Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 240357
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT SAT JUL 23 2016

.AVIATION...

The frontal boundary stalled near the Ohio border will begin to move
back through southern lower Michigan during the night. This front
will bring the return of increased moisture to support MVFR
restriction in a combination of fog, rain showers, and possibly some
IFR in a few thunderstorms. Expect remnants of ongoing thunderstorms
near the south end of Lake Michigan to combine with new development
from Wisconsin into lower Michigan during the predawn hours and then
take through early afternoon to clear eastward. That will leave the
SE Michigan terminals in position for VFR in another warm and humid
day before the next round of storms develops with the trailing cold
front toward Sunday evening.

For DTW... The stalled front near the Ohio border will make a
northward move during the night and bring increased humidity back
into the area. Remnants of ongoing storms will combine with new
development before reaching DTW around sunrise and last off and on
through early afternoon.

//DTW Threshold Probabilities...

* Low for thunderstorms toward sunrise through early afternoon.

* Moderate for ceiling at or below 5kft.

&&

.PREV DISCUSSION...
Issued at 950 PM EDT Sat Jul 23 2016

UPDATE...

Convective trends are the primary forecast issue for overnight
through Sunday morning starting with the activity ongoing to our
west at press time. Of the two convective complexes expect the
trailing cluster over northern IL to make the most eastward
progress during the night. The leading cluster should stay
tight to the instability axis/southern portion of the gradient
which would take it into NW Ohio if it does not dissipate sooner
with the loss of larger scale support and surface heating. Other
important aspects to keep in mind are the influence of the
associated MCV moving eastward and the synoptic scale front
moving northward. The current convective complexes have a history
dating back through early this morning over the central plains.
The upscale growth and longevity has led to a substantial MCV. The
circulation is masked by convection in satellite imagery but radar
mosaics indicate a clear circulation in the second cluster that is
part of a larger scale wave aloft analyzed in model data. Expect
the MCV will be able to regenerate showers/storms during the night
as the synoptic scale low pressure system pulls the front back
north through lower Michigan. The resulting larger scale moisture
transport/isentropic lift will be effective enough on its own to
generate convection that is expected to linger through Sunday
morning. The late evening forecast update will extend 30 POPS over
all of SE Michigan prior to 12Z and raise to 40 for points west
and north. Entry level 60 POPS for the Tri Cities and Thumb down
to Flint look good Sunday morning with some potential for
southward expansion upon further review of convective trends
during the night.

PREV DISCUSSION...
Issued at 314 PM EDT Sat Jul 23 2016

DISCUSSION...
Hot day today as mid level ridge axis continues to slide in from the
west.  Atmosphere over the area is relatively dry per 12z dtx
sounding with pw around an inch.  This is seen as dewpoints that
started the day around 70f have fallen to as low as the low 50s
with diurnal mixing.  This drier air has allowed temperatures to
climb well into the 90s most locals under sunny skies.  Humidity has
also continue to fall helping to offset the higher temperatures as
far as heat indices have gone past two days.  Expect mostly clear
skies rest of this afternoon and evening with a few cu along
some lake breeze boundaries and some high thin cirrus from convection
over Wisconsin may be seen towards sunset.

Very hot and humid air over the Mid West will begin working its way
toward southeastern Michigan overnight as temperatures this
afternoon out there have climbed into the upper 90s with dewpoints
around 80.  Will see dewpoints bottom in the 50s most location early
tonight then rise into the 60s by daybreak. Mid and high level
clouds will also be on the increase later as convection over
Minnesota and Wisconsin in the highly unstable airmass works its
way east.  This convection will weaken as enters the western
portions of the CWA as better instability will continue to remain
just to the west so will just carry slight chc for precip far western
portions of the area.

Hot moist air will quickly overtake the forecast area Sunday ahead
of approaching cold front that will push through Sunday night.
Showers and thunderstorms Sunday will be dependent mostly on any
type of meso boundaries for initiation so precise time or location
will be hard to come by.  So expect showers and thunderstorms to be
scattered and not an all day event.  Temperatures will also be
dependent on how much if any precip occurs early in the day and
amount of cloud cover.  If precip is scarce early and enough
sunshine occurs, could easily see temps in the mid 90s with mid 70
dew points leading to possibly a heat advisory.  If rain is a bit
more widespread in the morning along with clouds, then most locations
may only see upper 80s to around 90.  At this point looking how
substantial the heat is to the west today and lack of any solid
focus for convection initiation, feel like low to mid 90s are more
likely.

Cold front will slowly move through the forecast area Sunday night
and exit the area by mid Monday morning.  Scattered showers and
thundestorms expected to accompany frontal passage.  There is a
marginal risk for severe weather as forcing is mainly frontal
convergence as upper dynamics will lag the front and also be far
removed to the north.  The main threat will be wind gust from load
shedding of precip as pwats will be quite high.

Monday still remain quite warm as frontal passage is more of drier
air then cooler.  Expect highs still in the upper 80s to around
90 far south as clouds exit the state by afternoon.

Absence of forcing and fairly weak mid/upper-level flow indicated by
midrange guidance argues for a dry forecast Tuesday/Wednesday.
Shortwave energy for the end of the week will cause the flow to
transition to more broadly trough-y, which may be enough to generate
periods of rainfall late week into next weekend. Still low
confidence on narrowing down the timing so broad chance PoPs will
suffice for now. Temperatures expected to remain above normal
Tue/Wed before easing back toward normal Thu into the weekend.

MARINE...

Light wind conditions will transition to modest south/southwest flow
on Sunday. Speeds will increase the most across Lake Huron into the
15-20 knot range with lighter wind conditions on Lake St. Clair and
Lake Erie. The wind will transition to lighter northwesterly Sunday
night into Monday. Thunderstorms are possible toward daybreak
Sunday...especially across Lake Huron. Additional thunderstorms are
possible again later Sunday and will mainly affect Lake St. Clair
and Lake Erie.

HYDROLOGY...

Showers and thunderstorms are possible early Sunday and again toward
Sunday evening. Any activity Sunday morning should be weakening as
it moves across Southeast Michigan - resulting in amounts generally
less than a half inch. Thunderstorms that develop later Sunday will
be capable of heavier downpours and localized rainfall amounts
exceeding one inch.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

AVIATION.....BT
UPDATE.......BT
DISCUSSION...DRC/DT
MARINE.......Mann
HYDROLOGY....Mann


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