630
FXUS63 KDTX 170724
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
324 AM EDT Fri May 17 2024

.KEY MESSAGES...

- Scattered to numerous showers with some isolated thunderstorms will
  continue this morning, exiting east of the state by the late
  morning hours.

- There is a chance (40-45%) for renewed shower and thunderstorm
development this afternoon and evening. Highly localized wind gusts
around 45-50 mph will be possible with any stronger thunderstorms

- Very warm this weekend through early next week. Increased chances
for thunderstorms Tuesday into Wednesday next week.

&&

.DISCUSSION...

A plume of enhanced deep layer moisture (PW values between 1.15 to
1.35") continues to build in across SE MI through the morning hours
downstream of an upper-level trough, which will maintain scattered
to numerous showers this morning, generally outside of the Tri-
Cities. Some rumbles of thunder remain possible given the modest
mid-level lapse rates and elevated instability.

Surface instability will then quickly build in by the late morning
hours in the wake of the trough, fueled by diurnally heating. A
surface boundary is expected to stall out across SE MI this
afternoon, extending from around Bad Axe to Adrian (or slightly
east), which will capitalize on the building instability and will be
the focal point for renewed showers and thunderstorm activity. The
kinematics are extremely poor for sustained thunderstorm activity
with weak 1- 3/1-6km shear, thus convective mode will be for pulse
thunderstorms. However, very steep 0-3 km lapse rates near 9C/km and
DCAPE values to 800 J/kg do support the potential for highly
localized wind gusts up to 45-50 mph with thunderstorm development.
This is further supported by the large amount of dry air located with
the mid to upper-levels of the atmosphere which can be entrained to
enhance evaporative cooling...But on the contrary, this can also be a
negative factor which may inhibit convective cloud depths. Sub-
severe hail will also be possible given the favorable dry mid-
levels. Expansion of shower and thunderstorms east of the initial
surface convergence boundary will be possible with the very slow
meandering of the boundary and along outflows. Convective coverage
and intensity will wane after sunset with the loss of instability.
Timing for this shower and thunderstorm activity will be favored
between 17Z to 01Z Sat (1 PM EDT - 9 PM EDT). Considering this
morning`s activity and additional chances this afternoon, the very
light boundary layer winds and clear cloud trends overnight could
afford areas of fog through tomorrow morning.

Multiple upper-level waves are expected to build in across the
northern Plains through the weekend and into early next week while a
secondary upper-level trough builds in through the Tennessee Valley.
This will enhance shortwave ridging across the Great Lakes and will
pool in warm air from the continental SW into Michigan,
characterized by h850 values between 14-16C. This brings high
confidence to see increasing temperature trends leading into early
next week, with temperature highs firmly breaking 80 degrees by
Sunday. This setup will also bring limited chances for precipitation
through early next week given weak synoptic forcing. A slight chance
(<15%) for diurnally fueled showers will hold for Saturday, but weak
instability and poor shear makes this unlikely. An additional low
end (15%) chance holds Sunday evening and again Monday afternoon and
evening as shortwaves ripples through.

The higher confidence rain/thunderstorm setup will enter within the
Tuesday-Wednesday time frame once a stronger upper-level trough
builds in across the pacific west, which will help usher in much
better moisture downstream across the Midwest and Great Lakes. A
potent mid-level wave derived around Baja California is also
projected to path near the Texas Panhandle which will strengthen a
weak surface low and drive it northeast into the western Midwest or
up towards the northern Great Lakes. Still being out many days from
this, there is uncertainty regarding potential phasing of these two
systems, however, at this time there is excellent agreement between
the EPS and NAEFS regarding cyclone location holding over or
northwest of the cwa, bringing moderate confidence for a more active
period by the midweek. The eventually passage of the low pressure
system will draw a cold front across the state, bringing cooler
temperatures by the mid to late week (most likely Wed-Thu period).

&&

.MARINE...

Scattered to numerous showers with embedded thunderstorms will cross
the central Great Lakes this morning as a weakening frontal boundary
works eastward through the region. Isolated showers/storms may
persist into this evening but the bulk of the activity is likely to
occur before noon. Winds will remain light, generally 10 knots or
less, and predominantly from the south or southeast before backing
to the east tonight as weak high pressure builds in. Fog, possibly
dense at times, will be possible Saturday given the lighter winds and
elevated surface moisture. Light winds and mainly dry conditions
persist through the weekend with a weak cold front moving through on
Sunday possibly bringing some more showers. Potential for more
unsettled conditions Monday night into Tuesday as a stronger
disturbance tracks into the vicinity. This system will likely bring
slightly stronger southerly winds as well as showers and
thunderstorms.

&&

.PREV DISCUSSION...
Issued at 1139 PM EDT Thu May 16 2024

AVIATION...

Increasing lower VFR cigs in the 5-10kft range will occur into the
overnight with eventual scattered showers (and possibly an isolated
thunderstorm or two) late tonight into early Friday morning. By
Friday morning, MVFR cigs will be more likely even as showers move
east of the region. Additional showers/isolated thunderstorms will
be possible late in the day as well (20z-02z). Light southeast to
south flow will veer to southwest Friday and then become light and
variable Friday night.

For DTW/D21 Convection... An isolated thunderstorm is possible
within a broader area of showers late tonight. The storms will be
elevated and weak but capable of a brief lower visibility downpour
through Friday morning. A second window for a thunderstorm or two
will occur 21z-01z Friday afternoon/evening. Again, locally heavy
downpours will be the main concern (and the exception).

DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling 5000 ft or less late tonight and Friday
  morning.

* Low for thunderstorms late tonight into early Friday morning and
  then again by late Friday afternoon/early evening.


&&

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

$$

DISCUSSION...AM
MARINE.......TF
AVIATION.....DG


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