Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 262305
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
605 PM EST Sun Feb 26 2017


.AVIATION...

Southwest flow will diminish steadily this evening as daytime mixing
subsides and the pressure gradient slackens with the approach of a
surface ridge. This ridge will maintain light south/southwest flow
into Monday with winds backing to southeast late in the day as this
feature translates eastward. Lower vfr cigs will be possible late
tonight KMBS/KFNT as surface trough settles into area with passage
of shortwave to the north. A southern stream wave will then move
across the Ohio Valley on Monday bringing the possibly of ceilings
in the 4-5kft range by the end of the day, especially I-94 tafs.

For DTW...Any gusts over 20 knots will subside in the 01z-02z time
frame with southerly flow 10 knots or less overnight into Monday.
Scattered vfr clouds will be the rule into Monday afternoon with an
increasing chance of lower vfr bkn cigs after ~22z.

//DTW THRESHOLD PROBABILITIES...

* Low in ceilings aob 5000 feet after 22z Monday.

&&

.PREV DISCUSSION...
Issued at 342 PM EST Sun Feb 26 2017

DISCUSSION...

Upper wave will continue working across the Northern Great Lakes
this evening, pushing surface low pressure eastward from Ontario
into Quebec tonight. Weak ascent at the leading edge of warm air and
theta-e advection has allowed some virga to show up on radar over
the southern portion of Michigan. Cold front is meanwhile settling
into Northern and Central Michigan, with stronger forcing allowing a
snow showers to reach the ground there. These showers may brush the
Saginaw Valley or far northern Thumb through mid-evening, but will
keep pops low due to very dry air observed in the low levels. Wind
gusts are expected to pick up for several hours this evening as we
reach peak heating and as low-level jet punches up into Southeast
Michigan. Steep low-level lapse rates may allow gusts near 40 mph to
reach the surface, particularly north of I-69, for several hours
between now and 800 PM before diurnal cooling allows surface-based
inversions to begin forming and gusts diminish.

The front will lose upper support and wash out over Central Michigan
tonight and early Monday. Main impact from this boundary will be an
increase in clouds late tonight and Monday as it not only pushes
moisture southward, but also interacts with moisture streaming
northward between low pressure over the Southern Plains and a strong
dome of high pressure off the Mid-Atlantic coast. Southerly flow
will boost temperatures into the mid and upper 40s tomorrow. Winds
will also be much lighter, cutting wind chill factor and making for
a pretty nice late winter day.

Upper trough off the Pacific Northwest will swing into the Nation`s
mid-section Tuesday into Tuesday night, pushing an area of surface
low pressure up across the Great Lakes. As typical this many days in
advance, there are still model variations with the center of the low
track that leads to uncertainty with onset time and location of
precipitation. Despite other differences, models remain in line with
the idea of surface temperatures being warm enough for all rain late
Monday night through Tuesday night. Theta-e advection and
instability will ramp up late Tuesday and Tuesday night as 60 knot
low-level jet noses up into Lower Michigan. This is when the best
chance for rain will be, with perhaps a few thunderstorms occuring
as well. The surge of warm air will also send temperatures back to
well above normal, in the 50s for most locations on Tuesday.

Surface low pressure east of Lake Huron will bring the continued
chance for precipitation throughout Wednesday, with PoPs diminishing
into the evening and overnight hours as the dry slot edges its way
into the Great Lakes region. Both GFS and GEM models show a robust
swath of drier air enter behind the low, while the NAM and ECMWF
models exhibit a second, disjointed surface low pushing through
southern Michigan throughout Wednesday morning and afternoon,
allowing precipitation to fall throughout the day. Additional
convergence between model runs will be needed in order to increase
confidence in both timing and PoPs. In any case, model runs do
converge on colder air entering the region behind the low. 850 mb
temperatures averaging 5-7 C on 12Z Wednesday will quickly drop
below freezing by 21Z Weds. Surface temperatures will peak in the
upper 40s to lower 50s throughout the afternoon, dropping to
freezing/below freezing by the evening and overnight hours. As a
result, an all rain solution is forecasted for morning and early
part of the day on Wednesday, with a swift transition to a wintry
mix to snow solution by the evening from north to south. Otherwise,
a weak surface low will bring light snow chances Thursday into
Friday.

Well above normal temperatures are still on track for Wednesday as
warmer air ahead of the surface low allows temperatures to peak in
the upper 40s to lower 50s. Wednesday`s cold front will return
temperatures into the 30s by both Thursday and Friday, with warmer
air once again expected to return for the weekend, bringing a second
chance to see another round of 40s/50s.

MARINE...

A gale warning remains in effect today through this evening for
Saginaw Bay and central Lake Huron with small craft advisories in
effect for the remaining marine areas. A cold front will settle over
Lower Michigan and central Lake Huron tonight and dissipate in favor
of high pressure by Monday morning. Favorable marine conditions in
the form of light south wind and milder air will then continue
through Tuesday. The next low pressure system is projected to arrive
Wednesday on a track through the central Great Lakes followed by
colder air on moderate northerly wind for the end of the week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Warning until 10 PM EST this evening for LHZ362-363-421-422-
     441-462.

     Small Craft Advisory until 7 PM EST this evening for LHZ442-443.

Lake St Clair...Small Craft Advisory until 7 PM EST this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 7 PM EST this evening for LEZ444.

&&

$$

AVIATION.....DG
DISCUSSION...HLO/AM
MARINE.......CB


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at www.weather.gov/detroit.



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