Sunrise 6:17 AM   Sunset 8:46 PM Moonrise 4:48 AM   Moonset 7:41 PM

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LHZ422 Inner Saginaw Bay Sw Of Point Au Gres To Bay Port Mi- 334 Am Edt Tue May 7 2024
Today - East winds 10 to 15 knots. Sunny in the morning, then partly cloudy with numerous showers and isolated Thunderstorms in the afternoon. Waves 2 feet or less. Tonight - East winds 15 to 20 knots becoming southeast 10 to 15 knots in the late evening and early morning, then veering to the southwest after midnight. Mostly cloudy with numerous showers and scattered Thunderstorms in the evening, then partly cloudy with scattered showers and isolated Thunderstorms after midnight. Waves 2 feet or less. Wednesday - Southwest winds 10 to 15 knots becoming west 15 to 20 knots in the late morning and afternoon. Partly cloudy in the morning then clearing. Waves 2 feet or less. Wednesday night - North winds 10 to 15 knots becoming northeast 20 to 25 knots. Partly cloudy in the evening, then mostly cloudy with a chance of showers after midnight. Waves 1 to 3 feet building to 3 to 5 feet after midnight. Waves occasionally around 7 feet. A small craft advisory may be needed.
see lake huron open lake forecast for days 3 through 5.

LHZ400
No data

FXUS63 KDTX 070703 AFDDTX

Area Forecast Discussion National Weather Service Detroit/Pontiac MI 303 AM EDT Tue May 7 2024

KEY MESSAGES

- There is a chance of isolated to scattered strong to severe thunderstorms south of a Midland to Port Huron line this evening, the greatest chances are along/south of the I-94 corridor.

- Damaging winds, large hail and isolated tornadoes are the severe weather risks.

- Warm and breezy conditions are expected Wednesday, followed by cooler conditions with a chance of rain Thursday.

DISCUSSION

A strong mid to upper level jet core circulating around the deep large scale upper low over the northern high plains will advance from the Mid Mississippi Valley into the northern Ohio Valley/srn Great Lakes today. Mid level isentropic ascent and deep layer moisture transport along the lead edge of an 85kt 500mb speed max will be driven across Lower Mi this afternoon and evening. The lead edge of elevated frontal forcing is expected to weaken as it advances into Se Mi early this afternoon given the lingering influence of a departing low level anticyclone, likely causing the lead edge of showers to diminish as the move into Se Mi. The RAP then indicates a respectable ribbon of forced ascent developing along an axis from west-central Ohio into Sw Lower Mi in the 21Z to 23Z time frame, in tandem with increasing upper level divergence along the nose of a 120 kt upper jet streak. This will correlate with an influx of sfc based instability (with sfc dewpoints in the low 60s) lifting northward along an approaching sfc warm front. The result will be the development of deep convection in the wake of the initial band of showers. This convection is expected to move into Se Mi during the course of the evening.

In terms of kinematics, 0-6 km bulk shear values are forecast to be an impressive 60-80 knots across the northern Ohio Valley into Srn Lower Mi this afternoon/evening. Rap and NAM hodographs also show excellent low level curvature in the vicinity of the approaching sfc warm front; 0-3km SR Helicity values over 350 m2/s3. The main caveat for Southeast Michigan will be whether or not the surface based instability is able to advect in from the southwest, especially given the easterly component to the surface winds off Lake Erie.
While available SB CAPE is in question, 00Z model solutions still drive anywhere from 500 to 1500 J/kg of elevated CAPE across Se Mi this evening, with model soundings indicating respectable CAPE density. These factors would suggest storms that develop upstream will be rooted in the boundary layer, then become more elevated as they move across Se Mi during the evening. Given the close proximity to the sfc instability reservoir (as well as the instability gradient), the southern portions of the forecast area remains in a slight risk for all types of severe weather including tornadoes.
Severe weather risk will be more a result of hail and isolated strong wind gusts risk farther north where the depth of the sfc stable layer will become much greater. Upstream convective mode is expected to be supercellular, transitioning to multi cell cluster and/or linear as storms move across Se Mi.

Ample mid level drying will expand across the area in the wake of the evening convection and will persist through Wednesday. This will warrant a dry forecast as developing low pressure within an amplifying short is forecast to remain focused across the northern lakes. Deep mixing depth per model soundings and a respectable westerly flow (25-30 knots within the mixed layer) will support breezy conditions Wednesday. A low level thermal gradient will extend across the forecast area, with highs across the thumb hard pressed to break 70, while metro Detroit/Ann Arbor and points south should break 80.

There continues to be ample spread among model ensemble members as to the track of the remnants of the upstream upper low. There is at least agreement that this system will quickly dampen/shear apart as it tracks across the Ohio Valley and srn Great Lakes Thurs/Thursday night. Model spread involves timing and the degree of interaction with short wave impulses dropping down from Canada and precise timing and location of the associated mid level deformation, which leads to a low confidence rain forecast. Any instability will remain well south and given the expected northeast surface flow, which will be a cool rain wherever it sets up over southern Mi.

MARINE

Influence of high pressure wanes over the course of today as Midwestern low pressure lifts a warm front into the region late this afternoon-evening. Some strong to severe storms will be possible over the southern Great Lakes this evening. System's cold front quickly follows tonight setting up slightly cooler westerly flow Wednesday that then turns northeasterly Wednesday night. Cooler airmass combined with a tighter gradient due to secondary low development over the Ohio Valley supports a moderate uptick in wind strength Wednesday and Thursday with gusts topping out between 15- 25kts each day. Saginaw Bay could see gusts near 30kts Thursday due to NE winds channeling down the bay.

HYDROLOGY

Numerous showers and scattered thunderstorms will impact southeast Michigan late this afternoon through this evening. Despite a very dry start to the day, ample moisture advection into the area during the latter half of the day will allow some of the thunderstorms to produce locally heavy rainfall. As is typical in these type of convective situations, rainfall amounts will be highly variable across the region, with high end amounts up to a quarter to half inch possible. Overall, basin average rainfall should not pose flooding concerns.

PREV DISCUSSION
Issued at 1157 PM EDT Mon May 6 2024

AVIATION...

A gradual transition away from high pressure influence takes place late tonight and in the morning. Surface wind remains easterly while cloud layer wind veers SW as a warm front organizes in the Ohio valley. Low end VFR clouds along and ahead of the front are patchy and disorganized at issuance time but are expected to fill in nocturnally and begin moving into Lower Mi to as far north as FNT by sunrise. Low end VFR holds into the afternoon while the ongoing line of storms across the Plains makes it into Lower Mi on a weakening trend by mid afternoon. A second round of thunderstorms is then expected to develop as instability recovers across WI/IL/IN by late afternoon. This leads to a stronger trend down into MVFR as the activity increases coverage and intensity over SE Mi late in the day into Tuesday evening. The best chance of thunderstorms is after 22Z with very similar timing along the terminal corridor.

For DTW/D21 Convection... Thunderstorm potential increases across the region in the afternoon through Tuesday evening. There is a marginal to slight risk of severe intensity storms across the DTW/D21 area. The first round of activity moves in on a weakening trend by mid afternoon followed by a round of stronger storms after 22Z Tuesday evening.

DTW THRESHOLD PROBABILITIES...

* Medium for ceiling 5000 feet or less in the morning, high in the afternoon.

* Low for thunderstorms after 18Z Tuesday, moderate after 22Z Tuesday evening.



DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.

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