011
FXUS63 KDTX 210803
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
403 AM EDT Sun Jul 21 2024

.KEY MESSAGES...

* Low coverage of showers and isolated thunderstorms each afternoon
  today through Tuesday.

* Widespread showers and thunderstorms arrive Wednesday.

&&

.DISCUSSION...

A weak cold front will settle southward into central Lower Michigan
by around sunrise this morning. There is enough moisture along this
front supporting corridor of mid clouds that will move into northern
portions of the forecast area during the early morning hours. A
closed mid/upper low pressure will also be meandering over the mid
Mississippi River Valley throughout today and be responsible for weak
mid level vorticity advection into the central Great Lakes. Lower
level flow will be weak as clear anticyclonic flow is depicted at 850
mb moving across lower Michigan this afternoon which will greatly
limit deep layer shear across southeast Michigan. Dewpoints in the
60s dewpoints into central Lower Michigan will support increasing
instability into the afternoon with models showing MLCAPE values to
around 1000 J/kg closer to the the frontal zone north of I- 69. The
weak lift with a weakly capped unstable environment will support
isolated to scattered showers and thunderstorms during the mid to
late afternoon period today. Convection will be of the weaker pop up
variety given very limited shear. Most activity will be focused
across the Tri-Cities and Thumb, but some isolated showers and
thunderstorms will also be possible down to near the M-59 corridor.

A chance for isolated to scattered showers and thunderstorms exists
on Monday as the aforementioned trough lifts into southern Great
Lakes providing some weak forcing. Diurnal instability builds again
to 1000 J/kg or greater helping to support the isolated thunderstorm
chances during the afternoon. Similar to today, there will be an
lack of deep layer shear bringing a pulse type storm mode again.
Models point towards the best instability and CAPE depth focused
along the glacial ridge up towards the Tri-Cities.

Monday`s shortwave trough eventually gets absorbed into the mean
flow of the Canadian trough and southern stream jet by Tuesday as
another round of height falls drops out of Ontario. Favorable timing
of this shortwave with building diurnal instability will bring
another chance of pop up showers and isolated thunderstorms Tuesday
afternoon. Tuesday will have greater coverage of 20-30% PoPs across
southeast Michigan.

Wednesday will see a stronger trough swing into the Great Lakes and
drive a cold front through southeast Michigan bringing likely
widespread convection. Slight increase in overall flow will increase
wind shear to 30-40 knots and instability will be sufficient with
MLCAPE up to 1000-1500 J/kg. Cooler temperatures aloft will also
increase mid level lapse rates to 6-6.5 C/km. All of this will be
supportive of more organized convection. Lower end PoPs (20%) linger
on Thursday afternoon, but a more progressive wave may bring and end
to PoPs earlier. High pressure builds into the region Friday and
Saturday resulting in dry conditions.

&&

.MARINE...

A weak cold frontal boundary gradually sags through the central
Great Lakes today through Tuesday supporting scattered shower and
thunderstorm chances focused in the afternoon-evening each day.
Winds shift to N-NE behind this front though speeds remain light at
or below 10kts. Wider spread shower/storm chances don`t arrive until
midweek when a trough dives out of Canada into the Great Lakes.

&&

.PREV DISCUSSION...
Issued at 1139 PM EDT Sat Jul 20 2024

AVIATION...

A weak cold front will drop into Se Mi from the north on Sunday. Low
level moisture pooling along this boundary will be supportive of the
development of a broken cu field 4-6k feet by Sun afternoon. Weak to
moderate instability will develop Sunday afternoon within the
moisture pooling along the front, primarily affecting locations from
PTK northward. The overall weak forcing should keep convection
changes late Sun afternoon to 30% or less. The probabilities for
thunderstorms are highest at MBS and will warrant the introduction
of a PROB30 group for late afternoon convection.

For DTW/D21 Convection...Isolated to possibly scattered
thunderstorms are forecast late Sunday afternoon. The chances are
across the northern portions of the airspace in closer proximity to
a frontal boundary.

DTW THRESHOLD PROBABILITIES...

* Low in ceilings aob 5000 feet Sunday afternoon.

* Low in thunderstorms Sunday afternoon and evening.


&&

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

$$

DISCUSSION...AA
MARINE.......KDK
AVIATION.....SC


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