Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 242303
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
703 PM EDT Sun Mar 24 2024

.KEY MESSAGES...

- Warmer weather returns Monday and lasts through the week. Highs
  will be in the 50s most of the week with 40s expected Wednesday and
  Thursday.

- Rain is expected late Monday night and Tuesday.

- Gusty winds early in the week reaching 20 to 30 mph on Monday and
  30 to 40 mph on Tuesday.

&&

.AVIATION...

A large area of low pressure continues to organize and strengthen in
the central Plains while sending thicker high clouds into Lower Mi
tonight. A few flurries could brush the MBS area this evening,
however low level dry air is expected to dominate resulting in a
pronounced virga signal from radar composites. Conditions are
otherwise VFR above 5000 ft tonight over a steady SE surface wind.
LLWS trends will be monitored for later forecast updates as current
expectations are for a brief and borderline intensity setup late
tonight and Monday morning. VFR above 5000 ft continues through
Monday over increasing SE wind pickup up to gusts around 25 knots by
mid afternoon.

.DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 346 PM EDT Sun Mar 24 2024

DISCUSSION...

Fairly quiet weather the next 36 hours as the longwave pattern makes
a big shift from split flow, northern stream dominate over the Great
Lakes to a deep southern stream trough that encompass most of the
conus by Tuesday night. The southern stream is already beginning to
deepen over the western conus, which is resulting in a low amplitude
shortwave ridge downstream (currently over the central Plains) that
will advance across the Great Lakes tonight. With the current
surface high pressure system in place, this will hold off much of
light snow falling from waves of mid/high level moisture that has
been advecting over the region through the day already. Will keep
the low chance/slight chance POPs in place for the Saginaw Valley as
they stand the best chance of squeezing out some flakes as the next
arm of warm advection lifts through the region. High pressure
lingering through Monday will keep the area dry and the increasing
southeasterly flow will boost temperatures back into the 50s.

As the longwave trough deepens with the aid of a 150+ knot jet
streak, the surface low moves over, and strengthens, over the lee of
the Rockies. This low will then start to advance northeast from the
central Plains Monday up to the Midwest by Tuesday. Deep layer
southerly flow will align nearly south to north Monday night through
Tuesday which will send a series of mid level waves up through the
region. Low end pops will begin Monday night as the lead ribbons of
vorticity rotate around the low, with higher end pops then forecast
through the day Tuesday as the low level jet arrive focusing the
deepest moisture over SE MI. For what it`s worth, the NAM suite
offers a LLJ around 60 to 70 knots down to 3-5kft. GFS is slightly
tamer with only 50 knots. PWATS will be up around 1 inch with the
main surge of moisture early in the morning Tuesday. The intense
warm air advection lead to the question of wind gust potential.
We`ll keep a mention of gusts exceeding 30 knots Tuesday, knowing
we`ll either be stable with the intense warm air advection aloft,
+10C at 850mb, but any amount of deeper mixing will start tapping
into the stronger winds. The other factor would be whether the
showers could bring down higher gusts. So wind will be something to
watch as we enter the hires model window. The cold front will get
pulled through the region Tuesday evening. The warm nose front 3-
6kft will severely limit the convective chances through the day, but
models keep hinting at the possibility of a short window just ahead
of the front in the evening where some non-zero CAPE gets
introduced. At a minimum this shows the front should provide another
period of higher pops across the region. SPC has general thunder
over most of the state which is fine for now.

After the low lifts up into Ontario Wednesday, high pressure builds
across the region quieting things down quickly again. There will be
a thermal trough to deal with Wednesday and Thursday, -5C at 850mb,
which will drop highs back down into the 40s with lows in the 20s.
The next longwave ridge will be soon to follow though bringing
warmer temps back by the end of the week.

MARINE...

Departing high pressure and developing surface low over the Plains
support increasing southeast flow tonight into Monday. A brief
window for snow exists across northern Lake Huron tonight, before
drier conditions prevail Monday. The low draws in a warm and stable
airmass Monday, which keeps southeasterly gusts capped around 30
knots beneath a strong inversion. Elevated gusts and wave action are
enough to surpass Small Craft Advisory thresholds for the Lake Huron
nearshores. Further impacts from the low arrive Tuesday, with the
arrival of a strong 60 to 65 knot low level jet maximized between 2-
3 kft agl and a band of rain/rain cooled air that weakens the
inversion Tuesday morning. While it is still plausible that the
resident stability keeps gusts below gales on Tuesday, it will not
take much extra mixing to bring gale force winds down to the surface
given the strength and height of the incoming jet. Thus a Gale Watch
has been issued for Tuesday and Tuesday evening. High pressure fills
in by mid-week, with winds and waves subsiding in its wake.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Watch from late Monday night through Tuesday evening for
     LHZ361>363-462.

     Small Craft Advisory from midnight tonight to 6 AM EDT Wednesday
     for LHZ421-441>443.

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

$$

AVIATION.....BT
DISCUSSION...DRK
MARINE.......MV


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