Sunrise 6:09 AM   Sunset 9:22 PM Moonrise 3:29 PM   Moonset 3:11 AM

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LSZ244 /o.con.kmqt.ma.w.0056.000000t0000z-231005t2115z/ 458 Pm Edt Thu Oct 5 2023
.a special marine warning remains in effect until 515 pm edt - .
for the following areas - . Eagle river to manitou island mi - . 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 - . Lake superior from upper entrance to portage canal to manitou island mi 5nm off shore to the us/canadian border - . Manitou island to point isabelle mi - .
at 457 pm edt, a severe Thunderstorm capable of producing waterspouts was located near brockway mountain, or 28 nm northwest of stannard rock, moving northeast at 40 knots.
hazard - .waterspouts, wind gusts 34 knots or greater, and small hail.
source - .radar indicated.
impact - .waterspouts can easily overturn boats and create locally hazardous seas. Small craft could be damaged in briefly higher winds and suddenly higher waves.
locations impacted include - . Manitou island.
precautionary/preparedness actions - .
move to safe harbor until hazardous weather passes.
Thunderstorms can produce sudden waterspouts. Waterspouts can easily overturn boats and create locally hazardous seas. SEek safe harbor immediately.
&&
lat - .lon 4763 8760 4743 8747 4732 8786 4749 8801 4766 8762 time - .mot - .loc 2057z 241deg 40kt 4745 8781
waterspout - .possible hail - .<.75in wind - .>34kts

LSZ200
No data

FXUS63 KMQT 182154 AFDMQT

Area Forecast Discussion National Weather Service Marquette MI 554 PM EDT Sat May 18 2024

KEY MESSAGES

- Increasing threat for severe thunderstorms capable of damaging winds and large hail across western Upper Michigan late this afternoon into the evening hours.

- Borderline elevated fire weather conditions on Sunday with very dry conditions, but winds on the lighter side.

- Frequent periods of showers Monday through late week, but mainly focused on Monday and also Tuesday afternoon and Tuesday night.

- Above normal temperatures early in the week falling to below normal late week.

SHORT TERM /THROUGH EARLY THIS EVENING/
Issued at 309 PM EDT Sat May 18 2024

Forecast is mostly on track early this afternoon except for a few pesky rain showers that continue to percolate across the Copper Country on the cool side of a ~40 kt low level jet. There was some thunder/lightning with this activity before it moved into our area, but has just been showers since then. Looking around local weather stations indicates morning rainfall has been difficult to measure, probably due to the deep inverted-v signature evaporating most of the droplets. Otherwise temperatures have warmed into the 70s and 80s in line with the morning forecast with the warmest spots being L'Anse, Harvey, and Covington that all observed 84F around 2PM.
Relative humidity values decreased to 28% at Baraga Plains, Golden Lake, and Michigamme sites with everywhere else staying at or above 30% at this time. The eastern edge of lower RHs appears to be a subtle Lake MI lake breeze with a subtle wind shift from SSW to SSE and dew points a few degrees warmer.

The main forecast challenge going through this evening continues to be thunderstorm chances as a cold front sweeps east across Upper Michigan. Many different observation platforms reveal a cold front extending south from the MN arrowhead toward La Crosse, WI. A lake breeze boundary over the Bayfield Peninsula is also apparent on DLH radar with SPC mesoanalysis of surface vorticity and divergence highlighting these features well. The latest 18z mesoanalysis also shows SBCAPE around 1500 J/kg along the MN/WI state line beneath 0-6 km bulk shear of 30-40 kts, which is conducive to marginally severe thunderstorms. Large hail and damaging winds are the most likely hazards and deep inverted-vs with DCAPE of similar magnitude as MUCAPE suggests damaging winds may be more prevalent. Several recent HRRR/NAM nest runs have shown gusts at or near severe thresholds with the most common location being near and northeast of the Porcupine Mountains.

Satellite/radar imagery shows orphan anvils over northern WI indicating updrafts are trying to get going, but have so far failed to persistently break a mid level capping inversion. However, HRRR guidance indicates rapid initiation over northern WI around 20Z/4PM eastern with coverage increasing as it moves into Gogebic County by 22Z/6 PM eastern then well into the western UP by 00z/8 PM eastern.
Thunderstorm activity is expected to be weakening as it moves into the central UP due to the loss of surface heating. However, the threat doesn't end until the cold front moves through and the frontal boundary apparent on DLHs area is about 5 hours away according to the time of arrival tool. This is a fair amount slower than CAMs implying storms may be outflow-dominant, surging ahead of the boundary. As far as rain totals ensemble guidance favors a quick 0.10-0.20in of rain for the most part, but there is a chance (30- 40%) for heavier amounts up to a half inch in any heavier downpours.
Skies quickly clear from west to east behind the front while winds veering westerly before becoming light and variable under surface ridging.

LONG TERM /TONIGHT THROUGH SATURDAY/
Issued at 551 PM EDT Sat May 18 2024

An active pattern will continue across the U.S. during this week.
Troffing currently over western Canada into the northern U.S.
Rockies will amplify over the next few days, leading to western Canada/western U.S. troffing this week. A series of shortwaves dropping into this trof from the N Pacific will then eject e and ne across the U.S., supporting the active pattern. For Upper MI, the result will be several opportunities of rainfall this week. The first is just beginning and continues into tonight. The second follows late Sun night thru Mon evening, the third Tue aftn thru Wed, possibly lingering into Thu, associated with the strongest low pres of the week, and finally the fourth at some point Fri thru the weekend. Models are in overall good agreement thru midweek. Timing of the last system is most uncertain, but that's expected given the farther time range out in the model runs. So, expectation is for overall above normal pcpn across Upper MI over the next 7 days. This will work to ease still lingering drought over portions of western Upper MI where, per the 5/16 U.S. Drought Monitor, severe drought was still indicated, centered around the Porcupine Mtns, and also in eastern Upper MI where moderate drought was still indicated from eastern Delta to western Mackinac counties. As for temps, above normal readings will be the rule thru Mon, warmest on Sun. Temps will then trend downward to blo normal Thu/Fri, due to the flow around the deep low that passes across the area midweek. A return toward normal expected over the weekend.

Beginning tonight, a mostly narrow band of convection associated with cold front still currently w of Upper MI will continue progressing eastward with a tendency to diminish with time once it reaches central Upper MI due to loss of daytime heating and resulting waning instability. Risk of damaging winds/large hail exists across roughly the w half of Upper MI owing to 500-1000j/kg of MLCAPE over the next few hrs and deep layer shear of 30-40kt.
Last of the diminishing shra/tsra will exit the eastern fcst area 06- 09z. Skies will quickly clear from w to e after fropa. Expect lows generally in the upper 40s to lwr 50s F across the area.

On Sun, sfc high pres ridging will move to the Upper Great Lakes along with and an associated very dry air mass. Full sun thru the morning will give way to some mid/high clouds arriving from the w in the aftn. Strong insolation will result in deep mixing into extremely dry mid-levels. NAM shows late morning dwpts at 800mb/~5kft AGL ranging from -20 to -40C, though this is the low end of the model guidance. Moisture aloft does increase during the aftn, but mixing potential still supports sfc dwpts falling thru the 30s F. Some locations will see upper 20s F. The low dwpt potential is evident thru local mixed dwpt tool and simply in raw model guidance, HRRR most dramatically (it often captures mix down drying quite well). With high temps in the mid/upper 70s F across the interior, the low dwpts will drive RH down to around 20pct across much of Upper MI Sun aftn. The good news is winds will be on the lighter side, though a little higher than previously expected. Sustained winds will be around 10 mph with gusts to around 15 mph. Winds will be strongest across the Keweenaw with gusts to around 25mph there.
Will need to monitor for lightning strike started fires, especially if rainfall from storms is more limited tonight. Lake breeze development will limit fire wx concerns close to the Great Lakes shorelines due to cooling conditions (temps falling into the 60s F), and higher dwpts, resulting in higher RH.

Out of the amplifying mid-level trof over the western CONUS, next shortwave will lift to the Upper Great Lakes on Mon, accompanied by a surge of precipitable water up to ~190pct of normal. This increase in moisture along with increasing isentropic ascent will lead to shra/isold tsra and a widespread wetting rain across much of the fcst area. EPS ensemble probabilities show much of the area, except the Keweenaw, with a 30-50% chance of seeing 0.5 inch of rain from this system. Shra will arrive late Sun night and end most areas Mon evening. After a period of drier weather late Mon night thru Tue morning, a notably stronger shortwave ejecting from the western trof will reach the Upper Mississippi Valley Tue night. With this wave potentially closing off a mid-level low, it may be slower to exit across Upper MI into Ontario Wed/Thu. The GFS has been and continues to be on the faster edge of the model solutions. This fcst leans toward the slower consensus. Associated deepening sfc to 985-990mb range will be in the vcnty of western Lake Superior Wed morning.
While the low track passing to the w of Upper MI will support the widest coverage of heaviest rainfall to the w of Upper MI, mdt to locally hvy rainfall will still be possible across the fcst area during the period of strong isentropic ascent/strong 850mb theta-e advection to the e of the low Tue night. Precipitable water increases to ~200pct of normal as well. Expect widespread rainfall across the area. EPS probabilities show a 30-70% chance for at least a half inch of rainfall from this system with the highest probabilities se and w. Shra coverage will diminish significantly for Wed, some areas may slip in dry weather for much or all of the day, especially e half. As the low lifts across northern Ontario, isold/sct shra may linger under cyclonic flow on Thu.

Timing shra potential Fri/Sat is uncertain. For now, of the 2 days, Fri has the better shot at being a dry day.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
Issued at 138 PM EDT Sat May 18 2024

VFR cigs/vsby prevail thru this fcst period except for a brief 2-4 hour window when a cold front brings shower and thunderstorm chances as it sweeps east across Upper Michigan. Uncertainty in thunderstorm timing was addressed with a 4-6 hour VCTS group and a 2 hour TEMPO group highlighting the most likely timing of thunderstorms.
Confidence in thunderstorms is lowest at SAW, but strong thunderstorms capable of large hail and damaging winds are possible at IWD/CMX this evening. Otherwise, gusty southerly winds up to 30- 35 mph today veer westerly and diminish to less than 10 mph behind the cold front. Cloud cover also rapidly diminishes behind the front with skies becoming clear by Sunday morning.

MARINE
Issued at 325 AM EDT Sat May 18 2024

Stable conditions will lead to light winds of generally 20 knots or less prevailing over the lake into early next week, except for some 20-25 kt southeast gusts today over the east half ahead of an approaching cold front. Thunderstorms are possible today into tonight as the cold front marches across the lake. 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. Models and ensembles indicate winds will ramp up Tue night into Wed as a stronger low pressure center tracks across the western and northern portions of the lake. Ensemble probabilities show a 40-60 pct chance of gale force gusts to 35 knots late Tue night into Wed across western and northern sections of the lake.

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

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