Sunrise 5:23 AM   Sunset 8:12 PM Moonrise 3:29 PM   Moonset 3:10 AM

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LMZ646 Wind Point Wi To Winthrop Harbor Il- 505 Am Cdt Sat May 18 2024
Today - South wind 5 to 10 knots becoming southeast 10 to 15 knots with gusts to around 20 knots in the afternoon. Patchy dense fog in the morning. Waves around 1 foot. Tonight - South wind 10 to 15 knots easing to 5 to 10 knots late in the evening, then veering southwest after midnight veering west early in the morning. Partly cloudy. Waves around 1 foot. Sunday - North wind 10 to 15 knots becoming northeast 5 to 10 knots in the afternoon. Sunny. Waves around 1 foot. Sunday night - Northeast wind 5 to 10 knots veering south early in the morning. Slight chance of showers and Thunderstorms after midnight. Waves around 1 foot.

LMZ600
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FXUS63 KMKX 180932 AFDMKX

Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 432 AM CDT Sat May 18 2024

KEY MESSAGES

- Chance of isolated thunderstorms Saturday evening

- Warmer and more humid today through Sunday

- Rain and a chance of thunderstorms Monday and Tuesday

SHORT TERM
Issued 432 AM CDT Sat May 18 2024

Today through Sunday:

On the western edge of exiting high pressure this morning dry and quiet weather is expected to continue. Some ground fog has developed mainly in low lying areas across southern Wisconsin.
Fog is very patchy with many areas maintaining visibilities of 4 SM or greater. Overnight temperatures have been higher, especially in our larger urban landscapes which has kept the dew point depression high (effectively preventing dense fog). While temperatures will continue to decrease until after the sun has risen, many areas may not reach the dew point value and thus will evade any dense fog. Southerly winds will begin to increase this morning as well which will aid in preventing further fog development.

Clear skies and another warm day is ahead of us here in southern Wisconsin today. Given the warmer temperatures this morning and the fact that temperatures overperformed yesterday, daytime highs were bumped up a bit. To further support the slightly increase temperatures is the 925mb temperatures near 22 degrees and adiabatic lapse rates. This will bring surface temperatures closer to 86 to 88 degrees.

This evening a low pressure system to our north will drag a frontal boundary across the state. The best of the synoptic forcing and moisture is expected to stay to our north. Guidance has been pretty bullish with this line of showers and isolated storms especially across central Wisconsin where the synoptic forcing will be weak due to the distance from the low pressure system. Many of the guidance have mid level dewpoints much higher than what is currently in place and upstream from us, which includes when the breezy southerly winds kick in this afternoon. Which likely contributes to the bullish response. Now there will be great sfc based instability with clear skies and warm temperatures and the weak frontal boundary will provide some lift even with how weak it is. So there is a small chance (roughly 20-30% chance) across south central Wisconsin for some showers and a couple rumbles of thunder this evening. This line of showers should be diminishing and falling apart as it travels eastward as the timing puts the frontal boundary moving through after dark. Thus the chance showers becomes a slight chance (15% or less) across southern and eastern portions of the forecast area. Overall, not super enthused about the chance for rain this evening, but given the weak lift and great instability any available moisture no matter how small could be squeezed out.

Beyond this, dry and quiet weather will remain for much of the day Sunday. A low pressure system will be advancing from the Rocky Mountain west and central Plains for Sunday night into Monday. This system has ever so slight increased its speed meaning a slightly earlier arrival in POPs than previously.
Regardless of this slight shift much of the day will remain dry and cloud cover will increase throughout afternoon. Sunday is expected to be slightly cooler than today with high temperatures in the 60s along the lakeshore to near 80 inland.

Patterson

LONG TERM
Issued 432 AM CDT Sat May 18 2024

Sunday night through Friday:

Sunday night into Monday the first of a number of upper level shortwaves will traverse Wisconsin. The associated sfc low pressure system will traverse the Great Lakes Region. Timing still remains the biggest concern with this system as discrepancies will remain. The current guidance trend has brought this system through a bit earlier than previous runs.
Regardless of the timing of this system the potential for a few thunderstorms remains with warm sfc temperatures bringing in some instability and modest 0-6km wind shear. If the diurnal heating trend over the previous days continues to overperform then the instability could increase even more and with the mid and upper level support a few stronger to severe storms cant be out of the question. The overall concern for any strong storm Monday would be wind and some hail.

The next shortwave trough and surface low eject into the Great Lakes Region Tuesday afternoon will be a much better showing on the severe weather potential. Out the gate the low pressure system look deeper and stronger than the previous. Guidance soundings are indicating there would be some steep mid level lapse rates with warm temperatures and good sfc instability.
This has resulted in higher CAPE values. 0-6 km shear wont be anything to scoff at either , thus the SPC 15% probability remains for all of southern Wisconsin. As this system pulls through the area the organized convection will likely be along or ahead of a cold front. Rain will likely linger on the back side of this system Wednesday with a more stratiform rain set up.

By the end of the work week, high pressure looks to make a return. This will bring a return some more dry and quiet conditions. Some of the ensembles try to bring in another weak low pressure system, but these solutions are greatly outnumbered by those with high pressure. Thus some low end POPs did make there way into the forecast for Friday, but dont expect that to persist for long.

Patterson

AVIATION
Issued 432 AM CDT Sat May 18 2024

Widespread VFR conditions are expected to continue through the period. Patchy ground fog early this morning could bring a brief period of MVFR conditions, but visibilites are expected to remain 4 SM or greater. Lake shore terminals that are closer to the marine air will have the best chance of seeing these 4 SM visibilites. Light and variable winds tonight will become southerly and slightly increase by this afternoon. This evening a weak cold front is expected to traverse the region causing winds to shift to northerly. An isolated to scattered shower/storm will be possible as this boundary pushes through.
The best chance for an rain will be across south central Wisconsin. Clear skies will return behind this frontal boundary for Sunday.

Patterson

MARINE
Issued 432 AM CDT Sat May 18 2024

The last of the dense fog across Lake Michigan has or will dissipate as we approach sunrise this morning. The few small pockets of dense fog along the west central lake have been shrinking over the last couple of hours. Satellite shows the majority of the lake clear, thus the Dense Fog Advisory has ended. The light and variable winds this morning will become southerly and increase slightly. While winds will be breezy, both winds and waves will remain below small craft criteria. The light and variable winds return Sunday. Monday and Tuesday winds will again switch to southerly and increase as low pressure systems move into the Great Lakes Region bringing chances for thunderstorms.

Patterson

MKX WATCHES/WARNINGS/ADVISORIES
WI...None.
LM...None.

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