-- Discussion containing changed information from previous version are highlighted. --
306
FXUS63 KDTX 240801
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
401 AM EDT Fri May 24 2024

.KEY MESSAGES...

-- Changed Discussion --
- Showers and thunderstorms move in tonight largely after midnight
(60-70%) and continue into Saturday morning.

- Dry weather returns Saturday afternoon through Sunday morning.

- Showers are likely again with a chance of thunderstorms Sunday
afternoon and Sunday night.

- The Memorial Day outlook calls for cool temperatures with showers
likely Monday and Monday night.
-- End Changed Discussion --

&&

.DISCUSSION...

-- Changed Discussion --
Longwave pattern remains fairly flat and progressive leading to
multiple chances for showers and thunderstorms over the next few
days. This pattern also has, and will, lead to more active weather
upstream over WI as the main drivers continue to reside north and
west of lower MI with only remnants advecting over us. Shortwave
ridging and surface high pressure locally will also add stability to
the environment further hurting chances for stronger storms.

For today, shortwave ridge will be amplifying downstream of the next
compact but strong mid level trough working across the northern
Plains. Increasing heights and southerly flow will help temps return
to the low 80s. Dry airmass will help keep skies pretty clear until
later this afternoon when cloud debris from upstream starts working
into the region. Models have been pretty consistent with curling
this next mid level trough northeastward from the northern Plains
into western Manitoba tonight while developing a strong complex of
storms over the Midwest. The occluded front will extent SE through
the Great Lakes with enough residual low level jet energy and a
final punch of 500mb jet flow lifting northward that hires models
try to spin up a surface low along the occlusion that will pass
through lower MI. Any upstream convection will have a very stable
profile to work through while forcing wanes but moisture will be
ample with PWATS around 1.25 inches, and some elevated CAPE around
500 J/kg and 30 knots of shear so expectations are for a portion of
the upstream convective cluster to pass through SE MI roughly 06-
12Z. The SPC Day 2 Marginal Risk area clipped a portion of SE MI
east of a line from Bad Axe to Monroe based on this and a frontal
passage around 12-15Z. Thinking more general thunderstorms would be
the norm with only an isolated storm possibly getting to severe
limits. Saturday will dry out quickly behind the front as drier air
and surface high pressure builds across the area. Low amplitude,
nearly zonal, flow aloft keeps some degree of warm air around so
expect afternoon highs in the mid/upper 70s.

Attention then turns to the next wave passing through the zonal flow
up toward the Midwest/Great Lakes. This system has origins further
south than the previous few which looks to let it get farther east
near Lake MI before doing the curl northward. A compact mid level
wave and strong 990mb surface low will bring widespread showers and
thunderstorms to the region Sunday evening as the warm front
attempts to lift into southern MI, and then continuing over night as
the cold front pulls through. Severe weather chances will be
dictated by how far north the occlusion/triple point reaches.
Current guidance has it reaching as far north as I69. SPC again has
a portion of the area, south of I69, in Marginal Risk keying in on
these main features.

Memorial Day looks cloudy and cooler as cold air filters in behind
the passing system and 850mb temps drop into the single digits.
Highs may struggle to hit 70 in some locations further hampered by
the cloud cover. There is potential for cold core showers with the
wrap around moisture as the system pulls away. Longwave trough then
sets up shop over the region for the week keeping temps cooler with
highs in the 60s during the mid week and lows down in the upper 40s.
-- End Changed Discussion --

&&

.MARINE...

-- Changed Discussion --
An upper level ridge works across the Great Lakes today offering dry
and stable conditions as surface high pressure builds in between a
low over Quebec and a deeper low over the Upper Midwest. Light and
variable gradient winds take on an easterly trajectory with time
while a strengthening low-level subsidence inversion limits gust
potential. A shortwave feature shearing off the Upper Midwest wave
makes eastward progress Friday night into Saturday as a secondary
surface low develops along the primary system`s cold front. This
presents an opportunity for thunderstorm development and locally
higher winds/waves. Storms peak in coverage Saturday morning, but
most of the stronger dynamics will depart before thermodynamic
profiles become more favorable for mechanical mixing processes. An
occluded low then tracks across Wisconsin and into The UP Sunday
night and Monday which drags an energetic LLJ across the waterways.
Some potential exists for Small Craft Advisories marked by gusts
approaching 30 knots.
-- End Changed Discussion --

&&

.PREV DISCUSSION...
-- Changed Discussion --
Issued at 1201 AM EDT Fri May 24 2024

AVIATION...

Upper level confluence this evening will give way to geopotential
height rises Friday as mid to upper level ridging builds over Lower
Michigan. Forecast soundings show at least two distinct rounds of
active subsidence during the next 24 hours. Satellite trends show
that altocumulus/altostratus convective debris cloud has dissipated
on its trip into Southeast Michigan. Significant moisture advection
is forecasted to hold off until Friday night across Southeast
Michigan. Did introduce VFR ceiling of mid and high cloud Friday
evening. Low confidence exists on timing Friday evening regarding
preexising upstream convection arriving at the taf sites.

DTW THRESHOLD PROBABILITIES...

*  None
-- End Changed Discussion --


&&

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

$$

DISCUSSION...DRK
MARINE.......KGK
AVIATION.....CB


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