National Weather Service United States Department of Commerce


000
FXUS63 KDTX 191941
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
341 PM EDT Sat Oct 19 2019

.DISCUSSION...

Expect quiet weather through the weekend and seasonably mild
temperatures through Monday before a strong low pressure system
lifts through the Great Lakes late Monday into Tuesday bringing
showers and windy conditions across the region. Broad upper level
trough will then hold over the Great Lakes through the week keeping
cool air in place with a couple more chances of showers.

First order of business is dealing with a weakening cold front
currently to our west extending from western Ontario southward
through Missouri. The parent low is well to the northwest of the
area over northern Manitoba and appears to be tracking farther north
overnight. This will pull the best forcing northward while the front
continues its push east through lower MI. Models keep a narrow
ribbon of moisture and weakening fgen along the front tonight as the
front passes but lack of moisture and dry low levels owning to the
current ridge in place should result in mainly mid clouds advancing
over the area tonight. There could be a few drops of rain mainly
over the Saginaw Valley but a very low chance thus will leave out of
the forecast. Current regional radar loop shows the southern extent
of the front becoming fairly scattered which gives credit to the
continued weakening trend. The clouds will keep min temps a bit
higher tonight, 40s across the area, preventing the frost we`ve been
seeing in recent days.

High pressure builds back into the region Sunday as flow flips
southerly and shortwave ridge slide over the region ahead of the
deepening trough. This will lead to another pleasant fall day with
temps rising into the mid 60s and plenty of sunshine.

By Monday morning the strengthening trough will be over the central
Plains with lee cyclogenesis taking place on the nose of a potent
140+ knot jet max. A shortwave jet max exiting the trough will align
north/south Monday afternoon which will excite a short period of
decent warm air advection with a narrow corridor of moisture lifting
north of the cold front before it sweeps through Monday night. PWATs
look to jump from around the current 0.75" to possibly over 1.25".
The rapidly deepening surface low will track northeast through the
northern Great Lakes Monday night and Tuesday. This track will pull
the best forcing on the isentropic arm north of the region while the
instability gradient focuses south of the region. We`re left in an
all too common position with a high shear low CAPE environment in
the vicinity of an occluding front splitting the two favorable
regions of forcing. Will advertise showers with embedded isolated
thunderstorms for now Monday and Monday night. Temperatures will be
mild Monday back into the mid 60s but gusty winds over 30 mph and
cloudy skies will take some enjoyment out of that even before the
rain starts in the afternoon.

Troughing then encompasses the region Tuesday through the remainder
of the week as the upper level low stalls over Ontario/Quebec with
reinforcing shortwaves entering the trough to keep it over the
region. Highs will hover in the 50s with lows around 40. There is a
chance of showers on Tuesday as the trailing trough and deformation
region swings through lower MI. Boundary layer mixing and cold air
advection will lead to strong low level lapse rates aiding in
afternoon shower development. Westerly flow then looks to set up
heading into the latter part of the week before hints of the next
trough start taking shape heading into the weekend.

&&

.MARINE...

Fresh southerly flow of 10 to 15 knots with gusts of 20 to 25 knots
will diminish this evening and remain light and variable into Sunday
as a surface ridge builds east into the region. Southeast winds will
begin to increase by Monday morning as a low pressure system deepens
and lifts northward into the Upper Mississippi River Valley and far
western basin of Lake Superior.

Winds will increase further late Monday into Monday night as this
system approaches. A Gale Watch has been issued as gusts over
portions of Lake Huron may very well push 40 knots by Monday
evening. Winds will then shift to the southwest overnight Monday
night with any remaining gale force gust potential focusing from
Saginaw Bay into central Lake Huron as the wind funnels up the bay.
Winds will then shift to the west and gradually weaken from Tuesday
night into Wednesday as the low pressure system lifts north to the
southern shores of Hudson Bay.

&&

.HYDROLOGY...

Strong low pressure will track into the northern Great Lakes on
Monday with a trailing cold front then pivoting east/northeast
through the region Monday night. Widespread rainfall is expected
from Monday afternoon into Monday night as this system encroaches on
and then passes through the area. At this time, it appears that
rainfall amounts of three quarters of an inch will be quite possible
in many locations with local amounts of around an inch not out of
the question. Such rainfall totals should not cause any significant
flooding risks although ponding of water on area roadways and other
prone areas can be expected.

&&

.PREV DISCUSSION...
Issued at 1255 PM EDT Sat Oct 19 2019

AVIATION...

VFR conditions are expected this forecast with cirrus thickening and
lowering, especially tonight into Sunday. Some lower clouds may work
into KMBS/KFNT on Sunday (5-10kft) as southwest flow begins to take
shape on the back side of passing surface ridge. A period of patchy
fog will be possible again early Sunday morning as calm conditions
will exist within this ridge.

DTW THRESHOLD PROBABILITIES...

* None.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Watch from Monday afternoon through late Monday night for
LHZ361>363-421-422-441>443-462>464.

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

$$

DISCUSSION...DRK
MARINE.......DG
HYDROLOGY....DG
AVIATION.....DG


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