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LMZ521 Green Bay South Of Line From Cedar River To Rock Island Passage And North Of A Line From Oconto Wi To Little Sturgeon Bay Wi- Green Bay South Of Line From Oconto Wi To Little Sturgeon Bay Wi- 1252 Pm Cdt Mon May 6 2024
This afternoon - E wind 5 to 10 kts. Sunny. Waves 2 ft or less. Tonight - E wind 5 to 10 kts. Mostly clear. Waves 2 ft or less. Tuesday - E wind 10 to 20 kts with gusts to around 25 kts. A chance of rain showers in the morning, then rain showers in the afternoon. Waves 2 ft or less. A small craft advisory may be needed. Tuesday night - NE wind 5 to 10 kts backing nw after midnight. Light rain showers likely in the evening. Waves 2 ft or less.

LMZ500
No data

FXUS63 KMQT 061743 AFDMQT

Area Forecast Discussion National Weather Service Marquette MI 143 PM EDT Mon May 6 2024

KEY MESSAGES

-Complex mid-week weather pattern with rain chances increasing on Tuesday and multiple passing low pressures keeping rain in the forecast through the end of the week.

SHORT TERM /THROUGH TODAY/
Issued at 142 PM EDT Mon May 6 2024

Upper air pattern consists of a 500 mb trough in the central Rockies and a shortwave in the mid Mississippi River Valley. The trough heads northeast and develops a closed 500 mb low that moves into the Dakotas by 12z Tue. Weather will be quiet through tonight with very few changes made to the going forecast.

LONG TERM /TONIGHT THROUGH SUNDAY/
Issued at 448 AM EDT Mon May 6 2024

The extended forecast is largely dominated by a trough currently over the Rockies and its complex evolution and influence on the few sfc lows moving across the CONUS through the upcoming week. We then see a bit of a pattern shift over the weekend where model guidance begins to diverge, but cooler and drier southeast flow over the Great Lakes is expected this weekend into next week.

Starting tonight, the trough will be negatively tilted over the Central/Northern Plains with ridging over the Great Lakes. The trough deepens over the northern plains supporting cyclogenesis over the western Dakotas. Cyclogenesis will also be ongoing over Kansas supported by a shortwave rotating northeast along the deep trough as well as the left exit region of a ~115 kt upper level jet. While the northern sfc low deepens as it retrogrades into Montana and the southern more weaker sfc low moves northeast into the Mid- Mississippi Valley, weak high pressure is shifted northeast from the Great Lakes. Taking that all into account, dry and quiet weather holds for the UP with lows in the 40s under a some high level clouds. Cooler temps are forecast for the eastern UP.

Moving onto Tuesday, the trough forms a closed off low over the Northern Plains as the shortwave continues northeast from Iowa to the Upper Great Lakes. At the sfc, the weaker low will have lifted into the western end of the Great Lakes Basin by Tuesday evening occluding as it approaches near our CWA While there still is some spread yet on this track, expect an occluded front to lift north through the UP late Tuesday morning/early afternoon bringing with it a round of showers. With the incoming occluded front, high temps in the upper 50s to upper 60s are expected earlier in the afternoon with higher temps holding on longer in the east. The HRRR is the fastest to bring in showers around 12-1 PM EDT while the NSSLWRF is closer to 3-4 PM EDT. The better chances for showers arrive later in the day when the shortwave swings north over the UP. Instability will be lacking and bulk shear is low (20-35 kts); the NAM Nest and HRRR show the highest MUCAPE values with a thin stream of up to ~200- 400 j/kg of MUCAPE lifting with the shortwave. Given the set up, strong thunderstorms can be ruled out, but a few rumbles of thunder are possible along the WI/MI state line. If the drier solution is favored, a longer period of mixing ahead of precip will yield lower RHs in the upper 20s to low 30s in the northern half of the UP save for the Keweenaw. Gusty southeast winds up to 20-30 mph will also be a fire weather concern. That said, anticipated precip does look to bring some relief with a few hundreths to 0.25" of rain; a few areas in the south central may see up to 0.5-0.75". With uncertainty in precip arrival time and mixing, will need to monitor the potential for elevated fire weather conditions in future forecast packages.

The sfc low then begins to meander east through the Great Lakes Basin Tuesday night into Wednesday with periods of showers possible during that period. A third low pressure develops over the Southern Plains Tuesday night with the support of weak embedded shortwaves and the right entrance region of the upper level jet. As the mid level closed low weakens on Wednesday, so does the sfc low as they both move southeast. Meanwhile the southwestern sfc low is moving northeast with the upper level jet. The two sfc lows look to phase together mid day on Wednesday over the Mid-Mississippi Valley. At the same time, chances for showers continue in the UP as a shortwave drops south across the region.

Wednesday night and Thursday have two potential solutions given the uncertainty in the guidance at this point in the forecast. The first one being a brief dry period Wednesday night followed by showers across the southern half of the UP on Thursday as the new low pressure tracks east along the southern edge of the Great Lakes Basin. The other possibility is that this sfc low's track is further south and showers stick to the south of the CWA, letting dry weather hold through the rest of the work week. Determinist GFS and ECMWF seem to favor the drier solution, but opted to leave in some chance PoPs in for now. Will continue to monitor if this drier trend continues.

There is growing confidence in anomalous ridging setting up over British Columbia this weekend with broad anomalous troughing over the eastern CONUS. This would set up the Upper Great Lakes for northwest flow with shortwaves and clipper type lows providing the next precip chances. Given the significant spread in the guidance this weekend onward, opted to leave the NBM slight chance PoPs as is.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
Issued at 1237 PM EDT Mon May 6 2024

VFR conditions will continue to prevail with the area under the influence of high pressure. IWD will have MVFR conditions late in the forecast period.

MARINE
Issued at 448 AM EDT Mon May 6 2024

With high pressure over the Upper Great Lakes, resulting stability will keep winds mainly below 20 kts through Monday night. The exception to this would be over the far western portion of the lake near the Duluth Harbor where some northeast channeling may yield some gusts up to 25 kts. An approaching low pressure Tuesday morning will force northeasterly to east winds to funnel over the western half of Lake Superior to 25 kts by noon Tuesday with a few gusts to 30 kts in the far west and along the Minnesota shorelines. With probability of winds exceeding 34 kts below 20% and the short duration of the highest winds, opted for no Gale Watch. Winds across the east half of the lake increase to around 20-25 kts Tuesday afternoon. A brief break in 20+ kt winds is expected Tuesday night.
Periodic chances for winds in the 20-30 kt range dot the forecast through Thursday as multiple weak low pressure systems pass through the Upper Great Lakes region, but uncertainty still remains.

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

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