Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 221823

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
223 PM EDT Thu Mar 22 2018


Very dry northwesterly flow will persist over the central Great
Lakes throughout the TAF period. Very little moisture to speak of as
a period of midlevel isentropic downglide occurs late this afternoon
then another period of low-midlevel isentropic downglide late
tonight. Surface winds have overachieved so far today with northwest
ranging 10 to as high as 25 knots. Heavy diurnal component to the
mixed layer, decaying at/around sunset. No strong signal in model
data for lower level boundary layer cloud late tonight. Best support
should miss to the east as a shortwave digs southward over Lake
Huron tonight.


* None.


Issued at 340 AM EDT Thu Mar 22 2018


Current stretch of cool and dry conditions will continue through the
weekend as strong surface high remains anchored north of Lake
Superior. The high will hold over Ontario through Friday before
likely strengthening this weekend while drifting eastward over
Quebec. This will keep the deep cold advective northeasterly flow
persisting through about Sunday. Resultant temperatures will
continue to come in around 5 to 10 degrees below normal through this

Though high pressure continues to dominate at the surface, a compact
mid level vort max will dive through the eastern lakes tonight along
with a week cold front. Should amount to little more than an period
of clouds tonight into Friday morning with winds veering slightly
more northeasterly from north. Expect a decent temperature gradient
SW to NE due to the onshore NE flow keeping the Thumb in the mid 30s
once again with locations inland getting into the low/mid 40s due to
more sun and less of a lake influence. This pattern hold true again
on Friday although the amplified longwave ridge will slide ever
closer to the western lakes. This will lead to a slight increase in
heights aloft which may just be offset by the pulse of cooler air
behind the front.

The next low pressure system is still on track to dive south of MI
on Saturday keeping southern lower MI dry, but with some mid/high
clouds lifting into the area. The upper ridge continues to try to
build over MI but will run up against a strong trough digging into
the eastern lakes stalling its progress eastward. This thermal
trough will linger through Sunday keeping the cool air in place
through the weekend.

The ridge axis aloft finally crosses lower MI on Monday allowing
southerly flow and warm air advection to return to the region.
Temperatures will be near 50 degrees Monday trough midweek. The next
chances of precipitation will be Tuesday into Wednesday as a trough
sweeps across MI. A wave is forecast to eject out of the base of the
deepening trough over the western conus and lift up along the front
aiding in development of precipitation. Best chance of rain will be
12Z Tuesday through about 18Z Wednesday. Looks like mainly a rain
event as temperatures locally will be fairly warm with the southern
origins of the system itself resulting in a warm column.


Cold north to northwest wind will be just strong enough to keep
waves elevated over southern Lake Huron today and small craft
advisories remain in effect for all nearshore zones south of Port
Austin. A backdoor cold front will then move through the region
tonight. Dry conditions are expected with the front but it will be
able to reinforce cold air and northerly flow tonight through Friday
morning. The resulting higher waves will mainly affect the Port
Austin to Port Sanilac nearshore zones before diminishing later
Friday morning. However, the diminishing trend will be short-lived
as northeast flow is expected to strengthen Friday night due to
building high pressure over northern Ontario and as the next low
pressure system moves into the Ohio valley Saturday. The renewed
northeast wind will likely require small craft advisories for all
Lake Huron and Lower Michigan marine areas into Sunday.


Lake Huron...Small Craft Advisory until 10 AM EDT Friday for LHZ441-442.

     Small Craft Advisory until 4 PM EDT this afternoon for LHZ443.

Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.



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