Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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782 FXUS63 KMQT 170818 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 418 AM EDT Mon Jun 17 2024 .KEY MESSAGES... -Possible strong to severe thunderstorms this evening and tonight. Large hail, damaging winds, frequent lightning, and heavy downpours will be possible. - Strong to severe storms possible Tuesday night into Wednesday. - Very warm to start the work week, then temperatures trend towards normal from midweek onward. - Frequent chances for rainfall continue the rest of the week. && .SHORT TERM /THROUGH TONIGHT/... Issued at 142 PM EDT Sun Jun 16 2024 Rain showers continue to lift through the forecast area atop a very moist surface layer. As of publishing this AFD, rain showers were spread across the eastern and central UP with dewpoints in the mid 50s to low 60s across the region. Destabilization ahead of mid-level ridging building into the west may support additional shower development, or some thunderstorms in this afternoon across the east half before they exit into Ontario. Severe weather is not expected in this wave. The atmosphere will further destabilize ahead of a cold front/low pressing eastward through Minnesota this afternoon. Guidance continues to suggest this will result in shower and thunderstorm development with quick upscale growth into an MCS, which will progress east-southeast into Wisconsin and Upper Michigan this evening. The strong destabilization in the pre-frontal space stretching from Wisconsin into the U.P. is characterized by 2000- 3000 j/kg of elevated CAPE. While the region where this will develop is expecting much stronger deep layer shear, guidance over Lake Superior generally suggests around 30-40kts of 0-6km bulk shear oriented off the boundary, suggesting the linear complex may survive the transit and move into Upper Michigan. With DCAPE 500-1000j/kg and increasing mid-level lapse rates to around 8C/km, strong to severe thunderstorms will be possible if so. Main hazards will be large hail up to 1 inch in diameter, strong or damaging winds upwards of 60mph, frequent lightning, and heavy rain upwards of 1+ inches this evening. Primary risk areas will be across the west/central, but some guidance packages, namely the RAP, ARW and FV3, suggests the thunderstorms could hold together as they move into the east half around midnight. A warm and muggy night is projected after the convection ends. As temps begin to cool, patchy dense fog may develop overnight. Overnight lows and dewpoints are likely to remain in low to mid 60s for most of the forecast area. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 418 AM EDT Mon Jun 17 2024 The active weather pattern doesn`t look like it will relent over the rest of this week as troughing deepens over the western U.S. and ridging amplifies over the Eastern Seaboard early this week. This keeps us on tap for very warm and moist conditions Monday through Tuesday, before the troughing pattern moves east and brings cooler temperatures across our area Wednesday into Thursday; be careful if working outside Tuesday, as the hot and humid weather could cause heat exhaustion and heat stroke! Meanwhile, expect showers and thunderstorms chances to continue across Upper Michigan throughout the rest of this week into next weekend, with a few strong to severe storms being possible Monday and Tuesday night/Wednesday. The severe weather threat, should any occur, would be hail, winds, and repeated heavy rainfall causing ponding. Additional details follow below. The frontal boundary lifts north of the area Tuesday, and should stall out across northern Lake Superior and northern MN. Skies turn sunny, then expect muggy and even warmer weather Tuesday as we sit directly underneath the warm sector of a low lifting through the Lake Winnipeg area. A tight pressure gradient and a 30-40kt LLJ over the area all point to a potential for a breezy day (will also note the EFI continuing to highlighting unusually strong winds for Tuesday). However, with a low-level cap in place, it may be difficult to get the winds to gust much more than 30 mph, save for the downslope areas near Lake Superior where mixing could be locally enhanced. Expect temperatures to get into the high 80s to low 90s during the afternoon hours, with dewpoints reaching up into the low 70s. This will cause the heat index to get into the 90s across much of the area, with a spot or two possibly flirting with the 100 degree mark. Breezy conditions may help to keep things from feeling so oppressive, but be mindful of the heat and take precautions regardless. Stay hydrated! Moving into Tuesday night, the aforementioned low near Lake Winnipeg will continue to move through Ontario while weakening, then the cold front off to our west slowly swings through overnight into Wednesday. Showers and storms begin to move back into the western UP as early as Tuesday evening along the front, which would be favorable timing for strong to severe convection. MUCAPE across the western UP could exceed 1000 J/kg and 0-6 km bulk shears approach 40 to 50 knots. Our main threat would be hail, with damaging wind a secondary concern. In addition, expect heavy rainfall, with ensembles showing PWATs near the max of climatology/around 2 inches! With storms possibly training ahead of the frontal boundary, ponding of water in poor drainage would be a concern. However, as episodes of rain in the preceding days have chipped away at hourly flash flood guidance, some flash flooding is not out of the question (around 5% chance) in smaller streams and even in somewhat better- draining areas. The central and eastern UP may miss out on severe convection Tuesday night as we`ll have long since run out of daylight by the time the front moves in. Meanwhile, nighttime won`t do much to alleviate heat concerns as temperatures only fall back as far as the mid/upper 60s for a large portion of the area. Wednesday, the front finally begins to settle just to our south. Weak waves rippling through will provide some additional lift to keep chances for convection to fire along the boundary Wednesday through Friday. Will note that PoPs are concentrated mainly across the southern half of the UP given the potential for weak high pressure over Ontario to further suppress the frontal boundary southward. Going into next weekend, a low pressure lifting off of the Colorado Rockies and an upper level Clipper low look to phase with each other over the Upper Midwest. This will bring additional showers and thunderstorms across our area via warm frontogenesis through at least the first half of next weekend, then the cold front moves through late in the weekend with lingering PoPs. Ensembles continue to favor PWATs as high as 2in, well above normal, highlighting another couple of days worth monitoring for the heavy rainfall potential. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 122 AM EDT Mon Jun 17 2024 Expect maybe some isolated showers across the area tonight with showers affecting mainly IWD and CMX. The moist conditions could still lead to MVFR conditions overnight in patchy fog or stratus. Around round of convection is expected to move in from the west after sunrise as ceilings will likely go to MVFR during the day on Monday. Showers will be most prevalent at IWD and SAW with SAW having the best chance of getting a thunderstorm. A break in the showers in the afternoon could be followed by more scattered showers Monday evening. Look for MVFR ceilings to lower to IFR Mon evening and fog formation possible again. && .MARINE... Issued at 418 AM EDT Mon Jun 17 2024 Light winds around 5-10kts start off mainly from the west this morning, but shift over to the east this afternoon. The light winds continue through tonight before increasing from the south to 20 to 25 knots over the eastern half of the lake Tuesday. In addition, expect some downsloping winds near the southern shoreline to gust up to 20 to 30 knots, with a few gale force gusts up to 35 knots possible (10% chance or lower), particularly in the nearshores from Marquette to just west of Whitefish Point. The winds fall back down to 20 knots or less again by early Wednesday morning as the frontal boundary just west of the area finally begins moving across the lake. Winds stay light through the rest of the week as weak high pressure ridging settles over northern Ontario. Several rounds of showers and storms are expected across the lake from this afternoon through Wednesday. Some strong to severe storms are possible during this time, with hail and wind being the main threats. Areas of fog, dense at times, are possible following rounds of rainfall. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JTP LONG TERM...LC AVIATION...Voss MARINE...LC