432
FXUS63 KDTX 030137
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
937 PM EDT Thu May 2 2024

.KEY MESSAGES...

- There is a chance of showers and a few thunderstorms tonight
  through Friday morning and again Friday afternoon as a cold front
  tracks across SE Michigan.

- Severe weather is not expected on Friday, although thunderstorms
  will be capable of downpours, lightning, and isolated wind gusts
  to 40 mph. Storm motion will be southwest to northeast at 40 mph.

- High pressure fills in briefly on Saturday offering drier weather
  ahead of the next cold front that tracks through SE Michigan early
  Sunday morning.

- Seasonably warm temperatures expected through early next week with
  high temperatures in the 70s and lows in the 50s.

&&

.UPDATE...

Convective trends are the subject of the update this evening as
activity to the south and west shows some staying power after
sunset. The surface warm front is still south of the Michigan border
and was the focus for strong thunderstorms during peak afternoon
instability. Intensity has since diminished while coverage shows
signs of near surface to slightly elevated redevelopment responding
to quick veering of flow to SW by the 850 mb level. Upstream radar
derived VWP`s support model depictions of relatively weak 20-25 kt
flow that has proven adequate to improve the moisture and lapse rate
profile at least up to the I-75 corridor judging by the 00Z DTX
sounding. There is still some uncertainty on intensity and longevity
with northward extent until later tonight when current trends add
some confidence to expectations for the survival of upstream IL to
mid MS valley activity into Lower Mi as nocturnal moisture transport
and elevated instability peak toward sunrise. The evening update
will make an incremental increase in POPs from south to north this
evening becoming borderline numerous across SE Mi late tonight and
Friday morning.

&&

.PREV DISCUSSION...
Issued at 703 PM EDT Thu May 2 2024

AVIATION...

Broken coverage of VFR mid level clouds across much of Lower Mi are
part of a well defined warm frontal system with a surface position
across northern IL/IN/OH this evening. The surface front is
providing moisture and a focus for a cluster of thunderstorms
strongly dependent on afternoon instability which is expected to
fade with sunset. The evening activity will be monitored for
northward extent while a renewed chance for elevated showers and
embedded storms improves across the SE Mi terminal corridor later
tonight. The surface warm front moves slowly into southern Lower Mi
late tonight and Friday morning with little to no ceiling
restriction and visibility restriction limited to a few heavier
showers or isolated storms. Greater coverage of MVFR ceiling arrives
with the trailing cold front set to move through SE Mi Friday
afternoon. The front also provides a focus for a more organized
pattern of showers with a chance of thunderstorms until exiting
eastward by Friday evening.

For DTW/D21 Convection... Thunderstorms in progress in northern IN
and western OH are expected to fade with the loss of daytime
instability. This trend will be monitored for any stray remnant that
could approach DTW mid to late evening. Otherwise, showers increase
coverage over a greater portion of southern Lower Mi after midnight
through Friday morning with an isolated/elevated storm possible. A
renewed time window for thunderstorms then occurs Friday afternoon
as a cold front moves through the region. Scattered coverage occurs
among numerous showers along the front, although strong to severe
storms are not expected.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms tonight and Friday.

* Moderate for ceiling 5000 ft or less Friday.

PREV DISCUSSION...
Issued at 346 PM EDT Thu May 2 2024

DISCUSSION...

Another seasonably warm day has ensued across SE MI today, with
temperatures for most inland locations peaking in the low 70s.
Elevated portions of the inbound warm front already starting to
bring a band of convectively enhanced cloud cover into western lower
MI at issuance, with expanding cloud cover expected through the
evening. Very dry low levels, denoted by T/Td spreads of 20+
degrees, confirm that present radar echoes are just virga so will
hold on to a dry forecast through the evening.

In typical warm advection fashion, precipitation chances increase
with the arrival of the low level moisture axis late tonight.
Leading wave of low level moisture advection is tied to a
convectively enhanced shortwave that lifts into lower MI after 06z
(2am local) tonight, but initial attempts at low level saturation
will struggle to overcome the dry resident airmass (12z DTX RAOB
observed PWAT of 0.62" this morning). Can already see this struggle
ongoing over northern IN/OH (per GOES-16 visible imagery) where a
sharp gradient in the cumulus field is observed. Nonetheless, broad
isentropic ascent and weak instability aloft (HREF ensemble mean
MUCAPE up to 500 J/kg) should assist the saturation process to allow
increasing coverage of showers and potentially a few thunderstorms
Friday morning. Best coverage will likely be across the Tri Cities,
as the SW-NE orientation of an incoming cold front pushes a narrow
corridor of moisture into SW lower Michigan and the northwest
portions of the cwa during the morning hours. The cold front will
then drift eastward throughout the day, becoming a renewed albeit
weakening forcing mechanism for surface-based convection to develop
Friday afternoon. Even in the absence of showers/storms, the deep
column moisture will support a cloudy day across lower MI.

Did reduce forecast high temperatures on Friday by several degrees,
owing to the increased potential for cloud cover and shower activity
to interfere with diurnal heating. Still, 850mb temperatures around
10-12 C are indicative of a seasonably warm airmass which will still
support daytime highs Friday in the low 70s. These cooler boundary
layer conditions, combined with mid level lapse rates below 6 C/km
will keep MLCAPE prospects around 500 J/kg. With the front extending
well ahead of the more dynamic parent system (over MN/WI), there
will be a notable absence of upper jet forcing and mid/upper level
flow. So while thunderstorms may develop along the fropa Friday
afternoon, environmental conditions will not be favorable for storm
organization/longevity, so severe weather is not expected.

The front will have little impact on thermal profiles heading into
the weekend, as the boundary will be stretched and eventually wash
out as its parent system stalls again, this time over Hudson Bay.
This results in an extended period of above normal temperatures,
with highs comfortably in the 70s and lows in the 50s through early
next week. Mid-level ridging pattern generally holds steady through
early week, with dry weather expected Saturday ahead of another cold
front Sunday morning. Strongest signal for a pattern shift holds off
until middle of next week when a strong Pacific low tracks across
CONUS, bringing the next meaningful window for precipitation.

MARINE...

High pressure over Lake Huron is resulting in light and variable
flow this afternoon, but an approaching warm front to the southwest
will help flow to become more easterly, but remain below 20 knots,
for tonight. A low pressure system will then track through the
northern Great Lakes on Friday pulling the warm front up through the
region early in the day. This will allow winds to flip around to the
south-southwest which will bring in a warmer airmass, helping to
keep gusts down. Scattered showers and thunderstorms will occur
Friday morning across the area on the warm front with continued
activity later in the day along the cold front. Shower chances carry
through Friday night. High pressure brings quieter weather on
Saturday with another cold front coming on Sunday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.

&&

$$

UPDATE.......BT
AVIATION.....BT
DISCUSSION...MV
MARINE.......DRK


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