Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 162303
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
703 PM EDT Mon Oct 16 2017

.AVIATION...

VFR will continue tonight through Tuesday as southwest wind
increases through the period. This will occur as low pressure tracks
through far northern Ontario while high pressure settles into the
Ohio valley. Pockets of broken/shallow altocu will give way to
scattered/broken cirrus during the evening which will then persist
overnight through Tuesday morning. Model soundings indicate some low
level jet development late tonight and marginal conditions for wind
shear, less than 30 knots at the top of the shear layer. Southwest
surface gusts near 25 knots do appear likely during Tuesday
afternoon.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 313 PM EDT Mon Oct 16 2017

DISCUSSION...

12Z DTX sounding revealed a lot of dry air in the 925-800 MB layer,
which has allowed for a good deal of sunshine today as the 700 MB
cold pool (-12 C)/thermal trough has just pulled east, and allowed
Lake Michigan clouds to finally be released and track into the CWA
late this afternoon, which should help hold max temps in the
mid/upper 50s.

Further mid level warming will take place tonight as rather flat
upper level ridge builds into the Central Great Lakes this evening.
Pretty good low level warm advection as well with the southwest
gradient developing tonight, as cold front tracks through Lake
Superior. With the gradient and warm advection, low temperatures
expected to hold around 40 degrees, despite the current dew pts in
the lower 30s. With surface high along the Ohio River, locations near
the Ohio Border will probably come in with the coolest readings, as
there is an opportunity for winds to decouple around midnight.

Weak 925-850 MB theta-e ridge axis to drop south into southern Lower
Michigan Tuesday afternoon, but too dry and stable (showalter index
around 10 C) to worry about many clouds, much less any precipitation
concerns. 925 mb temps reaching 13 C (per 12Z nam/euro) suggest highs
in the upper 60s, with Wednesday looking just as warm, if not
slightly warmer, as renewed increasing southwest flow gets going
ahead of another shortwave trough/cold front tracking through Lake
Superior Wednesday evening. This front will be stronger, but moisture
axis is still pretty lean tracking through Wednesday night, with PW
values getting up around three quarters of an inch. Another dry fropa
appears likely with majority of the upper level forcing displaced
well to the north.

Upper level ridging to move in Thursday and persist into the first
half of the weekend. Southerly flow around the high pressure center
over the eastern CONUS and warm air advection will help keep temps
above average and support a slight warming trend. Conditions will be
very pleasant with mostly sunny skies and highs reaching the low 70s
by Saturday.

Potent energy moving into the Pacific northwest will work to push
this ridge out of the area beginning Sunday. The next chance of
widespread rain returns to the area late Sunday into early Monday as
an upper trough digs through the Great Lakes. This trough is progged
to stick around the area through mid next week, leading to much
cooler temps and unsettled conditions.

MARINE...

Moderate westerly flow through the early afternoon across the Lakes
through this afternoon as the upper trough exits further to the
east. Surface high pressure will build in across the Ohio River
Valley and southeastern US as another low pressure system to our
north pass through northern Ontario. Michigan will be placed in
between these two system and it allow the gradient flow to
strengthen out of the southwest late tonight through tomorrow
afternoon. A long fetch of gusty winds out of the southwest at 20-30
knots will set up for much of Lake Huron basin and Saginaw Bay.
These winds should persist over the next couple of days as gradient
winds will remain elevated within this regime.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.

Lake Huron...Small Craft Advisory from 6 AM to 6 PM EDT Tuesday for LHZ421-422-
     441.

Lake St Clair...NONE.

Michigan waters of Lake Erie...NONE.

&&

$$

AVIATION.....BT
DISCUSSION...SF/TF
MARINE.......AA


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