Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 171902
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
302 PM EDT Fri Mar 17 2017

.DISCUSSION...

Lead band of precipitation along elevated warm front in advance of
approaching low pressure and parent shortwave has pretty much gone
completely to slowly saturating the lowest 10-15kft atmospheric
column (12z KDTX sounding depicts the dry airmass in place below 500
mb this morning).

Expect rain and snow shower activity to increase to some extent
along this first frontal boundary early to mid afternoon. That said,
no accumulations are expected initially as this moisture continues
to dry up and surface temperatures hold in the 35 to 40 degree range
for most locations.

Secondary frontal boundary lower in the atmosphere will progress
steadily eastward into the forecast area in behind this lead front.
Shower activity being forced by this feature has been on the uptick
over southern Lake Michigan late this morning and expect this trend
to continue as this front moves into the area mid to late afternoon.
With some degree of instability along this frontal band, a number of
the convective elements have become rather vigorous midday (even a
few in cloud lightning strikes noted in cell over southern Lake
Michigan) and see no reason for this trend not to persist into peak
heating late this afternoon.

Precipitation chances will increase notably with this second front
after 18z-20z, and given the convective nature, snow accumulations
will still be possible despite the relatively mild boundary layer
conditions. The caviot(s) in this scenario will be that the snow
accumulations on the order of an inch or a bit more will be limited
in areal coverage and also limited mainly to grassy and/or elevated
surfaces given the degree of solar insolation that has occurred
today in advance of the precipitation/thickening clouds.

The main shortwave/low pressure digs southeast over area late
tonight into Saturday morning, maintaining a chance of rain/snow
shower activity or perhaps periods of drizzly weather tonight into
Saturday as this system basically pivots down frontal boundary as it
settles over area. Even with this system moving into the area from
Canada, very little cold air is tapped with temperatures only
settling down to around freezing tonight before climbing back into
the 40s Saturday as mid March sunshine overcomes shallow cold pool
of air to a large degree.

Dry and relatively mild conditions persist through Sunday as the
temperatures again climb into the 40s after bottoming out in the 25
to 30 degree range Saturday night.

Next week will begin and end with the potential for precipitation,
however the majority of the week will feature dry conditions.  A
cold front will push across the region on Monday bringing a chance
for mainly rain showers as temperatures remain above freezing.
Arctic high pressure then fills in behind the cold front Monday
night and holds through Thursday, keeping the area dry. Temperatures
will start off a little warmer at the front end of the week before
cooling off slightly by the middle of the week.

&&

.MARINE...

A low pressure system will track across southern Michigan on
Saturday. Increased southerly flow ahead of the system will be
tempered by stable warm air aloft which should cap any gusts to
around 25 knots through tonight. Winds will then back over Lake
Huron while veering over Lake St Clair and Lake Erie due to the
track of the low. Wind speeds should decrease under the low pressure
center which should minimize the impacts of the changing wind
directions while becoming light and northerly across the region by
Saturday night.

&&

.PREV DISCUSSION...
Issued at 144 PM EDT Fri Mar 17 2017

AVIATION...

Complex aviation forecast out ahead of an approaching trough of low
pressure. Conditions vary greatly across the area with pockets of
IFR and VFR within an airmass that is trying to be predominately
MVFR. Dry boundary layer air has been slow to yield to the incoming
moisture in part due to the fact the low level moisture field is
less than impressive. Ribbon of deeper moisture is currently working
across the region which should bring most taf sites to MVFR. Second
surge of moisture and forcing is passing through SW MI at press time
which looks to impact SE MI sometime around 21-00Z. This could bring
more widespread IFR conditions to the area. Ptype will be shakey
throughout most of the forecast as temperatures profiles hover
around the rain/snow line. Drier mid level air moving in this
evening will change ptype over to drizzle for several hours
overnight. Will likely be some drizzle and/or fog lingering through
the overnight as moisture gets trapped below an inversion. Light
precipitation will likely continue Saturday again as snow changing
to rain or a mix.

For DTW...Conditions will deteriorate through the afternoon as
additional mositure and forcing works into the area. Timing the
ptype changes and incoming IFR stratus will likely need adjusting as
it`s not a clean picture at the moment do to more cellular nature of
the precipitation and dry air lingering around the region. Expect
primarily MVFR conditions with periods of IFR possible now through
tonight.

//DTW THRESHOLD PROBABILITIES...

*  High in ceilings dropping below 5000 ft through Saturday.

*  High for ptype as snow this afternoon. Low for ptype this evening
   with snow mixing with rain.


&&

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

$$

DISCUSSION...DG/SS
MARINE.......DRK
AVIATION.....DRK


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at www.weather.gov/detroit.



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