Sunrise 6:35 AM   Sunset 8:58 PM Moonrise 1:27 AM   Moonset 9:11 AM

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LSZ249 115 Pm Edt Tue Apr 23 2024
a marine weather statement has been issued for the following areas - . 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 114 pm edt, doppler radar indicated a cluster of strong Thunderstorms, capable of producing winds to around 30 knots and small hail. The leading edge of these Thunderstorms were located over shelter bay, moving east at 20 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.
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lat - .lon 4648 8702 4647 8712 4654 8714 4669 8651 4653 8642 4640 8663 4640 8671 4643 8677 4640 8690

LSZ200
No data

FXUS63 KMQT 282243 AFDMQT

Area Forecast Discussion National Weather Service Marquette MI 643 PM EDT Sun Apr 28 2024

KEY MESSAGES

- Much cooler today with showers lifting from south to north during the afternoon.
- Active pattern continues as three low pressure systems track across the region over the next week. Above normal temps/precip are expected including thunderstorm chances.
- Elevated fire weather conditions are possible over the west half of Upper Michigan on Wednesday, but will depend on the preceding precipitation.

SHORT TERM /THROUGH MONDAY NIGHT/
Issued at 346 PM EDT Sun Apr 28 2024

Upslope/onshore ne winds have lead to chilly temps today (mid to upper 30s) into west and north central portions with even some patchy dz at times into north central portions. Downsloping into the eastern portion of the cwa has allowed temps there to reach into the lower 50s under abundant cloud cover.

Water vapor imagery and RAP analysis show a shortwave over the eastern NE and eastern KS that models project will be lifting ne toward the Upper Great Lakes later tonight and Monday. As the associated sfc low pres centered over eastern NE and southern IA lifts nne into southern MN and southern/central WI late tonight, strengthening WAA/isentropic ascent ahead of the system's advancing sfc-850 mb warm front and increasing transport of Gulf moisture and PWAT values around an inch or more will result in steady showers (now over into the south central UP) to lift north across most of the cwa later this afternoon and evening.
In turn, will have categorical PoPs lifting north for widespread showers across the cwa. Models mid-level RH plots hint at dry-slotting reaching into the western UP later this evening and overnight which could result in a break from the steadier showers so have lowered PoPs back to chance over these zones.
Overall, from this afternoon through tonight have QPF totals ranging from around a .25 inch over the Keweenaw to more than an inch over se portions of the cwa where best isentropic lift will be focused the longest across the sharp 850 mb thermal gradient along the warm front. Elevated CAPE values of a couple hundred j/kg could lead to isolated t-storms late tonight into se portions, also boosting QPF totals. Expect lows tonight mostly in the mid to upper 30s, except for some lower 40s readings south central and east.

Despite a very shallow mixed layer of 1-2 kft off the sfc as depicted on soundings, the arrival of a 45-50 kt LLJ could result in easterly wind gusts approaching near advisory criteria later tonight across the Keweenaw Peninsula, particularly on the downslope westerly side of the Keweenaw. Not enough confidence to issue a wind advisory at this point for the Keweenaw as it looks the higher gusts may be just localized on the western side of the Keweenaw but this will be something to monitor on the evening and mid shifts. The rest of the cwa will see easterly gusts more in the 20-30 mph range.

LONG TERM /MONDAY THROUGH SUNDAY/
Issued at 445 PM EDT Sun Apr 28 2024

With three different low pressure systems in the extended forecast, there is fairly good agreement in the medium range model guidance for plenty of precip chances. Uncertainty builds in the latter part of the week as guidance begins to diverge ahead of the third low pressure system.

The first low pressure system will be ongoing at the beginning of the extended forecast. Starting on Monday, a negatively tilted mid level trough will be situated over the Dakotas/MN state line, extending south into IA with weak ridging over the east U.S. coast and a trough over the Pacific Northwest. The midwest trough pivots over the UP on Monday and the sfc low slowly follows northward behind it. Better q-vector convergence will be located over Lake Superior already Monday morning with a dry slot highlighted in PWATs dropping ~0.2" behind the warm front. This leads to diminishing showers over the west in the morning hours. With increasing PVA in the afternoon, showers are reinvigorated mainly over the west half of the UP. This may be enough forcing to provide some thunder and lightning, however severe weather is not expected. Lingering showers and cloud cover will limit instability with model guidance hinting at ~200-300 j/kg of MUCAPE and mid level lapse rates mainly below 6 C/km. Also, by the time the low level inversion is eroded, the very limited instability will have nearly diminished. The 4/28 0z ECMWF EFI still highlights this period under anomalous QPF with SoT>0 and shaded values to 0.7 to 0.9. Morning showers look to add 0.01" to 0.15" in the west with 0.15" to 0.5" in the Keweenaw and eastern UP.
Showers in the afternoon could result in an additional 0.25" in heavier downpours. That said, hydro hazards are not expected.

Showers lift north out of the UP Monday night as the trough and sfc low lift over Lake Superior, temporarily bringing dry weather back to the UP for Tuesday. WAA during the day accompanied by clearing skies will bring above normal highs in the 50s near Lake Superior and in the east with 60s in the interior west and south central.
Meanwhile, a shortwave will quickly ride east off the Northern Rockies toward the Upper Great Lakes during the day as it takes on a negative tilt and replacing the dry weather Tuesday night into Wednesday as it swings northeast over the UP. While there is some spread yet in the associated sfc low pressure, the general consensus is to take it northeast from MN into northern Ontario, but both GEFS and ECMWF ensembles have members that take the low further to the east over Lake Superior. The ECMWF also is a bit slower with the timing, which would drag precip longer into Wednesday. This means that timing and track still have some uncertainty yet, but a brief round of showers Tuesday night into Wednesday is expected, with better odds over the northwestern UP. Instability again is fairly low (MUCAPE below 100 j/kg), but the support of the cold front moving east across the UP may support a few rumbles of thunder near the WI/MI state line.

Dry weather then returns on Wednesday, likely continuing through Wednesday night. Pressure rises behind the cold front and clearing skies will result deep mixing. This will yield warmer than normal temps in the 60s to low 70s and some breezy west winds during the day. Sounding analysis shows the interior west mixing up to around 800-850mb with up to 900mb in the east and the Keweenaw. The last two runs of ECMWF ensemble probabilities of wind gusts exceeding 34 kts were around 20-40% in the west with the 4/28 13Z NBM probabilities around a similar magnitude, except higher to 60% in the Keweenaw. This would also result in lower dew point temps in the west and thus RHs dropping near 25%. The combination of gusts and low RHs would increase fire weather concerns. The limiting factor here is the timing of the previous low pressure system. If the ECMWF solution is favored, precip will linger further into Wednesday resulting in delayed mixing, lower wind speeds, and higher RHs.

Uncertainty continues to grow in the forecast Wednesday night onward, but chances for precip increase Thursday with 20-50% PoPs continuing into the weekend as we track out the third low pressure system.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
Issued at 642 PM EDT Sun Apr 28 2024

An advancing warm front and increasing moisture ahead of low pressure lifting ne through the Upper Mississippi Valley will result in MVFR cigs at IWD and CMX lowering to IFR and as low as LIFR/VLIFR late tonight after widespread rain into the region later this evening and overnight. Lingering LIFR conditions at SAW will continue under steady rain. ENE winds this afternoon will be gusty to around 20kt. At CMX, easterly winds tonight will become sustained at 20-25kt with gusts to 35-40kt possible. LLWS will set in at SAW this evening into the early overnight.

MARINE
Issued at 445 PM EDT Sun Apr 28 2024

Northeast gales to 35 kt are expected across the western third of the lake this afternoon increasing to easterly gales to 40 kts across most of the lake tonight, continuing into Monday morning.
While a few gusts may exceed 40 kts late tonight into Monday, probabilities remain on the low end (25-50%). The strongest winds are expected in the far west as well as the north central portion of the lake between the Keweenaw and Isle Royale where there could be some channeling. The far eastern zone may see a few gale force gusts to 35 kts Monday morning, but confidence was not high enough to issue a Gale Warning for that zone. Gales quickly diminish Monday afternoon as the low pressure moves over western Lake Superior.

Significant wave heights up to 14 ft are possible Monday morning between Duluth Harbor to the Bayfield Peninsula and near Isle Royale. Waves fall below 8 ft Monday evening.

Winds fall below 20 kts in the west half of the lake Monday evening and after midnight in the east. Winds are then expected to remain mainly below 20 kts through Tuesday. East to south east winds increase to 20-30 kts Tuesday night, becoming west behind a cold front on Wednesday. With stronger pressure rises behind the cold front, west gales to 35 kts are possible on Wednesday over the west half of the lake. Highest probabilities of winds exceeding 33 kts are around 50-75% between the Keweenaw and Isle Royale. Winds quickly return below 20 kts Wednesday night.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
None.
Lake Superior...
Gale Warning until 5 PM EDT /4 PM CDT/ Monday for LSZ162.

Small Craft Advisory until 11 PM EDT /10 PM CDT/ Monday for LSZ240-241-247-248.

Small Craft Advisory until 11 PM EDT this evening for LSZ242>246.

Gale Warning from 11 PM this evening to 5 PM EDT Monday for LSZ242>246-263>266.

Small Craft Advisory until 5 PM EDT Monday for LSZ249>251.

Lake Michigan...
Small Craft Advisory until 11 AM EDT Monday for LMZ221.

Small Craft Advisory until 4 PM EDT Monday for LMZ248-250.

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