Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 011452
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1052 AM EDT Fri Jul 1 2022

.UPDATE...
Attention today remains on storm potential this afternoon and
evening. The weak cold front currently stretches from Tawas down to
Muskegon and will continue to drift southeastward through the day.
The front offers little in the way of forcing to work with but will
provide a track for a shortwave upstream over Iowa to travel along
during the day. With the moisture axis now in place across SE MI,
will leave the low chance mention of showers/tstorms through early
afternoon, but don`t expect more widespread activity until closer to
4pm when the shortwave arrives. With the cold frontal forcing being
so weak, and good amount of dry air to overcome at the moment,
forcing and moisture will have to advect in with the shortwave.
Looking upstream, dewpoints in the low to mid 60s are present and
expected to fill in across lower MI. CAPE will rise to around 1000
J/kg with shear increasing to around 30 knots which will be enough to
support some strong to severe storms. Hail growth layer will be
elevated around 20kft and CAPE will be thin through that layer so
large hail is not expected today. DCAPE is forecast up to around 800
J/kg so damaging winds will be possible. Storms may start popping
back up around 2pm, increasing in coverage between 4-8pm, with some
lingering activity til 10pm. Still watching for a secondary cold
front dropping into the Thumb behind the main front this evening with
could touch off a few stronger cells late. SPC has just slightly
expanded the Day1 marginal risk area a bit north and east which
basically covers the region south of the cold front.


&&

.PREV DISCUSSION...
Issued at 647 AM EDT Fri Jul 1 2022

AVIATION...

Some lingering elevated showers/isolated thunderstorms may brush MBS
this morning. The overall trend will be for these showers to
diminish during the morning. Shower/thunderstorm redevelopment is
then expected during the afternoon/evening as daytime instability
develops along/ahead of a cold front. Convective development is
expected around FNT and PTK during the afternoon, with convective
chances then focusing farther south around metro Detroit mainly
after 21Z. Some convective redevelop is possible late in the day off
a secondary front moving in off Lake Huron. This convection is
likely to remain limited to the thumb region. Dry and stable air
will then advance across the area in the post frontal environment
late this evening.

For DTW... Scattered to possibly numerous convection is forecast to
develop during the mid to late afternoon hours. The higher
concentration of thunderstorm activity is forecast south of metro.
The coverage of convection at metro airport and points north is
expected to be a little more scattered. The most probable time
period for thunderstorms across metro Detroit is between 20Z and
02Z. Given the slow progress of the cold front across the area,
there may be multiple periods of scattered convection across the
airspace during this time period.

DTW THRESHOLD PROBABILITIES...

* Moderate for thunderstorms mainly late afternoon, after 20Z.

PREV DISCUSSION...
Issued at 404 AM EDT Fri Jul 1 2022

DISCUSSION...

A cold front will be tracking across the central Great Lakes today.
Showers and thunderstorms ahead of this front have been ongoing for
a good portion of the night with the bulk of activity across northern
Lower Michigan. A few radar echoes passed across the Tri-Cities and
Thumb, but are competing with a dry airmass in the lower levels with
around 20 degree dewpoint depression early this morning. Greater
moisture ahead of the front will be moving into southeast Michigan
between 09-15Z this morning as a corridor of higher 850-500 mb
arrives. This area will be supportive of elevated showers and general
thunderstorms through the morning hours, but the anticipation is for
activity to be more subdued to start the day. Some of the hi-res
guidance suggestions a weakening or dissipation of this morning
activity, but will maintain a chance across the central and northern
CWA given a favorable environment to sustain some activity. Clouds
and precipitation will bring a subtle temperature gradient across the
forecast area this afternoon with low-mid 80s across the north and
mid-upper 80s across the south.

Greater potential for strong to possibly severe thunderstorms will
increase throughout the mid to late morning hour within the
instability axis stretching from southwest Michigan northeast through
the Thumb. There is moderate to high confidence for MLCAPEs to climb
to 1000-1500 j/kg by around noon. The Great Lakes will be at the
base of the northern Ontario low bringing increasing westerly flow
and increasing 0-6 km bulk shear values to 35-45 kts within this
area of greater instability. This would be supportive of more
vigorous updrafts ahead of this cold front as it approaches from the
northwest. In addition, more favorable dynamic forcing from a
shortwave moving through the greater trough and the tail end of a
local jet will move over southeast Michigan early Friday afternoon.
Mid-level lapse rates will be weakening throughout the late
morning/early afternoon to around 6 C/km or less, though low level
lapse rates will be high along with elevated DCAPE values. This
brings an environment more favorable for downbursts with a secondary
threat of large hail. A Marginal Risk for severe weather is now in
place across southeast Michigan south of I-69 where conditions will
be most favorable for possible isolated thunderstorms. Though, it is
also possible that locations along and north of I-69 could see
strong to possible severe storms as well if enough instability can
develop early enough in the day as convection either moves through
or redevelops. Timing for better severe potential will be between
12-8 pm with several windows within this time frame for scattered
convection to flare up and become more organized.

As the front moves over Lake Erie later this evening, high pressure
will begin to build into the region and bring an end to
precipitation. Not expecting strong cold air advection behind the
front into tomorrow with 850 mb temperatures only falling a few
degrees. This should bring temperatures down more solidly into the
low-mid 80s for most of southeast Michigan for Saturday and then
only slightly cooler for Sunday. Overnight low over the weekend will
be in the upper 50s to low 60s. Overall pleasant weekend ahead with
lower humidity.

High pressure ridge becomes established across the southern plains
to southeast US into next week. The next chance for rain appears to
be Monday night as ridge axis slides east and embedded shortwaves
within the northwest flow pass over the region. The persistent lower
amplitude ridge will keep limit any intrusion of colder air and keep
temperatures fairly consistent in the 80s during the early to mid
week period. Stronger high pressure ridge becomes establish over the
Rockies towards next weekend setting up the potential for a more
active stretch as waves move around the ridge and into the
Great Lakes.

MARINE...

Scattered to numerous showers and a chance of thunderstorms continue
across marine zones today as a cold front associated with a low
pressure system over Hudson Bay drops through the region. Best
chance for precipitation over the next few hours will be over
central and northern Lake Huron. Shower and thunderstorm chances
shift south with the cold front to affect the southern half of Lake
Huron and Lakes St. Clair and Erie today into this evening. Mariners
should be prepared for gusty winds, hail, and lightning within any
thunderstorms. Northwesterly flow behind the cold front shifts to
southwesterly for the first part of Saturday before shifting to
northerly later in the day as our next high pressure system
approaches, bringing in favorable marine conditions for the weekend.

HYDROLOGY...

Showers and thunderstorms are expected to move across southeast
Michigan ahead of a cold front moving southeast through the region.
Average rainfall amounts will be around one quarter of an inch. The
increase in moisture into the area will bring potential for some of
the stronger thunderstorms that may develop to produce brief periods
of heavy rainfall. Rainfall totals between 0.50 to 0.75 inches will
be possible with the strongest storms. The progressive nature of
activity will not present any significant flooding threat.

&&

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

$$

UPDATE.......DRK
AVIATION.....SC
DISCUSSION...AA
MARINE.......ST
HYDROLOGY....AA


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