Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 201731

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
131 PM EDT Tue Jun 20 2017


Frontal boundary will continue to push into the area this afternoon
into the evening.  Diurnal cumulus have developed this afternoon and
so have some spotty shower activity over northern portions of the
area.  Best chances for showers (isolated thunder) will be northern
TAF sites as activity coming in from the west continues to hold
together. This activity will diminish later this evening as high
pressure starts to work into the area overnight and brings clearing
skies. Westerly/southwesterly winds continue to gust into the 20 mph
range ahead of the front before diminishing this evening.

For DTW...Broken ceilings around 5k feet will continue to work in
this afternoon.  Will maintain previous forecast which leaves the
area dry.  Better shower chances continue to be north of metro.
Decent pressure gradient will continue before the cold front passes
and allows the gradient to weaken later this evening.


* Very low for thunderstorms late afternoon into early evening.

* Medium in ceilings around 5000 feet this afternoon.


Issued at 945 AM EDT Tue Jun 20 2017


Small batch of organized showers currently tracking across Wisconsin
in advance of a vigorous shortwave embedded within northwest flow
aloft. Radar presentation yields sufficient confidence to bump pops
up to likely mainly along/north of M-59 this afternoon within the
corridor of strongest forcing. Lack of system moisture and dry air
noted in 12z DTX sounding suggest high based light rain outside of
any locally stronger convective cores. Lead showers associated with
warm advection mainly north of I-69 will be possible during the late
morning/early afternoon prior to arrival of the main batch of rain.
Given the dry air noted in the column, an isolated precip loaded wind
gust to 45 mph will be possible.

Issued at 338 AM EDT Tue Jun 20 2017


Active weather pattern through the week as we first continue to deal
with persistent upper level low and associated troughs rotating
about it. Later in the week it looks like we may have frontal
boundaries laid out over, or very near, southern lower MI. This will
provide several days of possible showers and thunderstorms depending
on where this boundary falls.

Showers and a few isolated thunderstorms have been able to linger
through the overnight hours over the Thumb. Forcing appears to be a
shortwave seen on WV imagery tracking across northern lower MI aided
by broad cyclonic flow and residual axis of moisture and
instability. Activity will briefly die down this morning before the
next trough axis and shortwave combine over southern MI this
afternoon. Similar setup to Monday although moisture quality is
less, instability is lower (sub 500 J/kg) due to cooler surface
temps and warmer air beginning to advect into the mid levels.
Freezing levels will start off lower than Monday, down to about 7-
8kft, keeping small hail in play. Shear will be notably higher,
averaging 40-50 knots across SE MI. DCAPE suggests some potential
wind gust issues, especially considering core of winds is lower in
the column with 50 knots down to around 15kft. As the trough swings
through this afternoon, the shortwave rounding the base of the broad
mid level trough, will shear out with a portion lifting into the mid
level low to the north and a portion diving south further into the
trough. This could result in both the Thumb and Ohio border seeing
higher coverage then mid portions of the CWA. Regardless it looks
like scattered showers and thunderstorms will persist through the
afternoon hours before waning once again.

Surface high pressure will build in tonight with low amplitude
longwave ridge aloft. This should effectively scour out the
remaining showers and bring a brief dry spell to the area.
Temperatures will increase back into the upper 70s, on their way to
80 by Thursday as the ridge brings 850mb temps back into the mid

Dry conditions will come to an end by Wednesday night or Thursday
morning as models hint at some nocturnally driven convection
upstream tracking across southern MI around 12Z Thursday while an
elevated warm front ushers in theta e rich airmass with models
developing showers on the lead gradient. The convective cluster or
shortwave will leave a baroclinic zone in its wake laid out
somewhere across the region. The boundary will be aligned with the
mean flow leading to it meandering about the region. Several rounds
of precipitation will be possible with this setup, but will be very
dependent on location of the front at any given time. Models keep
the front over the region into Friday night before a strong
shortwave tracks through pushing it south and east. The passage of
this cold front will bring back cool cyclonic flow with more
potential for showers and thunderstorms.


A broad trough of low pressure over the Great Lakes will maintain a
moderate westerly component flow through tonight enhanced slightly
by a shortwave passing through the region along the southern fringe
of this mean upper trough. This disturbance will bring scattered
showers or thunderstorms to parts of the area this afternoon and
evening. High pressure will then build into the region in the wake
of this wave, bringing relatively calm conditions on Wednesday.

Additional showers and thunderstorms will be possible again Thursday
as low pressure develops to the west and pushes a warm front north
through the central Great Lakes. The passage of this front will also
bring moderate southerly flow to the area.


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



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