Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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760
FXUS63 KDTX 262002
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
402 PM EDT Sat May 26 2018

.DISCUSSION...

Scattered thunderstorm activity will dissipate this evening with
loss of diabatic heating. Read earlier discussions for more detailed
information regarding thunderstorm coverage and impacts potential.
Model soundings show bulk of instability tied to the well mixed and
moist boundary layer which fades as the surface based inversion
develops tonight. Dewpoints in the mid 60s overnight will make
things muggy with lows dropping into that mid 60 range as well.

Deep midlevel trough axis tied directly with lower geopotential
height anomaly over northwestern Ontario will pass out of Lower
Michigan tonight. This will open the door to fairly aggressive
geopotential height rises for the region Sunday. Surface ridging
forecasted to expand eastward directly into the cwa with signal for
lake aggregate ridging. Main item for Sunday period is 850mb
temperatures warming some +3C degrees from today which will lead to
notable increase in high temperatures. Latest MOS and adiabatic
mixing technique is suggesting high temperatures in the 90 to 92
degree range for much of the cwa. Record highs at both DTW and FNT
will be possible. Model soundings depict a subsidence layer between
4.0 and 7.0 kft agl which will provide capping and a significant
amount of CIN. Given depth of the capping layer and compressional
heating, not expecting much potential for rain or thunderstorm
development. Guidance shows some higher terrain based activity
initiating over northern Lower Michigan during the afternoon that
may drift southeastward with time. Will maintain a entry chance PoP
for the northern cwa in support of collaboration. Conditional strong
storm risk would exist with any deep convection due to favorable
DCAPE thermodynamic setup.

Strong midlevel ridge center to become positioned over Wisconsin for
Monday which will put Southeast Michigan in deep anticyclonic flow
trajectories aloft. Interesting feature is enhanced anticyclonic
vorticity anomaly that will fold over and roll through the area
during the day. Given this dynamical forcing for descent and what
will be a preconditioned airmass for deep surface based mixing,
temperatures should warm additionally on Monday. Highs are
forecasted to climb above 90 degrees for most of the area.

Not considering any heat headlines for the early week period with
heat indices lowering into the middle to upper 60s tonight, Sunday
night and again Monday night. Undoubtedly hot and muggy weather with
heat indices rising into the low 90s Sunday and low to mid 90s
Monday.

Quiet and warm conditions expected Tuesday as surface high pressure
to the north and ridge aloft remain in place. Some relief from the
heat will be felt near the lakeshore as northeasterly flow around
the high brings some cooler air inland. 850 mb temps will hold out
in the upper teens C. High temps in the 80s still expected
regionwide, with lower 80s near the lakes and upper 80s elsewhere.
Clouds will be on the increase by early Wednesday as the remnants of
Alberto track northward into the Ohio Valley. Model guidance
currently in good agreement that these remnants will pass over SE
Michigan late Wednesday into Thursday, bringing periods of
potentially heavy rainfall through the day. This increase in cloud
cover and rain will help keep temps cooler in the lower 80s on
Wednesday and Thursday - still above average for late May.

A shortwave will approach the region from the west on Friday and
bring the potential for some showers and storms. Northerly flow on
the backside of this feature and the tropical remnants will usher in
a cooler airmass with highs Friday and Saturday expected to be in
the 70s. Amplified ridging will keep weather dry on Saturday.

&&

.MARINE...

Weak southerly flow through today as a weak low pressure moves in
from the northern Great Lakes. Favorable boating conditions today
with the exception of some scattered thunderstorm development this
afternoon and evening. Afternoon activity will affect mainly western
Lake Erie and north into the Detroit River with potential activity
across portions Lake Huron this evening. Aside from scattered
thunderstorms, generally weak flow through weekend will promote
favorable boating conditions through the rest of the holiday weekend
with a high pressure building across the Great Lakes early next
week.

&&

.CLIMATE...

Here is a list of record high temperatures for
this holiday weekend.

Sunday, May 27th:

Detroit                91 (set in 1941)
Flint                  90 (set in 1987)
Saginaw/Tri-Cities     94 (set in 1911)

Monday, May 28th:

Detroit                95 (set in 2012)
Flint                  93 (set in 2012)
Saginaw/Tri-Cities     92 (set in 1977)

&&

.PREV DISCUSSION...
Issued at 154 PM EDT Sat May 26 2018

AVIATION...

Main concern for this TAF period is development of thunderstorms
between 18Z and 01Z this afternoon and evening. Convective
initiation has already begun across areas southwest of YIP and DTW
in Lenawee and Washtenaw County. Have included tempo groups for -
TSRA this afternoon for expected activity. Scattered storms will
slide eastward through about 22Z affecting DTW, YIP, and DET.
Additional development is possible with incoming shortwave that
would affect the northern terminals. Tempo groups for -TSRA here for
slightly later in the afternoon and into the evening closer to
20/24Z. Expect lowering VSBYs under any thunderstorm that moves over
terminals. Aside from any terminals impacted by thunderstorms,
expect VFR conditions with southwest flow of 5-10 knots.

For DTW...Window for -TSRA will be from 18-22Z this afternoon.
Initiation has already started southwest of the terminal and will
move towards terminal airspace over the next few hours. Expect drops
in VSBYs and CIGs under with the stronger thunderstorms.
Thunderstorms will most likely bring ceilings below 5,000 ft if
terminal is impacted by thunderstorm activity.

DTW THRESHOLD PROBABILITIES...

* Medium confidence in thunderstorm occurrence. Low for directly
  impacting DTW.

* Medium in ceilings at or below 5 kft this afternoon with
  thunderstorms.


&&

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

$$

DISCUSSION...CB/TF
MARINE.......AA
CLIMATE......CB/TF
AVIATION.....AA


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at www.weather.gov/detroit.



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