Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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241
FXUS63 KDTX 301659
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1259 PM EDT THU JUN 30 2016

.AVIATION...

VFR with light sw wind will gradually veer to wsw in advance of an
approaching front. Exceedingly dry antecedent airmass is cause
for skepticism regarding initial cigs, but suspect a period of
MVFR will be possible in the wake of the front either way after a
couple of hours of light rain with limited vsby reduction. Daytime
heating on Friday will lift remnant cigs to around 5kft during the
day.

//DTW Threshold Probabilities...

* Moderate for cig aob 5kft

&&

.PREV DISCUSSION...
Issued at 323 AM EDT Thu Jun 30 2016

DISCUSSION...

High pressure will continue to sink south and east today as the
upper trough stretched from Ontario back through Saskatchewan swings
down towards the area. This trough is expected to pivot across
Michigan tonight, with a quick shot of deep layer forcing and narrow
theta-e plume bringing a chance for showers and thunderstorms late.
Until then, model forecast soundings look capped and pretty dry
through the daytime heating cycle today, and continue to support a
dry forecast. Temperatures will continue to warm today, with max
temps fairly close to 80.

Frontal boundary is expected to push across the area between 1AM and
10AM. Low-level FGEN, mid-level PVA, and left exit region forcing
will support the chance for showers and thunderstorms along the
front. Instability overall still does not look great but better than
24 hours ago. NAM cross-sections show a shallow layer of steep lapse
rates (750-850mb) positioned just above the FGEN layer. GFS/NAM also
now show a weak corridor of 25-30 kt low-level winds feeding into
southern Lower Michigan late, with warm air advection through this
layer likely boosting the elevated instability. Current radar shows
an area of showers (earlier there were thunderstorms) along the
front over Minnesota and Lake Superior. This raises confidence that
forcing should be strong enough to generate showers later tonight
despite very dry airmass preceding the system. Kept pops at high
chance however until we can see effects of diurnal heating cycle
upstream, although confidence is higher for south-central Lower
Michigan closer to the upper wave and cooler air aloft. Window for
showers will be short, with activity most likely only affecting each
location for a few hours. Negative showalter indices and models
kicking out a few hundred j/kg of CAPE continue to support low
thunder chances tonight and early Friday before showers/tstorms exit
east with the cold front.

High pressure should provide dry and quiet weather Friday evening
through Sunday night. Max temperatures will take a slight hit behind
the front, then moderate back up around 80 again by Sunday.

Upper wave lifting through the Ohio Valley now needs to be closely
watched for potential to impact the forecast for the Fourth of July
holiday and Monday night. All medium-range models have made a jog to
the north with the wave, although the GEM remains a northerly
outlier. For now consensus forecast with low chance pops from
Detroit southward looks appropriate for late Monday and Monday
night.

Upper ridge is still favored to build into the area for the middle
of the week, allowing heat and humidity to seep back into the area.

MARINE...

Marine wind will remain light and generally from the south today
prior to the passage of a cold front tonight. This front will bring
a pattern of showers and a few thunderstorms through the region
after midnight through Friday morning. Moderate northwest wind will
develop behind the front, especially over northern and central Lake
Huron. Wind speed and wave height remain below small craft advisory
levels over southern Lake Huron before high pressure arrives
Saturday and remains in place through the holiday weekend.

&&

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

$$

AVIATION.....JVC
DISCUSSION...HLO
MARINE.......BT


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at www.weather.gov/detroit.



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