Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 300358
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1158 PM EDT FRI JUL 29 2016

.AVIATION...

With slow approach of shortwave near southern Lake Michigan, the
coverage of convection may increase slightly from the very isolated
shra/tsra development of the past few days. Still, activity overall
will remain widely scattered and disorganized and probably better
left for shorter term forecasting. Will leave terminals void of
shras or tsras for this issuance. Outside this small chance of
convection affecting any one terminal, conditions will remain VFR
with steady northeast flow persisting throughout the forecast.

//DTW Threshold Probabilities...

* Low in thunderstorms affecting terminal overnight and again
  Saturday afternoon.

&&

.PREV DISCUSSION...
Issued at 348 PM EDT Fri Jul 29 2016

DISCUSSION...

Upper level trough over the western Great Lakes will guide the
forecast through most of the weekend. This feature lies in between
the dominate ridge over the southwestern US and upper low over
Quebec. Relatively weak flow in the vicinity of the trough will
result in slow forward propagation the next couple days.

As for the rest of today and into the overnight, scattered showers
and thunderstorms will continue to pop up within the band of high
theta e air across the southern half of the lower peninsula. With
the surface front over the Ohio Valley, there is no real low level
forcing to key in on for more organized convective development.
Instead we have a wave in the mid levels currently advecting across
southern MI with a more prominent wave expected overnight. The weak
flow previously mentioned is quite evident in the nearly stationary
storm motion with current convection. The mid level wave entering
the CWA will give cells a boost to the east. But in the meantime any
storm that goes up could result in brief heavy downpours and
localized flooding as PWATs remain high. Hard to give any area
likely pops or high as activity is quite sparse so will continue
with chance wording until activity looks worthy of more.

The upper level shortwave will release from the trough tonight and
hires models advertise the greatest height falls will track across
central Ohio with the deformation region skirting southern MI. This
lines up well with the current activity on radar across northern IL
and IN. Will increase pops south of I94 to around 50 and watch how
it persists with the loss of daytime heating. Another area to watch
tonight will be across the Saginaw Valley. There is a band of
isentropic ascent between 300-310K that has been active all day
producing scattered showers. It was most active last night with the
aid of nocturnal instability and models again try to light up that
layer tonight.

The upper level trough will track eastward across the area on
Saturday. Like the shortwaves, it will remain mostly to our south
with the northern periphery clipping southern MI. Timing looks to be
in the afternoon and evening which could increase coverage through
the latter half of the day.  Again, not getting too detailed at this
point as we deal with a weakly forced environment. System will be
pulling away on Sunday but models have it lingering a bit longer
over southeastern lower MI so will keep a slight chance mention on
Sunday for now.

High pressure seems to be the dominating theme across Southeast
Michigan for most of the week resulting in fairly quiet weather.
Moisture looks to stay out west until the end of the work week when
a low pressure system tracks across the area bringing the next
chance for precipitation. High temperatures will follow a warming
trend and reach into the upper 80`s by the end of the week.

MARINE...

Fresh northeast winds 20 knots focused over central and southern
Lake Huron this into tonight will allow for elevated wave heights in
the nearshore waters through late this evening. Small Craft
Advisories remain in effect for significant wave heights in excess
of 4 feet. Northeast winds will continue into the weekend, but
should hover more around 10 knots, allowing for significant wave
heights in the 2 to 4 foot range.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....dg
DISCUSSION...DRK/DE
MARINE.......JVC


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