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LSZ140 543 Pm Cdt Tue Sep 5 2023
.strong Thunderstorms over western lake superior...
the areas affected include... Grand marais to taconite harbor mn... Grand portage to grand marais mn... Lake superior west of a line from saxon harbor wi to grand portage mn beyond 5nm... Outer apostle islands beyond 5 nm from mainland... Port wing to sand island wi... Sand island to bayfield wi... Taconite harbor to silver bay harbor mn...
at 542 pm cdt, doppler radar indicated strong Thunderstorms, capable of producing winds to around 30 knots, small hail, and frequent cloud to water lightning. These strong Thunderstorms were located along a line extending from 19 nm north of grand marais harbor, to 11 nm east of tofte safe harbor, to near york island, moving east at 25 knots.
locations impacted include... Siskwit bay harbor, raspberry island lighthouse, sand island, horseshoe bay and safe harbor, tofte safe harbor, stockton island, devils island, tofte, taconite harbor, mouth of the cross river, bayfield peninsula sea caves, grand marais harbor, york island, apostle islands national lake shore, sand bay, outer island, and herbster.
precautionary/preparedness actions...
mariners can expect gusty winds up to 33 knots, locally higher waves, and lightning strikes. Boaters should seek safe harbor immediately until these storms pass.
&&
a severe Thunderstorm watch remains in effect until 1100 pm cdt for northeastern minnesota...northwestern wisconsin...and the adjacent waters of lake superior.
lat...lon 4762 8981 4690 9028 4687 9081 4690 9080 4693 9086 4692 9095 4685 9107 4684 9122 4756 9092 4772 9055 4791 8982 4796 8973

LSZ100
No data

FXUS63 KDLH 050018 AFDDLH

Area Forecast Discussion National Weather Service Duluth MN 718 PM CDT Wed Oct 4 2023

DISCUSSION
(This evening through Tuesday)
Issued at 325 PM CDT Wed Oct 4 2023

Key Messages

1) Cold front moving through the area today bringing with it showers and some light precipitation.
2) Unsettled weather through the rest of the work week.
3) Drying out with seasonable temperatures expected heading into next week.

Through the rest of Today:

After a stretch of unseasonably warm weather, we are getting our first taste of fall weather today from a passing cold front. The cold front is currently situated in a North/South orientation stretching from Ely, through Duluth, and down towards Minong.
Temperatures ahead of the front are in the mid to upper 60s with winds out of the south. Following the frontal passage, winds are out of the west with a drop of nearly 10 degrees across the diffuse front. Some scattered showers have popped up across our northern counties with some slightly deeper convective showers that will approach the North Shore areas in the next hour or so.
Behind these showers, some light drizzle and precipitation has been seen on radar further west back towards International Falls.
These should move through the area by late afternoon before our next round of precipitation arrives late tonight.

Wednesday night into this weekend:

Our active weather pattern continues through the next couple of days with our next chance of precipitation coming early Thursday morning. As a shortwave drops out of the Canadian Prairies it’ll bring with it the chance for more showers and rain. We’ll have two shots for precipitation Thursday; one in the morning and the second one later in the afternoon/evening. The first chance for rain will come from an occluded front tied to the surface low moving close to the Canadian/US border. Overnight convection across the Dakotas tonight will move eastward whilst slowly weakening but it’ll be able to tap into just enough moisture and ascent along the front for some showers across NE Minnesota near dawn. A brief lull in weather is expected until afternoon when the stacked upper low and surface low spread wrap around moisture across the region coupled with steep lapse rates. The steep lapse rate tied with some clearing in the clouds will promote marginal CAPE (<500 MUCAPE) to develop allowing for some convective showers to form in addition to the more widespread wrap-around stratiform precipitation. As a result of these showers, we could see our first winter precipitation of the season with some graupel or ice pellets possible in the afternoon with the freezing level only about 1km above the surface. Initially these showers are likely to be limited to closer to the Canadian Border/Minnesota Arrowhead.
However, through the rest of day they will be more widespread in nature stretching into NW Wisconsin and North Central Minnesota.
With Lake Superior still warm, we could see some better chances of rain on the South Shore of the lake where some lake enhancement could help maintain some of the stronger showers. Temperatures will continue to drop into Friday with temperatures struggling to get out of the 40s. Continual NW winds will make it feel a tad chillier with some isolated convective showers still possible throughout the area but overall less widespread. Weaker lapse rates and less favorable thermodynamics on Friday compared to Thursday should limit overall coverage and intensity of the showers. Total rainfall totals on Thursday and Friday should remain below 0.25” with up to 0.5” where some of the stronger showers are seen. Temperatures on Friday night will be modulated somewhat by a low cloud deck but where more clearing can be realized near the Canadian Border tied with cooler temperatures, some marginal frost could be seen.

Weekend through next week:

Highs on Saturday will struggle to get out of the 40s with persistent cold advection from Canada. Saturday night presents a better chance of widespread frost with light winds, temperatures falling into the upper 30s, and dewpoints in the mid to upper 30s.
Sunday will be slightly warmer than Saturday, but with winds out of the north temperatures will be limited to the upper 40s (Arrowhead) to the mid 50s (Brainerd Lakes Region). To start next week, persistent flow out of Canada will prevent any major warming with high temperatures limited to the 50s and low 60s. The next precipitation chance would come mid/late next week as another trough and associated frontal passage moves through the Northlands area.

AVIATION
(For the 00Z TAFS through 00Z Thursday evening)
Issued at 718 PM CDT Wed Oct 4 2023

VFR conditions will prevail into the overnight hours in the wake of a cold front. Winds are expected to diminish as well this evening. Another cold front will push into the region during the early morning hours with chances for showers and pockets of MVFR ceilings. INL will see the best chance for these lower ceilings being closer to the low moving across Manitoba and Ontario.
Showers should be light enough to not lead to any significant visibility restrictions, but any stronger showers may briefly reduce visibilities in spots. Winds are expected to pick up again Thursday morning after sunrise with gusts to 20 to 25 knots persisting through the remainder of the TAF period.

MARINE
Issued at 325 PM CDT Wed Oct 4 2023

Gusty southwest winds gusting into the 20-30knot range across the lake will continue this afternoon before diminishing this evening.
Have maintained Small Craft Advisories through this evening for most of the nearshore waters. Once these winds diminish, there is only a short period of quieter conditions before winds increase once again early Thursday. There are several hours where we may get some gales around the Bayfield Peninsula Thursday afternoon and early evening. Later Thursday night, we should see a wind shift from southwest to northwest as a front moves through the area. While the wind speeds drop off during the wind shift, waves will remain built up until winds increase again out of the northwest and build them once again. Northwest winds increase during the day on Friday, continue Friday night before diminishing again going into Saturday. Anticipate needing Small Craft Advisories and possibly some Gale Warnings beginning Thursday, and continuing through the end of the work week.

PRELIMINARY POINT TEMPS/POPS
DLH 48 57 41 48 / 40 50 60 70 INL 45 52 38 47 / 60 90 70 40 BRD 48 56 39 50 / 30 30 60 60 HYR 47 61 39 49 / 20 30 70 80 ASX 50 62 43 51 / 10 30 70 80

DLH WATCHES/WARNINGS/ADVISORIES
WI...None.
MN...None.
LS...Small Craft Advisory until 10 PM CDT this evening for LSZ121- 140>148.

Small Craft Advisory until 1 AM CDT Thursday for LSZ150.

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