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LMZ542 Sturgeon Bay To Two Rivers Wi-two Rivers To Sheboygan Wi- 1258 Pm Cdt Tue Apr 16 2024
.small craft advisory in effect until 6 pm cdt this evening - ..gale warning in effect from 6 pm cdt this evening through Wednesday morning - .
This afternoon - NE wind 15 to 25 kts with gusts to around 35 kts. A slight chance of rain showers. Waves 2 to 4 ft building to 3 to 5 ft late. Tonight - SE wind to around 30 kts with gale force gusts to around 40 kts. Rain showers and a chance of Thunderstorms. Waves 2 to 4 ft building to 8 to 12 ft. Wednesday - SE wind 15 to 25 kts veering sw 10 to 20 kts in the afternoon. Gusts to around 30 kts. Rain showers in the morning. A chance of Thunderstorms. A chance of rain showers in the afternoon. Waves 6 to 10 ft subsiding to 3 to 5 ft. A small craft advisory may be needed. Wednesday night - W wind 10 to 20 kts with gusts to around 25 kts. A chance of rain showers in the evening. Waves 3 to 5 ft subsiding to 1 to 3 ft after midnight.

LMZ500
No data

FXUS63 KGRB 161114 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 614 AM CDT Tue Apr 16 2024

Updated aviation portion for 12Z TAF issuance

KEY MESSAGES

- Elevated fire weather conditions will persist today across northern Wisconsin due to low relative humidity and increasing easterly winds.

- Showers and a few embedded thunderstorms are expected from this afternoon into Wednesday. Widespread severe weather is not expected, but strong winds aloft could mix to the surface with any storms or heavier showers. Heavy rainfall will be likely regionwide.

- Strong east to southeast winds are expected this afternoon into tonight, with gusts of 30 to 50 mph. The strongest gusts are anticipated across central, east-central, and portions of north- central Wisconsin, where a Wind Advisory has been issued.

DISCUSSION
Issued at 407 AM CDT Tue Apr 16 2024

Short Term
Today
Tonight...and Wednesday

Synopsis:

A strong low pressure system, currently analyzed over western Nebraska at 991 mb, will track east towards the Missouri Valley today, then the upper Mississippi Valley tonight, and the Wisconsin/Michigan border on Wednesday.

Surface Winds:

As the low approaches the area, the pressure gradient will tighten precipitously across the western Great Lakes region. Very gusty easterly winds are expected across central Wisconsin around midday and across the rest of the area later this afternoon and into the evening hours. Probabilistic model data indicates a high probability (70-90 percent) of hitting 45 mph or greater across much of central, east-central, and portions of north-central Wisconsin this afternoon into the early overnight hours. Winds will slacken off a bit late tonight into Wednesday morning as the surface low approaches and eventually tracks through northeast Wisconsin later on Wednesday. Given the relatively high probabilities of hitting Wind Advisory criteria as the low approaches the region, will issue a Wind Advisory for central, east-central, and portions of north-central Wisconsin from this afternoon through early Wednesday morning.

Precipitation:

A band of precipitation ahead of the main low, associated with isentropic lift and strong mid level frontogenesis, will lift northeast through Wisconsin today and through northeast Wisconsin later this afternoon and this evening. Abundant dry air ahead of these rain showers, as evidenced by the very low dew points across the region, will stall the onset of the precipitation from the previous forecast by a few hours.

There will be some modest elevated instability in place across the area with MUCAPE values of 300 to 600 J/kg. However, model soundings indicate there will be a substantial temperature inversion in place around 850 mb; therefore, the high winds speeds of 60 to 70 knots at this layer are not expected to reach the ground. It would not be surprising if a vigorous shower or thunderstorm brings down winds of 40 to 50 knots, which wouldn't be that much higher than the synoptic winds that will be in place across the region during this activity.

A second band of rain showers is then expected to lift northeast associated with the main low and mid level trough with attendant shortwaves late tonight/early Wednesday morning and track through the area throughout the morning. These showers will also have embedded elevated thunderstorms with continued MUCAPE values of 300 to 600 J/kg and a continued steep inversion in place around 900 mb.

Lingering showers and a few thunderstorms will then be possible behind the main low lifting northeast as daytime heating builds modest SBCAPE values of 100-300 J/kg. Although these thunderstorms will be surface based, the meager instability values indicate this activity will be generic non-severe thunderstorms.

Long Term...Wednesday Night Through Monday

Precipitation...Light rain showers will be on their way out of the region to the northeast Wednesday evening, as the surface low departs. Models are struggling with the details for the next chance for precip possibly on Thursday. All models indicate a system passing to the south of the forecast area on Thursday, and some have a secondary surface low developing over northern WI/Upper MI. The models that have a stronger surface low developing over northern WI/Upper MI have a surface boundary generating rain showers over portions of the forecast area on Thursday. Since not all models are in agreement with this occurring, kept the blend of models slight chance PoPs across the north and chance PoPs across central and east- central WI. By early Friday, an upper-level low will slide over western Ontario and bring cyclonic flow and CAA over the region. As the low shifts further east, a shortwave/trough looks to generate some light precip over the northern portion of the forecast area sometime Friday afternoon/evening. With the cooler air over the region, the light precip may fall as a mix of rain and snow, and possibly all snow into the evening as boundary layer temps fall below freezing. Dry conditions are anticipated for the weekend as the low shifts northeast of the region and surface high pressure moves into the area.

Temperatures...Thursday's temperatures will be tricky to nail down given the potential for a frontal passage with precip. For now, leaning towards temperatures to be above normal by a few degrees in the middle 50s to low 60s, but given the uncertainty would not be surprised to see values decrease in later forecasts. Temperatures will then dip below normal for Friday and Saturday with the prevailing CAA. Have highs ranging from the middle 40s to low 50s for both days. Temperatures then return to normal or slightly above normal (highs mainly in the middle to upper 50s) for Sunday and Monday with high pressure building into the area.

AVIATION
for 12Z TAF Issuance Issued at 614 AM CDT Tue Apr 16 2024

VFR conditions will prevail this morning with only some mid and high clouds across the region. Flying conditions will deteriorate from southwest to northeast this afternoon and evening as a strong low pressure system tracks towards the state. Look for low clouds and a large area of rain to spread into the area. Some embedded thunderstorms are also expected, especially across central and eastern WI. MVFR conditions look to arrive after 7-8pm with IFR conditions holding off until closer to midnight, with some LIFR possible Wednesday morning.

East surface winds will increase this morning, becoming gusty by mid-morning. Gusts will increase through the day, peaking in the afternoon/evening in the 30-40 kt range. Locally higher gusts are possible.

LLWS looks likely this evening as winds aloft increase significantly, reaching 50-60 kts at 2000 ft.

MARINE
Issued at 407 AM CDT Tue Apr 16 2024

A tightening surface pressure gradient will cause easterly winds to increase to small craft criteria early this afternoon then to gale force late this afternoon into early this evening. Gale force gusts to 40 knots will continue tonight until winds slowly subside Wednesday morning into Wednesday afternoon. Small craft conditions will likely persist into much of Wednesday as winds and waves slowly subside.

Given the fairly high confidence in reaching Gale Warning criteria will upgrade the Gale Watch to a Gale Warning with a preceding Small Craft Advisory this afternoon.

FIRE WEATHER
Issued at 407 AM CDT Tue Apr 16 2024

Very dry air in place across the region today will cause afternoon RH values to plummet to the upper teens to lower 20s across northern Wisconsin. In addition, very gusty easterly winds of 25 to 40 mph are expected across this region with temperatures in the upper 50s. Precipitation approaching from the southwest is not expected to make it to northern Wisconsin until late this afternoon or early this evening. The low RH values and gusty winds will cause elevated fire weather conditions across northern Wisconsin today until relief arrives with the approaching rain showers from the southwest. Therefore, will issue an SPS to highlight these conditions across the area.

GRB WATCHES/WARNINGS/ADVISORIES
Wind Advisory from 4 PM this afternoon to 4 AM CDT Wednesday for WIZ018-019-031-037>040-048>050.

Wind Advisory from 1 PM this afternoon to 4 AM CDT Wednesday for WIZ030-035-036-045.

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