Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 281941
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
341 PM EDT Wed Jun 28 2017

.DISCUSSION...

Surface low pressure advancing towards the northern Great Lakes
region will continue to push a warm front up across northern WI and
into western MI.  Convection from this morning has slowly weakened
and continues to do so as it crosses into Michigan.  The warm front
did spark development out ahead of the the morning convection as it
moved across eastern WI.  This is what we have been watching with
the activity slightly outpacing some of the model data.  12Z
soundings from both DTX and APX showed quite a bit of drier air in
the column with the ridging that has been in place.  While this has
helped in holding off precip, moisture advection coming into the
area should help in maintaining some of the precipitation. Forecast
is on par with the trends as the northern half of the CWA will see
better chances for activity through the later afternoon and into the
evening. Rainfall amounts are expected to stay on the lighter side
through early Thursday morning, generally less than half an inch.

Surface based convection has already started to develop back across
the Midwest this afternoon.  This activity is expected to weaken as
it pushes east overnight. Activity is then expected to increase in
coverage Thursday morning as the area remains in the warm sector
coupled with the advancement of the warm front across the area.
There is still uncertainly in just how much coverage there will be
as it moves into the warm sector tomorrow morning. With instability
increasing, SPC has nudged both the marginal and slight risks
northward with main concerns for strong winds during the afternoon
and evening periods. Going into Friday, chances are still there for
storms as the cold front pushes through.  Friday looks to be the
best chance for storms as opposed to Thursday, but again will be
dependent on how convection from the previous day plays out.  The
entire CWA continues to be highlighted in slight risk for Friday.

Warm air advection will continue to bring warmer temperatures into
the area through the end of the week.  Highs on Thursday are
expected to be the warmest for the week with highs warming into the
lower 80s.

A wet weather pattern looks to be in store for Southeast Michigan
during the weekend into early next week. The first wave of low
pressure will move in on Saturday bringing the chance for showers
and thunderstorms diminishing by the afternoon hours. A high
pressure system will then build into the Great Lakes region on
Sunday, bringing relatively dry weather, however, an isolated shower
would not be out of the question. Another wave of low pressure will
then move through the region Monday evening into Tuesday allowing
for chances of showers and thunderstorms yet again. High pressure
then looks to move into the area on Wednesday, bringing drier
conditions. Temperatures will remain seasonal, with high
temperatures hovering around the upper 70s to low 80s, and overnight
lows in the 60s.

&&

.MARINE...

Low pressure developing over the western Great Lakes will continue
to support increasing southerly wind over marine areas tonight
through Thursday. Moderate speed will be more common over Saginaw
Bay and over western Lake Erie where channeling and alongshore flow
respectively will enhance gusts. Small craft advisories are in
effect overnight through Thursday evening for these areas as well as
for Port Austin to Harbor Beach around the tip of the Thumb. This
wind pattern will bring in warmer and more unstable air into the
region before easing Thursday night into Friday. The warmer air will
fuel increased thunderstorm activity as low pressure over the
northern Great Lakes Thursday drags a diffuse surface trough through
the region Friday into Saturday.

&&

.HYDROLOGY...

Low pressure tracking into the northern great lakes tonight will
pull a warm front into lower Michigan. Thunderstorms in progress
over the Midwest and western Great Lakes will tend to focus more
along this front through central lower Michigan overnight through
Thursday morning. Rainfall amounts are generally expected to be in
the range of one quarter and one half inch north of I-69 through
Thursday morning. Locally higher totals around 1 inch will be
possible due to clusters of thunderstorms.

Additional storms may develop throughout Thursday and Thursday night
as warm and increasingly humid air builds into the region but with a
focus more to the south of the I-69 corridor. Average rainfall
amounts will be generally less than one half inch, but localized
higher amounts in excess of an inch will once again be possible
within any more concentrated areas of thunderstorms. This will be
followed by another low pressure system tracking west of the region
that will maintain the threat for thunderstorms Friday and Friday
night.

The potential for flooding will be dependent on the cumulative
rainfall totals during this active period. Should a more focused
region of heavy rainfall emerge, then the potential for a
corresponding rise of area rivers and streams, as well as minor
flooding will be possible. Central Lower Michigan will remain most
susceptible as the area continues to recover from recent flooding.

&&

.PREV DISCUSSION...
Issued at 1253 PM EDT Wed Jun 28 2017

AVIATION...

Upstream radar trends indicate showers and a few storms surviving
the usual morning weakening pattern for nocturnal convection. Mid
level moisture transport is strong enough to maintain at least
scattered shower coverage that is expected to brush through MBS
during late afternoon and early evening. This is projected to be VFR
outside of thunderstorms, coverage of which will be monitored for
possible inclusion in later updates. A new round of surface based
storms will then develop over the Midwest today and move into lower
Michigan overnight in a weakening phase. Coverage of showers will
then combine with the advancing warm front and warm sector to make
MVFR possible through Thursday morning. The strong low level jet
during the night prior to the warm front passage continues to
warrant mention of low level wind shear through mid Thursday
morning.

For DTW... Added a prob mention of weakening showers to the forecast
for late tonight through mid Thursday morning. This activity could
combine with the advancing warm front for ceiling below 5000 ft
while MVFR is more likely farther north.

//DTW THRESHOLD PROBABILITIES...

Low for ceiling 5000 ft or less overnight into Thursday morning.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from midnight tonight to 10 PM EDT Thursday
     for LHZ421-422-441.

Lake St Clair...NONE.
Michigan waters of Lake Erie...Small Craft Advisory from midnight tonight to 4 PM EDT Thursday for
     LEZ444.

&&

$$

DISCUSSION...SP/MV
MARINE.......BT
HYDROLOGY....BT
AVIATION.....BT


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