Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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396
FXUS63 KDTX 291952
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
352 PM EDT Mon May 29 2017

.DISCUSSION...

Forecast remains dominated by an upper low that will continue to
wobble around over Ontario and Quebec through the week. A series of
troughs will rotate around this low through the Great Lakes
presenting several opportunities for increased cloud cover and
possibly some precipitation. In addition, temperatures will
fluctuate around normal for the end of May, low 70s, as the
shortwave troughs and ridges slide through.

This afternoon we are dealing with possibly the best setup for
showers and thunderstorms through the end of the week as the first
of these shortwaves works through the area. Aided by the left exit
region of a jet streak to our south, decent vorticity lobe expanding
outward from the low, enhanced ribbon of theta e, and strong low/mid
level lapse rates to utilize around 500 j/kg of elevated CAPE, we
should continue to see a scattered coverage of showers and
thunderstorms through the evening hours. Should also mention the
lake breeze noted over Macomb and St Clair Counties this afternoon
at the onset of the showers. Typical leads to enhanced activity near
Lake St Clair and the St Clair River. The loss of daytime heating as
the shortwave moves east this evening should end precip chances
through the overnight.

Other issue for the remainder of the evening will be the enhanced
wind field across the area. Fairly tight pressure gradient from the
tightly wound stacked low combined with deep boundary layer mixing
will allow winds to continue to gust to around 25 to 30 knots. This
is fairly uniform across southern lower MI, although there is a
slight uptick in winds over the Saginaw Valley with a few gust
topping 30 knots. With the overall setup changing little for
Tuesday, one can expect gusts again to reach into the mid 20 knot
range.

The next shortwave will arrive Tuesday afternoon but with a drier
airmass and less instability we will expect to see less coverage of
showers as they likely struggle to develop. Lapse rates will still
be favorable as cooler airmass slides in aloft, and CAPE could still
reach a few hundred J/kg, thus we`ll keep the slight chance mention.

Wednesday will be a bit of a different scenario as the main upper
level trough axis sweeps through lower MI. Still dealing with a
drier airmass which will make showers struggle to develop, but broad
area of decent low level lapse rates, with some skinny CAPE aloft
and overall lift induced by the trough could result in some
scattered showers. Much drier air works into the region later in the
day behind the trough as flow more northwesterly.

Extended Forecast Wednesday through Tuesday: Quasi-stationary low
pressure center returns over northern Ontario by Thursday. This will
result in the familiar weather pattern that has persisted over the
past few weeks with several short waves being shuttled through lower
Michigan. At least chances for showers and or thunderstorms in the
forecast for late Thursday night through early Saturday morning.
Meanwhile, surface low pressure organizing over the central and
southern plains is expected to feed warm, moist air northward into
the pocket of the Ohio River Valley by early next week. Translation:
more chances for rain developing for Sunday and Monday.

&&

.MARINE...

Late day gusty southwest winds will ease some tonight as nocturnal
stability takes holds.  Renewed gustiness will then commence on
Tuesday as the region remains under the influence of upper level low
pressure.  Gusts in excess of 25 knots most likely over Saginaw Bay,
where a small craft advisory remains in effect through Tuesday.
Persistent southwest to westerly winds will a modest increase in
speed and gustiness each afternoon through the midweek period.

&&

.PREV DISCUSSION...
Issued at 118 PM EDT Mon May 29 2017

AVIATION...

Diurnal expansion of high based cumulus /6 to 7k ft cigs/ will leave
a period of bkn coverage through the latter half of the day.  Window
for a few showers/isolated thunder this afternoon, particularly
across the Detroit corridor.  The probability of thunderstorms will
remain too low to include.  Peak diurnal mixing will yield gusty
conditions, peaking into the 25 knot range from the southwest.  Loss
of diurnal support will bring a reduction in wind speed and
gustiness, along with decreasing cloud cover after 00z.

For DTW...Isolated TSRA remains plausible through 00z, but the
probability remains too low to mention.

//DTW THRESHOLD PROBABILITIES...

* None.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 10 PM EDT Tuesday for LHZ421-422.

Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

DISCUSSION...DRK/DE
MARINE.......MR
AVIATION.....MR


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