Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 221633

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1233 PM EDT Mon May 22 2017


A pocket of dry air will bring clear sky to scattered cloud
conditions through the remainder of the afternoon. That will leave
the gusty southwest wind as the most significant aviation condition
until early evening. The gust component will diminish with the loss
of daytime heating while light gradient wind continues through the
night. A noticeable increase in mid clouds is expected during the
evening associated with low pressure moving through the border
region of Iowa/Wisconsin/Illinois. Some high based showers are
projected by most model solutions to move across SE Michigan mainly
affecting the FNT to MBS area with some VFR rainfall. Upstream
observations also indicate some lightning over Iowa during the late
morning in support of some of the models with greater rainfall
intensity over lower Michigan tonight. The forecast approach for now
will be to carry a tempo group for VFR light rain at MBS and monitor
trends for coverage and intensity in later updates.


* None.


Issued at 350 AM EDT Mon May 22 2017


Weak longwave pattern setting up across North America this week with
models forecasting all jet streaks to be fairly compact and stay
below 100 knots. With the lack of flow, it will be hard to displace
the current trough in place centered over the Midwest. The slow
evolution of the trough will lead to a fairly dismal forecast with
plenty of clouds and periodic showers through most of the week.

Today will be possibly the driest day in the forecast as shortwave
ridge develops over the region in response to the upper low
fracturing. Half of the energy embedded in the upper low will shear
off to the northeast while the second half gets drawn southward,
phasing with an incoming jet streak which relocates the upper low
over the mid Mississippi Valley by Wednesday. This then places SE MI
in a region of SW flow down stream of the trough which will direct
several pieces of energy into the region mid week. Hard to determine
extent or converge of these weak impulses this far out, but
confidence is higher during the Wednesday night period as a stronger
lobe of vorticity rotates around the low up into southern MI with an
associated surface reflection. Otherwise look for chance pops most
of the week with the best chance of a dry day coming on Friday as a
mid level ridge slides across MI. The upcoming holiday weekend is in
limbo as models try to hold a ridge over the area but also start
bringing the next low up into the Ohio Valley with troughing laid
out across the western Great Lakes.

A few more notes about today. The daytime hours will be breezy with
west-southwest winds gusting to near 30 mph. Mixing depths up to
around 4-5k ft may tap into winds around 30 knots. Deep layer winds
averaging the mid teens will keep sustained winds elevated
regardless with higher gusts coming in the afternoon. Heading into
tonight we will introduce the next chance of precipitation as the
nose of theta e plume lifts into the area, likely after 06z. There
remains an opportunity for a few elevated thunderstorms but weak
CAPE will make it hard to get much coverage until Tuesday when
better low level lapse rates and elevated instability sets up.


Gradient will strengthen today in response to low pressure tracking
north of lake Superior.  This will bring a corresponding increase in
southwest wind across local marine areas today.  Gusts to 25 knots
are forecast to impact much of the nearshore waters, including
Saginaw Bay.  A small craft advisory is now in effect.  Winds will
ease after sunset, with a period of more modest south to southeast
wind developing for tonight and Tuesday.  Conditions will become
increasingly unsettled during the midweek period, as low pressure
sinks into the region.  This may result in a period of stronger
easterly winds on Wednesday.  In addition, the potential will exist
for bouts of showers with some thunderstorms.




Lake Huron...Small Craft Advisory until 8 PM EDT this evening for LHZ421-422-

Lake St Clair...NONE.

Michigan waters of Lake Erie...NONE.




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