Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 201909

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


Strong Canadian high pressure (1030+ MB) will remain anchored
along/near Ontario/Quebec border over the next several days.

12Z DTX indicated a very dry airmass in place over southeast
Michigan today, as 850 MB dew pt depression checked in at 32 C, with
a PW value of 0.14 inches.

Brisk northeast winds will continue through tonight (holding min
temperatures in the low/mid 20s), shifting to the North-Northeast
early tomorrow morning. Strengthening low-mid level circulation
tracking through southern Ohio will send 850-700 MB Theta-E gradient
over Lenawee/Monroe counties overnight. But with continued low level
feed of dry air, still looking at the snow shield holding near the
southern Michigan border. 12z Regional Gem would even argue for
light accumulations south of I-94 as 700 MB specific humidity rises
to 2.5 G/KG. Preference is more toward the slightly drier RAP
solution, but low chance pops for light snow late tonight still
seems warranted south of I-94, especially if that flow becomes a bit
more easterly off Lake Erie.

Upper level shortwave ridging to become established on Wednesday.
With northerly flow off cold waters of Lake Huron, looks like good
temp gradient setting up during the day, as 925 mb temps advertised
to range from -8 C over northern tip of the Thumb to -2 C along the
southern Michigan border, translating to highs in lower 30s to lower

Dry airmass and skies becoming clear Wednesday night will lead to a
favorable radiating night, sending temps into the lower 20s. Could
even see mins sneak into the teens in the normally colder locations
if winds fully decouple.

Thursday and beyond...

Confluent NW flow still forcing all meaningful precip south of the
area while ensuring mostly sunny skies with dominant high pressure
at the surface. The third week of spring will see temperatures
creeping ever-closer to average values as ridging builds over the
central CONUS for the remainder of the forecast period.



Large High pressure to the north and a low pressure system moving up
the Ohio Valley will continue a prolonged period of moderate
northeast wind which will continue this afternoon through Wednesday
before gradually diminishing Wednesday night.  Occasional gusts to
30 kts are likely through Wednesday. The long northeast fetch over
open water will build high waves through the period and small craft
advisories remain in effect through Wednesday for all marine areas
except Lake St Clair which is through tonight. Advisories will
continue into Wednesday night for outer Saginaw Bay and Lake Huron
near shore. 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.


Issued at 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.


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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