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000 
FXUS63 KDTX 232050
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
350 PM EST Fri Feb 23 2018

.DISCUSSION...

Shortwave ridging will amplify downstream of the next round of 
shortwave energy progged to lift out of the 4-corners region this 
weekend. Surface high pressure will correspondingly traverse the 
Great Lakes from west to east tonight through Saturday, allowing 
cooler air to infiltrate as the low-level flow veers through the 
northerly quadrant. Even so, lows will remain solidly in the low 
30s, about 10 degrees above average, as heights remain elevated 
downstream of western US height falls and extensive low clouds 
remain in place beneath the inversion.

Some erosion of cloud will be possible on Saturday, especially 
across the north, as anticyclonic flow in the boundary layer 
maximizes and dry easterly flow takes a toll on boundary layer 
moisture. Even so, will be hard pressed to see much sun as the 
inversion on strengthens. No arguments with 12z guidance suggesting 
highs around 40 given 850mb temps around 0C and plenty of cloud 
cover. Just a low chance for showers near the Ohio border during the 
day light hours Saturday as isentropic ascent increases with low 
amplitude, convectively-enhanced mid-level energy shears into the 
Lower Great Lakes region. Ejecting potent mid-level energy is 
progged to deepen surface low pressure toward 980mb as it lifts 
toward the Straits by Sunday morning. Corridor of strong dynamic 
forcing will remain largely northwest of the area while heavier 
convective precip along the deep tropospheric front within the 
resident right entrance region will be located much lower on the 
front, possibly just grazing the far SE CWA. By and large, expect an 
unimpactful round of showers within the narrow corridor of moist 
isentropic ascent along the surging LLJ.

Attention for Sunday turns to wind potential. The cold front at the 
surface will not be particularly strong, but much colder air above 
the ground will rapidly steepen lapse rates beginning early in the 
day Sunday. Subsequent convective instability in the deepening 
boundary layer will yield widespread gusty conditions. Without 
strong dynamic forcing for descent, wind gust potential will 
generally tend toward the average momentum present within the column 
or just a touch higher. Advisory criteria wind gusts of 45+ mph is 
certainly possible, but nearly entirely dependent on residual 
moisture quality and subsequent mixing depth. With this in mind, 
moved the wind gust forecast in the direction of the GFS forecast 
soundings which offer a middle-range low-level moisture quality 
outcome.

High pressure over the Ohio Valley will maintain surface ridging 
across the region early next week bringing dry, calm conditions 
through Tuesday. Temperatures will remain above average with highs 
in the upper 40s on Monday before increasing to the mid 50s on 
Tuesday courtesy of increasing southwest flow as the high translates 
eastward. The return southwest flow will also gradually advect 
moisture northward into Lower Michigan late Tuesday into Wednesday 
that could interact with a weak frontal boundary dropping into mid 
Michigan to produce showers late Tuesday into Wednesday. 

Attention then turns to a potent southern stream wave ejecting from 
the Southwest US on Wednesday that will bring the next low pressure 
system to the region late next week. Model solutions differ on 
handling the interaction of the southern stream wave with a northern 
stream wave and the subsequent development and evolution of the low. 
Regardless, precipitation chances look to increase across Southeast 
Michigan late Wednesday into Thursday as low pressure lifts into the 
region. Temperatures in the 40s on Thursday will keep precip type as 
rain before the low occludes and cold air wrapping into the system 
brings the chance for rain/snow showers by Friday.

&&

.MARINE... 

Light southwest flow this afternoon will shift to the northwest 
tonight as low pressure tracks through the Northern Great Lakes. 
Light and variable winds tomorrow as high pressure moves overhead. 
The flow will become east/southeasterly late Saturday and into 
Saturday night ahead of developing low pressure across the central 
Plains. This area of low pressure will rapidly deepen as it tracks 
northeast across the northern Great Lakes over the second half of 
the week, with gales expected across Lake Huron. Lighter southwest 
winds to follow for Monday and Tuesday as high pressure slides 
through southern Ohio Valley.

&&

.HYDROLOGY...

Flood Warnings remain in effect for most of the primary river basins 
over southeast Michigan as water levels continue to slowly recede. 
Another low pressure system will track northwest of the region late 
Saturday night and into Sunday. Rainfall amounts of a quarter of an 
inch to half an inch are forecasted. This rainfall is not expected 
to have any significant impacts to local rivers and streams.

&&

.PREV DISCUSSION...
Issued at 1204 PM EST Fri Feb 23 2018 

AVIATION...

Rain showers have exited. Southwest winds (10-14 kts) this afternoon 
allowing for improvement in ceiling heights and visibility. However, 
enough low level moisture likely around to lock cigs in at MVFR. 
Winds becoming light northwest this evening and then light northeast 
tomorrow morning. Confidence in cigs is lower this evening into 
tomorrow, as it is possible for clearing to take place late this 
evening, especially over the southern taf sites (DTW/YIP/DET). 

For DTW...As surface winds come around to the northwest this 
evening, it is possible for partial clearing of the low clouds. If 
MVFR clouds do scatter out in the 3-8Z time frame, descent chance 
they would return Saturday morning as winds become light northeast. 

/DTW THRESHOLD PROBABILITIES...  

* High for cigs below 5 kft through early this evening, then low to 
  medium.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Warning from 7 AM to 7 PM EST Sunday for LHZ363-421-422-
     441>443-462>464.

     Gale Warning from 10 PM Saturday to 7 PM EST Sunday for LHZ361-362.

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

$$

DISCUSSION...JVC/JD
MARINE.......SF
HYDROLOGY....SF

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