Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 272245 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 645 PM EDT Tue Jun 27 2017 .AVIATION... The departure of a weak mid level short wave and loss of daytime heating will bring an end to residual showers and diurnal cloud cover over the next couple of hours. The loss in daytime mixing will also allow the westerly winds to weaken and slowly back to the south- southwest. The south-southwest gradient will increase during the overnight and through Wed morning as high pressure advances to the mid Atlantic. The deepening of the mixed layer will allow a slight increase in these winds mid to late Wed morning. Otherwise, the high pressure system and dry ambient airmass will sustain tranquil aviation conditions through Wed morning. //DTW THRESHOLD PROBABILITIES... None. && .PREV DISCUSSION... Issued at 309 PM EDT Tue Jun 27 2017 DISCUSSION... Shortwave dropping through back side of mid level trough is clipping eastern Michigan this afternoon and evening. Very cold airmass aloft as this mornings sounding indicate freezing level around 6kft combined with strong diurnal heating is yielding capes upwards to around 1k joules producing scattered showers mainly from the Thumb and Saginaw Valley on north. Expect this activity to continue into the evening before dissipating around sunset. some light shower activity could make it down to the Detroit area briefly during prime heating. Some thunder is possible as -20c is just a mere 16kft above the surface. After...skies will clear early tonight as surface high pressure slides by to the south and mid level heights rise. Wednesday will start off mostly sunny but clouds will begin increasing from the west during the afternoon as waa around backside of departing high begins. Shortwave tracking through the upper midwest will spin up a weak surface low Wednesday that will track east across the northern Great Lakes. Showers and Thunderstorms will develop over Wisconsin and spread east-southeast along a strengthening warm front that will be lifting north through lower Michigan tomorrow afternoon. Expect the best chance for showers and thunderstorms to occur late afternoon/evening across the Saginaw Valley and Thumb. This area will be sensitive to any heavy rainfall after major flooding over the weekend. Activity shouldn`t last too long and expecting maybe upwards half an inch. There should be a break in activity after warm front passage but showers and thunderstorms will return later Wednesday night as a cold front moves through lower Michigan down to along the southern border Thursday morning where it will stall as main shortwave lifts northeast into Ontario. Thursday should be rather quiet for most of the forecast area as mid level ridge slides through but showers and thunderstorms will still be possible especially across the southern two tiers of counties in the vicinity of the stationary front. Another stronger shortwave in a broader deepening trough will advance towards the Great Lakes Thursday night. In response the stationary front will lift back north as a warm front bringing a chance for showers and thunderstorms across the area. Temperatures will be more seasonable the next couple of days. EXTENDED FORECAST Friday June 30th through Wednesday, July 5th: Models showing little change in the forecast from yesterday with wet weather pattern still expected to resume mid-week and continue into weekend as several waves of low pressure move through SE MI. Chances of showers/thunderstorms still look to increase by Friday afternoon and evening with a few showers lingering about for Saturday. Surface high pressure is delayed until Sunday on new run, along with the upper level trough. Upper level troughs could still be a bit of a fly in the ointment triggering scattered showers Sunday through Tuesday. At present, the vort maxes disappear for Wednesday as high pressure gets a slightly better footing over the area; translation, drier conditions and less clouds Wednesday. Temperatures continue to hold near the seasonal norm through the period with highs in the upper 70s to low 80s and overnight lows in the 60s. MARINE... Moderate westerly winds will hold throughout the afternoon as diurnal heating over land brings the slight chance to see isolated showers over the Saginaw Bay, and along the western coasts of the Great Lakes. Overnight, winds will shift from westerly to more southwesterly as nocturnal stability acts to keep winds light. High pressure moving east across the Ohio Valley will act to keep conditions dry throughout Wednesday and will usher in warmer air into the region, bringing more stable conditions over the lakes as gusts remain sub-15 knots. Thunderstorm chances then move in Wednesday night into Friday as a series of low pressure systems help to advect warm, moist air into the region. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....SC DISCUSSION...DRC/DE MARINE.......AM You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.

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