Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 252032
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
432 PM EDT Sat May 25 2019

.DISCUSSION...

The window for marginal severe thunderstorms closes as the corridor
of upper level support finishes sliding through SE Michigan. This
larger scale forcing was weak but just enough to help erode a modest
mid level cap that was evident earlier in the day. Afternoon
mesoanalysis measured surface based CAPE of 1500-2000 J/kg and
MLCAPE in the 500-1000 J/kg range which was strong enough to take
advantage of surface to 6 km bulk shear around 50 kts. Multicell
clusters were slow to intensify in this environment in terms of
lightning flash rate but showed hints of organization in radar
reflectivity depictions. The multicell storm mode initially
presented pockets of damaging wind and severe hail threats where
updrafts could organize with some mid level rotational enhancement.
A trend toward more organized line segments occurred as convection
matured with a larger damaging wind footprint occurring downriver to
the Ohio border.

Passage of the subtle upper wave nudges the weak surface cold front
south of the Ohio border tonight but not far enough for elevated
portions of the front to clear SE Michigan. This maintains a path
for new nocturnal convection to develop over the Midwest and move
downstream along/near the border. The source region across the
central Plains to mid Mississippi valley tonight provides low level
jet forced convection into the frontal zone that is further enhanced
and lifted northeast by the entrance region of the upper jet setting
up over central Lower Michigan toward sunrise. Model depictions of
the low level theta-e gradient point to the south four SE Michigan
counties for chance POPs late tonight through Sunday with some
potential for northward adjustment depending on the effectiveness of
the entrance region to manipulate the mid level frontal circulation.

A short pause in shower/storm potential occurs Sunday night and
Monday morning. The upper jet segment moves eastward and leaves low
amplitude short wave ridging overhead while the next low pressure
system organizes across the Plains. This system pulls the front back
north over Lower Michigan Monday night returning an active period of
showers and thunderstorms to the region through Tuesday.

&&

.MARINE...

Low pressure and the associated cold front moving across the central
Great Lakes supports scattered to numerous thunderstorms during the
evening mainly across Lake St Clair and western Erie. Marine
conditions otherwise consist of light to moderate wind and minimal
wave impacts outside of thunderstorms as the front stalls south of
Lake Erie. High pressure brings dry weather to a larger portion of
marine areas Sunday with the possible exception of western Lake
Erie. Showers and thunderstorms increase again across the central
Great Lakes Monday night as the next low pressure system moves into
the Midwest and pulls the stalled front back northward across the
western Great Lakes.

&&

.PREV DISCUSSION...
Issued at 125 PM EDT Sat May 25 2019

AVIATION...

TAFs are front end loaded with concerns as winds will be gusty out
of the southwest to around 25 knots and a period of scattered
thunderstorms from 18-22Z. Activity has already began as of 17Z with
storms initiating west, south and east of the area. Forcing will
arrive over the next few hours looking to focus better chances in the
aforementioned window of time. Outside of CIG/VSBY restrictions with
thunderstorm activity, primarily VFR conditions with rapid clearing
behind a cold front later this evening. Winds will drop off this
evening while veering from southwest today to northwesterly tonight.
The front will become stalled west to east near the state line with
the next system riding along it early Sunday morning. At this point
looks to be just a CIG issue with precip holding to the south.

For DTW...Best chance for thunderstorm activity will be from 19-22Z
though cannot rule out an isolated storm popping up prior to that.
CIGs will become MVFR near the storms and once again late tonight
with a weak system passing to the south, otherwise VFR.

DTW THRESHOLD PROBABILITIES...

* Moderate for tstorms in DTW airspace 18-22z.

* Moderate for CIGS of 5kft or less this afternoon. Low for early
  Sunday morning.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

DISCUSSION...BT
MARINE.......DRK
AVIATION.....DRK


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