Special Weather Statement, NWS Detroit, MI

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
740 PM EDT Mon Jun 28 2021

.AVIATION...

A widely scattered coverage of showers and thunderstorms regionally
will gradually diminish with the loss of daytime heating late this
evening. A lingering chaotic coverage of mid level cloud for the
overnight period. Environment may again support a limited coverage
of stratus development around daybreak, although confidence in
development remains quite low. Similar conditions exists again on
Tuesday, with a very moist and gradually destabilizing environment
bringing the chance for afternoon/early evening showers and
thunderstorms.

For DTW...Small area of showers and isolated thunderstorms will
remain in the vinicity of DTW through 01-02z window. Potential
diminishes quickly thereafter.

.DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 feet through Tuesday.

* Low in thunderstorms impacting DTW through 02z.

&&

.PREV DISCUSSION...
Issued at 403 PM EDT Mon Jun 28 2021

DISCUSSION...

Dome of high pressure across the mid-Atlantic will continue to
encroach upon the northeastern seaboard through the day today which
has resulting in gradually building heights across Southeast
Michigan. Gradually building heights allowed a warm front to enter
north into Michigan early this morning, with the warm/stationary
front now in place north of the Ann Arbor/Metro Detroit region. This
frontal boundary will be the focal point for afternoon and evening
shower and thunderstorm production with the weaker convergence along
the frontal zone, with main activity holding on or south of I-69. Hi-
res nam also showing a secondary source of CI from the differential
heating boundary/lake breeze over Lake Erie, and over southern Lake
Michigan, with storm motion bringing some activity over SE MI,
possibly north of I-69, later this evening.

Overall, effective bulk shear values between 20 to 25 knots (near
uni-directional wind field with modest wind speeds) and weak mid-
level lapse rates will limit severe weather potential today. SWODY1
has included locations south of I-69 in a marginal risk for severe
weather for wind gust concerns, thus will not discount the chance
for an isolated strong wind gusts to 60 mph given building
instability with the better low-level lapse rates and precipitation
loading potential. But overall, the main hazard will continue to be
tied with the anomalously moist conditions in place where PW values
remain between 1.75 to 1.90 inches over SE MI. Stronger storms will
be capable of periods of torrential rainfall. Will need to watch for
any repeated rounds of heavier rainfall with repeated rounds of
shower and storm activity along the front. Hi-res output suggests
accumulation totals between .50 to 1 inch will be possible somewhere
along or between I-94 to I-69 if repeated storm activity occurs,
with localized higher amounts under stronger thunderstorm activity.

Heights continue to gradually increase across SE MI into Tuesday
while the enamel's ridge of high pressure over the Pacific NW
starts to move more inland and break down. This will cause a
shortwave & surface low pressure over the Midwest to eject north
across Lake Superior late Tuesday into Wednesday. As a result,
surface warm front over southern Michigan will draw north into
northern lower Michigan throughout the day and will maintain dew
points in the lower 70s across SE MI. Building moisture will bolster
instability with internal probabilistic guidance trending more
likely to see CAPE values in excess of 1,500 J/kg over the Metro
region, with HREF mean values showing values in excess of 2,000
J/kg. Needless to say, better instability to work with tomorrow with
better bulk shear values around 30 knots. Current thinking is that
PoP coverage may not as widespread as initially thought in the
morning/early afternoon with weaker mid-level convergence, but will
maintain low-end likely PoPs as it will not take much forcing for CI
in this subtropical environment. PoPs then much more likely late
Tuesday into Wednesday with better proximity to the trough and right
entrance dynamics. Mid-level lapse rates remain poor over SE MI, but
better instability and slightly between shear suggests late day
organization will bring another chance to see isolated wind gusts to
60 mph and torrential rainfall with any activity.

Additional shower and thunderstorm chances exist on
Wednesday/Thursday tied to the eventual passage of a cold front and
upper-level shortwave which will look to finally start to break down
the persistent pattern that Michigan has been stuck in over the past
week. Drop in temperature and humidity to follow the passage of the
front late next week with along decreasing chances for rain and
thunderstorms.

MARINE...

A warm front lifts across the region this afternoon into tonight
with an increasing coverage of showers and storms filling in. Heavy
downpours and localized higher wind and waves will be possible in
any convection. Outside of any storms, light and variable marine
winds expected through the remainder of today and again on Tuesday
amidst an overall diffuse pressure pattern. Rain chances stay in the
likely category into Tuesday as the front lingers over the central
Great Lakes. Low pressure develops over the northern Lakes Tuesday
night and forces the front back south on Wednesday as a cold front.
This leads to additional showers/storms before cooler and drier air
is ushered in for the late week on modest northerly flow.

HYDROLOGY...

A weak frontal boundary will be the focal point for widely scattered
rain showers and thunderstorms, mainly south of I-69. Torrential
rainfall will again be possible with stronger activity given the
high moisture content across Michigan. Multiple rounds of
precipitation will be possible along the front, with accumulation
totals ranging between .5 to 1 inch by late tonight for locations
that do experience multiple rounds of activity. Localized higher
amounts will be possible with stronger storms.

Widely scattered to numerous showers and storms will again be likely
on Tuesday where rainfall totals will be highly variable across
Southeast Michigan depending on where the heaviest precipitation
sets up. Any repeated rounds of thunderstorm activity can again
bring precipitation totals to an inch or more. Thus, localized
flooding concerns remain in place for Tuesday and Wednesday for low-
lying areas and urban locations.

&&

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

AVIATION.....MR
DISCUSSION...AM
MARINE.......TF
HYDROLOGY....AM

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

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Special Weather Statement
National Weather Service Detroit/Pontiac MI
736 PM EDT Mon Jun 28 2021

MIZ069-075-076-290015-
Oakland MI-Washtenaw MI-Wayne MI-
736 PM EDT Mon Jun 28 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN WAYNE...SOUTHWESTERN
OAKLAND AND EASTERN WASHTENAW COUNTIES UNTIL 815 PM EDT...

At 736 PM EDT, Doppler radar was tracking a strong thunderstorm over
Dixboro, or near Ann Arbor, moving northeast at 25 mph.

Winds in excess of 40 mph will be possible with this storm.

This strong thunderstorm will be near...
  Dixboro around 740 PM EDT.
  Salem around 755 PM EDT.
  South Lyon around 800 PM EDT.
  Northville around 810 PM EDT.
  Novi and West Bloomfield around 815 PM EDT.

Other locations impacted by this storm include Franklin, Pittsfield
Township, Orchard Lake, Redford, Plymouth, Commerce, Oak Park, Garden
City, Barton Hills and Walled Lake.

LAT...LON 4229 8384 4243 8368 4243 8366 4245 8366
      4263 8346 4244 8313 4213 8365
TIME...MOT...LOC 2336Z 221DEG 23KT 4232 8371

TF

Special Weather Statement
National Weather Service Detroit/Pontiac MI
754 PM EDT Mon Jun 28 2021

MIZ060-061-068-290045-
Shiawassee MI-Livingston MI-Genesee MI-
754 PM EDT Mon Jun 28 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN SHIAWASSEE...
NORTHWESTERN LIVINGSTON AND SOUTHWESTERN GENESEE COUNTIES UNTIL 845
PM EDT...

At 754 PM EDT, Doppler radar was tracking a strong thunderstorm over
Perry, moving northeast at 35 mph.

Wind gusts up to 50 mph will be possible with this storm.

This strong thunderstorm will be near...
  Byron and Bancroft around 810 PM EDT.
  Durand, Corunna and Gaines around 815 PM EDT.
  Lennon around 825 PM EDT.
  Swartz Creek around 830 PM EDT.
  Flushing around 840 PM EDT.
  Flint and Burton around 845 PM EDT.

Other locations impacted by this storm include Juddville, Rankin,
Conway Township, Shaftsburg and Vernon.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4315 8390 4295 8366 4266 8415 4278 8416
      4277 8432 4281 8436
TIME...MOT...LOC 2354Z 230DEG 32KT 4280 8419

TF

Special Weather Statement
National Weather Service Detroit/Pontiac MI
810 PM EDT Mon Jun 28 2021

MIZ075-076-082-290100-
Lenawee MI-Washtenaw MI-Wayne MI-
810 PM EDT Mon Jun 28 2021

...SIGNIFICANT WEATHER ADVISORY FOR WEST CENTRAL WAYNE...NORTHEASTERN
LENAWEE AND EASTERN WASHTENAW COUNTIES UNTIL 900 PM EDT...

At 810 PM EDT, Doppler radar was tracking a strong thunderstorm near
Clinton, or near Tecumseh, moving northeast at 25 mph.

Winds in excess of 40 mph will be possible with this storm.

This strong thunderstorm will be near...
  Milan around 830 PM EDT.
  Saline around 835 PM EDT.
  Ann Arbor around 845 PM EDT.
  Ypsilanti around 855 PM EDT.
  Dixboro around 900 PM EDT.

Other locations impacted by this storm include Bridgewater,
Pittsfield Township, Macon and Barton Hills.

LAT...LON 4208 8401 4243 8372 4225 8342 4208 8368
      4208 8377 4202 8377 4198 8383
TIME...MOT...LOC 0010Z 219DEG 20KT 4208 8386

TF

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