321
FXUS63 KDTX 230753
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
353 AM EDT Sun Jun 23 2024

.KEY MESSAGES...

- A cooler and less humid air mass gradually builds into Lower
Michigan today and tonight.

- High temperatures in the upper 70s to lower 80s Monday are right
around normal for mid to late June.

- Showers and thunderstorms become active again during the mid week
period.

&&

.DISCUSSION...

Cold front supported showers and thunderstorms exit eastward this
morning followed by cooler and less humid air for this afternoon. A
considerable cloud component follows the front across Lower MI
lending some confidence to temperature guidance that offers highs
only in the upper 70s most areas except lower 80s metro Detroit to
the Ohio border. Surface Td projections show just a gradual decrease
into the lower 60s but on breezy W-NW wind. The air mass then becomes
more fully exchanged tonight as Td drops into the 50s.

A northern stream mid level circulation and upper level jet max move
from central Canada into the upper Midwest today and across the
northern Great Lakes tonight. Agreement among the latest model runs
is improved on the associated rain pattern grazing the Thumb region
while affecting much of Lake Huron by late evening into the
overnight hours. Mid level moisture is better than adequate judging
by the structure of model 700 mb theta-e fields, and the circulation
strength provides an energetic surge of DCVA to help force the
pattern of showers. Scattered coverage on the west flank of the
moisture pattern looks good until the system exits into Ontario by
sunrise Monday.

Progression of mid level wave structures continues Monday which
brings a short wave ridge into the Great Lakes. The ridge builds
surface high pressure across the region to reinforce a low humidity
air mass. It also offers a higher than average confidence forecast
of dry weather. Guidance projected high temperatures around 80 are
right around normal for mid-late June.

The next Plains low pressure system is close on the heels of Great
Lakes high pressure Monday night into Tuesday. There is a faster
trend in model timing of arrival on the leading warm advection and
associated showers/storms into Lower MI late Monday night into
Tuesday. Onset timing predictability is affected by the larger scale
mid level pattern moving toward a more zonal configuration while
confidence in development of renewed convective activity is higher
than average. The setup looks like a textbook low level jet driven
nocturnal MCS pattern limited by a sharp west to east instability
gradient late Monday night into Tuesday morning. Low pressure
tracking through northern Ontario then pulls the instability axis
into Lower MI for round 2 Tuesday night into early Wednesday.

The cold front trailing the mid week system moves through Lower MI
by Thursday morning followed by a round of high pressure similar to
Monday with the possible exception of less short wave ridging in the
mid levels. This just means zonal flow persists within the larger
scale pattern to keep systems progressive and convectively active
across North America into next weekend.

&&

.MARINE...

A low pressure system over Lake Huron is pulling a cold front across
the Great Lakes this morning. Widespread showers and thunderstorms
will continue early this morning before the surface cold front
passes east of the area later this morning. Winds will flip around
to the north behind the front which will allow the small craft
advisory to come to an end. A secondary cold front will then drop
southward across the region tonight which may touch off a few more
showers and reinforce the northerly winds. Overall wind speeds will
hold below 20 knots as high pressure will be trying to push in from
the west helping to weaken the gradient. High pressure becomes
centered over the region Monday bringing improved conditions but the
next frontal passage comes Tuesday bringing the next chance of
increased southwesterly flow and thunderstorms.

&&

.PREV DISCUSSION...
Issued at 1158 PM EDT Sat Jun 22 2024

AVIATION...

Complex of showers and thunderstorms will track across southeast
Michigan through the early morning hours. While a steady decline in
coverage of thunderstorms will occur with time as instability wanes,
radar trends warrant an inclusion to highlight the potential at all
locations. Trailing area of MVFR stratus with some lingering showers
to accompany the fropa mid-late morning. Enough instability may
exist to allow for an isolated thunderstorm, but coverage to limited
too highlight attm. Daytime heating leaves a broad lower VFR diurnal
cu field, with some widely scattered showers/thunderstorms for
Sunday afternoon. Pre-frontal winds from the south to southwest,
becoming northwesterly and turning modest gusty Sunday afternoon.

For DTW/D21 Convection...Main window for thunderstorm development
centered 07z-09z early Sunday morning. An isolated thunderstorm
possible mid-late morning Sunday with the cold frontal passage and
again with daytime heating late Sunday afternoon, but likelihood of
occurrence remains very low.

DTW THRESHOLD PROBABILITIES...

* Moderate for thunderstorms late tonight. Low Sunday.

* High for ceilings aob 5kft Sunday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.

Lake Huron...Small Craft Advisory until 10 AM EDT this morning for LHZ421-422.

Lake St Clair...None.

Michigan waters of Lake Erie...None.

&&

$$

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


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.