207
FXUS63 KDTX 061956
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
356 PM EDT Mon May 6 2024

.KEY MESSAGES...

- There is a risk for isolated strong to severe storms Tuesday
  evening southwest of a Midland to Port Huron line between 6 PM
  and 11 PM.

- Some gusts to 60 mph are possible with potential for isolated
  large hail to 1 inch in diameter.

- Cannot rule out an isolated weak tornado or two Tuesday evening.

- Mainly dry, breezy, and warmer Wednesday, then cooler again
  Thursday with additional opportunities for showers and
  thunderstorms.

&&

.DISCUSSION...

Ridging with central surface pressure of 1018 mb continues to anchor
the Great Lakes by flanking the northward progression of scattered
showers and storms attributed to troughing over the Ohio Valley.
Locally, expect near seasonable temperatures and dry conditions the
rest of today and tonight with prevailing easterly flow and a
persistent stream of high cirrus.

Expansive closed low occupying the western two-thirds of CONUS
(producing widespread severe convection) retrogrades from the
western Dakotas into eastern Montana Tuesday while the wave broadens
meridionally. This pushes the system`s elongated warm front
northeastward into Lower Michigan with rapid moistening arriving
after 15Z. Mean 850-700 mb layer dewpoints jump from around -30C
early Tuesday morning to +5C after 18Z as the magnitude of water
vapor transport increases sharply with the transition to cyclonic
southwesterly flow. Current analysis depicts a line of convection
extending from the Mid-Mississippi Valley up to the southern
Canadian Prairies, closer to the actual surface low. CAMs highlight
a tendency for decay as storms cross Lake Michigan and interface
with a dry and stable ambient airmass. Most areas remain dry, at
least through 18Z.

Height field adjustments along the eastern periphery of the system
lend some uncertainty to the upstream evolution of convection as a
secondary shortwave emerges and shears into southern Lower. The warm
sector will fully encompass the region by 22Z, as a secondary (and
more robust response) convection response arrives with additional
storms track west to east. Given the slightly later arrival time and
flatter diurnal curve, confidence in SBCAPE has trended lower as the
main instability axis remains better centered over southwest Lower.
All hazards are in-play Tuesday evening for Southeast Michigan given
the +60 knots of 0-6 km bulk shear, southeasterly winds, and pockets
of higher instability as mid-level lapse rates cool. A secondary
surface low emerges as the triple point, and given the current
curvature reflected in forecast hodographs, isolated rotating
structures will be capable of generating some weak mesocyclones,
augmented by the frontal intersections. Cannot rule out a few
isolated weak tornados and some overachieving thunderstorm gusts.
SPC has upgraded the CWA to a Slight Risk near the MI/OH border with
a Marginal risk elsewhere (excluding The Thumb). Storms largely
depart/dissipate by 03Z with increasingly zonal flow aloft.

Warmer and more stable as dewpoints drop into the upper 40s to lower
50s Wednesday with decreasing sky opacity. Well-mixed boundary-layer
supports some decent afternoon gusts in the 25-30 mph range. The
next system crosses through Indiana and Ohio Wednesday with some
additional shower/storms possible for southern Lower. The primary
upper trough then splits again Thursday, taking aim at the Great
Lakes Thursday while the broader longwave jet pattern remains quasi-
stationary. Additional showers and storms are likely with much
cooler temperatures Thursday, related to cold frontal forcing. The
synoptic pattern unlocks Friday as an amplified ridge drops through
the Upper Midwest. Drier weather will be short lived as a trailing
PV anomaly drops into the region Saturday.

&&

.MARINE...

High pressure currently centered over Lake Huron gradually drifts
east into Ontario tonight through the first half of Tuesday
maintaining light easterly flow. Midwestern low pressure lifts a
warm front into the central Great Lakes Tuesday afternoon/evening
bringing widespread showers and thunderstorms with some strong to
severe storms possible over the southern Great Lakes. System`s cold
front quickly follows overnight setting up cooler westerly flow
Wednesday, turning northeasterly Wednesday night. Cooler airmass
combined with a tighter gradient due to secondary low development
over the Ohio Valley supports a moderate uptick in wind strength
Wednesday and Thursday with gusts topping out between 15-25kts each
day. Saginaw Bay could see gusts near 30kts Thursday due to
NE winds channeling down the bay.

&&

.PREV DISCUSSION...
Issued at 203 PM EDT Mon May 6 2024

AVIATION...

VFR conditions will prevail through today and tonight as a surface
high pressure drifts east across Lake Huron into Ontario. This will
bring a light east to northeast wind at 10 knots or less through the
remainder of the afternoon and evening. High clouds will clear out
further this evening leaving mostly clear skies overnight. A warm
frontal zone lifts into lower Michigan tomorrow morning. Increasing
low level moisture will boost lower cloud potential in the morning
and afternoon with a more southeast wind direction.

For DTW/D21 Convection...Chance for thunderstorms increases after
18Z tomorrow.

DTW THRESHOLD PROBABILITIES...

* Medium in cigs aob 5000 feet Tuesday morning, high Tuesday
  afternoon.


&&

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

$$

DISCUSSION...KGK
MARINE.......KDK
AVIATION.....AA


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