Marine Forecasts

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7 Day Forecast for Marine Location Near Dearborn, MI

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Area Discussion for - Detroit/Pontiac, MI

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FXUS63 KDTX 290806 AFDDTX

Area Forecast Discussion National Weather Service Detroit/Pontiac MI 406 AM EDT Thu Jul 29 2021

DISCUSSION.

A Flash Flood Watch remains in effect for urban type flooding potential across the Metro Detroit region through 10 am as a complex of thunderstorms with heavy rainfall moves Lower Michigan this morning.

At the surface a warm frontal zone is draped from north/central WI southeast through central lower MI and into Ohio. Early night strong convection tracked more NNW to SSE feeding on the the strong instability in southern WI into northern IL. Will be watching for greater development that will drive southeastward ahead of the surface reflection as it moves into western MI. The low level jet of 30-35 kts will also be moving over southern Lake MI in west/southwest Michigan helping support stronger convection. Late night trends leaning towards this event ending up as more of a heavy rainfall threat than a damaging wind threat, as the greater threat will stay to the west and southwest of southeast Michigan. However, there will still be potential for some isolated to scattered damaging winds through the early morning with the warm front still hanging around. A Marginal/Slight Risk still in place through 12Z across most of the CWA seems appropriate still.

Timing of the strongest convection into southeast Michigan still expected within the 08-012Z time frame in conjunction with the arrival and progression of the low level jet this morning. High moisture content will accompany this system. Upstream 00Z RAOBs last evening picked up PWATs around 1.50 to 1.75 inches. Latest RAP forecast still has PWATs at 1.75 to just over 2.00 inches over southeast Michigan by 12Z. The high degree of moisture should bring potential for high rainfall rates during the aforementioned time frame as well as any development associated with a surface low as it drifts into central MI later in the morning.

This morning still carries some degree of uncertainty with regards to intensity and/or coverage of both the lead convection as well as any trailing convection. At press time, heaviest rainfall is moving southwest of the CWA with elevated convection rippling off the front across central MI and into the Saginaw Valley. There will be a bookend vortex forecast to move into central Michigan and result in slower moving and training convection producing heavy rainfall. This feature will be what likely brings the potential for 1-3 inches of rainfall across Lower Michigan through the morning hours. There is a scenario where heaviest rainfall just grazes the southwest portions of the CWA.

By the afternoon the main complex will push south of the state. Lower level cold air advection behind the system with surface height rises moving in from the northwest will result in temperatures cooling off and clearing skies. Pleasant weather expected for Friday with high temperatures in the low to mid 70s and much less humid conditions as dewpoints fall into the 50s. Mostly stable conditions hold through Saturday morning until broad cyclonic flow aloft ushers in the next shortwave diving out of Ontario directly and over the central Great Lakes. This will be the next chances for rainfall. Timing appears to be late Saturday into Sunday.

After a slightly warmup on Saturday towards the upper 70s before a reinforcing shot of cooler air settles back into the region by late Sunday. This will be the result of broad troughing over taking the eastern half of the CONUS the early to mid next week. Forecast high temperatures to start next week back fall back into the low 70s. Overall rain chances should be limited given the deeper moisture will be pushed back towards the Gulf Coast states. Any rainfall chances will be governed by the evolution of shortwaves within the cyclonic flow and the eventual breakdown of the trough into late next week.

MARINE.

A thunderstorm complex and associated low pressure move through the central Great Lakes this morning with heavy rainfall and scattered strong to severe wind gusts in excess of 50 kt possible, especially across southern Lake Huron, Lake St. Clair, and western Lake Erie. The cold front follows by midday with the bulk of the showers/storms moving out and cooler northwest wind ensuing through the day. A secondary backdoor cold front drops southward across Lake Huron late tonight with winds veering to northeast and increasing to 20-25 kt Friday morning. This will lead to a growing wave field over southern Lake Huron with Small Craft Advisories likely becoming needed around the Thumb late overnight through Friday morning. High pressure then builds in from the west late Friday with lighter northerly flow backing to the northwest.

HYDROLOGY.

A Flash Flood Watch is in effect through 10 am this morning for a portion of Southeast Michigan including Metro Detroit. The potential exists for total rainfall amounts of 1 to 3 inches resulting from high rainfall rates with PWATs near or at 2.00 inches. This could lead to flooding of low lying and prone urban areas along with rises in area creeks and streams. Rainfall rates will exceed 1 inch per hour in thunderstorm activity with the favored area for highest rainfall totals south of the I-69 corridor.

PREV DISCUSSION. Issued at 1158 PM EDT Wed Jul 28 2021

AVIATION .

Potential remains for showers and thunderstorms to increase in coverage throughout the southeast MI airspace mid morning /09z-12z/ as a mid level wave tracks across the area. Recent radar trends currently suggest the strongest convection currently over central Wisconsin will tend to shift south-southeast and remain west of the corridor. Some degree of development east of this current activity affords this window for possible tsra/shra, with an accompanying reduction visibility and some gusty winds. Lingering rainfall within brief MVFR conditions in the wake of this complex carries into the latter half of the morning, before cloud bases lift during the afternoon. Winds will shift to northwesterly for the afternoon period.

For DTW . Main window for thunderstorms centered 09z-11z, with potential for brief gusty winds from the northwest and some visibility restrictions. Lingering convective showers maintains potential for cloud bases to remain below 5000 ft through midday.

DTW THRESHOLD PROBABILITIES .

* High for cigs aob 5000 ft after 09z through late morning Thursday. Low Thursday afternoon and evening. * Moderate for thunderstorms 09z-11z Thursday morning.

DTX WATCHES/WARNINGS/ADVISORIES. MI . Flash Flood Watch until 10 AM EDT this morning for MIZ068>070-075- 076-082-083.

Lake Huron . NONE. Lake St Clair . NONE. Michigan waters of Lake Erie . NONE.

DISCUSSION . AA MARINE . TF HYDROLOGY . AA AVIATION . MR

You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.

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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
CLSM4 - St. Clair Shores, MI	18 mi	51 min	SSW 7 G 12	75°F			1012.9 hPa (-2.7)
45147 - Lake St Clair	28 mi	51 min	SSE 12 G 14	75°F	74°F	1 ft	1011.2 hPa (-2.9)
AGCM4	39 mi	51 min		72°F	73°F		1012 hPa (-3.0)
45165	47 mi	21 min	S 12 G 14	76°F	79°F	1 ft
TWCO1	47 mi	31 min	SSW 14 G 17		79°F
THRO1 - 9063085 - Toledo, OH	50 mi	51 min	WSW 6 G 9.9				1012.2 hPa (-1.5)

Wind History for Toledo, OH

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
Coleman A Young Municipal Airport, MI	10 mi	58 min	SSW 9	10.00 mi	Fair	77°F	71°F	82%	1011.6 hPa
Troy, Oakland/Troy Airport, MI	11 mi	56 min	SW 4	10.00 mi	Fair	76°F	72°F	87%	1013.2 hPa
Detroit, Detroit Metropolitan Wayne County Airport, MI	12 mi	58 min	SSW 9	6.00 mi	Fog/Mist	74°F	72°F	94%	1012.1 hPa
Detroit/Grosse Ile, Grosse Ile Airport, MI	19 mi	56 min	SSW 8	10.00 mi	Partly Cloudy	76°F	73°F	91%	1012.2 hPa
Detroit, Willow Run Airport, MI	20 mi	58 min	SW 8	10.00 mi	Fair	75°F	68°F	79%	1012 hPa
Pontiac, Oakland County International Airport, MI	23 mi	58 min	S 6	10.00 mi	Fair	75°F	68°F	79%	1011.2 hPa

Link to 5 minute data for KDET

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