Flint, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

529
FXUS63 KDTX 182005
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
405 PM EDT Wed Jun 18 2025

.KEY MESSAGES...

- Slight to Enhanced Risk for severe storms continues late this
afternoon and this evening. Damaging wind gusts (70+ mph) and a few
tornadoes are the main hazards, with large hail (1+ inch) as a
secondary threat.

- Heavy rainfall and localized flooding remain possible, especially
in areas that receive repeated thunderstorm activity, gradually
shifting north toward the Tri Cities and northern Thumb tonight
into Thursday morning.

- Additional thunderstorm clusters are possible leading into a major
build up of heat and humidity this weekend. High temperatures in the
90s and heat index around 100 are likely with minimal relief at
night.

&&

.DISCUSSION...

The Slight to Enhanced risk of severe thunderstorms is unchanged in
the afternoon forecast update with the primary hazard being damaging
wind followed by a secondary tornado threat for the evening phase of
this event. A time window for recovery of instability back northward
into Lower Mi is offered by morning/early afternoon storms exiting
eastward. A corridor of nearly full sun south of the surface front
is helping lift temperatures back into the lower and mid 80s
reflected in 1500-2000 J/kg of MLCAPE shown in RAP based hourly
mesoanalysis. This axis of instability feeds northward ahead of the
IN convective complex and from the Ohio border into the front
stalled in the I-69/M-46 corridors making a new round of isolated to
scattered thunderstorms possible there. These would have more of a
discrete mode capable of capitalizing on backed low level wind and
localized wind profile enhancement along and near the front to
maintain a tornado threat. The instability axis also provides an
avenue for maintenance of the inbound MCS rapidly growing upscale
through Indiana at forecast issuance. This complex obviously brings
the main damaging wind threat as the cold pool matures, but also a
tornado threat associated with increased wind shear enhanced by the
MCV nested within larger scale low pressure system. A time window of
6 PM to Midnight captures the bulk of activity before it sweeps
eastward into Ontario while the main low pressure system tracks
roughly along a line from southern Lake Michigan to the northern
Thumb by Thursday morning. A lingering heavy rainfall threat follows
the low track detailed in the Hydrology section of this discussion.

Trailing mid level deformation sustains a lingering pattern of
showers Thursday morning, diminishing in the afternoon as the
surface low moves farther into Ontario and Quebec. A fragile period
of dry weather is expected Thursday night that depends on brief
larger scale subsidence associated with the inbound broad upper
level ridge. This is a transition period toward a textbook nocturnal
convective scenario that becomes better organized Friday and
Saturday. Multiple waves of low pressure are model projected to
ripple along a front stalled along the Canadian border. Associated
nocturnal low level jet surges support convective clusters mostly
upstream Thursday night followed by a strong signal across the
northern Great Lakes Friday night. The long wave pattern then
steadily amplifies this weekend with the building upper level ridge
keeping increasing heat and humidity on schedule. Guidance high
temperatures well into the 90s and heat index around 100 look solid
for several days into early next week.

&&

.MARINE...

The evening phase of thunderstorm activity unfolds across Lake Huron
and Lower Mi with storms of severe intensity likely south of
Saginaw Bay. Small Craft Advisories then take effect late tonight
and Thursday for outer Saginaw Bay to Harbor Beach, and for Lake St
Clair and Lake Erie, associated with wind and waves trailing the
governing low pressure system as it exits the region. An active
shower and storm pattern continues through the end of the week while
gradually shifting farther north across the Great Lakes while heat
and humidity build across the region during the weekend.

&&

.HYDROLOGY...

Radar estimates indicate corridors of 1 to 2 inch rainfall that
occurred across SE Mi with the morning to early afternoon storms.
This is highlighted by a pocket of totals around 4 inches that
occurred in a 1-2 hr period in southern Macomb county that prompted
the Flash Flood Warning. This type of localized flood threat remains
possible as the evening phase of the this event progresses, then
once the evening line moves eastward, heavy rain potential shifts
northward toward the Tri Cities and northern Thumb with the surface
low track. The system continues to feed off Gulf moisture bringing
PW to near daily records (at or above 1.75") with warm cloud depths
of 12-15kft as measures of precipitation efficiency.

For the tonight period, additional average rainfall in the 1-2 inch
range is likely with localized higher totals possible tonight into
Thursday morning. The Tri-Cities to northern Thumb is most likely to
see a larger areal footprint of higher end totals given both the
potential for thunderstorm training and also noting any deformation
with the low pressure system leading to longer duration.

&&

.PREV DISCUSSION...
Issued at 143 PM EDT Wed Jun 18 2025

AVIATION...

A stalled frontal boundary near the I-69 corridor remains a focus
for convective initiation and additional storms early this
afternoon. Meanwhile, a disturbance is driving a cluster of storms
across the Metro area that will depart over the next hour or two. A
humid air mass holds in place with enough instability recovery
expected to support a round of organized/linear convection later
this afternoon into the evening as a strong low lifts in from the
Mississippi Valley. This round is highlighted in the prevailing
+TSRA group. Some of these storms may be severe with gusts up to 50-
60 kt as well as torrential downpours dropping vsby to IFR or
briefly LIFR. Ceilings lower to MVFR/IFR as the low tracks through
the area tonight through Thursday morning, and showers are likely to
linger overnight as well. Slightly less humid northwest flow follows
through early Thursday with ceilings trending back toward VFR during
the afternoon.

For DTW/D21 Convection...Ongoing convection exits shortly with a
relative lull in activity this afternoon before a broken line of
showers arrives from the southwest between 22 and 23z. This will be
capable of severe weather as well as torrential rainfall. This is
followed by a dry slot with gusty southwest wind overnight.

THRESHOLD PROBABILITIES...

* High for thunderstorms between 22 and 02z this afternoon and
  evening.

* Moderate for ceiling aob 5000 ft this afternoon, then high tonight.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.

&&

$$

DISCUSSION...BT
MARINE.......BT
HYDROLOGY....BT
AVIATION.....TF


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