Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 261046
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
646 AM EDT Mon Jun 26 2017

.AVIATION...

Equivalent potential temperature plan view analyses show the main
axis of midlevel moisture remains sheared out across the northern
cwa. This corresponds well with light shower activity that persists
over the northern forecast area particularly downwind of Saginaw
Bay. There is little forecasted movement of this moisture axis
tonight. With the moisture flux upstream off of Lake Michigan, a low
chance for a shower will continue throughout the night. VFR to MVFR
stratocumulus will be widespread solely due to the magnitude of cold
air in the lower troposphere. Maintained the tempo group for showers
during the late afternoon for KMBS and KFNT. Compact surface trough
and main cyclonic circulation will push down into the northern cwa
and track across during the afternoon. This added convergence should
be more than enough to focus another persistence forecast.

//DTW THRESHOLD PROBABILITIES...

* Low to moderate for cigs aob 5kft tonight.

* Low for winds reaching crosswind thresholds from 270 degrees

&&

.PREV DISCUSSION...
Issued at 353 AM EDT Mon Jun 26 2017

DISCUSSION...

Michigan will remain entrenched within an upper trough encompassing
the Great Lakes once again today. Upper heights will fall this
morning as a strong upper shortwave over northern Minnesota and
Wisconsin approaches. The wave will cross Lower Michigan this
afternoon and evening, helping to provide a focus for showers and a
few thunderstorms. Cold pool associated with this wave will track
through Central Michigan, once again focusing the highest coverage
of showers/tstorms over the northern portion of the forecast area.
That being said, will keep pops in the low to mid range as low-level
dry air remains in place below 7000 feet and we see little in the
way of moisture advection today. Instability does not look too
strong given cool temperatures, with ML CAPE expected to remain less
than 500 J/KG. This should limit potential for thunder to isolated,
along with accompanying heavy rainfall. Conditions will become
breezy this afternoon and continue through the early evening.
Surface low pressure near Lake Huron will deepen today as the strong
upper wave approaches. This will create a moderately tight westerly
gradient between this low and high pressure building into the Plains
and Ohio Valley. Mixed layer looks to support gusts to around 30
mph. Cool air will remain in place under the upper trough, while
clouds during peak heating limits insolation. This should keep max
temperatures down in the mid 50s to near 70 today, fairly similar to
yesterday.

Upper wave and instability generated by its cold pool will slide east
this evening, leaving subsidence in its wake. Showers should push
out of most of Southeast Michigan during the evening, with just a
few showers persisting over the Thumb late. Skies are not expected
to begin clearing until towards sunrise however, as moisture axis
now over the northern Great Lakes pivots down through the area as
the low exits. Limited radiational cooling potential will hold min
temps in the upper 40s and low 50s.

Some of the moisture lingering from behind the low will remain over
the area, especially the eastern portion of the forecast area, into
Tuesday as moisture builds during the heat of the day. This could
potentially fire off a few showers or even a thunderstorm,
particularly closer to the lake shores if the gradient relaxes
enough for lake breezes to work inland. High pressure expanding into
the area from the Ohio Valley may suppress any convection, however.
Quieter weather is expected for most of Wednesday as the high
becomes the dominant feature.

More active pattern then looks to become established from Wednesday
evening through the end of the week as upper energy off the West
Coast moves into the Upper Midwest and Great Lakes. Strong low-level
jet under a region of upper diffluence combined with steep mid-level
lapse rates Wednesday night could ignite complex of storms along a
warm front as it lifts through the Upper Midwest and Western Great
Lakes. This area of rain/thunderstorms would then move into Lower
Michigan late Wednesday night, maintained by the low-level jet.
Severe weather is not yet a concern for Southeast Michigan overnight
as activity looks to remain elevated and lapse rates don`t really
begin to steepen until after sunrise. Primary threat right now looks
like potential for heavy rain as precipitable water values rise to
around 1.75 inches.

MARINE...

Another period of gusty westerly conditions will emerge today, again
warranting small craft advisories for Saginaw Bay, Lake St Clair and
the Michigan waters of Lake Erie.  A standand response with gusts
peaking during the afternoon, before rapidly easing by sunset. Light
to moderate wind will then dominate until the arrival of the next
system Wednesday into Thursday. Moderate southerly wind will
transition to fresh southeasterly during this time, the stable
southerly fetch limiting gustiness.

HYDROLOGY...

Scattered showers will again develop today, with the greatest
coverage during the afternoon and early evening hours.  Though rain
may briefly be heavy on a local basis, basin average rainfall is
expected to remain under one tenth of inch today and no noteworthy
response to area rivers and streams is anticipated. The next chance
for organized rainfall will be Wednesday night into Thursday when up
to one half inch of rain will be possible. Rivers levels along the
Tittabawassee River continue to slowly fall, with the river expected
to drop to moderate flood stage later this morning.  Meanwhile, The
Saginaw River continues to slowly rise and will crest on Tuesday
morning at moderate flood stage.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 10 AM this morning to 8 PM EDT this
     evening for LHZ421-422.

Lake St Clair...Small Craft Advisory from noon today to 8 PM EDT this evening for
     LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from noon today to 8 PM EDT this evening for
     LEZ444.

&&

$$

AVIATION.....MR
DISCUSSION...HLO
MARINE.......MR
HYDROLOGY....MR


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