326
FXUS63 KDTX 222322
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
722 PM EDT Wed May 22 2024

.KEY MESSAGES...

- Windy conditions subside this evening but become breezy again
Thursday to around 20 mph.

- A brief warm-up is expected Friday with a 50 to 70% chance for
showers and storms late Friday into early Saturday.

- Slightly cooler conditions early next week with additional showers
and storms likely late Sunday into Monday.

&&

.AVIATION...

A significant spoke of absolute vorticity will push across the
forecast area between 00-04Z. The combination of daytime heating and
synoptic forcing for lift has result in a fair amount of boundary
layer cumulus across much of the northern forecast area. Subsidence
in the wake of the shortwave and loss of daytime heating will cause
much of the cumulus to dissipate this evening. A relatively neutral
temperature advection this evening with increasing confluent flow
aloft should result in low sky fraction the duration of tonight. A
cooler and drier morning is expected to result in a slow development
of boundary layer cumulus late Thursday morning.

DTW THRESHOLD PROBABILITIES...

*  None

&&

.PREV DISCUSSION...
Issued at 346 PM EDT Wed May 22 2024

DISCUSSION...

Stacked low pressure just north of Lake Superior is sending a cold
front across the region this afternoon. The cumulus field noted
ahead of the front (now positioned from Bad Axe to Adrian) continues
to exhibit very little vertical development, indicating the lack of
low-level convergence and upper support as well as modest capping
are sufficient to suppress convection despite 1000+ J/kg MLCAPE
analyzed across the region. Deep mixing and a tight pressure
gradient associated with the low are responsible for gusts in the 30
to 40 mph range. The windy conditions will subside with the loss of
daytime heating, but remain breezy to around 15 to 25 mph this
evening. Surface dew points settling into the lower 50s behind the
front will bring a noticeable improvement in humidity over the next
few hours.

With a much drier column settling in, precipitation-free conditions
are forecast this evening into tonight. An area of PV advection and
modest height falls tied to the mid-level low over central Ontario
will pass over the state late this evening but with little
consequence other than a reinforcing shot of cooler air. 850mb temps
settle to near 8 to 9 C, down from the 14.4 C observed in the 12z
DTX RAOB. This sets the stage for Thursday AM lows to fall to the
mid to upper 50s under mostly clear skies. Daytime Thursday will be
spent positioned between the Ontario low moving over James Bay and
high pressure building in across the Ohio Valley. This keeps a light
southwest breeze going but with wind speeds much lower than today -
around 10 to 20 mph. The relatively cooler air mass will have short
residence time with near full late May sun helping boost temps into
the around 80, still on the high side of the seasonal norm.

The Canadian low sends one more lobe of vorticity across the
northern Great Lakes Thursday night, pushing a shallow cold front
across Lake Huron and possibly into the Thumb/Tri-Cities Friday
morning. This will encounter a still very dry environment with PWATs
near or below 0.50 inches, so not expecting more than a northeast
wind shift with this feature. The next low emerges over the northern
High Plains Thursday night, quickly deepening on Friday as it lifts
northeast across the Dakotas. This squeezes a shortwave ridge over
the Great Lakes and maintains the dry conditions through most of the
day. The ridge axis passes overhead by late afternoon with
developing southwest wind quickly advecting in a wedge of higher
theta-e. Convective trends for Friday evening/night are unclear at
this stage and will be reliant on how upstream activity gets going
along the warm front. For now it appears the best chances for
showers/storms arrive after midnight when the better height
falls/synoptic forcing align with deeper moisture.

Saturday shows a decreasing precip trend through the day after a
cold front clears the area from west to east. High pressure fills in
behind this system to keep late Saturday into early Sunday dry and
seasonable. A deeper low then ejects out of the Plains late Sunday
into Monday, bringing a high likelihood for showers and storms.
Still some timing specificity to work out with this system, but if
12z model trends hold it looks like the more widespread rain may
occur overnight Sunday night into early Monday morning before a dry
slot brings more of a scattered coverage for the Memorial Day
holiday. This system will usher in a cooler air mass for early next
week with highs in the 70s likely.

MARINE...

A strengthening low pressure system will stall over Ontario today
offering a stronger gradient wind. The systems`s cold front has
moved through resulting in breezy westerly flow for most of the
Central Great Lakes. Mainly dry conditions are expected the rest of
today with winds and waves over Saginaw Bay dropping below Small
Craft Advisory criteria late this evening. Winds flip to the east
over the weekend and remain rather as a surface ridge builds in
across the eastern Plains, expanding into Michigan as the day
progresses. Another wave ejects across the Mid-Mississippi Valley
and into the Ohio Valley Sunday, but most of the showers/storms
should remain to the south with favorable marine conditions through
the period.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422-
     441.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....CB
DISCUSSION...TF
MARINE.......KGK


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