Sunrise 6:07 AM   Sunset 9:24 PM Moonrise 5:43 PM   Moonset 3:38 AM

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LSZ244 Expires:202405190030;;451228 Fzus73 Kmqt 190005 Mwsmqt
marine weather statement national weather service marquette mi 805 pm edt Sat may 18 2024
lsz242>244-263-264-190030- /o.con.kmqt.ma.w.0006.000000t0000z-240519t0030z/ 805 pm edt Sat may 18 2024
.a special marine warning remains in effect until 830 pm edt - .
for the following areas - . Eagle river to manitou island mi - . Lake superior from saxon harbor wi to upper entrance to portage canal mi 5nm off shore to the us/canadian border including isle royale national park - . Lake superior from upper entrance to portage canal to manitou island mi 5nm off shore to the us/canadian border - . Ontonagon to upper entrance of portage canal mi - . Upper entrance of portage canal to eagle river mi - .
at 805 pm edt, a severe Thunderstorm was located 18 nm northeast of the upper entrance of portage canal, or 35 nm south of mott island park headquarters, moving northeast at 50 knots.
hazard - .wind gusts 34 knots or greater and large hail.
source - .radar indicated.
impact - .small craft could be damaged in briefly higher winds and suddenly higher waves. Large hail could result in structural damage.
the severe Thunderstorm will remain over mainly open waters.
precautionary/preparedness actions - .
&&
lat - .lon 4730 8866 4741 8877 4774 8823 4751 8802 time - .mot - .loc 0005z 237deg 49kt 4752 8844
hail - .>.75in wind - .>34kts

LSZ200
No data

FXUS63 KMQT 201120 AFDMQT

Area Forecast Discussion National Weather Service Marquette MI 720 AM EDT Mon May 20 2024

KEY MESSAGES

- A round of showers passes through the UP today. While brief heavy downpours and occasional lightning are possible (15-30%), severe weather is not expected.

- 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 318 AM EDT Mon May 20 2024

GOES-16 Nighttime Microphysics shows multiple cloud layers overspreading the UP this early morning, with a lower water cloud deck around 8kft per METARs and higher cirrus pouring in downstream of a complex of storms over the Upper Mississippi River Valley. RAP analysis shows this as a 500mb shortwave currently over Iowa and tracking northeast. Indeed, the forecast is for this shortwave and associated showers to arrive in the UP throughout the morning. The aforementioned cloud cover will prevent much destabilization, though the 00Z HRRR 90th percentile of SBCAPE over much of the west half does show up to 600 J/kg, so a few thunderstorms are not out of the question, though severe weather is not expected. PWAT values climbing to 1.25+ inches (90+ percentile per NAEFS climatology)
means ample moisture is present and some showers may have briefly intense downpours, though widespread impacts are unlikely as HRRR 50th percentile QPF by Tuesday morning is only 0.1-0.4 inches.

As the initial wave of showers departs around sunset tonight, attention will need to be paid upstream tonight. The available 00Z CAMs are split as to the presence of a decaying MCS over northern WI passing through the western UP overnight into Tuesday morning. The HRRR and HRW ARW are the strongest proponents of that MCS solution, but the remainder of the CAMs hold off on further noteworthy precipitation until later Tuesday. Should the MCS hold together (an already unlikely solution), the western UP could see some isolated strong winds from the decaying MCS, but more likely (80%) is that even if the MCS holds, it will be moving into a weaker convective environment and damaging weather will not maintain into the UP.

LONG TERM /TUESDAY THROUGH SUNDAY/
Issued at 513 AM EDT Mon May 20 2024

An active pattern will continue across the Upper Great Lakes in the coming week as an amplifying mid-upper level trough over western North America allows for a series of shortwaves to eject ne from this trough to support more rounds of rainfall for Upper Mi.

Beginning Tue, After a period of dry weather late tonight into Tue morning behind today's shortwave and associated bout of rainfall, another stronger shortwave is expected to eject ne from the western CONUS trough and continue to deepen on Tue as it lifts through the Plains and reaches the Upper Mississippi Valley Tue night. The deepening of the system 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) is reflected in healthy 12hr 500mb height falls of 150m predicted by the models over the Upper MS Valley/Upper Great Lakes region late Tue night/early Wed. At the sfc, models indicate the associated low pres will deepen to between 985-990mb as it approaches and then lifts across western and northern Lake Superior on Wed. While this low track passing to the w of Upper MI will support the widest coverage of heaviest rainfall over MN and nw WI, moderate to locally heavy rainfall will still be possible across Upper Mi during the period of strong isentropic ascent/strong 850mb theta-e advection to the e of the low track Tue night. Precipitable water also increases to around 1.5 inches or near the climatological daily max for the day at ~200pct of normal.
Expect widespread showers and scattered t-storms across the area as mid-level lapse rates steepen across the area. 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 late Tuesday into the southern UP may be a bit overdone considering we will be in an unfavorable e-se flow ahead of the approaching low for much of the day and with the strongest forcing from the system probably not arriving until after sunset, expect convection to be most likely elevated. GEFS probabilities show a 40-80pct chc of at least a half inch of rainfall from this system with the highest probabilities w and se.
Models show shower coverage diminishing significantly for Wed as we get into the dry slot and q-vector divergence/subsidence behind the system as it lifts north. Some areas may see dry weather for much of or all of the day, especially e half.

The biggest impacts from this system may end up being strong winds.
ECMWF EFI/Shift of Tails continues to increase into Wed with Upper MI mostly around 0.9 range now, suggesting a climatologically strong wind event for this time of year based on last 20 years of model climate. The EPS probabilities basically shows a 80-100% chance that the entire fcst area will see wind gusts exceeding 40 mph Wed afternoon into Wed evening with a 10-30 pct chance of western U.P.
higher terrain areas seeing high wind warning criteria gusts of 50 knots or greater. While winds for this fcst were increased from what NBM indicates, they are not as high as the median from the EPS and will likely need to be bumped up more. There will still be time to reevaluate for higher winds in later fcsts. For now, will mention the potential for higher wind gusts on Wed in the HWO product.

As the low lifts across northern Ontario toward James Bay on Thu, isolated showers will remain possible under lingering cool, cyclonic flow. Thu should be the coolest day of the week with highs in the lower 50s to the lower 60s F warmest s central.

Another shortwave trough lifting through the Plains into central Canada late week will send a sfc low pressure trough/frontal boundary into Upper Mi late Friday/Fri night which could linger over the area into Sunday bringing yet more opportunities for showers.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
Issued at 720 AM EDT Mon May 20 2024

VFR conditions are currently being observed at all TAF sites. As -SHRA threatens all sites (and has already begun at IWD), the additional moisture will bring ceilings down and threaten to bring visibilities down as well. IWD is likely (75+%) to have a period of at least MVFR ceilings with a 25% chance of falling to IFR this afternoon. CMX and SAW originally were expected to fall to MVFR this afternoon but models have trended better and it is now more likely to be VFR than not-VFR this afternoon. Overnight, as showers depart, models are split on whether or not a significant deterioration in flight categories occurs, but most predict conditions falling to at least MVFR at IWD by 12Z tomorrow and IFR at SAW and CMX with a 1-in- 3 chance of LIFR at those two sites.

MARINE
Issued at 513 AM EDT Mon May 20 2024

Weak pressure gradients will keep winds less than 20 knots across Lake Superior into Tuesday morning. Deepening low pres will then lift toward western Lake Superior, reaching the lake Wed morning.
Expect e to ne winds to ramp up late Tuesday as the low approaches.
NE winds will increase to 25-30kt over western Lake Superior by late Tue afternoon, reaching gales of 35-40 knots by Tue evening. Winds increase further Tue night. Probabilistic guidance indicates a 50-80 percent chance of reaching gale gusts later Tue night into Wed across w and central Lake Superior. Although, model probabilities were low (generally less than 20%) for gales over the east half of the lake, I did bump up the gusts to 35 to 40 knots late Tue night into Wed due to a 60 to nearly 70 kt southerly low-level jet moving across the area at that time east of the low track. Gut feeling is despite the strong stability depicted over the lake by model soundings, believe that some of this wind will be realized near the sfc of the lake over higher platform observing stations. In short, decided to issue Gale Watches for LSZ162 00Z Wed-00Z Thu, for LSZ263- 264 04Z Wed-06Z Thu and for LSZ265>267 06Z Wed-21Z Wed. It is worth noting that some of the models that track a deep low just w of Lake Superior into northern Ontario show a potential for higher end westerly gales across the lake Wed into Wed night, especially across the w half. Will be something to monitor. At any rate, west- northwest winds should gradually diminish to 20 to 30 knots late Wed night into Thu and fall generally to 20 knots or less late Thu night into Friday while gradually becoming easterly.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
None.
Lake Superior...
Gale Watch from Tuesday evening through Wednesday evening for LSZ162.

Gale Watch from late Tuesday night through late Wednesday night for LSZ242>244-263-264.

Gale Watch from late Tuesday night through Wednesday afternoon for LSZ245>251-265>267.

Lake Michigan...
None.

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