Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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263
FXUS63 KDTX 231712
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
112 PM EDT TUE AUG 23 2016


.AVIATION...

Surface high pressure ridging over the area will pull off to the
east this afternoon while a warm front approaches the area on
Wednesday.  Southerly flow will continue across the area through the
period.  Scattered to occasional broken diurnal cu will occur this
afternoon in the 4-6k ft range as surface dewpoints slowly increase.
Models have some difference in timing of warm front and associated
precip with it Wednesday. Timing seems to range from late morning
to late afternoon. Will carry a prob 30 towards the end of taf
period for all sites. Bases with ceilings should remain vfr.

For DTW...Mainly scattered to possibly broken cu 4-6k ft this
afternoon dissipating with loss of daytime heating.  Mid to high
level clouds will advect in around 12z.  Models differs slightly
with warm front arrival and associated precip from late morning to
later afternoon. Consensus past few days has been later so will
carry tempo group of showers and thunderstorms late afternoon with a
prob30 for some early arrival of some rogue showers.

//DTW Threshold Probabilities...

* low for ceilings aob 5kft today. Medium Wednesday afternoon.
* Medium for thunderstorms Thursday afternoon.

&&

.PREV DISCUSSION...
Issued at 332 AM EDT Tue AUG 23 2016

DISCUSSION...

Upper ridge axis will slide into Michigan today, providing large-
scale subsidence as surface high pressure over the eastern U.S. also
remains dominant over the area. This should keep Southeast Michigan
dry and mostly sunny with just some afternoon cu popping up
underneath the subsidence inversion. More sunshine and a roughly 5C
rise in H850 temps should allow for a modest boost in temperatures
today, with highs expected to reach from near 80 to the low 80s.

The upper shortwave firing off convection over the Central Plains
will lift up across the Central/Northern Great Lakes Wednesday and
Wednesday evening, out ahead of the larger upper low as it tracks
from Alberta into southern Manitoba. Strengthening southwest flow
will advect deeper moisture into the area Wednesday through
Wednesday night, supporting mid-range pops as the shortwave works
across the area. Low-level jet looks weaker in latest model runs,
closer to 35 knots, reducing the threat for severe weather as SB
CAPE also now looks to remain near or less than 1000 J/kg as surface
heating is limited by earlier arrival of the wave and associated
clouds. PW values reaching between 1.75 and 2.0 inches will support
a heavy rain threat, however. Moist and unstable environment will
support a continued chance for showers and thunderstorms overnight
with any smaller shortwaves that work across, but most activity is
expected to end during the evening.

Surface trough and cold frontal passage will follow on Thursday as
the upper low opens up and moves through Ontario. This is expected
to trigger another round of showers and thunderstorms. Timing of the
cold frontal passage has varied over the past several model cycles,
with latest consensus showing a more favorable timing convection-
wise during the afternoon and evening. Stronger mid-level wind field
near the Ohio border may support a few stronger storms there. Warm
air advection ahead of the front, and possibly some early day peaks
of sun, will allow temperatures to warm more solidly into the 80s by
Thursday afternoon, especially across the far Southeast corner of
the state where the cold front will be later to arrive.

Upper wave will exit Thursday night allowing high pressure to build
for Friday into Saturday. This will bring another dry period before
the next upper trough renews chances for showers and thunderstorms
by Sunday.

MARINE...

Area of high pressure in place over the Ohio Valley will drift
eastward reaching the east coast by this evening. A tightening of
the pressure gradient will lead to increasing southwesterly flow
this afternoon. Surface winds are expected to reach the 15 to 20
knot range. The area that will be most impacted is Saginaw Bay where
wave heights are expected to increase to 2 to 3 feet by this
afternoon. The southwesterly winds will persist again on Wednesday
where windspeeds are expected to reach and exceed 20 knots Wednesday
afternoon. It appears that a small craft advisory may be needed in
some areas Wednesday or Wednesday night. Shower and thunderstorm
chances will also increase Wednesday night.

&&

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

$$

AVIATION.....DRC
DISCUSSION...HLO
MARINE.......CB


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at www.weather.gov/detroit.



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