131
FXUS63 KDTX 021946
AFDDTX

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

.KEY MESSAGES...

- There is a chance of showers and a few thunderstorms late 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 heavy 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.

&&

.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.

&&

.PREV DISCUSSION...
Issued at 208 PM EDT Thu May 2 2024

AVIATION...

VFR conditions will persist throughout the afternoon and evening
hours with an amplifying ridge overhead and anticyclonic
trajectories. Any lake breeze response will remain muted with a
prevailing southeast wind direction this afternoon already in
advance of the mesoscale forcing. A deep potential vorticity lobe
will pivot across northern Minnesota this evening and tonight
driving a narrowing axis meridional moisture transport across
Southeast Michigan Friday. Precipitation chances begin to increase
after 09Z Friday as southern stream/mississippi River Valley
moisture does lift northward and streamlines immediately in advance
of the northern tier trough. Two specific time windows of concern at
the Detroit terminals, a quick chance for elevated shower activity
between 09-11Z and the potential for some shower/tstorms developing
along a weak cold front Friday afternoon. Confidence in coverage and
occurrence is lower Friday afternoon and did account by a Prob30.

For DTW/D21 Convection...Shower activity is expected to lift
northward out of northern Ohio between 09-11Z Friday with a low
potential for thunderstorms. Additional shower activity with
thunderstorms will develop over portions of Southeast Michigan after
19Z. Low confidence in occurrence at Metro as activity could remain
north and west. Strong to severe thunderstorms are not anticipated
Friday.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms tonight and Friday


&&

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

$$

DISCUSSION...MV
MARINE.......DRK
AVIATION.....CB


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