Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 152338
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
738 PM EDT Sun Apr 15 2018

.AVIATION...

The main band of precipitation has moved east of the terminal
corridor leaving just scattered light rain showers possible within
the surface trough as it pivots south to north over Lower Michigan
during the evening. The surface trough will also support diminished
wind and continued IFR/LIFR ceiling tonight with a few breaks into
MVFR in the DTW area as westerly wind develops there. Ceiling
improvement will struggle back into MVFR during Monday as colder air
moves in on moderate west wind. The struggle will be due to moisture
wrapping around the low pressure system from the north that could
bring lower ceiling and snow back into play Monday afternoon.

For DTW... Light and variable wind will become light west at the
start of the forecast. Upstream observations indicate mostly IFR
will hold at DTW with widely variable ceiling possible as west wind
increases slightly during the night.

/DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less through the forecast period.

* Low for ceiling 200 ft or less tonight.

* High for precipitation type as rain through tonight.

&&

.PREV DISCUSSION...
Issued at 348 PM EDT Sun Apr 15 2018

DISCUSSION...

Temperatures have warmed above freezing across the southern half of
the CWA from I-69 southward, which has brought the widespread
freezing rain threat mostly to an end. The center of the upper low
pressure is slowly meandering northeastward and will eventually move
over Michigan tonight. This placement is leaving southeast Michigan
in the warm conveyor with a plume of moist isentropic ascent over
southeast Michigan this afternoon and evening resulting in continued
precipitation. While temperatures were quick to warm up this morning
across the south, they have been slow to warm above freezing across
the northern areas mainly towards the Tri-Cities, portions of the
Thumb and some of the higher elevations. The dry air funneling in
from the northeast winds has also pushed some drier surface
dewpoints across the north and kept temperatures from responding as
quickly to the warm air advection. Surface obs show the warmer air
trying to push north with Flint, Howell, and Pontiac at 33 degrees.
Bad Axe currently sits at 35 degrees. These have remained steady
through the early afternoon. Still believe temperatures should warm
up above freezing eventually this evening for the remaining areas
across the north with this push of warm air advection.

Winter Storm Warnings for I-69 and north will be extended into
tonight to account for this slower warm up. Additional ice
accumulations one to two tenths along with additional sleet
accumulations will be possible across the Saginaw Valley and
portions of the Thumb. Ice and sleet accumulations will hinge on
exactly when these areas reach above freezing. Precipitation trends
throughout the evening will be on an overall decrease in coverage
and intensity from south to north. This will also limit higher
accumulations through the evening if temperatures do not warm up as
expected.

The surface low that helped draw some warmer air northward will lift
off to the northeast across southeast Michigan and northwest Ohio
and result in winds shifting from the northeast to the west
overnight. The transition will start this evening across the south
and eventually flip to the west across the north by tomorrow
morning. Mid level dry air will also be pushed into the region on
the back side of this system, which will help cut into the heavier
precipitation that is seen throughout today. Lighter rain/drizzle
conditions may persist through the night as low pressure moves
through. A plume of moisture working back west around the low will
help keep higher precipitation chances in the forecast for the areas
north of I-69. Mainly rain chances will exist when temperatures warm
above freezing and remaining so overnight. Winds will also be on the
decrease, which will ease the lake shore flooding concerns along
portions of western Lake Erie and Inner Saginaw Bay.

The upper low will pivot across the region on Monday as it lifts
across Lake Huron. Northwesterly flow will send colder air aloft
into southeast Michigan throughout the day helping to cool the column
enough to transition the rain into snow showers throughout the day
on Monday. Snow showers will continue into Monday night and into the
early part of Tuesday as the upper low is slow to exit far enough
east of the region. Good shot at accumulating snowfall throughout
this time period before this impactful upper low finally lifts into
the northeastern US. Cold air will remain in the region on Tuesday
with high temperatures in the upper 30s and low 40s.

Dry conditions will not be around long as the next system looks to
impact the Great Lakes area in the midweek.  Current model runs are
indicating a low pressure system moving eastward across the area on
Wednesday and into early Thursday.  However, as it stands, the track
of the low is still uncertain.  Mixed precipitation is possible
depending on the track, especially given the temperatures hovering
around freezing.  Good news is this system does not look to hang
around long as dry as expansive high pressure moves in late Thursday
and holds into the weekend.  This will allow temperatures to slowly
climb back into the 50s by the end of the extended forecast period.

MARINE...

Low pressure set to track from the Ohio valley into southern lake
Huron through tonight. Ongoing gales under strong easterly flow
north of this system will persist into early tonight, before
gradually easing early Monday as the gradient relaxes. Winds shift
to westerly and strengthen modestly on Monday in the wake of this
low. Moderate west to northwest flow expected to persist through
Tuesday, downstream of high pressure set to build into the region
Tuesday night and Wednesday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...Winter Storm Warning until 10 PM EDT this evening for MIZ047>049-
     053>055-060>063.

     Lakeshore Flood Warning until 10 PM EDT this evening for MIZ076-083.

     Lakeshore Flood Advisory until 10 PM EDT this evening for MIZ048-
     054-070.

Lake Huron...Gale Warning until 2 AM EDT Monday for LHZ361>363-441>443-462>464.

     Small Craft Advisory from 2 AM to 8 AM EDT Monday for LHZ441-442.

     Small Craft Advisory until 10 PM EDT this evening for LHZ422.

     Small Craft Advisory until 8 AM EDT Monday for LHZ421.

Lake St Clair...NONE.

Michigan waters of Lake Erie...NONE.

&&

$$

AVIATION.....BT
DISCUSSION...AA/SP
MARINE.......MR


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