Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
000
FXUS63 KDTX 140249
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1049 PM EDT Wed Mar 13 2024

.KEY MESSAGES...

- Shower chances to increase overnight into Thursday morning with
  a few thunderstorms possible near the Michigan and Ohio state line.

- Thunderstorms will remain possible Thursday afternoon and early
  evening with an isolated severe storm possible from I-94 south.

- Colder temperatures in the 30s arrive Sunday and linger into early
  next week.

&&

.AVIATION...

During the course of the morning, there will be a robust transport
of low to mid level moisture into Se Mi in advance of an upper short
wave and associated sfc low lifting from the Mid Mississippi Valley
into the southern Great Lakes/northern Ohio Valley. The initial
moisture surge will result in increasing clouds and decreasing
ceiling heights this morning. Although there will be some weak
elevated instability with the initial moisture surge in the morning,
probabilistic guidance suggests thunderstorm chances will remain
low. The warm sector and thus instability axis will nudge into
southern Michigan Thursday afternoon. This will result in much
higher thunderstorm chances, particularly from PTK south. Given the
amount of moisture being transported north of the sfc warm front,
which is likely to stall around or just south of the I-94 corridor,
much of Se Mi will be within IFR and/or LIFR conditions with
persistent showers and/or drizzle through the day Thursday.

For DTW...The most probable time for thunderstorms to affect metro
will be in the mid to late afternoon hours on Thursday. This will
the time period when the elevated instability axis expands across
metro Detroit.

.DTW THRESHOLD PROBABILITIES...

* High in ceilings aob 5000 feet Thursday.

* Moderate in thunderstorms Thursday afternoon.

* Low in ceilings and/or visibilities aob 1/2SM or 200 Feet.

&&

.PREV DISCUSSION...
Issued at 903 PM EDT Wed Mar 13 2024

UPDATE...

The 00Z DTX sounding shows a significant low level dry layer below
700mb. Sfc observations are still showing dewpoints in the 30s over
much of Se Mi. Mid level ascent will continue to overspread the
region tonight. Given the amount of low level dry air, much of the
initial radar returns will likely only result in sprinkles. After
08Z, moisture transport and isentropic ascent will markedly increase,
leading to improved rain chances. A forecast update was issued
simply to nudge rain chances a little later into the night.

PREV DISCUSSION...
Issued at 329 PM EDT Wed Mar 13 2024

DISCUSSION...

Weak frontal boundary has stalled near the Michigan and Ohio/Indiana
state line this afternoon. With main (weak) low level convergence to
the south and minimal upper forcing through the evening, will remove
minor precipitation chances until the overnight period. With time,
increased southwesterly flow up/over this frontal boundary will lead
to an increasingly mild/moist environment with shower chances slowly
increasing after midnight.

The best focus for activity will hold fast along the aforementioned
frontal boundary draped near the far southern forecast area with
shower and thunderstorm chances really increasingly dramatically by
the 10z-12z time frame as main 30+ knot southwesterly low level jet
works into far southern lower Michigan in advance of approaching low
pressure. While best convective coverage seems focused in this area,
a broader area of elevated showers and perhaps a rumble or two of
thunder will extend north through the remainder of the region.

With lower based convection expected to fire so far south early in
the day, suspect the low level convergence will remain anchored
basically south of the state line into the afternoon and possibly
evening Thursday. This should limit the overall severe weather
potential as only modest elevated instability is able to wedge a bit
north over parts of the forecast area. This may garner a few storms
capable of severe (1" diameter) hail, but wind and/or tornado risk
will remain very low assuming the surface front remains just south
of the area. That said, convective chances will remain rather high
in the afternoon and evening as upper level forcing increases with
the encroachment of the shortwave driving the aforementioned low
pressure system.

Lingering showers/embedded thunder will remain possible into parts
of the overnight Thursday night as the low pressure passes south of
the area. This activity should clear the area fairly quickly though
will little more than stray sprinkles Friday morning before activity
ends altogether.

Temperatures during this time frame will trend colder than recent
warm conditions with a tight temperature gradient (upper 40s north
to around 60 south) setting up Thursday and 40s to lower 50s on
Friday as colder air sags south through the remainder of the area.

There will be a brief rebound into Saturday in advance of the next
encroaching shortwave/cold front with lower 50s common. This next
shortwave drives southeast into the area within the northern stream
and brings substantially colder air to the region late this weekend
into early next week. After initial cold front crosses the area on
Sunday, additional shortwave energy will drive progressively colder
air into the area through Monday night with only slightly moderation
into Tuesday.

After topping in the lower/mid 40s Sunday, expect the temperatures
to drop steadily into the evening/overnight period with highs only
in the 30s Monday and perhaps back up to around 40 Tuesday. Isolated
to scattered snow showers can be expected in such a pattern both
from forcing along the passing cold front(s) and also from the lake
effect activity that becomes established within the developing cold
northwest flow.

MARINE...

A cold front has stalled across the southern Great Lakes and will
remain there through Thursday while becoming a warm front. A pair of
low pressure systems will then track along the front and through the
southern Great Lakes and Ohio Valley Thursday through Friday. Rain
showers are expected across southern Lake Huron and locations south
through this time with a window of thunderstorms possible Thursday
evening. In addition, as high pressure builds in from the north the
gradient will tighten which will increase the northeasterly winds to
around 25 knots and the onshore flow will build wave heights along
the shoreline of the Thumb and into Saginaw Bay. A Small Craft
Advisory has been issued to account for this period of elevated wind
and waves Thursday afternoon through Friday afternoon.

HYDROLOGY...

Rain showers and embedded thunderstorms will increase from Thursday
into Thursday night as low pressure tracks into the region along a
stalled frontal boundary. Locally heavy downpours can be expected
with total rainfall amounts averaging around half an inch. Locally
higher amounts closer to an inch will be possible near the Michigan
and Ohio state line where thunderstorm coverage is greatest. While
flooding is not expected with this activity, ponding of water of
roadways and poorly drained areas will occur where the heavier rain
falls.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 4 PM Thursday to 4 PM EDT Friday for
     LHZ421-422.

     Small Craft Advisory from 10 PM Thursday to 4 PM EDT Friday for
     LHZ441-442.

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

$$

AVIATION.....SC
UPDATE.......SC
DISCUSSION...DG
MARINE.......DG
HYDROLOGY....DG


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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.