316
FXUS63 KDTX 041841
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
241 PM EDT Sat May 4 2024

.KEY MESSAGES...

- Scattered showers and possible non-severe thunderstorms this
evening through Sunday morning.

- High pressure builds in latter half of Sunday through Monday
bringing drier conditions and closer to average temperatures.

- Developing low pressure over the Midwest brings widespread shower
and thunderstorm chances Tuesday into Wednesday.

&&

.DISCUSSION...

Southeasterly lower level flow has developed this afternoon in
response to a weak cold front gradually sagging into the western
Great Lakes. This wind shift supports modest moisture advection from
Ohio, where dewpoints are holding in the mid 60s, nudging local Td`s
into the low 60s late this afternoon-evening. Even with this extra
moisture, both SB/MLCAPEs are expected to stay fairly meager,
holding closer to 500 J/kg. Forecast soundings advertise an uncapped
environment with weak column winds (<20kts thru 500mb) which
supports scattered pop-up showers and perhaps a thunderstorm into
early tonight as height falls move in from the west and a diffuse PV
anomaly lifts NE over far northwestern Ohio. Surface cold front
crosses the area Sunday morning offering another window for
scattered showers, particularly along/north of I-69 owing to closer
proximity to parent shortwave which offers slightly better upper
support/forcing compared to locales further south.

Marginally cooler airmass fallows the frontal passage as 850mb temps
drop to around 4-5C keeping highs Monday in the upper 60s to around
70 for most areas. Easterly flow beneath the surface high that will
be centered over northern lower MI by this point keeps areas
downwind of the lakes like Monroe and especially the Thumb cooler-
upper 50s to lower 60s favored.

Upper ridging and associated surface high are shunted east by early
Tuesday as a potent mid-upper wave ejects out of the Rockies into
the northern Plains. A secondary surface low is progged to develop
over the upper Midwest along the original, now stacked, low`s triple
point. This system lifts a warm front into southern lower MI over
the course of Tuesday bringing the area`s next appreciable chances
for showers and thunderstorms. The attendant cold front quickly
follows Tuesday night generating additional widespread showers and
storms. Worth noting that longer range solutions suggest a ~40kt LLJ
could work into the area from west MI setting up a higher shear
environment with severe potential dependant on how much
destabilization occurs once the warm sector fully expands of the
area. SE MI resides on the edge of SPC`s Day 4 15% severe weather
outlook so will be something to keep on eye on as we get closer.

&&

.MARINE...

An elongated area of low pressure over Wisconsin/Illinois this
afternoon tracks east into the central Great Lakes tonight, pulling
a warm front north ahead of it. This will result in an increasing
coverage of showers as well as modest southeasterly winds tonight.
There will be a slight chance of thunderstorms but severe weather is
not expected. A cold front follows on Sunday morning with continued
shower/t-storm chances and a shift to northwest wind of around 15 to
20 knots as conditions dry out for the afternoon. High pressure then
builds in to bring quiet marine conditions for Monday and much of
Tuesday. The next round of likely precip arrives late Tuesday as a
warm front moves into the area. This marks the beginning of a more
active period through the rest of the week with several disturbances
working through.

&&

.PREV DISCUSSION...
Issued at 102 PM EDT Sat May 4 2024

AVIATION...

Moisture will increase from south to north again this afternoon and
evening as mid level wave ejects into the general area in advance of
approaching frontal system. Expect a trend from lower VFR back to
MVFR with a few showers possible with this moisture especially into
evening. IFR/lower MVFR stratus still looks likely overnight as the
moist southerly flow persists before frontal passage early Sunday
morning. While this front looks pretty dry, a few showers will be
possible with its passage. Ceilings will slowly erode/lift within
west to northwest flow in its wake on Sunday (especially by aft).

For DTW/D21 Convection...Southeasterly winds today will drive weak
instability across the airspace after 21Z. Isolated thunderstorms
are possible within this environment. Forecast probabilities suggest
a 20 percent chance across the southern portions of the airspace.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms late this afternoon into tonight.

* Moderate for ceilings aob 5000 feet this afternoon, high by
  the overnight period into Sunday morning.


&&

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

$$

DISCUSSION...KDK
MARINE.......TF
AVIATION.....DG


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