Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 231151
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
651 AM EST Tue Jan 23 2018

.AVIATION...

Brief low level drying under pre-frontal southwest flow will be
short-lived this morning, as deeper moisture aggressively pivots
back in. This will bring renewed MVFR stratus in periodic light
showers. Current temperature trends would favor any precipitation
falling as rain this morning. Cold frontal passage this afternoon
will bring a greater potential for rain to potential mix with snow,
particularly at MBS. Limited potential for accumulation given
expected temperatures, but upwards of an inch will be possible at
MBS. Winds turn gusty this afternoon with the frontal passage,
reaching 25 kts at times out of the west.

For DTW...Low cloudiness expected to work back into the airpsace
over the next hour. Precipitation type concerns mitigated by
temperatures still near 40 degrees this morning, supporting just
rain.  Window for rain to mix with snow mid-late afternoon as
temperatures drop with the frontal passage. No accumulation
expected. Westerly wind gusts to 25 kts accompanies this front.

/DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less through tonight.

* High for rain as precipitation type this morning, transitioning to
  a rain snow mix during the afternoon.

&&

.PREV DISCUSSION...
Issued at 338 AM EST Tue Jan 23 2018

DISCUSSION...

One more day of dealing with the stacked low pressure system that
started moving into the region Monday. The surface low has
positioned itself directly over mid MI as of 06Z this morning having
just pulled a warm front up through southern MI. The surface trough
is stretching back to the southwest as a result of the mid level
closed low lagging behind. After a brief lull in rain showers early
this morning behind the warm front, the next surge of moisture will
get shoved into the area on the lead edge of the mid level cold pool
this morning. As the surface low drifts east, the trailing trough
axis will align through mid MI with deformation forcing with decent
moisture keeping best coverage of showers across that area. Looking
upstream at current radar, and comparing it to models, appears that
the cold pool and lingering low level moisture will result in
numerous showers through the day.

Temperatures across SE MI will start the day off in the low 40s, but
cooler air will spill back in through the day as the trailing
trough/cold front works through. This will lead to ptype changing
over from all rain to at least a mix of rain and snow by the time
the moisture exits. Both the RAP and HRRR are in good agreement of
an early temperature drop across the northern Saginaw Valley and tip
of the Thumb leading to a early changeover to possibly all snow by
15-18Z. Temperatures south of I69 pretty much stay around 38 through
most of the day which would keep mainly rain around. Other factor to
consider is the depth of moisture. Looks like mid level moisture
gets scoured out pretty early in the day with bulk of the saturated
layer (up to 6kft) warmer than -10C. So even if cooler temperatures
can work in, will there be ice crystals left in the column or more
of a lingering light rain? In the end, the forecast will feature
high POP, low QPF with any snow accumulations held generally north
of M46. Will stay reserved with an inch or less of accumulation.

The mid week period remains dry and cooler (more in line with
seasonal normals) as broad surface ridge slides under the lingering
mid level trough across the Great Lakes. Upper level ridge starts
building back into the area Thursday night bringing the return of
warm air and temperatures in the mid 40s. The next shortwave will
pass through Ontario with troughing extending south into the plains
states. The trough looks to slide through southern MI Friday night
into Saturday bringing the next chance of precipitation. Looks like
ptype will be mainly rain with main band of showers Saturday but a
secondary cold front later in the weekend could produce some snow
showers.

MARINE...

Low pressure centered over central Lake Huron this morning will lift
northeast into Ontario during the daylight period. Moderate
northerly winds currently residing north of this low over the north
half of lake Huron will expand across the entire lake Huron basin as
the low exits. This will be accompanied by colder air, which may
lead to a brief period of gusts to near gales late this afternoon
through early tonight. Winds and gusts will decrease Wednesday as
weak high pressure lifts across the region. Relatively light winds
will remain in place through the end of the week. Another increase
in winds will come for the weekend.

&&

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

$$

AVIATION.....MR
DISCUSSION...DRK
MARINE.......MR


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