623
FXUS63 KDTX 131058
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
658 AM EDT Sat Jul 13 2024

.KEY MESSAGES...

- There will be several windows for thunderstorms Sunday through
Tuesday. Severe weather and heavy rainfall will be possible with
these systems but with relatively low confidence on timing and
location.

- A period of hot and humid conditions is forecasted for Sunday and
Monday with temperatures reaching near 90 and heat index in the mid
90s.

- Cooler and drier weather will move in Wednesday through the rest
of the week.

&&

.AVIATION...

Today starts out with weak high pressure in control across the Great
Lakes resulting in clear sky and calm wind. This is allowing some
expansion of shallow fog around SE MI leading up to sunrise, however
trends in satellite imagery and in surface observations support the
shallow nature of the fog and expectations of rapid dissipation
during early morning. A generous scattered coverage of cumulus
follows as daytime heating builds this afternoon accompanied by
light wind gaining traction from the south into this evening. Any
brief ceiling would be above 5000 ft.

Favorable aviation conditions today and for most of tonight give way
to the influence of showers and thunderstorms toward sunrise Sunday.
Upstream trends will be monitored today for refinement of timing and
locations possibly affected by stronger thunderstorm activity with
at least a pattern of showers expected to survive into Lower MI.
MVFR restriction is likely even if showers/storms are on a weakening
trend upon entering the SE MI terminal corridor through Sunday
morning.

For DTW/D21 Convection... No thunderstorms today and this evening.
Storms across the upper Midwest today then have a chance to survive
into SE MI/D21/DTW late tonight through Sunday morning.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less this afternoon.

* Low for thunderstorms toward sunrise Sunday.

&&

.PREV DISCUSSION...
Issued at 345 AM EDT Sat Jul 13 2024

DISCUSSION...

Quiet weather today before multiple chances of showers and
thunderstorms enter the forecast starting Sunday morning. Hot and
muggy today as temperatures climb into the mid/upper 80s with
dewpoints in the mid 60s. This will lead to heat indices close to 90
this afternoon.

On Sunday the weather begins to get more active. A persistent strong
ridge centered over the SW conus will hold as a series of weak
shortwave troughs ripple through the nearly zonal mid level flow
with the jet located up along the international border. The first
trough will arrive on Sunday with all models pointing to some kind
of convective complex developing upstream over MN/WI then tracking
east into the Great Lakes Sunday morning. Plenty of different
flavors to the CAMS as to where to track this complex. Synoptic
features of note will be the strong piece of vorticity pivoting NE
through the northern Lakes while the better low level jet resides
well south over IA into IL which is positioned over the area of
strong instability so one would think the complex would turn SE
along the instability gradient with fuel from the LLJ. There is a
strong theta e gradient pushing east across the area early Sunday
afternoon though. So even if the complex can skirt us to the west
through SW MI and N IN, we could see convective development along
this strong gradient with around 20 knots of shear locally and
roughly 1500 J/kg of CAPE. So a couple scenarios that could play out
Sunday. SPC stretched the Marginal Risk area across southern MI to
account for the morning complex possibly sustaining itself across the
area. This would bring the risk of strong wind gusts and hail. Heavy
rain will also be possible once again owning to PWATS approaching 2
inches and dewpoints back up into the 70s. Temperatures will make a
run at 90 as the heat plume to the west gets forced into the Great
Lakes. This of course will depend on cloud cover through the
afternoon.

Monday will be another hot and humid day with 850mb temps still
hovering around 20C and dewpoints still in the 70s. Models are
starting to key in on little better defined mid level wave that
would track across southern MI through the day Monday. This would
provide a good focus for convection chances through the afternoon.
It is a fairly compact system so any deviation in track would change
chances quite a bit for any one location.

Little better setup on Tuesday with some well defined synoptic
features to key on. A stronger vort max rotating through the broader
Canadian trough will sweep by the northern Great Lakes with the nose
of a strengthening upper level jet feeding into it. This will all
help force a cold front across the area with a chance of
thunderstorms along it. This system will be strong enough to
displace the resident hot and humid airmass and allow a cooler
Canadian high pressure system to build into the region for the end
of the week. High will be in the 70s to around 80 with lows in the
50s to near 60.

MARINE...

High pressure migrates further east today while a secondary (and
more diffuse) ridge lifts toward the Tri-State area offering
continued weak gradient flow and gusts AOB 15 knots. Marginal Small
Craft Advisory conditions will be possible Sunday afternoon as flow
shifts southwesterly over Saginaw Bay and peak gusts approach 25
knots. Broader coverage of showers/storms to follow Sunday and
Monday with the arrival of a warm front and approaching upper level
trough from the west. Stronger storms are possible both days which
could pose a heightened risk for locally higher winds/waves and some
hail.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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


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