Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 190748
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
348 AM EDT Thu Oct 19 2017

.DISCUSSION...

A dry cold front is beginning to march across the Great Lakes as
advertised with little in the way of even clouds with it.
Compression of the the SW gradient is keeping winds elevated through
the rest of the night/morning. Afternoon mixing will keep some gusts
through the afternoon, otherwise winds will die off tonight. A
narrow band of clouds will slide across MI with the front, but will
impact the forecast minimally. Most notable change to the forecast
in the near term is the downward adjustment to dewpoints into the
afternoon. Obs show the dry air and subsidence over WI resulting in
quick drops in dewpoints from 40s into the upper teens. With the
front weakening, the driest air more to the north, and airmass
modification over the lakes, we shouldn`t be getting that dry but
could flirt with values near 30F across the north. Otherwise,
another day with temperatures rising into the mid/upper 60s.

Friday and Saturday will continue the pleasant weather we`ve been
experiencing for the last week or so now. Large area of surface high
pressure quickly builds back into southern Great Lakes while we
still reside on the western side of the ridge with warm
southwesterly flow. Longwave ridge will undergo strong amplification
Friday in response to strong troughing moving inland off the
Pacific. The pattern will stall temporarily as it continues to
deepen but will eventually get forces east by the next strong wave
surging across southern Canada. This will send a stalling frontal
boundary into southern MI late Sunday and overnight. Models begin to
diverge significantly heading into the start of the new week. Euro
wants to stall the front over southern MI while the GFS keeps it
more progressive. So will continue to forecast precipitation
centered around Sunday night and will adjust as necessary in the
coming forecasts.

Model do tend to agree that cooler weather looks to be in store for
the middle of next week.  An upper level trough will drop into the
region with northerly flow originating from northern Canada. This
would bring one of the coldest airmasses of the season into the
region likely lingering through the end of the week.

&&

.MARINE...

Gusty southwest winds have persisted overnight over much of the
central Great Lakes ahead of an approaching cold front. Widespread
observations have been reported with southwest winds of 25 to 30
knots. Winds will begin to ease late this morning and afternoon in
response to increasing high pressure behind a shallow cold front.
Winds this afternoon will still range between 15 to 20 knots in many
areas. Dry conditions are expected for the end of the week and for
much of the upcoming weekend. However, southwest winds are expected
to remain in the 15 to 20 knot range in response to strong gradient
ahead of a northern Plain States low pressure system.

&&

.PREV DISCUSSION...
Issued at 1153 PM EDT Wed Oct 18 2017

AVIATION...

Gusty southwest wind during the afternoon subsided to a light
gradient flow as boundary layer mixing subsided with sunset. This
will allow a moderate low level jet to develop through the night
that model soundings continue to suggest will be marginal for the 30
knot LLWS threshold. The wind pattern will continue through early
morning before the upstream cold front arrives. Late evening
satellite imagery only indicated a band of mid and high clouds along
and ahead of the boundary with little if any low clouds south of
Lake Superior. Considering the very dry low level conditions, expect
low cloud development will remain sparse as the front moves through
SE Michigan during the morning and early afternoon weakening while
moving south with time. Postfrontal wind will shift toward 300 deg
with a few gusts near 20 knots until late afternoon.

//DTW THRESHOLD PROBABILITIES...

* None.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 10 AM EDT this morning for LHZ421-422-
     441.

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

$$

DISCUSSION...DRK
MARINE.......CB
AVIATION.....BT


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