Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 252310
AFDDTX

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


.AVIATION...

The jet stream overhead will become more zonally orientated
overnight. This will suppress geopotential heights over the central
Great Lakes forcing  a cold front to sag/backdoor through the area
overnight. Persistence of strong S.E. U.S. ridging will cause the
front to hang up immediately south of Metro Detroit or the MI/OH
state line for Sunday. Very modest cold air advection will occur over
southern Lower Michigan, but drying from midlevel subsidence will
lead to a stable column for much of the cwa. At this time, will go
with dry tafs as any shower potential Sunday will occur south of DTW.
Model soundings are trying to show some hz potential overnight, and
will be monitoring the trends this evening in latest model guidance.
Certainly possible to see some MVFR vsby reductions. For now, models
are a little aggressive in generating stratus instead. Maintained a
VFR ceiling for the Detroit terminals with some right entrance region
dynamics interacting with the frontal boundary to the south.
Relatively weak easterly winds Sunday, but potential does exist for
sustained winds to exceed 7 knots.

For DTW...VFR skies tonight with some potential for MVFR vsby
restrictions overnight due to br/hz. VFR cigs throughout Sunday with
precipitation remaining south of DTW Sunday afternoon.

.DTW THRESHOLD PROBABILITIES...

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

&&

.PREV DISCUSSION...
Issued at 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.

&&

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

$$

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


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