Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 010418
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1218 AM EDT WED JUN 1 2016


.AVIATION...

Light NE low level flow will continue to carry dry air into the
region from surface high pressure over northern Ontario and Quebec
tonight. This will leave VFR in the form of patchy high clouds
associated with the frontal system over the Midwest that is
producing several clusters of showers and thunderstorms reaching the
western Great Lakes. None of this activity will reach SE Michigan
until late day into Wedneday night. Marginal MVFR/IFR restriction is
then likely with a heavier shower or thunderstorm in the main band
of frontal precipitation. Confidence is high enough to carry the
showers but a little too early to pin down thunderstorms at the
terminals. Also, the frontal wind shift is not expected until
roughly the 07-09z time frame Thursday morning.

//DTW Threshold Probabilities...

* Moderate for ceiling 5000 ft or less Wednesday night.

&&

.PREV DISCUSSION...
Issued at 339 PM EDT Tue May 31 2016

DISCUSSION...

Ridging aloft with high pressure extending south over the area from
Hudson Bay will keep pleasant weather over the Great Lakes into
Wednesday. Low levels will remain dry with a mainly easterly
component to the surface wind field, owing to being on the southern
periphery of the surface high. With dewpoints hovering in the low
50s tonight, low temperatures will bottom out in that range.

Things get a little more interesting on Wednesday as a mature mid
level low over the northern plains lift northeastward through
Ontario and into Quebec by Thursday afternoon. The associate surface
low, which is nearly stacked under the mid level low, will also
follow this same path/timing. Both features reach maturity over the
plains and are in the weakening phase as they track through the
northern Great Lakes region. The fronts will already be occluding as
the system passes through the Great Lakes thus the warm sector will
be limited to only a narrow wedge as it passes through southeast
Michigan Wednesday night. Drier southeast flow will preclude the
warm front which will keep potential for showers low most of the
day. A warm layer around 800-900mb will also help keep the area
capped ahead of the warm front, resulting only in an increasing
mid/high cloud deck. The warm front will lift through the area
Wednesday evening, with the cold front following around 09Z
Thursday. Will be difficult to get good moisture up ahead of the
front with such a narrow corridor of return flow overnight. Showers
and thunderstorm chances will peak between 00-12Z Thursday though
chances of severe storms is not looking overly impressive. Model
average for CAPE values is right around 500 j/kg. Looks to be a tall
skinny CAPE profile with most occurring in the mid levels above
800mb. Bulk shear is on the lower side around 30 knots and both LI
and Showalter Index briefly touch levels for decent convection. All
in all, looks like a broken line of showers and thunderstorms will
work through the lower Michigan Wednesday night. Higher
chances(likely pops) further north over the Thumb closer to the low
and the better forcing. Could get a few elevated showers ahead of
the main line so will leave the chance pops in for Wednesday
evening.

Depending on the speed of the cold front we could have a few
lingering showers over our eastern counties Thursday morning.
Outside of this low chance pop to get us through the first few hours
of the day, high pressure will bring drier air back into the region
which will try to clear the skies out for the rest of the day. A
weak thermal trough will be overhead which will attempt to keep us
out of the 80s for the first time in over a week. Will be close as
flow at the surface is westerly and nearly zonal keeping some
warmer air advecting in.

Pseudo zonal flow along the northern United States will buckle on
Friday...as Gulf of Alaska/Pacific Northwest upper level
energy/height falls lead to closed 500 mb low developing over the
Upper Mississippi River Valley on Friday. This large upper level low
(supported by majority of ensemble members) will be slow to push
through the great lakes region over the weekend, leading to good
chance of showers and possible thunderstorms (mainly second half of
weekend). 850 mb temps falling into the mid single numbers by Monday
(per 12z euro)...likely supporting highs only in upper 60s to around
70 degrees on Monday...with temperatures just a touch warmer for
Tuesday as partly sunny skies return.

MARINE...

Strong northeast winds, around 20 knots over Saginaw Bay will
diminish with loss of daytime heating, with light and variable winds
around late this evening. Light southeast flow will develop late
tonight and increase modestly by Wednesday as high pressure moves
into Quebec and the next low pressure system organizes over the
upper Midwest.

A cold front will cross the region Wednesday night into early
Thursday. This front will bring a good chance for showers and
thunderstorms, as well as leading to a wind shift to the west.
However, winds on Thursday still look to top out below 20 knots
before high pressure brings a weakening pressure gradient again by
Thursday night and Friday, leading to light to variable wind regime.

&&

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

$$

AVIATION.....DG
DISCUSSION...DRK/SF
MARINE.......SF


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at www.weather.gov/detroit.



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