Tornado and Hail in Michigan, July 14, 2023

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
126 PM EDT Fri Jul 14 2023

.AVIATION...

A plume of higher moisture has spread across Southeast Michigan
ahead of a weak mid-level disturbance. This feature will bring
additional scattered showers and storms through the afternoon and
early evening as it tracks west to east across the area. Isolated
storms may be strong to severe and produce wind gusts in excess of
40 kt, hail, and heavy downpours as well as MVFR to IFR conditions.
Otherwise, mainly VFR conditions prevail through this evening before
an organized area of showers with a few embedded storms is expected
to track into the area late tonight into Saturday. This will bring
lower clouds in with potential for MVFR ceilings to develop after
12z Saturday. Ambient winds predominantly out of the southwest will
weaken and trend southerly tonight before becoming southwesterly
again tomorrow.

For DTW...Probabilities have increased for thunderstorm development
in the airspace between 20z and 23z, so have introduced a TEMPO
group. Confidence is low on additional convection later this
evening, so will continue a dry forecast before probabilities for
showers increase again overnight into Saturday. Heavy rain will be
more likely with this latter activity.

.DTW THRESHOLD PROBABILITIES...

* Medium for thunderstorms late this afternoon and evening. Low
  Saturday morning.

* Medium for ceilings at or below 5000 ft after 12z Saturday morning.

&&

.PREV DISCUSSION...
Issued at 1040 AM EDT Fri Jul 14 2023

UPDATE...

Inherited forecast seems to be in pretty good shape.

Latest water vapor imagery shows multiple shortwaves/jet streaks
lined up to move through the Great Lake region as the large upper
level low over northern Manitoba directs the traffic. Very difficult
forecast as these small upper level disturbances are moving through
quickly, and have little separation and may interfere with each
other. This morning one such wave is moving through lower Michigan,
with 700 MB Theta-E surge/moisture advection triggering scattered
shower/thunderstorm activity, mostly moving through and in the
vicinity of Saginaw Bay.

Next wave(s) already racing through Wisconsin/western Great Lakes.
Strengthening southwest low level flow will allow for moisture
transport into the State for the rest of the day, with surface dew
pts already rising in the mid 60s, on their way to upper 60s by this
evening. This will allow for MLcapes to reach between 1500-2000 J/kg
as temperatures are on track to rise into the mid 80s. With 0-6 Km
bulk shear aoa 40 knots slicing through southeast Michigan with the
45+ knot jet streak at 500 MB, severe storms remain a valid concern
mid afternoon into the evening hours. The mid level jet core looks
to be tracking south of M-59, placing locations along and south of I-
94 at an elevated risk, with a closer proximity to the deeper
moisture over the northern Ohio Valley as well. However, there is a
surface reflection which will be tracking through northern Lower
Michigan as well, with troughing extending south through Saginaw Bay
region, and it looks like northern Thumb region will be a favorable
location as well for storms as surface based instability ramps up as
500 MB cold pool of -11 of -12 C tracks through that region early
this evening.

Coverage and impact of the stabilizing influence of the storms will
determine our shower/thunderstorm potential tonight, as continued
moderate southwest low level winds and solidly negative showalter
index values potentially allow for elevated convection to re-
develop within the backdrop of ridge building into between the
Central/Eastern Great Lakes region toward Saturday morning, as
a shortwave attempts to track in from the western Ohio Valley. With
700 MB dew pts rising into the low single numbers, excessive/heavy
rainfall becomes an increasing concern as we head into Saturday as
well. Will take a closer look at this for the 4 PM package.

PREV DISCUSSION...
Issued at 417 AM EDT Fri Jul 14 2023

DISCUSSION...

Review of CONUS radar mosaic this morning features several areas of
nocturnal convection, although local conditions have remained dry
with just some patchy mid/high cloud debris emanating from elevated
storms over Wisconsin. On the larger-scale, mid level water vapor
loop continues to highlight the impressive upper low circulating on
the southern edge of Hudson Bay with smaller, convectively-enhanced
shortwaves scattered across central CONUS. It is the scale
interactions of these features that will govern local weather today
and into the weekend for southeast Michigan.

Will need to monitor the aforementioned Wisconsin convection as its
corresponding outflow crosses Lake Michigan early this morning. The
14.00z HREF and majority of deterministic guidance suggests it will
at least partially hold together and could even redevelop amidst the
lake influence between now and 12z, which is holding true at press
time. This would result in an earlier arrival, mid to late morning,
of showers to the Tri Cities. While thunder chances cannot be ruled
out if this complex holds together, surface-based instability will
likely still be recovering from the nocturnal minimum so there is a
good chance convection stays elevated. Did add low chance PoPs for
northwest portions of the cwa to account for this.

Even with the prospects of morning convection, forecast soundings
show no issues with boundary layer destabilization by this
afternoon. With H850 temps right around the mid-July average of 14-
15 C, expectation is for daytime highs to be around normal in the
mid 80s. The well-mixed boundary layer combined with mid-level lapse
rates peaking at 6-6.5 C/km sets the stage for afternoon
thunderstorm redevelopment in a decent MLCAPE environment of 1000-
1500 J/kg. As we have seen the past several days, this instability
set up is enough to fuel a few organized, strong to severe cells in
the right shear environment. From a dynamics perspective, a feature
to note this morning on mid level WV is the compact vort max that is
currently over Fargo, ND but will arrive in lower Michigan later
this afternoon. Not only will this provide a synoptic lifting
component to the environment, but will also direct a belt of ~50
knot westerlies into southeast Michigan this afternoon. The result
is a steady increase in deep layer shear later today, and increasing
potential for organized cell development. That said, a limiting
factor today is the lack of strong surface-based forcing and
dependence on remnant outflow boundaries to trigger storms. This
generally means lower predictability in timing and location for
storms. Nonetheless, main threats today will be damaging winds
and/or hail as primarily unidirectional hodographs and minimal low
level shear suggest updrafts rotation would struggle in this
environment. Convection wanes with loss of daytime heating, offering
just a brief reprieve from precipitation chances until a more
organized wave arrives late tonight and Saturday.

While the upper low stays put today, an amplifying ridge over the
Pacific Northwest alters the height field over much of northern
CONUS. This directs a shortwave toward the Ozarks, which eventually
phases with the parent low and its vorticity reservoir by Saturday
morning. As this process occurs, the wave tilts negatively and
drives the PV anomaly directly overhead. Additional forcing comes
from the left exit region as the developing upper level jet wraps
cyclonically toward lower Michigan. Given the subtle amplification
to the wave, a more southwesterly component to the flow
simultaneously ushers in a very moist airmass with PWATs in excess
of 1.6 inches, which is over the 90th percentile for SE Michigan per
SPC climatology. All signs point to heavy rainfall potential as this
system organizes overhead, although models struggle to pin down the
exact magnitude/location of convective influence on QPF totals.
Broad QPF totals at the moment look to be between a half to three
quarters of an inch on Saturday, with localized swaths well over 1"
showing up in the CAMs. Refer to the hydrology section for more
details.

In addition to heavy rainfall, there is concern for strong to severe
thunderstorms again on Saturday, outlined in the Day 2 Marginal
Risk. While instability will likely suffer from moist adiabatic
profiles, the quick organization of this system offers pockets of
stronger deep layer shear that could promote storm organization. Once
again, hail and damaging winds will be the main threat in any
isolated stronger cells.

The upper low dislodges and drifts south Sunday into early next
week, maintaining an unsettled pattern until the passage of a cold
front early next week. Following the frontal passage, expect
slightly below normal temperatures and generally comfortable
humidity for July standards as the drier Canadian airmass works its
way into southeast Michigan.

MARINE...

Weak flow organizes out of the southwest after daybreak ahead of the
next system which brings renewed concerns for localized wind and
wave overachievement this afternoon and evening with convective
activity. Gradient flow should be tame enough to forego Small Craft
Advisories for elevated offshore waves while any gust concerns
remain independent of ambient mechanical mixing. Confidence has
decreased in a secondary line of thunderstorms late tonight and
early Saturday morning as the broader complex now appears to decay
significantly by the time it reaches the central Great Lakes. A
stronger upper level disturbance moves through Saturday bringing
additional convective activity through the evening hours, thus will
likely rely on short-fused Special Marine Warnings as necessary.

HYDROLOGY...

Several rounds of showers and thunderstorms are possible today and
this weekend as an upper low slowly drifts toward northern CONUS.
The first round of showers and storms comes today as isolated to
scattered thunderstorms trigger along residual outflow boundaries.
Localized amounts of a quick inch or more are possible in any
thunderstorms today, although broader rainfall totals should hold
under a quarter inch. Several rounds of showers and thunderstorms
then arrive late tonight into much of Saturday. Rainfall amounts
generally fall into the half inch to three quarter inch range,
although localized amounts in excess of 1 inch will be possible
especially toward the Ohio border. More substantial rainfall
amounts, in excess of 2 inches, also cannot be ruled out although
confidence is low at the moment.

&&

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

AVIATION.....TF
UPDATE.......SF
DISCUSSION...MV
MARINE.......KGK
HYDROLOGY....MV

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

Hazardous Weather Outlook
National Weather Service Detroit/Pontiac MI
439 AM EDT Fri Jul 14 2023

MIZ047>049-053>055-060>063-068>070-075-076-082-083-150845-
Midland-Bay-Huron-Saginaw-Tuscola-Sanilac-Shiawassee-Genesee-Lapeer-
St. Clair-Livingston-Oakland-Macomb-Washtenaw-Wayne-Lenawee-Monroe-
439 AM EDT Fri Jul 14 2023

This hazardous weather outlook is for southeast Michigan.

.DAY ONE...Today and Tonight

Isolated to scattered strong to marginally severe thunderstorms are
expected this afternoon and evening. Wind gusts to 60 mph and hail
around 1 inch are both possible with these storms. Storm motion will
be west to east at 40 mph.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Numerous showers and thunderstorms are expected to develop by early
Saturday morning, especially south of M-59 where excessive rainfall
will be possible. Isolated strong to marginally severe thunderstorms
will again be possible Saturday, with wind gusts to 60 mph and hail
to 1 inch diameter possible. Thunderstorm chances continue Sunday and
Monday.

.SPOTTER INFORMATION STATEMENT...
Spotter activation may be needed this afternoon and evening.

LCZ460-LEZ444-LHZ361>363-421-422-441>443-462>464-150845-
Lake St Clair-
Michigan Waters of Lake Erie from Detroit River to North Cape MI-
Lake Huron from 5NM east of Mackinac Bridge to Presque Isle Lt
beyond 5 NM off shore-
Lake Huron from Presque Isle Light to Sturgeon Point MI beyond 5NM
off shore-
Lake Huron from Sturgeon Point to Alabaster MI beyond 5NM off shore-
Outer Saginaw Bay SW of Alabaster to Port Austin MI to Inner Saginaw
Bay-Inner Saginaw Bay SW of Point Au Gres to Bay Port MI-
Port Austin to Harbor Beach MI-Harbor Beach to Port Sanilac MI-
Port Sanilac to Port Huron MI-
Lake Huron from Port Austin to Harbor Beach beyond 5NM Off Shore-
Lake Huron from Harbor Beach to Port Sanilac beyond 5NM Off Shore-
Lake Huron from Port Sanilac to Port Huron beyond 5NM Off Shore-
439 AM EDT Fri Jul 14 2023

This hazardous weather outlook is for portions of Lake Erie, Lake
Huron and Lake St Clair.

.DAY ONE...Today and Tonight

Isolated to scattered strong to marginally severe thunderstorms are
expected this afternoon and evening. Wind gusts to 60 mph and hail
around 1 inch are both possible with these storms. Storm motion will
be west to east at 40 mph.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Numerous showers and thunderstorms are expected to develop by early
Saturday morning, especially south of M-59 where excessive rainfall
will be possible. Isolated strong to marginally severe thunderstorms
will again be possible Saturday, with wind gusts to 60 mph and hail
to 1 inch diameter possible. Thunderstorm chances continue Sunday and
Monday.

Still a low chance of thunderstorms Sunday and Monday.

.SPOTTER INFORMATION STATEMENT...
Spotter activation may be needed this afternoon and evening.

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

MV

Special Weather Statement
National Weather Service Detroit/Pontiac MI
1055 AM EDT Fri Jul 14 2023

MIZ048-141545-
Bay MI-
1055 AM EDT Fri Jul 14 2023

...A strong thunderstorm will impact portions of southern Bay County
through 1145 AM EDT...

At 1055 AM EDT, Doppler radar was tracking a strong thunderstorm over
Auburn, moving east at 25 mph.

HAZARD...Winds in excess of 30 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This strong thunderstorm will be near...
  Kawkawlin around 1110 AM EDT.
  Bay City around 1115 AM EDT.
  Essexville around 1120 AM EDT.
  Munger around 1130 AM EDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4364 8417 4367 8381 4365 8377 4363 8370
      4348 8370 4349 8382 4352 8382 4352 8405
      4357 8405 4357 8417
TIME...MOT...LOC 1455Z 271DEG 22KT 4359 8407

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...30 MPH

TF

Special Weather Statement
National Weather Service Detroit/Pontiac MI
1220 PM EDT Fri Jul 14 2023

MIZ049-054-141715-
Huron MI-Tuscola MI-
1220 PM EDT Fri Jul 14 2023

...A strong thunderstorm will impact portions of northern Tuscola and
southwestern Huron Counties through 115 PM EDT...

At 1219 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles west of Sebewaing, moving east at 20 mph.

HAZARD...Winds in excess of 40 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This strong thunderstorm will be near...
  Unionville around 1240 PM EDT.
  Sebewaing around 1245 PM EDT.
  Owendale around 105 PM EDT.
  Cass City and Gagetown around 115 PM EDT.

Other locations impacted by this storm include Colwood, Wisner, Bach,
Bay Park and Colling.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

If on or near Saginaw Bay, get out of the water and move indoors or
inside a vehicle. Remember, lightning can strike out to 10 miles
from the parent thunderstorm. If you can hear thunder, you are close
enough to be struck by lightning. Move to safe shelter now! Do not
be caught on the water in a thunderstorm.

&&

LAT...LON 4357 8312 4362 8376 4365 8376 4362 8368
      4374 8352 4379 8348 4382 8349 4385 8311
TIME...MOT...LOC 1619Z 271DEG 19KT 4371 8362

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

TF

Special Weather Statement
National Weather Service Detroit/Pontiac MI
1259 PM EDT Fri Jul 14 2023

MIZ049-054-141800-
Huron MI-Tuscola MI-
1259 PM EDT Fri Jul 14 2023

...A strong thunderstorm will impact portions of northeastern Tuscola
and southwestern Huron Counties through 200 PM EDT...

At 1258 PM EDT, Doppler radar was tracking a strong thunderstorm over
Sebewaing, moving east at 20 mph.

HAZARD...Winds in excess of 40 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This strong thunderstorm will be near...
  Owendale around 120 PM EDT.
  Gagetown around 125 PM EDT.
  Cass City and Elkton around 135 PM EDT.

Other locations impacted by this storm include Colwood, Ivanhoe, Bach
and Colling.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4368 8306 4367 8312 4356 8311 4360 8351
      4377 8346 4386 8306
TIME...MOT...LOC 1658Z 269DEG 17KT 4371 8341

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

TF

Special Weather Statement
National Weather Service Detroit/Pontiac MI
140 PM EDT Fri Jul 14 2023

MIZ054-055-141845-
Tuscola MI-Sanilac MI-
140 PM EDT Fri Jul 14 2023

...A strong thunderstorm will impact portions of east central Tuscola
and northwestern Sanilac Counties through 245 PM EDT...

At 139 PM EDT, Doppler radar was tracking a strong thunderstorm near
Caro, moving east at 25 mph.

HAZARD...Winds in excess of 40 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This strong thunderstorm will be near...
  Cass City around 155 PM EDT.
  Argyle around 225 PM EDT.

Other locations impacted by this storm include Decker, Deford,
Wilmot, Ellington, Snover, Elmer and Tyre.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4343 8335 4358 8340 4368 8286 4341 8284
TIME...MOT...LOC 1739Z 263DEG 21KT 4352 8330

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...40 MPH

TF