Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 261033

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
633 AM EDT Wed Jul 26 2017


Cirrus debris from convection to the north/northwest will thin
during the course of the morning, leaving partly cloudy skies by
midday as scattered upper clouds are joined by a smattering of
diurnal cumulus. Cold front to the north will progress slowly into
the region tonight, bringing thickening/lowering cigs (still VFR for
the most part). Any MVFR will be limited to scattered shra/tsra that
work into KFNT/KMBS along/in advance of front.

For DTW...VFR conditions expected throughout the forecast with
varying degrees of mid/upper clouds in the 10-20kft range. Other
than that, perhaps a few diurnal cu in the 4-5kft by midday into
early evening.


* None


Issued at 307 AM EDT Wed Jul 26 2017


Upper low tracking through Canada has flattened the ridge that was
over the region, paving the way for convectively induced shortwaves
stretching from Nebraska through Upper Michigan to track through the
area in westerly flow this evening and tonight. Southerly flow in
advance of the system and from around the retreating surface high
will usher in warmer air and higher dewpoints today. Will start the
day with plenty of high cloud off decaying storm complexes to our
west before approaching cold front allows clouds to fill in over
central Michigan especially. Early day pockets of sunshine,
especially south, combined with warm air advection should help boost
temperatures ranging from the upper 70s in the northern Thumb to the
mid-80s in the Detroit area.

The passage of the trough to our north will also push a weak cold
front and surface trough down into central Michigan tonight, and
allow a plume of high theta-e upstream to wash over the area with
moisture pooling ahead/along the front. The front will briefly stall
late tonight as low pressure tracks through the Ohio Valley, before
it drops through the remainder of southern Michigan sometime on
Thursday. Timing will be dependent in part on how convective
evolution over the region plays out overnight. The front should
trigger showers and thunderstorms over central Michigan tonight,
down to about the I-69 corridor, as it drops southward through the
area. Chances for showers and thunderstorms over the southern
portion of the area will hinge more on convective development from
the Central Plains to Ohio Valley where low pressure/warm front/low-
level jet will reside. A few models bring the apex of these features
just close enough to justify rain/thunder chances over the southern
CWA Thursday morning. Strongest and more organized activity is
expected to stay south of the area, however. The front will continue
dropping southward Thursday, with a good chance to trigger new
development over southeast Michigan. Strength will be limited by
early day clouds and possible earlier activity.

A few showers may linger over the far southeast part of Michigan on
Friday ahead of the strong upper wave diving through the area.
Subsidence behind the trough should end the risk for showers by the
second half of the day. Strong north to northeast flow on the
backside of the system will be augmented by Lake Huron, making for a
cool day with high temperatures only in the low/mid 70s, and even a
little cooler over the northern thumb. Strong upper ridging and
surface high pressure will then settle into the area Friday night
through the weekend, bringing quiet weather and a warming trend to


High pressure will continue east to the New England states this
morning. Light southeasterly winds will veer to the southwest on the
backside of the high and ahead of an approaching cold front. Gusts
could reach 20 knots ahead of the front, but fetch will keep higher
waves over the open waters. Showers and storms will be possible with
this front over Lake Huron, especially from mid afternoon into this
evening. The front will sag south and spread precipitation chances
through the rest of the eastern Great Lakes overnight into Thursday.
North to northeast winds will increase to near 20 knots Thursday
night into Friday in the wake of this front. Waves will build in
response to this flow, and a Small Craft Advisory may be needed late
Thursday night into Friday for portions of the nearshore waters.


A cold front will progress slowly southward through the region on
Thursday and stall as low pressure approaches from the west. Showers
and thunderstorms are expected to accompany this front with locally
heavy rainfall of generally one quarter to one half an inch possible
on Thursday. As this low passes south of the area on Friday, expect
a strong upper level disturbance to sweep in from the northwest. The
combination of these features will bring additional rain chances
with locally heavy rainfall of one quarter to one half an inch quite
possible late Thursday night into the first half of Friday. At this
time, this second batch of activity looks most likely south of the
I-69 corridor.


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



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