Lima Center, Michigan Weather Forecast Discussion

942
FXUS63 KDTX 200732
AFDDTX
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
332 AM EDT Sat Sep 20 2025
.KEY MESSAGES...
- Mainly dry today, with increasing chances for showers overnight.
- Scattered to numerous showers expected tomorrow with some embedded
  thunderstorms. Any stronger storm development can produce isolated
  wind gusts 40-50 mph.
- Shower chances continue Monday and Tuesday.
&&
.DISCUSSION...
Western periphery of surface high pressure and amplified ridge axis
over the Great Lakes continues to promote stable conditions which
will bring another round of dry weather through the day as
temperature highs warm up into the upper 70s to lower 80s, outside
of the lakeshore. Healthy coverage of cirrus will spread over the
cwa through the morning and will persist through the day, aligned
with the elevated moisture axis ahead of the encroaching low
pressure system. There are low-end probabilities of some showers
across the western third of the cwa late tonight, but ongoing
thinking is for activity to hold off until around and after Midnight
given the stability over the region.
Increasing proximity to the low will bring the first chance for
precipitation overnight initially along a vorticity lobe that will
pivot through the Tri-Cities and Thumb, with a second shortwave then
arriving through the late morning and early afternoon. Coverage in
showers with some embedded thunderstorms is expected to increase
during the afternoon and evening hours, aligning with peak moisture
transport characterized by pw values increasing closer to 1.50" and
850mb dew points nearing 12C. Pulse to multicell coverage will
expand across SE MI during this time frame. Expansion of CAPE to 600-
800 during the late daylight hours will bring increasing chances for
embedded thunderstorms. Effective bulk shear values ranging 20 to 25
knots do provide the chance for some storm organization and storm
relative hodographs do reiterate this chance for some organized storm
development, however given the muddled environment, the severe
thunderstorm threat is low. The stronger low-level lapse rates can
produce isolated stronger wind gusts in the 40-50 mph range with any
organized development.
This upper-level trough with embedded multiple interactions provide
additional shower chances Monday and Tuesday, with more favorable
coverage during daylight hours with afternoon heating. Additional
rain chances will be possible through the midweek period. Models
agree on the interaction between the Great Lakes/Ontario/Quebec
trough and secondary wave digging through the plains, with the
eventually pinch-off into a closed low. Uncertainty lies in where
phasing is maximized with models like the ECMWF briefly closing the
low across the Great Lakes while the GFS favors a deeper trough
interaction through the central Plains before meandering into the
Ohio Valley through the week. Development of this potential closed
low will strongly modulate downstream moisture return and
precipitation distribution.
&&
.MARINE...
High pressure shifts from the Ontario/Quebec border region into
southern Quebec and New England by this evening. Meanwhile, a weak
low pressure system meanders across the Upper Midwest. This holds a
tightened pressure gradient in place across the Great Lakes through
the day into tonight that maintains breezy east to east-southeast
wind of 10 to 20 kt. Locally higher wind with gusts up to around 25
kt will focus within longer fetch regions of northern Lake Huron and
western Lake Erie. Probability for showers and thunderstorms
increases tonight and especially Sunday as the aforementioned low
pressure system sends its warm front across the region. Any stronger
storm development will be capable of producing localized wind gusts
in excess of 34 knots. Wind will prevail out of the southeast at 10
to 15 kt through Sunday before shifting to southwest Monday.
&&
.PREV DISCUSSION...
Issued at 1231 AM EDT Sat Sep 20 2025
AVIATION...
Predominately VFR conditions through the early morning hours as
winds begin to veer east to southeast through this morning while
remaining around 10 knots or less. Wind trajectory off Lake Erie
will then offer possible MVFR stratocu. Have maintained TEMPO for
MVFR BKN clouds as observations are showing at least some scattered
clouds moving west early tonight. Cloud bases settle around 4kft
this afternoon again supplied by the moisture off the lake.
Precipitation chances hold off mostly after 06Z this evening.
For DTW/D21 Convection... No thunderstorms expected tonight and
Saturday.
DTW THRESHOLD PROBABILITIES...
* Low to medium for ceilings at or below 5,000 feet this morning
  and afternoon.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...Small Craft Advisory from 4 PM this afternoon to 2 AM EDT Sunday
     for LEZ444.
&&
$$
DISCUSSION...AM
MARINE.......AM
AVIATION.....AA
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at www.weather.gov/detroit.

NWS DTX Office Area Forecast Discussion