Sunrise 6:04 AM   Sunset 9:00 PM Moonrise 4:14 PM   Moonset 3:10 AM

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LHZ422 Inner Saginaw Bay Sw Of Point Au Gres To Bay Port Mi- 346 Pm Edt Sun May 19 2024
Tonight - Northeast winds 10 to 15 knots becoming east 5 to 10 knots early in the morning. Mostly clear. Waves 2 to 4 feet subsiding to 1 to 3 feet after midnight. Monday - East winds 5 to 10 knots becoming south 10 to 15 knots in the late morning and afternoon. Mostly Sunny with a slight chance of showers and Thunderstorms in the morning, then partly cloudy with a chance of showers and Thunderstorms in the afternoon. Waves 2 feet or less. Monday night - South winds 10 to 15 knots. Partly cloudy in the evening becoming mostly cloudy. A chance of showers and Thunderstorms. Waves 2 feet or less. Tuesday - Southwest winds 10 to 15 knots. Partly cloudy. A chance of showers in the morning, then showers likely and a chance of Thunderstorms in the afternoon. Waves 2 feet or less.
see lake huron open lake forecast for days 3 through 5.

LHZ400
No data

FXUS63 KDTX 191941 CCA AFDDTX

Area Forecast Discussion...CORRECTED National Weather Service Detroit/Pontiac MI 341 PM EDT Sun May 19 2024

KEY MESSAGES

- Warm and muggy conditions are expected today and during the early part of the week with daytime highs in the 80s.

- Showers and thunderstorms are likely this afternoon mainly from Port Huron southwestward to Adrian including Metro Detroit. Brief heavy downpours, gusty winds, and small hail are the main concerns this afternoon.

- Chances exist for thunderstorms Monday afternoon mainly north of I 69. There will be a potential for strong to severe thunderstorms, but low confidence exists with exactly the strong to severe threat will occur.

- A much less humid airmass is expected for the end of the week.

DISCUSSION

A weak frontal boundary moving through Michigan early today supporting isolated showers and thunderstorms within the narrow thetae plume mentioned in the morning update. A warm airmass remains in place today with 850 mb temperatures to 14-15C. Forecast soundings for this afternoon suggest mixing depths well up through 850 mb. This supporting high temperatures into the 80s again for inland areas. Temperatures will be cooler and more in the 70s along the lakeshore communities. The high mixing depths will not have any significant effect on the winds as lower level column flow is at 15 knots or less.

Differential heating and surface convergence focused along the lake breezes and remnant frontal boundary from around Port Huron through the Detroit Metro region down to Monroe County is expected to trigger additional convection this afternoon. Current observations at 1930Z for KONZ show SSE wind and 76 degrees while nearby KDTW is at a WSW wind at 88 degrees. Still, fairly good consensus amongst the hi-res model suite for greater coverage of showers and thunderstorms to develop later this afternoon. The narrow thetae plume has now move into the eastern CWA shown well on visible satellite with the afternoon agitated cumulus field. Activity picks up over the next hour or so with isolated cells currently getting underway along the I-69 corridor east of Flint and across southern Sanilac County. Peak of activity develops southwestward between 4 pm and 9 pm. The warm and moist airmass is supporting good instability.
Mesoanalysis showing upwards of 2500 J/kg of MLCAPE centered across southeast Michigan. Mid level lapse rates are not too great at 6.5- 7.0 C/km with low level lapse rates where greatest convection is towards 9 C/km or slightly better. Very little shear in place as well at around 15 knots of bulk shear. This brings more pulse type thunderstorms along these boundaries with any outflow boundaries driving additional updrafts. High moisture is in place with PWATs to around 1.25 inch. All of this brings potential for water loaded downburst winds and brief heavy rainfall with any stronger thunderstorm that can develop. CAPE from -10C to -30C is in the 500- 700 J/kg range with 50 dbz 1 inch hail heights at around 27kft to 30kft bringing potential for at least small hail with the stronger updrafts. There are some limiting factors today that bring uncertainty to the forecast. These are the ridging extending into the central Great Lakes, the notable anticyclonic flow at 700 mb directly overhead where convection is being advertised, and potentially some weak capping around 600-700 mb. All of this could limit stronger convection or perhaps suppress wider spread convection. There is moderate confidence that thunderstorms should hold largely under severe criteria.

A shortwave trough will be lifting out of the central plains into Wisconsin and through the northern Great Lakes on Monday. This will lift a warm front northward and bring a renewed surge of moist advection and a chance for showers and thunderstorms during the afternoon. Daytime instability will be sufficient again to support thunderstorms with 1500-2000 J/kg of MLCAPE forecast by the RAP.
Shear will increase to around 35 knots towards the evening hours.
Uncertainty remains as to what sort of coverage will look like throughout the day. A Marginal Risk for severe weather exists across most of southeast Michigan tomorrow. A more southerly track of the vort max into northern lower Michigan will bring better strong to severe thunderstorm chances to central portions of the CWA whereas the northerly tracks focuses better severe thunderstorm chances towards the Tri-Cities.

Active weather stretch continues on Tuesday as a more dynamic low pressure system develops over the upper Mississippi River Valley.
Longer range models point towards precipitation potential downstream of this strengthening low on Tuesday morning maybe into early afternoon with a relatively brief dry period before activity moves in Tuesday night well ahead of the main cold front. Slowing of this front maintains shower and thunderstorm chances for much of Wednesday with a continued risk of severe weather depending on available instability. Cold front will cool things down out of the 80s for Thursday with surface high pressure likely bringing dry conditions during the late week period.

MARINE

A weak cold front eases across southern Lake Huron, Lake St. Clair, and western Lake Erie through this evening with isolated to scattered showers and storms possible in the nearshore waters.
Severe weather is not likely but localized downpours can be expected where storms do occur. Winds remain light behind the front, veering to north/northeast tonight before continuing around to east/southeast Monday morning at 10 knots or less. The front lifts back north as a warm front on Monday ahead of a low set to track in Monday night into Tuesday. This will bring an area of showers and storms mainly focused across northern/central Lake Huron. Winds and waves remain below Small Craft Advisory criteria with this system. A stronger low develops over the Plains on Tuesday, lifting into western Lake Superior on Wednesday. This will send a cold front across the region with stronger southerly winds to 20 knots or above preceding it. Less humid air settles in on a westerly breeze Thursday as high pressure builds in through the late week.

PREV DISCUSSION
Issued at 1223 PM EDT Sun May 19 2024

AVIATION...

Higher based (6-10 kft) cloud bases this afternoon with light southwest flow giving way to weak and variable winds/lake breezes/outflow boundaries. Thunderstorm coverage remains challenging, as surface based capes reach and exceed 2500 J/kg.
However, mid levels remain very dry with an upper level ridge axis in place also attempting to hinder activity/coverage. Will be counting on some low level convergence from the cold front and marine influence to get additional activity going, and still have plenty of mixed signals in hires solutions, as subtle upper level wave currently tracks northeast through southern Lake Huron. Will continue to monitor real time trends and continue to fine tune/adjust inherited TAFS, which is advertising thunderstorms for the southern taf sites late in the day. Confidence remains shaky, as muted response with just isolated-scattered disorganized showers/thunderstorms is in play as well, which could lingering into early evening hours. Once diurnal activity dissipates, anticipating mostly clear skies tonight, as the low levels attempt to dry out with light easterly winds. Still could be some residual higher surface dew pts over the southern tafs to support light fog/MVFR visibility reduction late tonight.

For DTW/D21 Convection...Confidence is high clouds bases outside of any thunderstorms/showers will be above 5000 feet this afternoon/evening, but still seems like there is a reasonable chance for a slow moving thunderstorm/shower to impact the terminal late today, with potential for a strong wet micro-burst wind gust and heavy downpours leading to IFR visibility restriction. Timing is still uncertain, and could occur anytime between 19-01z, if at all.

DTW THRESHOLD PROBABILITIES...

* Low-moderate for scattered thunderstorms in the airspace between 19Z-01Z. Low for thunderstorms on Monday.



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

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