Sunrise 6:07 AM   Sunset 9:24 PM Moonrise 5:44 PM   Moonset 3:40 AM

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LSZ246 /o.can.kmqt.ma.w.0057.000000t0000z-231005t2115z/ 503 Pm Edt Thu Oct 5 2023
.the special marine warning is cancelled - .
the affected areas were - . Point isabelle to lower entrance of portage canal mi - .
the Thunderstorm has moved out of the warned area and no longer poses a significant threat to boaters.
lat - .lon 4697 8806 4711 8813 4714 8803 4698 8789 time - .mot - .loc 2102z 249deg 34kt 4704 8797

LSZ200
No data

FXUS63 KMQT 200719 AFDMQT

Area Forecast Discussion National Weather Service Marquette MI 319 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 /MONDAY THROUGH SUNDAY/
Issued at 350 PM EDT Sun May 19 2024

Southwesterly midlevel flow between deepening troughing over the northern/central Rockies and ridging extending form the Deep South through the Northeast will result in the preferred storm track being located over the local area through midweek. This will lead to periods of rainfall through at least Wednesday. Shortwave ridging favors a drier period to end the week Thu/Fri, with precip chances reentering the picture to start the holiday weekend Saturday. Aside from a brief cool-down Thursday, temperatures look to average near to slightly above normal for the upcoming week into the start of next weekend.

Initial shortwave of concern looks to touch off convection over the Central Plains today, and may itself be convectively enhanced as it ejects northeastward to the upper Great Lakes by Monday. Low-level jet strengthening to 30-40 kt at 850 mb will enhance moisture transport into the region, with PWATs increasing to 1.25-1.50 inches, or +1 to +2 stdev. High confidence in an area of rainfall continuing over the western UP by the start of the period (12Z/7 am CDT Mon), continuing into the central UP by mid-morning, and likely reaching the eastern UP by early afternoon. Although a couple rumbles of thunder will be possible, the corridor of better instability should remain well to the south. Confidence is lower on what happens during the afternoon and evening hours. It's reasonable to expect some subsidence on the back of this initial wave to dry things out for the afternoon, especially west/central. However, some CAMs, namely the 12Z.19 NAM3 and HRW-ARW have a trailing convectively- generated wave bringing in another round of rainfall for the afternoon central and east. Reduced PoPs a bit here for the afternoon/evening as I feel that this scenario is not the most likely. Forecast soundings suggest some lower clouds may linger through the day which would limit surface-based instability to redevelop; however, should the convectively generated wave materialize, some elevated convection would be possible. Monday night should be quiet and partly to mostly cloudy in the wake of Monday's rain.

Tuesday morning will start out quiet, then attention turns to the highest potential impact portion of the period, late Tuesday into Wednesday. The culprit is a negatively tilting, vigorous shortwave trough ejecting out of the central Plains into northern MN/Lake Superior. This will foster an unseasonably strong cyclone. The 00Z NAEFS mean has this low bottoming out at 996 mb near the Keweenaw at 12Z Wed, which is below the 1 percentile relative to climatology.
However, the 12Z EPS/GEFS mean have this low at 992 mb, and several members (and the 12Z ECMWF) have this low down in the mid/lower 980s, which is highly anomalous for this time of year. There is still considerable uncertainty on the track, with generally a stronger storm favoring a westward and slightly slower track.
Regardless, this storm will feature incredibly strong dynamics and moisture transport, with PWATs likely above 1.50 inches Tuesday night. Showalter values go negative Tuesday night as steeper midlevel lapse rates move in. With at least modest instability coupled with very strong wind shear, there is potential for large hail along with heavy downpours, as SPC has included portions of the central and southern UP in a Slight Risk (level 2/5). Thinking it's unlikely that we get into the warm sector with model soundings showing convection being elevated, especially as the strongest forcing is likely to arrive after sunset, so wind threat is more uncertain at this time. Heaviest rainfall looks to favor the western UP, with EPS probabilities of 2"+ at 20-30%. However, potential for a more widespread flooding event should be mitigated due to ongoing drought conditions in the region.

A westerly track of the system (e.g., 12Z ECMWF) would open the door for synoptic-scale wind concerns on Wednesday in the favorable location beneath the midlevel dry slot. If low-level moisture scours out, strong mixing could occur and tap into the strong low-level wind field. ECMWF EFI values exceeding 0.8 signify potential for unusually strong winds. EPS mean wind gusts are widespread 40 kt here. Something to monitor in the coming days, and will wait until storm track becomes more certain to message this threat more strongly.

Cold advection on the back side of this system will keep things on the cool and dry side for Thursday, with a modest warming trend Friday and the next system possibly (40-60% chance) bringing rain back Friday night into Saturday.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
Issued at 124 AM EDT Mon May 20 2024

VFR cigs/vsby prevail into Mon morning at all terminals. Conditions deteriorate Monday morning as a wave of rain lifts north across Upper Michigan. Model guidance brings in MVFR conditions first at IWD Monday morning and Monday afternoon at CMX and SAW as this area of rain moves through. Could be some IFR briefly at SAW late in the afternoon and at CMX Mon evening. IWD will improve back to VFR by Mon evening.

MARINE
Issued at 350 PM EDT Sun May 19 2024

With the exception of some locally higher gusts of 20-30 kt along the tip of the Keweenaw and in the vicinity of Isle Royale through early this evening, winds should remain around 20kt or less through Tuesday morning. Main period of interest is Tuesday afternoon through Wednesday as an unseasonably strong low pressure system tracks from the central Plains across Lake Superior and into southern Ontario. There are still important model differences that will dictate peak wind speed and direction, but right now the highest probabilities for northeasterly gales are Tuesday night over the western and north-central part of the lake, with 30-60 kt probabilities here. Winds remain elevated as they shift to a westerly component on Wednesday with 25-30 kt expected. If the low track ends up being further west than anticipated, Tuesday night northeasterly gales would be less likely, but Wednesday southwesterly gales would be more likely, possibly lingering into Wednesday night.

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

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