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Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
347 am EDT Wed Apr 26 2017


Deep trough has carved out over much of the western and central US
with a steady feed of strong westerlies feeding energy into it. The
Great Lakes will reside on the eastern periphery of this trough with
the best channel of moisture and instability located over WI/Lake Michigan
for the better part of today and tonight before a strong shortwave
rounds the base of the trough and through the region late Wednesday
night and Thursday. The parent upper low will be located over the
Midwest so when the strong jet forces the shortwave through the base
of the trough, it will result in a negatively tilted trough. The
wave then lifts through the area to become absorbed by the dominate
upper level low pulling a cold front through lower Michigan Thursday

Strong southerly flow today ahead of the trough with low level jet
around 40 knots will create good warm air advection into the region. 850mb temps
will rise into the mid teens which should be adequate to supports
highs around 80 for most locations, considering the resident airmass
with full sun was already producing low 70s. Clouds may be a little
tricky today as debris may be shed from upstream activity but dry
air will attempt to scour it out. All models support a dry forecast
for today with the exception of the Tri-Cities area. It's location
farther north and west will bring it into play for some
shower/tstorm activity later this evening as the nose of a strong ll
jet surges through western lower. Many models keep this activity
farther west but hires suite is starting to capture the feature
better and support some activity clipping this area.

Aforementioned shortwave and cold front then comes into play on
Thursday. Environment is one of very high shear and lower
instability. Models consistently showing shear values upwards of 50
knots but cape struggles due to strong capping inversion and deep
elevated warm layer. Surface based cape looks to stay below 500 j/kg
per most models including arw and nmm now capturing the fropa. The
cold front will occur around 21z with the bulk of the precipitation
likely occuring between 16z and 22z. Strong wind profile with 60
knots down to around 800mb will present a good wind threat even if
lack of instability reduces stronger convection from building. Could
see some strong wind gusts out of some lower topped cells. In
addition, winds throughout the mixed layer look to be around 30
knots so expect a breezy day with southerly winds gusting to 30-40
mph through the afternoon. Storm Prediction Center has a marginal risk over the area
which seems quite reasonable.

Cool high pressure will start building in on Friday knocking temps
back down to closer to season normals, low 60s. There does remain a
low chance of showers Friday afternoon as the next wave quickly
develops with a warm frontal boundary just south of the area. Some
isentropically forces showers may pass through the region but bulk
of the activity should stay south over the Ohio Valley. This warm
front and developing low will be the main player through the
weekend. Depending on where this front sets up, the area could be
mostly dry for the day but there stands a good chance (especially
closer to ohio) for periods of showers. Sunday looks better in terms
of pops as the upper level low lifts through the region.



A long duration of moderate southeasterly flow will exist through
Thursday with a gradually veering to the south by the end of that
time frame. This flow will exist within modest pressure gradient
between high pressure to the east and low pressure lifting into the
mid Mississippi Valley. Expect sustained wind of 15 to 20 knots over
Lake Huron.

While higher gusts will likely occur, rather stable low levels
within this warming southerly flow will limit the highest gusts to
around 25 knots today and 25-30 knots on Thursday as the low
pressure and attending cold front encroach on the area. Winds will
turn southwesterly in the wake of this system from late Thursday
into Thursday night with scattered showers or storms also
accompanying the cold front.


Previous discussion...
issued at 1204 am EDT Wed Apr 26 2017


Late evening radar composite depicted some respectable convection
over Central Lake Michigan down through western Indiana that has
shown a diminishing trend up to press time. The remaining light
showers are expected to continue weakening with time while
associated mid clouds continue to expand. These clouds, along with
surface wind lingering around 5 knots through the night, supports
less fog in line with our going forecast for the terminals. A brief
mention of borderline VFR/MVFR restriction remains warranted from
before sunrise through about mid morning, slightly longer over fnt
to mbs. The possibility remains for some stratus as well which would
materialize with greater coverage if mid clouds fail to hold while
the low level moisture axis moves toward and into lower Michigan to
the vicinity of the terminal corridor. Model soundings remain weakly
capped for convection along the boundary through the afternoon while
daytime heating helps produce a gusty south to southeast wind.
Showers and thunderstorms are then expected to move in from the
associated cold front over the Midwest Wednesday evening possibly
brushing the mbs area through midnight.

//Dtw threshold probabilities...

* low for ceiling 5000 ft or less during the morning.


DTX watches/warnings/advisories...
Lake Huron...none.
Lake St Clair...none.
Michigan waters of Lake Erie...none.



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