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fxus63 kdtx 211106 
afddtx

Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
606 am EST Thu Nov 21 2019

Aviation...

Extensive higher level cloud cover will exist through the early day
period within strengthening southerly flow. This will sustain an
extended window for VFR conditions as rain lifts into the region
midday. Gusty conditions will emerge during this time, reaching 20
to 25 knots at times. There remains the potential for slightly
higher gusts near 30 knots should greater daytime mixing develop.
Increasing boundary layer stability within a rain cooled environment
may also offer a window for low level wind shear, with the gust
component easing in this situation. Wind shift to northwesterly
tonight with a cold frontal passage, as rainfall tapers off during
this time. Extensive lower stratus within the immediate wake of this
frontal passage with continued gusty winds.

For dtw...a lower ceiling will emerge again this afternoon as rain
lifts into the area. Precipitation will remain as rain through the
evening, before ending prior to the arrival of cooler air. Gusty
southerly winds into the evening, shifting to northwest tonight.

Dtw threshold probabilities...

* high in ceiling aob 5000 ft late this afternoon and tonight.

&&

Previous discussion...
issued at 447 am EST Thu Nov 21 2019

Discussion...

Low pressure system can be seen on satellite during the overnight
hours spinning its way out of the plains and into the Midwest with
the center of the surface low now over northern Iowa. Warm air
advection downstream of this system has begun evidenced by the
erosion of low clouds in the early morning hours. Expecting a slight
warming trend towards sunrise as plenty of mid/high level clouds
streaming overhead has limited nocturnal cooling and kept
temperatures generally around 40 degrees in areas that remained
under low clouds. Bad Axe has also rebounded nicely into the upper
30s after seeing clearing earlier today and starting the night
dropping to 32f.

These warming thermal profiles with highs reaching into the 50s
across lower Michigan today will allow for an all rain p-type as the
aforementioned low pressure system brings widespread precipitation
to Southeast Michigan with showers reaching western portions of the
County Warning Area by mid/late morning. This rainfall will mainly be supported
by strong isentropic lift as the surface low strengthens during
its track across Lake Michigan reaching Northern Lake Huron this
evening. Good moisture will accompany this system as a strong low
level jet of 50-60 knots Ushers in a moist airmass with ties to
the Gulf of Mexico. This will help precipitable water values increase to around
1.00 inches by the early afternoon. The track of this system will
place the higher rainfall amounts towards the Tri- Cities and
thumb where forecast rainfall amounts range between a quarter and
a half inch.

The winds associated with this system may also bring potential
impacts. The first window will be during the early/late afternoon
within warm sector southerly winds. The increasing pressure gradient
will help increase sustained winds with the higher wind gust
potential tougher to nail down. Forecast soundings still showing a
variety of boundary layer profiles. Given the potential for incoming
rain to limit mixing heights, the best gust potential will be when
daytime Max temperatures are reached in the early afternoon
resulting a more unstable boundary layer profile. Overall wind gusts
should be around 30-35 mph with an occasional gust in the 40 mph
range possible. The second window will be late evening and early
overnight with the systems cold front as winds veer towards the
northwest. Forecast soundings indicate a better opportunity for wind
gusts as cold air advection brings more effective downward momentum
transport. Wind gust potential during this time will again be in the
30-35 mph.

Precipitation is expected to push east of the area by around
midnight tonight before enough cold air arrives to transition any
trailing precipitation to snow. Large scale subsidence through the
mid-levels officially shuts down precipitation chances along with a
building surface high pressure which keep conditions dry through
Friday night. The Post frontal cold air will then bring high
temperatures for Friday afternoon back below normal into the mid 30s
to around 40 across the southern zones.

Low end precipitation chances will return to the forecast late
Saturday afternoon and early Saturday night across lower Michigan. A
low pressure system associated with the southern stream jet is
forecast to move across the Tennessee and Ohio valleys during this time and
interact with a northern stream wave. The potential for these two
waves to phase with one another may lead to the northern edge of
moisture reaching lower portions of the County Warning Area as the bulk of the
system passes to the southeast. The Euro has trended towards the more
northerly track, but presents just a glancing blow with little
impact while the GFS is more bullish with snowfall potential. High
uncertainty with this system as timing of these waves and potential
phasing remains in question. Will maintain the low chance pops with a
light mix of rain and snow across the Detroit area late Saturday and
Saturday evening with adjustments likely needed in later forecasts.
Temperatures to close out the weekend will be in the lower 40s with
closer to normal temperatures in the mid and upper 40s to start next
week.

Marine...

Area of high pressure will slide east this morning as a low pressure
system tracks into the Midwest from the Central Plains. The low will
then continue northeast through The Straits this evening. The track
of this low will present a pair of opportunities for gale force
winds to impact the eastern Great Lakes over the next 36 hours.
Southerly winds will begin to increase ahead of the warm front
starting this morning. This unstable setup will allow winds to gust
to gale force across southern and Central Lake Huron thus a Gale
Warning has been issued. The warm front will lift through in the
evening with a more thermally stable airmass allowing winds to
briefly relax but will rapidly increase again with the passage of
the cold front overnight. The cold northwest flow will again cause
gusts to low end gale force though this time the fetch would focus
the highest winds over the northern and central portion of Lake
Huron. The Gale Warning for central Huron will continue to capture
this part of the event as well. A Gale Warning is also in effect for
the northern most portion of the lake tonight as there is potential
for winds to reach low end gales with the cold air and northwest
wind flow. Winds and waves will likewise rise to Small Craft
Advisory levels for the nearshore zones for both today and Friday.
High pressure will then build across the region Friday into the
beginning of the weekend.

Hydrology...

A strong low pressure system moves through the western/central Great
Lakes today. It draws mild air into the region with plentiful
moisture for widespread showers by this afternoon and into the
evening. The relatively fast movement of the pattern limits rainfall
totals to a range from less than a quarter inch across the Detroit
Metro area and ranging between a quarter to a half inch toward the
Tri Cities and northern thumb. Rainfall comes to an end early this
evening. Rainfall totals in this range could produce some standing
water on roads and in other prone areas.

&&

DTX watches/warnings/advisories...
Michigan...Lakeshore Flood Warning from 10 am this morning to 10 PM EST this
evening for miz063-070.

Lake Huron...Gale Warning from 10 am this morning to 10 am EST Friday for lhz362-
363-462-463.

Small Craft Advisory from 10 am this morning to 10 am EST Friday
for lhz441>443.

Gale Warning from 11 PM this evening to 10 am EST Friday for lhz361.

Gale Warning from 10 am this morning to 9 PM EST this evening for
lhz421-422.

Lake St Clair...Small Craft Advisory from 10 am this morning to 4 am EST Friday for
lcz460.

Michigan waters of Lake Erie...Small Craft Advisory from 10 am this morning to 4 am EST Friday for
lez444.

&&

$$

Aviation.....Mr
discussion...aa

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