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LMZ643 Sheboygan To Port Washington Wi- 705 Am Cst Mon Dec 4 2023
Today..Northwest wind 10 to 15 knots backing west late in the afternoon. Partly Sunny. Waves 1 to 2 feet.
Tonight..West wind 5 to 10 knots backing southwest in the late evening and early morning, then veering west early in the morning. Chance of snow and rain after midnight. Waves around 1 foot.
Tuesday..North wind 5 to 10 knots rising to 10 to 15 knots in the late morning and early afternoon, then becoming north 10 to 15 knots late in the afternoon. Slight chance of rain and snow in the morning. Waves around 1 foot.
Tuesday night..Northwest wind 10 to 15 knots. Partly cloudy. Waves 1 to 2 feet.
wave heights are for ice free areas.

LMZ600
No data

FXUS63 KMKX 040901 AFDMKX

Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 301 AM CST Mon Dec 4 2023

SHORT TERM
(Issued 301 AM CST Mon Dec 4 2023)

Today through Tuesday:

The main focus in the short term is with the potential for light snow tonight into Tuesday morning.

Currently, weak surface ridging is in place from the southern plains up into southern Wisconsin while a departing low tracks through New England with an inverted surface trough extending west from it back through the southern Great Lakes/southern WI. This feature produced some brief snow showers/flurries overnight as it sagged south into northern IL. Back to the northwest, our next weather system is currently analyzed as a 999mb low over southern Saskatchewan. This low and mid/upper level trough will dig southeastward today into tonight and give us our next chance for some light snow.

Recent model trends are interesting for this system and appears to be a Global model vs Meso model battle. For the global models, there actually is really good agreement between the 04.00z NAM/GFS/ECWMF/GEM with taking the surface low through central Iowa by midnight tonight on into northern Illinois by daybreak Tuesday.
They also all depict snow/precipitation developing across southern Wisconsin during the 3z(9pm) to 9z(3am) timeframe along a NW to SE oriented arc which follows the 500-700mb trough and some deepening/negative tilting that appears to occur during that timeframe. Thermal profiles from the NAM/GFS all show the T/Tw staying below freezing for this event as well, so am expecting the precipitation-type to be all snow for this event. While the dendritic growth zone doesn't look to be too deep at around 100mb, it does happen to be in the area of strongest lift (700-600mb) and winds are not too strong at 15kts or less through the column...so think some dendrites could occur to provide some brief (1-3 hrs)
decent snow rates. QPF amounts from the global models are showing around 0.05" with 90th percentile ECMWF and GEFS ensembles showing 0.15" as a high end amount located more so along the WI/IL border. Liquid to snow ratios look like they'll be somewhere around 10/1, which leads to about a 0.5-1" snowfall. The wrinkle in this is what the past few runs of the HRRR has been showing with the low track trending even further south which actually keeps most of the snow completely south of southern WI. This would obviously knock down snow amounts even further from where they're at now, which isn't too high. The HRRR would actually say that our better chance for any precipitation may be during the day/afternoon on Tuesday as the inverted surface trough passes by.
Regardless, the main thing is that at least some light snow is likely (~60%) tonight, particularly in southern/SW Wisconsin but shouldn't be a big issue.

Halbach

LONG TERM
(Issued 301 AM CST Mon Dec 4 2023)

Tuesday night through Sunday:

With the passing of the system Wednesday, higher pressure will slide through the lower Mississippi Valley, bringing back drier conditions to southern Wisconsin. The higher pressure will slowly exit with lower pressure building across the north central US/south central Canada. This will bring a fairly strong pressure gradient across southern Wisconsin Wednesday evening into Thursday before the low pressure system slides into the northwestern Great Lakes region.

This system is expected to be dry across southern WI due largely to a lack of moisture in the low levels and not much forcing in the upper levels to work with. In addition to the lack of precip there will likely be some clearing skies to allow some pretty good mixing down of the winds especially with a decent LLJ. Overall Thursday should feature some breezy southerly winds and warming temps. This should continue for the most part into Friday as well.
Highs Thursday should (70%) reach the mid 40s to low 50s with Friday looking even slightly warmer with highs in the upper 40s to mid 50s (60%) though Friday appears more uncertain as the progression of the low may (40%) bring the front through and prevent the higher end warm temps.

The passage of the front will bring us back to cooler conditions Saturday and this will also bring in our next chance for precip though chances (20-30%) for most of the area seem fairly slim. A low connected to the system pushing the through the northern Great Lakes will track through the central Mississippi Valley and possibly (40%) clip far southeast WI. This system will definitely be wetter with very good upper level forcing and plenty of moisture to work with. The issue with this system is essentially entirely track related with regards to potential precip, though precip appears likely to remain rain if we do see some precip in our southeast. Sunday looks more interesting with the system as there is significant disagreement among models. The GFS/Canadian ens have the system largely pushing well out to the east with no further precip while the Euro ens shows the potential for the upper low to close and severely slow the system as it gradually lifts north. The Euro track would be very conducive to heavy accumulating snowfall Sunday into Monday across southern WI.
While it is difficult to pinpoint what the system will do it is certainly worthy to note of this potential as we go through this week, but we want to pump the brakes on any excitement until we get a bit closer to the event to better understand how things will develop.

Kuroski

AVIATION
(Issued 301 AM CST Mon Dec 4 2023)

Initial focus is on the MVFR ceilings which range from around 1kft to 3kft in spots. The expectations are that there could be some brief improvement along the Lake Michigan shoreline this morning before the lower ceilings come back in. A low pressure system will approach southern WI tonight which should bring visibilities down as snow develops. This doesn't look like it will be an intense snow, so visibility will likely linger around 2sm or higher. There are some indications that this system could go south as well, which would mean less of a chance for snow. The main period for this potential snow would be from about 9pm tonight through 6am Tuesday morning.

Halbach

MARINE
(Issued 301 AM CST Mon Dec 4 2023)

Generally looking like a lighter wind period over the next few days as a couple ridges of high pressure move through the region through mid week. The next shot at some higher winds appears to be on Wednesday evening after a ridge of high pressure moves through and stronger southerly flow takes hold briefly. Looking like it will be sub-gales, but will have to keep an eye on it. Beyond that, there's quite a bit of uncertainty with the next low pressure system as guidance shows a deepening low to the east of the Great Lakes, which could at least bring some higher winds as colder air gets pulled south on the backside of the low.

Halbach

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

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