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LSZ248 320 Pm Edt Fri Aug 25 2023
.a strong Thunderstorm approaching the waters...
the areas affected include... Huron islands to marquette mi... Marquette to munising mi...
at 320 pm edt, doppler radar indicated a strong Thunderstorm, capable of producing winds to around 30 knots and small hail. This Thunderstorm was located 7 nm southwest of presque isle, 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 4649 8741 4658 8751 4655 8695 4645 8697 4648 8702 4644 8724

LSZ200
No data

FXUS63 KMQT 042244 AFDMQT

Area Forecast Discussion National Weather Service Marquette MI 644 PM EDT Wed Oct 4 2023

SHORT TERM
(Through Tonight)
Issued at 223 PM EDT WED OCT 4 2023

Highly amplified pattern continues across the CONUS with a pair of ridges over the eastern Pacific and eastern seaboard/Quebec, with troughing across the Intermountain West into the Plains states.
These features are gradually shifting eastward. At lower levels, a 1023 mb high is centered over the Mid-Atlantic while a 990 mb low is analyzed over northern Ontario. Strong lower-tropospheric south- southwesterly flow continues to maintain an unseasonably warm airmass over the local area, although the airmass is tempered compared to the last two days, especially given the mostly cloudy skies across the central and eastern portions of the CWA.
Coverage of showers has been fairly paltry so far due to weak to nonexistent surface-based instability and weakening low-level jet magnitudes. Some CAMs still suggest an uptick in coverage for the eastern UP later this afternoon, but so far HRRR has had the best handle on things and it keeps coverage isolated to scattered (20-40%). We reduced PoPs a bit across the board with an update earlier this afternoon. Some peeks of sunshine are occurring over the west half of the UP as a dry slot moves into the area. This is accompanied by a slight wind shift at the surface from southerly to southwesterly. The actual system cold front is moving into NW WI/W LS, and is accompanied by a band of showers with brief heavy downpours. These will likely work their way across the western half this afternoon and early evening. It will remain breezy this afternoon with gusts of 15-25 kt continuing, with some near 30 kt in the Keweenaw.

Tonight, isolated to widely scattered (20-40% coverage) showers will continue eastward over the eastern half along the cold front. Skies should scatter out behind the front with cold advection occurring and eventually low-amplitude surface ridging building in. The cold advection will knock low temperatures down from the unusually warm values of the last couple of nights back to something closer but still above normal. Lows should range from the mid-40s interior west to the low 50s along the lakeshores.

LONG TERM
(Thursday through Wednesday)
Issued at 527 PM EDT WED OCT 4 2023

Key Messages: -Cold fronts on Thursday and Friday bring rain shower chances and progressively cooler air masses.
-Below normal temperatures and north winds off Lake Superior bring lake effect rain showers and clouds Friday afternoon into the weekend.

Starting with Thursday morning, shortwave ridging keeps the whole UP dry but an approaching cold front brings rain showers and perhaps a few rumbles of thunder Thursday afternoon and evening. Instability is minimal but the relatively warm waters of southern Lake Superior may add enough extra moisture to enhance activity across the lake.
Cold air advection behind the front results in lake-induced instability/steep low level lapse rates. The westerly wind direction is favorable for strong wind gusts on the Keweenaw where the current forecast advertises gusts in the 30-35 mph range late Thursday evening and early Thursday night. The period of strongest winds may be accompanied by lake effect rain showers as 850 mb temps drop to around 0C, but drying mid-levels and shallow inversion heights around 4-5 kft suggest light rain rates.

Continued CAA and increasing synoptic scale ascent Friday morning suggest increasing rain shower coverage. Synoptic scale ascent is associated with the passage of a surface trough that tracks southeast across Upper Michigan on Friday. Shower coverage should be fairly high with this feature and steep lapse rates up to the tropopause combined with favorable diurnal timing may allow for deep convection and a few more rumbles of thunder. Considering the cool environment any stronger updrafts will be capable of graupel or small hail. There's also a low-end potential for waterspouts with the Szilagyi nomogram indicating a marginally favorable environment, especially near Lake MI where water temps are warmer.

Behind Friday's trough, 850mb temps cool into the -2 to -4C range increasing lake delta-T values closer to 20C with lake effect processes becoming dominant Friday night. Model soundings show the mid/upper levels drying out by Saturday morning indicating purely lake effect precip. The lake effect environment slowly becomes less favorable over the weekend as inversion heights gradually lower and inverted-Vs gradually raise. However, the upper level low deepens and phases with a subtropical low on Sunday and shortwaves pivoting around this amplified low may bring more meaningful rain chances back into the eastern UP early next week. This low gradually decays while lingering near the Ontario/Quebec province line before shifting east late next week. Over the past 24-hours, EPS ensemble members have trended toward cooler fall-like weather persisting through next week.

AVIATION
(For the 00Z TAFS through 00Z Thursday evening)
Issued at 644 PM EDT WED OCT 4 2023

VFR conditions are expected to prevail through the TAF period. A frontal boundary may bring a few showers Thu afternoon to the taf sites.

MARINE
(For the 4 PM Lake Superior forecast issuance)
Issued at 527 PM EDT WED OCT 4 2023

A prolonged period of winds around 30kt will be the main story for this forecast period with the potential for wsw gale gusts on Thu and nnw gales Fri aftn thru Fri night. S winds at 20-30kt will continue ahead of a cold front currently moving over western Lake Superior. Immediately after the cold front passes, there will be another short period when a few sw gale force gusts to 35kt are possible over western Lake Superior (chance of gales is less than 20pct). SW winds diminish slightly overnight into early Thu before increasing again Thu morning into Thu night as the next cold front approaches and then passes. Expect the strongest winds over western Lake Superior after frontal passage Thu aftn/evening. There has been a slight increase in the risk of gales since the last forecast with the chc of gales over the w half of Lake Superior Thu aftn/evening now in the 40-50pct range. If stronger trends continue in the next round of model guidance, a gale warning may be warranted. A third cold front passes on Fri, bringing a wind shift to nw Fri then to northerly Fri night into Sat. The coolest air mass since last spring follows this front with NW to N gales already in the 40-70% chance Friday afternoon and night, mainly across central portions of the lake. Winds diminish below 20 kts across western Lake Superior on Saturday, but winds of 20-30kt winds will likely continue over the eastern half of the lake this weekend. A deepening low pressure near the Quebec/Ontario province line Sunday evening may increase winds across the eastern lake Sunday night.

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

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