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7 Day Forecast for Marine Location Near Bay City, MI

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Area Discussion for - Detroit/Pontiac, MI

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FXUS63 KDTX 141427 AFDDTX

Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1027 AM EDT Fri Aug 14 2020

UPDATE.

There is a an axis of deep moisture now extending from central Ohio into Western Lake Erie/Southern Ontario, focused along a sfc trough axis. This moisture has been advancing into Se Mi this morning within the low to mid level easterly flow now in place across the region. The 12Z DTX sounding was still quite dry, particularly in the mid levels. However, this sounding actually captured the dry side of the moisture gradient.

This moist plume will work east-northeast during the course of the day, actually forecast to lift across the Saginaw Valley late this afternoon/early this evening. The lead push of the mid level moisture across Se Mi is now marked by a an alto cu field. Thanks to the easterly flow off the warm waters of Lake Erie, sfc dewpoints from Monroe up to Detroit are in the upper 60s/low 70s. Diurnal mixing processes will likely keep the dewpoints a little lower farther inland this afternoon. Nonetheless, 01km ML CAPE around 1500 J/kg certainly seems reasonable this afternoon with temps expected to rise into the mid/upper 80s. Low to mid level moisture convergence will occur along the lead edge of the moisture gradient today and there will be increasing boundary layer convergence along the sfc trough as it organizes over srn Mi this afternoon. This seems to suggest that convective development will focus along the instability gradient over Se Mi today, slowly moving to the north-northwest during the course of the day. The 12Z DTX sounding did have a formidable mid level cap. There will be some mid level cooling today, which in combination with the increasing diurnal instability will weaken the cap. Nonetheless, this cap will pose enough of a limiting factor to keep pops on the chance/low chance category today.

The only main update to the forecast will be to nudge pops upward across the Saginaw Valley late in the day based on the expected arrival of the instability gradient. The northern thumb region appears far enough removed from the moist plume and instability axis to maintain a dry forecast today.

PREV DISCUSSION. Issued at 711 AM EDT Fri Aug 14 2020

AVIATION .

Generally dry low levels will maintain VFR conditions this forecast. However, isolated diurnal showers may develop for a few hours late today as wedge of higher moisture on southeast flow leads to a bit of instability under dry mid/upper levels. At the very least, expect the coverage of diurnal cumulus to increase in the afternoon period. Locally, LIFR stratus/fog within moist low level flow from Saginaw Bay will impact KMBS for a short time early in the forecast.

DTW THRESHOLD PROBABILITIES .

* Low for cigs aob 5000 ft this afternoon.

* Low for thunderstorms impacting the terminal this afternoon.

PREV DISCUSSION . Issued at 300 AM EDT Fri Aug 14 2020

DISCUSSION .

Very dry mid levels in place over southeast Michigan, as the 00z DTX sounding indicated a 700 mb dew pt depression of 46 C. However, southeast winds at 850-700 mb level will be transporting a good deal of moisture in from the Western Mid Atlantic states today, with PW values forecasted to rise at or above 1.75 inches. Upper level energy/wave(s) tracking through the Western Ohio Valley/Great Lakes this afternoon will also help support some broad ascent, coupled with daytime instability/mlcapes of 1000-2000 J/kg supporting a low chance of showers and thunderstorms, especially toward the southern Michigan border. Weak mid level lapse rates and 0-6 KM bulk shear under 20 knots supports non-severe storms. Some semblance of an inverted trough as well to help focus activity, but the trough may reside just west of the CWA by afternoon. Good agreement amongst guidance for highs, mid to upper 80s, with the increase in clouds and low level moisture keeping maxes under 90 degrees.

Muddled pattern for Saturday as southeast Michigan is caught in between two systems, the upper level low/trough over/near Kentucky and the stronger northern trough/greater height falls tracking through the upper Mississippi River Valley. Shortwave ridging in place during the day suggests bulk of the day will be dry, but the remnant moisture axis from today lingers, and considerable instability suggested, with MLcapes around 2000 J/kg, to carry chance/scattered pops with the weak surface low/trough in place. If that amount of cape is realized (NAM would suggest up to 3000 J/kg), with the increase in 0-6 KM bulk shear to 30 knots, than isolated severe storms will be possible.

Even better chance for rain Saturday night into Sunday as secondary 850-700 mb Theta-e ridge/moisture axis slides over the area, with modest height falls/right entrance region forcing from the upper jet over Ontario Saturday night. Left exit region forcing then arrives Sunday morning with the upper level energy swinging through the Western Great Lakes. Moisture axis looks to slide east of southeast Michigan by around 18z, with low level drying taking place in the late afternoon, and will taper off pops quickly.

Yet one more weak upper wave coming over the top of ridge over the Rockies progged to swing through the Central Great Lakes Sunday night, so not inconceivable for a shower or two to be touched off, as cooler airmass (700 mb temps approaching zero) tracks across the warm waters of Saginaw Bay/Lake Huron.

The longwave pattern for early next week is expected to feature an very strong upper level ridge (600 DAM at 500 mb) out west, with a broader upper level trough east of the Mississippi River Valley. Cooler northwest flow over the Great Lakes region will keep temps in check (as 850 mb temps bottom near 10 C), with average temps coming up slightly below normal.

MARINE .

Stable high pressure over eastern Canada will begin to drift east today with weak surface troughing developing over the southern waterways. This may promote a few brief afternoon showers or thunderstorms, but mainly dry conditions are expected with light E/NE flow. Could see a few non-thunderstorm wind gusts near 20 knots in the 18-22Z timeframe with mixing from enhanced 925 mb winds. Flow will veer southeasterly Friday night into Saturday with additional shower/thunderstorm chances as weak low pressure develops over the northern Ohio Valley. Impact will be limited on the surface gradient and respective wind fields. A cold front is forecast to sweep across the region on Sunday veering winds southwest then northwest on the back edge and also continuing chances for showers and storms. Waterspouts may be possible with this activity given the antecedent conditions. Stronger northwest gradient and cooler air arrives on Monday supporting increased wind and wave action into Tuesday.

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

UPDATE . SC AVIATION . DG DISCUSSION . SF MARINE . KK

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
SBLM4 - Saginaw Bay Light #1, MI	18 mi	143 min	ENE 9.9 G 12	75°F			1018.3 hPa
45163	32 mi	23 min	ENE 9.7 G 12	78°F		1 ft
GSLM4 - Gravelly Shoals Light MI	35 mi	43 min	ENE 11 G 12	75°F
TAWM4 - Tawas City, MI	52 mi	43 min	E 8.9 G 11	78°F			1019.3 hPa

Wind History for Harbor Beach, MI

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
Saginaw County H W Browne Airport, MI	10 mi	28 min	NE 7	10.00 mi	Fair	79°F	64°F	61%	1017.9 hPa
MBS International Airport, MI	11 mi	30 min	ENE 7	10.00 mi	Fair	82°F	57°F	44%	1017.9 hPa
Jack Barstow Airport, MI	21 mi	28 min	ENE 6	10.00 mi	Fair	81°F	62°F	54%	1018.3 hPa

Link to 5 minute data for KHYX

Wind History from HYX (wind in knots)

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Weather Map

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NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
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Wind Forecast for Detroit/Pontiac, MI (12,3,4,5)

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Ground Weather Radar Station Detroit, MI

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