Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 250505
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1205 AM EST Sun Feb 25 2018


.AVIATION...

Split between two areas of widespread precipitation is currently on
track to work across southeastern Michigan overnight. Main apex of
strongest moisture advection and deep theta e advection will largely
pass to the south of the forecast area. Low static stability to weak
convective instability under moist adiabatic lapse rates will lift
across the state during the 6-12Z timeframe, thus, still supportive
of an isolated thunderstorm. Otherwise, it appears that less
precipitation will fall than earlier anticipated. IFR to LIFR
conditions in cig heights will exist under midlevel occlusion. Line
of low topped convection, convective rope along the cold front will
lift north and eastward with time. Best timing for remnant low
topped convection is 08-10Z. Strong winds will then develop in near
surface mixed layer environment with wind gusts Sunday reaching and
exceeding 35 knots.

/DTW THRESHOLD PROBABILITIES...

* High for cigs below 5 kft through TAF period.

* High for ptype as rain.

* Low for thunderstorm tonight.

* Medium for reaching crosswind threshold hold 10-16z Sunday.

&&

.PREV DISCUSSION...
Issued at 324 PM EST Sat Feb 24 2018

DISCUSSION...

A high pressure will drift northeast of the Great Lakes this
afternoon resulting in a light easterly surface flow. Inversion has
kept low level moisture and clouds trapped with additional clouds
moving in from the southwest. This will keep mostly cloudy
conditions through this afternoon and evening. High temperatures
this afternoon remain on track to top out in the upper 30s and low
40s. A few light rain showers earlier today across the lower
portions of the area along the Ohio border have cleared out. There
will a brief break in rainfall during the early evening before the
next system tracks northeast into the Great Lakes and increases rain
chances after 0Z tonight.

A dynamic mid level trough is ejecting out of the Rockies and into
the Plains this afternoon. The trough will become negatively tilted
as it lifts northeastward into the Great Lakes. A surface low is set
to develop in association with the upper trough and strengthen
overnight as it reaches the western lower Great Lakes. The center of
the surface low is forecast to move across the Upper Peninsula by
around midnight. At the same time, the low and mid level jets will
strengthen around the base of the trough and bring with it favorable
lift across southeast Michigan. Strong southwesterly flow will drive
some warm and moist advection up through the Ohio Valley. Some of
the higher dewpoints look to remain south of the Michigan border,
but there will be enough moisture available within the large scale
ascent and frontal convergence to produce widespread rainfall
tonight into tomorrow morning. Highest theta-e may also stay south,
but mid level lapse rates of around 6 C/kg would support a chance of
a thunderstorms for the southern half of the CWA. Even though the
better moisture may likely remain to the south, there will still be
potential to see pockets of localized heavy rainfall with the
passage of this system.

The low pressure system will send a cold front through Michigan
tomorrow morning. Deep dry air advection will get underway amidst
somewhat weak cold air advection. However, the presence of strong
winds just above the surface and strong isentropic decent in the
immediate wake of the front will result in strong winds reaching the
surface during the morning hours. The highest wind gust potential
should occur right behind the front within strong downward ascent
and last for a brief period. However, gusty southwest winds should
linger into the late morning and early afternoon as diurnal mixing
will begin to tap into those strong winds aloft. Peak wind gusts
residing in a narrow corridor behind the front will be nearing Wind
Advisory criteria in the 35 to 45 mph range.

High pressure will begin to build across the Ohio Valley Sunday
night. Winds will be on the lighter side for Monday and remain out
of the west. Weak ridge moving overhead will allow quite, dry
weather to start the work work. Low temperatures to start the day
will be slightly below freezing for the majority of southeast
Michigan. High temperatures on Monday afternoon will remain above
normal in the mid to upper 40s, with a few locations across Metro
and the southern Michigan border reach 50 degrees.

Dry, mild conditions will continue on Tuesday with highs in the mid
to upper 50s while high pressure moves to the Eastern Seaboard.
Return southwesterly flow will then advect increasing moisture to
the region late Tuesday while a weak frontal boundary sags southward
before stalling across Lower Michigan on Wednesday. Along this
boundary, some light rain showers will be possible across Southeast
Michigan Tuesday night into Wednesday as mild temperatures continue
with highs in the low to mid 50s.

Low pressure developing in conjunction with a potent upper wave
ejecting out of the Southwest US will then bring the next chance for
widespread precipitation to the region late next week. Model
guidance is in good agreement that low pressure will slowly track
into Lower Michigan on Thursday before transferring energy to a
coastal low Thursday night into Friday. Widespread rain appears
likely on Thursday as temperatures again approach 50 across much of
SE Michigan. Cold air wrapping into the system Thursday night will
bring the chance for a rain/snow mix before precipitation gradually
tapers off on Friday.

MARINE...

Rapidly deepening low pressure tracking through the Western Great
Lakes tonight will send a strong cold front through the Central
Great Lakes around sunrise Sunday. Southwest gale force winds will
develop behind the front, persisting for much of Sunday as colder
air surges to the area. Strongest winds look to be near the
Straights and across the Central Lake Huron, where they look to
slightly exceed 40 knots Sunday morning. Winds will drop below Gales
Sunday evening and continue to diminish Sunday night into Monday as
high pressure ridges into the region from the southwest.

HYDROLOGY...

River levels continue to slowly come down, but moderate flooding was
still occuring along the Saginaw and Hamburg rivers. A strong low
pressure system will track northwest of the region, with widespread
rain showers developing late this evening, and continuing tonight.
Rainfall amounts look to range between a quarter of an inch to a
half of an inch. This rainfall is not expected to have any
significant impacts to current river flooding. Dry weather then
expected tomorrow through at least Tuesday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Warning from 7 AM this morning to 7 PM EST this evening for
     LHZ363-421-422-441>443-462>464.

     Gale Warning until 7 PM EST this evening for LHZ361-362.

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

$$

AVIATION.....MR
DISCUSSION...AA/JD
MARINE.......SF
HYDROLOGY....SF


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