NWS Forecast Discussion

FXUS63 KDTX 201620

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1220 PM EDT Tue Mar 20 2018


SE Michigan will remain sandwiched between large high pressure
centered north in Canada and a low pressure system slowly moving up
the Ohio Valley.  Tight gradient will continue brisk northeast flow
that will gradually back to the north by the end of the forecast
period. Daytime mixing will continue to produce gusts in the mid
20kt range. Gusts will diminish toward sunset. Ceiling issues will
only effect MBS as flow is coming directly across Lake Huron and
down Saginaw Bay. This is producing a lake stratus band of bkn-ovc
around 2500 ft.  Expect daytime mixing to lift ceilings up slightly
this afternoon and possibly produce sct-bkn, but after sunset,
inversion will likely bring back bkn-ovc around 2500 ft again.  A
slight shift in wind direction could steer the band just north of
the airport. Elsewhere, expect an increase in mid and high level
clouds from the system to the south as it continues to lift up the
Ohio Valley.

For DTW... Brisk northeast wind will gradually back to the
northwest by Wednesday evening. Gusts in the 20kt range will
dissipate toward sunset but may reappear shortly after sunrise
Wednesday morning. Winds will weaken somewhat Wednesday afternoon as
the gradient relaxes.  Expect just mid and high level clouds to
increase from the south this afternoon and continue into Wednesday
as the system to the south passes by.


* None.


Issued at 337 AM EDT Tue Mar 20 2018


Dry and cool week ahead as the main jet axis to the south of the
region with split flow aloft and a thermal trough locked overhead.
In addition, broad surface high is now anchored over northern Ontario
where it will remain more or less through the coming weekend. This
high will usher in cool and dry air through the coming days as flow
wavers from northeasterly to northerly. High temperatures will hover
around 10 degrees below normal through the week.

Though it will be dry, the storm track just to our south will bring
a couple storms near the MI/OH border. First storm is coming
together right now over TN as a compact vort max tracking east spins
up a surface low beneath it. This pairing of lows will continue
toward the east coast today while a stronger wave surges into it
from the west. Difluent flow aloft and developing area of pressure
falls will stretch and enhance the trailing trough through the Ohio
Valley. Most of the short range and hires models are keeping the
precip shield to our south, while the EC/GFS/GEM still want to nudge
it into southern MI. Soundings are very dry with deep layer of dry
air from 900-600mb (some even deeper), meaning snow will have a very
difficult time reaching the ground. Will remove the chance pops for
extreme southern MI tonight in favor of the drier suite of models.

For the latter half of the week, upper level ridge will begin to
build into the Midwest, but persistent trough will hold over the
Great Lakes. Slight moderation to the airmass as the flow becomes
more north/northwesterly and highs start to increase slightly. This
will bring highs into the low 40s.

Our next chance of rain will come this Saturday night as a low
skirts the region to the south yet again. Model trends have been
drier over SE MI as they again split the flow over the region with
the southern stream drawing the system southward. Surface high over
Ontario and Quebec is forecast to be even stronger than the current
high thus it should also help shunt the activity southward. Will
keep a chance pop going for now while we monitor trends further.

Amplified ridge aloft and at the surface should lead to favorable
and warmer conditions Sunday thru Monday before the next trough
swings through the region bringing the next chance of precip either
Tuesday or Wednesday.


A prolonged period of moderate northeast wind will continue from
high pressure over northern Ontario across Lake Huron and Lower
Michigan today through Wednesday. The gradient will be strengthened
by low pressure moving through the TN Valley and will support gusts
near 30 knots today, especially with channeling across Saginaw Bay,
and across the Michigan waters of Lake Erie closer to the low. The
long northeast fetch over open water will build high waves through
the period and small craft advisories remain in effect today into
Wednesday for all marine areas except Lake St Clair. The wind will
weaken and back north by Wednesday night as the low exits the mid
Atlantic coast and as the Ontario high builds over the western Great
Lakes. This will allow waves to gradually diminish below advisory
levels all areas by Thursday and last through Friday.


MI...Lakeshore Flood Advisory until 10 AM EDT Wednesday for MIZ083.

Lake Huron...Small Craft Advisory until 2 AM EDT Thursday for LHZ421-441>443.

     Small Craft Advisory until 4 PM EDT Wednesday for LHZ422.

Lake St Clair...Small Craft Advisory until 8 AM EDT Wednesday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 8 AM EDT Wednesday for LEZ444.




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NWS DTX Office Area Forecast Discussion