535
FXUS63 KDTX 270343
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1143 PM EDT Fri Apr 26 2024

.KEY MESSAGES...


- Showers arrive this evening with a chance for a few embedded
  thunderstorms starting late tonight.

- Southwest winds gusting around 35 mph Saturday afternoon north of
  Metro Detroit.

- Some additional thunderstorms are possible Saturday evening with
  an isolated severe storm possible northwest of Metro Detroit.

- Additional showers and a few storms are possible Sunday as above
  normal temperatures continue through mid-week.

&&

.AVIATION...

Several inbound short wave impulses along with increasing low level
southwest flow along an advancing warm front will drive another
round of showers across Se Mi late tonight into Saturday morning.
This will also be accompanied by weak elevated instability, enough
to suggest a 20 to 30 percent chance of a thunderstorm embedded
within the broader region of showers. Moistening in the low levels
will also support high probabilities for MVFR based ceilings. The
warm front will lift northeast of the terminals late Sat morning as
associated surface low pressure approaches western Upper Michigan.
This will drive the warm sector into Se Mi. Deepening of the daytime
mixed layer and the strengthening SSW wind fields will push wind
gusts up to or over 25 knots at times during the afternoon Saturday.
Late day convection on Saturday/Saturday evening is forecast to
initiate across northern and central Lower Mi.

For DTW/D21 Convection...Numerous showers are expected to move into
and redevelop across the airspace overnight and last into late
Saturday morning. Recent model guidance remains lean on the amount
of available instability, so only isolated thunderstorms are
expected across the airspace, primarily between 09Z and 13Z.

DTW THRESHOLD PROBABILITIES...

* Low in thunderstorms tonight into early Saturday morning.

* High in ceilings aob 5000 feet tonight into Saturday afternoon.

&&

.PREV DISCUSSION...
Issued at Issued by National Weather Service Grand Rapids MI

DISCUSSION...

Main changes to this forecast was to increase wind gusts Saturday
afternoon primarily north of Metro Detroit. The other was to maintain
dewpoints/relative humidities below guidance overnight into early
Saturday. Still expect rain to reach southeast Lower MI region chiefly
after 8 PM. However, the antecedent lower troposphere is
exceptionally dry and it should take longer than usual to rebound in
spite of robust lower to mid level tropospheric pressure/moisture
advection associated with isentropic ascent. In fact, Metro Detroit
may not even experience accumulating rainfall until after 11 PM.

In terms of thunder prospects, it appears that MUCAPE for the
Metro area rapidly increases towards noon Saturday with a slightly
earlier onset and larger instability magnitude farther northwest
towards the Tri-Cities region. SPC reasoning for the Marginal Risk
area northwest of Metro Detroit has not changed much and the
interested reader is encouraged to check out the latest SWODY2
outlook for additional details.

Additional showers and storms are likely Sunday into Monday
associated with forcing from an upper-level jet streak and aided by
a frontal boundary sitting across northern Michigan and a shortwave
from the parent trough ejecting through the region. Convection will
be favored across Central Lower for our CWA closer to the warm
frontal boundary, with MUCAPE values north of 500 J/kg suggesting
there will be an attendant thunder risk. SPC currently has the region
in general thunder which is reasonable given that the favored region
instability is separated from deep later shear and the highest
likelihood of showers/storms.

Widespread showers then expand into the remainder of the CWA Sunday
night and continue into early Tuesday as a cold front drifts across
the area. MUCAPE suggest thunder chances continue. By Monday night
accumulated rainfall looks to range from a quarter of an inch around
Metro Detroit to around an inch west of Saginaw Bay. Additional
amounts after this into the remainder of Tuesday look negligible.

Dry conditions then take over late Tuesday into Tuesday night as a
high pressure system quickly pushes through the area. Conditions then
become more active Wednesday as we see a cold front driven through
Lower Michigan by a northern stream shortwave followed by additional
rain chances into Thursday as a surface low ejects north into the
upper Ohio Valley.

Temperature wise, highs in the 70s are expected to continue into mid
week. By late week, expect highs to fall back to near normal in the
60s as a thermal trough slides into the central Great Lakes.

MARINE...

Strong low pressure moves from the central Plains to the upper
Midwest tonight and then across Lake Superior on Saturday. The
strengthening pressure gradient ahead of this system results in
southeasterly flow ramping up tonight, peaking late tonight into
Saturday morning. Wind veers southerly on Saturday with gusts
touching gale force during the morning before gradually weakening
through the day as much warmer air moves into the region to
stabilize flow over the cold lake water. The warm air also fuels
thunderstorm potential Saturday through Sunday as the associated
cold front stalls over the region. The front awaits yet another low
pressure system moving in from the Plains Sunday into Monday.
Outside of the brief window Saturday morning, winds are expected to
remain below gale force.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 PM EDT Saturday for LHZ421-422-441>443.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....SC
DISCUSSION...TJT
MARINE.......DBT


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