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Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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687 FXUS63 KMQT 020515 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 115 AM EDT Tue Jul 2 2024 .KEY MESSAGES... -Our next round of rain showers, with some rumbles of thunder, moves in by early Tuesday morning. -Two distinct rounds of precipitation for Tuesday: one in the morning and one late at night. Thunderstorm chances are around 20%- 30% for each round. -Low chance (~25%) of afternoon and low to medium chance (25-40%) of evening showers/storms across Upper Michigan on Independence Day. Rain spreads over the region Thursday night and Friday. -Weather pattern remains active into the second week of July. && .SHORT TERM /THROUGH TONIGHT/... Issued at 306 PM EDT Mon Jul 1 2024 The upper ridge axis is sliding across the Great Lakes this afternoon, with surface high pressure centered over the Lower Peninsula. With increasing southerly winds over the UP and a warmer airmass working in, temperatures have been able to climb into the 70s across the UP; some spots in the western half of the UP, where southerly winds are downsloping, are even flirting with the 80 degree mark. Clouds will gradually spread in through the first half of the night ahead of a shortwave that is currently ejecting out of the Plains. Not far behind will be the next round of rain showers by Tue 06Z. As the showers track eastward across the UP tonight, also cannot rule out a few rumbles of thunder...but will note that instability remains quite limited with capped soundings. Meanwhile, much warmer lows can be expected tonight unlike the last few nights as the clouds/rain limit radiational cooling. Widespread 50s will prevail Tuesday morning. && .LONG TERM /TUESDAY THROUGH MONDAY/... Issued at 411 PM EDT Mon Jul 1 2024 A pair of troughs traversing the central CONUS through this week will be the driver of multiple rounds of precipitation which may impact recreation around Independence Day. While uncertainty grows significantly into the weekend, the general pattern indicates the general active and wet pattern to continue, though with prevailing northwesterly flow aloft, temperatures look to not be particularly warmer than normal for July. Tuesday morning, showers will be ongoing in the western UP and will be passing into the central and eastern UP throughout the day. Models continue to trend downwards regarding available instability, so chances of thunderstorms are limited to around 20% early in the west and any thunderstorms should be weak. Rainfall totals are also expected to be fairly low with the 12Z HREF showing 24-hourly precipitation chances greater than an inch of 10% or less. A lull is expected by afternoon in the west, which will shift east through the evening as the initial swath of precip exits into Ontario. As this initial wave moves through, a strengthening pressure gradient over the region will ensue as a strong 925-850mb 40-50kt low level jet presses overhead. Even with modest diurnal mixing, gusty southerly winds will develop, particularly near the Bay of Green Bay, Lake Michigan, and the downslope and higher terrain locations in the Gogebic Range, Michigamme Highlands, and lakeshore areas of Marquette and Alger counties. The HREF highlights wide swaths of area over the UP that could see 40-60% chance of 40+mph gusts, though the 12Z Euro mostly limits this to the higher terrain along Lake Superior. Model soundings that suggest effective mixing suggest potential upwards of 40 mph. The second wave will lift northeast into the UP Tuesday night ahead of the eastward migrating cold front draped from the GEFS-mean 992mb low over far northern Ontario. MUCAPE looks a little better with this round of precipitation, but thunder chances still remain 30% or below. A surface ridge extending northwest should help support a mostly dry day on Wednesday, although there is a brief period in the east that could destabilize enough for afternoon showers/storms to develop before the cold front clears. The 4th of July should start off dry thanks to the lingering effects of the surface ridge and a meso high developing over Lake Superior at around 1015mb. Upstream though, another trough exits the northern Rockies and presses through the Plains. Guidance amplifies the shortwave and lifts a surface low through the eastern Dakotas and into Minnesota in the afternoon/evening. There`s good agreement among the guidance packages that this wave will shift east through Minnesota and Wisconsin through the day Friday, then lift northeast through Upper Michigan Friday night into early Saturday. Best chances for precip with this wave will be Thursday night and Friday. Its unclear if it will remain dry Thursday afternoon and evening in the western half of Upper Michigan. While probability is currently low (~25%), Thursday afternoon destabilization could result in convection developing. Additionally, increasing isentropic ascent may support showers lifting into the region during the evening hours (25-40%). Anyone with evening firework plans across the western half of Upper Michigan should continue monitoring the forecasts. Ensembles then diverge significantly beyond the departure of showers on Saturday, but the general overall pattern remains amplified with plenty of distinct chances for precipitation under passing low pressure systems. Ensemble mean 500mb charts show the preference for ridging over the western Atlantic and western CONUS, putting the UP under a preferred northwesterly flow, which helps keep temperatures from getting too hot, but is still active enough to keep wetter than normal precipitation into the second week of July. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 114 AM EDT Tue Jul 2 2024 VFR conditions prevail at the start of the TAF period with high clouds increasing from the west. A strengthening pressure gradient will keep southerly winds gusting to 20-25 kt for the rest of the night at IWD/SAW. The southerly winds will eventually usher in more moisture, allowing showers to spread across the terminals from west to east through this morning. A 40-50 kt low level jet will result in low level wind shear conditions developing shortly at IWD, and slightly later this morning at CMX/SAW. Some of the stronger winds will mix to the surface, with southerly wind gusts of 30 kt possible for much of the day. MVFR cigs are expected to gradually develop later this morning, persisting much of the day. There is around a 30% chance of IFR cigs developing at IWD/SAW during the day today, but probs not high enough to keep prevailing in the TAFs at this time. CMX/IWD expected to return to VFR around 00Z Thu, but cigs remain lowered at SAW, with potential for IFR 00-06Z as well (though still not high enough to include in the TAF). && .MARINE... Issued at 411 PM EDT Mon Jul 1 2024 High pressure continues to create light wind conditions over Lake Superior, but this high is weakening and shifting east this evening, so tranquil conditions will be short-lived. A system will begin lifting from the Plains into Canada tonight, then continue lifting northward Tuesday into Wednesday. The passage of this system will result in at least two rounds of rain and storms and two periods of stronger winds. Expecting the first round of showers, with a 20% chance of thunderstorms embedded within, to shift through Lake Superior late tonight and Tuesday. These showers may (20-40% chance) support fog developing and periods of low visibility on the lake. As the system approaches tonight, tightening pressure gradient will develop while a strong 40-50kt 925-850mb low level jet moves over eastern Lake Superior. Model guidance remains uncertain in how much of these stronger winds will mix to down to the surface given the increasing stability of the over lake environment. However, recent internal probabilistic tools are beginning to highlight nearshore areas downwind of the Michigan lakeshores and the stretch from Marquette northward into Canadian waters as those most likely to experience low end gales. Between internal guidance, the HREF, and Euro guidance, probabilities of gales remain around 20-40%. These ~40% values may also be somewhat representative downwind of the lakeshores east of Marquette and along the northern shores of the Keweenaw, where models struggle with the land/lake interface and localized terrain driven influences have been known to mix down stronger winds to the surface. At this point, given the uncertainty and the isolated nature of the stronger mixing downwind of the lakeshores, will continue to hold off on gale headlines. Another round of moisture will lift through Tuesday night into Wednesday while the effects of the low level jet wane. The cold front presses through west to east Tuesday night into Wednesday morning, allowing winds to become westerly/southwesterly for Wednesday. Another period of stronger winds up to 20-30kts, looks possible between the Keweenaw and Isle Royale Wednesday in this southwesterly flow. High pressure returns briefly for Thursday with a weaker low pressure system expected to pass over the Upper Great Lakes late Friday and Saturday. Light winds below 20 kts returns Wednesday night, continuing likely into the weekend. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...LC LONG TERM...GS/JTP AVIATION...Thompson MARINE...GS/JTP