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000
FXUS63 KDTX 060740
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
340 AM EDT Thu May 6 2021

.DISCUSSION...

Abundant mid-level cloud cover now resides over western Michigan
ahead of an approaching shortwave trough, situated over Wisconsin
and eastern Iowa. Thickening cloud cover will overspread Southeast
Michigan throughout the morning hours as increasing mid-level
moisture saturates down to the near-surface. This will eventually
result in light and persistent rain production across Southeast
Michigan moving in from west to east starting in the late morning
hours for the western portion of the cwa before moving into the
Metro region and Thumb by the afternoon. Shortwave trough axis will
move through Southeast Michigan between 00-06Z which will coincide
with ending rain chances late tonight into early Friday morning.
Abundant cloud cover and persistent light rain will result in
another day of temperatures highs in the low to mid 50s.

A pseudo-omega blocking pattern will hold over much of the
Continental US on Friday given the near stationary upper-level low
over the Hudson Bay and a second Pacific Northwest low, which will
continue to move inland through the weekend. This will continue to
place the Great Lakes region underneath an expansive thermal trough.
Impressive h500 temperatures down to or below -30C will drop into
the Great Lakes ahead of a strong shortwave set to move over
Southeast Michigan between 21Z - 06Z. This will result in convective
based showers given the steepening low and mid-level lapse rates and
building weak MUCAPE values to or under 250 J/kg. Some rumbles of
thunder will be possible given the above, with additional chances to
see some pea-sized hail with freezing levels below 3kft. Diffuse
surface high pressure to gradually move into the Great Lakes
starting Saturday morning and will limit rain chances heading into
the weekend. Frost will be possible in the Thumb and around the Tri-
Cities Saturday as period of limited cloud cover will help drop
temperatures to around the freezing mark.

A baroclinic zone will set up across the southern Ohio River Valley
region on Sunday, ahead of a surface low and weak mid-level impulse.
Interaction with the baroclinic zone looks limited with the wave and
thus the bulk of qpf output will fall well south of the state line,
however, overrunning ahead of the low pressure could provide light
rain chances to closer to the MI/OH border and Metro region. This
will be sensitive to the track of the low, where a fair bit of
uncertainty exists. Ensemble analysis showers cyclone center
locations could range anywhere between central Indiana, or southwest
into southern Missouri by 18Z Sunday. Will continue to advertise the
chance for rain until additional convergence is noted within long
range models. Otherwise, better consensus exists regarding a Canadian
high pressure system filling in across the Midwest and Great Lakes
late Monday and holding through at least the middle of the week. This
will limit precipitation chances through the early and midweek
period. Below normal temperatures will continue well into early next
week given little change to the thermal pattern.

&&

.MARINE...

The broad area of high pressure positioned across the upper Midwest
and plains states along with the broad troughing in the upper levels
will persist for the next couple of days. This pattern will keep a
cooler air across the region for the remainder of the week. A more
stable thermal profile over the waters will prevail given the still
relatively cold water across the lakes. This will hold any wind gust
below 25 knots. There will be a couple weak low pressure troughs
that move through the region on Thursday and Friday. Both will offer
some rain chances and reinforce the cooler airmass already present
over the Great Lakes.

&&

.HYDROLOGY...

An upper-level disturbance will bring light prolonged rain chances
to SE MI mainly through the afternoon and evening hours. While most
locations are expected to accumulate less than a quarter-inch by
early Friday morning, locations across the Metro region may see
between two to three tenths of accumulation given the longer duration
of rain. Secondary rain chances with some rumbles of thunder are
again expected by Friday afternoon. Accumulation totals will be
highly variable depending on where the stronger showers set up.
Locations experiencing repeated showers through the day could see up
to an additional quarter-inch of new accumulation.

&&

.PREV DISCUSSION...
Issued at 1153 PM EDT Wed May 5 2021

AVIATION...

Clear sky or just some thin patches of cirrus carry conditions
through the late night hours as weak high pressure settles over
Lower MI. The high is then quickly overtaken by the next wave of low
pressure moving in from the Midwest. Increasing high clouds is the
first sign of this system which thicken and lower to mid levels by
early morning. Light rain spreads out ahead of the surface low as it
approaches near the southern MI border this afternoon. This moisture
adds to MVFR ceiling potential as the low moves along the Ohio
border late in the day and Thursday evening.

DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling at or below 5000 ft this afternoon and
  Thursday evening.


&&

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

$$

DISCUSSION...AM
MARINE.......AA
HYDROLOGY....CB
AVIATION.....BT


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at www.weather.gov/detroit.