 PM Moonrise 6:43 PM   Moonset 3:49 AM

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LSZ250 Expires:202405122045;;097577 Fzus73 Kmqt 122012 Mwsmqt
marine weather statement national weather service marquette mi 412 pm edt Sun may 12 2024
lsz249-250-266-122045- 412 pm edt Sun may 12 2024
.a strong Thunderstorm over the waters of lake superior between marquette and munising just north of the lakeshore - .
the areas affected include - . Lake superior east of a line from manitou island to marquette mi and west of a line from grand marais mi to the us/canadian border beyond 5nm from shore - . Marquette to munising mi - . Munising to grand marais mi - .
at 411 pm edt, doppler radar indicated a strong Thunderstorm, capable of producing winds to around 30 knots. This Thunderstorm was located near au train island, or near shelter bay, moving east at 25 knots.
precautionary/preparedness actions - .
mariners can expect gusty winds to around 30 knots, locally higher waves, and lightning strikes. Boaters should seek safe harbor immediately until this storm passes.
&&
lat - .lon 4652 8642 4642 8658 4643 8665 4642 8665 4650 8712 4665 8698 4667 8640

LSZ200
No data

FXUS63 KMQT 211151 AFDMQT

Area Forecast Discussion National Weather Service Marquette MI 751 AM EDT Tue May 21 2024

KEY MESSAGES

- Strong storm system will bring rain and thunderstorms late Tuesday into Tuesday night.

- Windy conditions develop behind the system on Wednesday.

SHORT TERM /THROUGH TONIGHT/
Issued at 523 AM EDT Tue May 21 2024

Some patchy fog has developed this morning under weak high pressure. Expect this fog to lift out later this morning.

Latest water vapor imagery has shortwave energy rounding the base of the western mid-level trough through the Southern Rockies early this morning. This shortwave trough will take on an increasingly negative tilt as it lifts nne through the Plains and Upper MS Valley today and then across northern MN and into Ontario later tonight. The associated sfc low will rapidly deepen today aided by strong upper divergence from a coupled upper jet structure (right entrance region of a 130 kt jet max over northern Ontario and the left exit region of a 110 kt jet max over the Southern/Central Plains). The deepening low is reflected nicely by models with healthy 12hr 500mb height falls of 150-170m fcst ahead of system over the Arrowhead of MN and northern Ontario by Wed morning. At the sfc, models indicate the associated low pres will deepen to around 983 mb near the MN/Canadian international border by 12Z Wed as the center tracks just west of Lake Superior later tonight.

What weather/impacts can we expect from this impressive, and perhaps historically deep, late spring storm system? Increasing isentropic ascent, 850 mb theta-e advection and q-vector convergence on the leading edge of the system will bring scattered showers and a few thunderstorms into west half portions of the U.P. this afternoon.
Precipitable water increasing to around 1.5 inches or near the climatological daily max for the day at ~200pct of normal along with destabilization and steepening lapse rates out ahead of the approaching frontal boundary and at the nose of an impressive 60-70 kt LLJ will set the stage for widespread showers and thunderstorms by evening as the best mid-upper level forcing coincide with the arrival of the frontal boundary. Elevated CAPE values around 1000 j/kg as depicted by the fcst models may even result in a few strong to marginally severe storms given the very strong shear profile noted on fcst soundings. However that said, believe SPC's slight risk of SVR issued for the southern UP may be a bit overdone considering best forcing along the front won't occur until after sunset, so expect convection to be most likely elevated as depicted by model soundings and the main threat would be marginally SVR hail.
Most locations will see between half an inch to inch of rainfall from this system with the highest amounts west. Models show shower coverage diminishing significantly late tonight as we get into the dry slot behind the front along with q-vector divergence/subsidence as the system continues to lift north.

LONG TERM /WEDNESDAY THROUGH MONDAY/
Issued at 611 AM EDT Tue May 21 2024

The long term forecast will mainly be driven by a pair of troughs, one over the MN/Canada line by Wednesday morning and another over the Seattle vicinity that will arrive in the Upper Great Lakes by Friday and Saturday. Despite the surface low associated with the first trough already being northwest of Lake Superior by Wednesday morning, the impacts from this low will be the main storyline of the long term forecast as strong winds are expected.

By Wednesday morning, the surface low pressure will be over northwestern Ontario at around 984 mb per the 00Z GEFS mean. CAMs show a dry slot over the UP for much of the day Thursday with the HRRR hourly probabilities of measurable precipitation never exceeding 40 percent and mainly being under 20 percent. While rain will not be a major factor in the weather forecast, the winds will take center stage. With 850mb winds on the south side of the low pressure up to 50 kt, improving mixing throughout the day will bring some of those winds to the surface, with the 12Z Euro ensembles suggesting 30-50% chances of afternoon wind gusts in excess of 50 mph over the west half and near-certainty that gusts will exceed 35 mph across the UP. This is highly unusual for this time of year, shown by EFI values for wind gusts in excess of 0.8 and NAEFS SLP north of Lake Superior being below the last 20 years of climatology for this time of year. Headlines will need serious consideration following Tuesday's active weather.

Thursday, as the low pressure lifts towards James Bay, the pressure gradient relaxes and winds return to more normal speeds. A slight (15-20%) chance of precipitation lingers, with daytime heating and a weak remnant boundary supporting some isolated light showers, but otherwise a seasonal day is in store with NBM highs around the mid 60s across the central UP, with mid 50s to the north and low 70s to the south. While the weather is mostly benign over the Upper Great Lakes Thursday, troughing moving over the Rockies will support lee cyclogenesis, with the 00Z GEFS showing a mid-990s low over the KS/CO border by 00Z Friday. This low will eject northeast Friday and Saturday, but there's considerable spread in the track and timing of the storm. If the forcing lines up well with peak heating Friday, some thunderstorms are possible, with a few GEFS members showing 500- 1000 J/kg of SBCAPE, but uncertainty is high. Ensembles go to chaos beyond Saturday, but the pattern going into next week looks to favor ridging over the west and troughing over the east, which should help keep temperatures closer to normal relative to the warmer conditions of recent, along with continued periodic rainmakers.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
Issued at 749 AM EDT Tue May 21 2024

Areas of fog were over the central and western U.P this morning with LIFR conditions at KSAW and KIWD. Expect this fog to lift over the next hour or so. Low clouds will linger in the west around KIWD but expecting VFR conditions to prevail at KSAW and KCMX by mid morning.

As a strengthening low pressure lifts north from the Central Plains into northern MN tonight multiple areas of showers and thunderstorms will move though the area, from this afternoon into the late night hours. Expecting the first wave of showers and a few thunderstorms reaching the west by early afternoon and remainder of the area by mid afternoon. Stronger thunderstorms could accompany a front lifting through the area this evening into the late night hours. IFR conditions could be possible with any of the showers and thunderstorms but kept conditions mainly MVFR at this time.

LLWS is expected this evening and tonight as a strong low level jet moves across the area.

MARINE
Issued at 353 AM EDT Tue May 21 2024

Early this morning, wind gusts across the lake are light. However, an unseasonably strong low pressure system approaches Lake Superior this afternoon and evening resulting in rapidly increasing northeast winds across western portions of the lake. Northeast winds increase above 20 knots midday Tuesday over the far western lake then increase to 35-40 knot gales by Tue evening (60-90% chance). While the likelihood of gales is high, there is uncertainty in whether high-end gales can be achieved. Late May gales are rare due to the stable air immediately above the lake, but the strength of the surface pressure gradient close by the low pressure should support at least gales to 40 knots today. While a brief respite from gales is expected overnight in the west, the environment behind the low will make it much easier to tap into the low-level jet Wednesday, leading to high end gales expected (50+%) over the west half of Lake Superior with a few storm-force gusts possible (~20%), but current model guidance has storm force gusts isolated and brief, so most marine products will reflect gales to 45 knots. As the low continues to quickly depart, winds fall below gales late Wednesday and below 20 knots Thursday afternoon. Another low pressure will pass through the Upper Great Lakes region Friday, but is likely (75+%) to be much weaker and uncertainty exists regarding the track of the low, so the current forecast reflects 20-25 knot gusts Friday afternoon with gusts near 20 knots through Saturday.

Other marine hazards include chances (30-50%) of thunderstorms over the lake this afternoon in the west and across all of Lake Superior tonight, with a 5-15% chance of severe winds associated with the thunderstorms along with small hail. With the first round of gales this evening, significant wave heights will be highest in the far west at near 12 ft, with the Wednesday gales forcing waves as high as 15 feet in the north-central portions of the lake.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
None.
Lake Superior...
Gale Warning from 5 PM EDT /4 PM CDT/ this afternoon to 8 PM EDT /7 PM CDT/ Wednesday for LSZ162.

Gale Warning from 7 AM EDT /6 AM CDT/ to 8 PM EDT /7 PM CDT/ Wednesday for LSZ240-241.

Gale Warning from 10 PM this evening to 11 PM EDT Wednesday for LSZ242>244-263-264.

Gale Warning from 2 AM to 11 AM EDT Wednesday for LSZ245>251- 265>267.

Lake Michigan...
None.

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