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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 021722
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1222 PM EST Tue Mar 2 2021


.AVIATION...

-- Changed Discussion --
High pressure off to the southeast will continue to be in control
resulting in VFR conditions through this afternoon and into the
overnight hours. A low pressure system moving across Ontario will
assist in increasing the pressure gradient as the areas resides
between this low and the high pressure. Southwest winds are now
beginning to increase across the area with wind gusts up to 20-25
knots possible this afternoon. The approaching low will also bring
in some mid to high level clouds. VFR conditions this afternoon will
continue through tonight as the low to the north pushes east. This
low will bring a front across the area on Wednesday with increasing
mid to high clouds.

.DTW THRESHOLD PROBABILITIES...

* None.
-- End Changed Discussion --

&&

.PREV DISCUSSION...
Issued at 329 AM EST Tue Mar 2 2021

DISCUSSION...

Surface high pressure now extends across the Ohio Valley and srn
Lower Mi within the mid level confluence that developed last night
in the wake of the departing mid level low trekking across ern
Canada. A northern stream short wave impulse now over srn
Saskatchewan will quickly advance to nrn Ontario and Lake Superior by
evening. This will force the sfc high to the south of the forecast
area today, allowing a strengthening southwest gradient to take hold
across Lower Mi. As a result, there will be good warming in the 800
to 700mb layer today. This will suppress diurnal mixing to a degree
(3-4k feet per RAP). There will also be some transient mid/high
clouds today, especially in the north, within the mid level warm air
advection pattern. Nonetheless, sub 900mb winds increasing to 20 to
30 knots this afternoon and a very dry boundary layer will still
support a respectable daytime warming trend with highs reaching 40 by
late afternoon over much of the area.

The aforementioned short wave will race east toward quebec tonight.
A trailing cold front will then be forced south across the Great
Lakes, aided by strengthening sfc high pressure across Hudson Bay
and northern Ontario. The front will largely remain north of Se Mi
tonight. An increase in the wind fields atop the nocturnal inversion
tonight will allow low level warming to persist across Se Mi. This
will limit nighttime boundary layer cooling despite clear skies,
supporting min temp just down around 30. The NAM is much faster
than other model solutions in driving the cold front south across
the forecast area on Wednesday and is also more aggressive with post
frontal stratus. The ARW and HRRR seem to offer a more reasonable
solution which also fits how these back door fronts typically behave
this time of year. They drive the front into the thumb region early
in the day on Wednesday, which keeps the areas near Lake Huron cool
and allows inland locations to warm through diabatic heating. These
solutions then drive the front inland during the latter half of the
day. Based on these solutions, forecast highs Wed will be well into
the 40s inland (with some low 50s in the south) and much cooler near
Lake Huron.

Some retrogression of an upper low over ern Canada Wed and Thurs
will drive some colder air into the eastern Great Lakes during the
latter half of the week. This will keep temps on the cool side of
early March norms. The medium range model suite than show a shift in
the long wave pattern over the weekend and into next week that will
feature ridging expanding across the eastern US and will offer a
warming trend across the Great Lakes. Overall, dry air and some
semblance of sfc high pressure in the vicinity will maintain a
forecast that is void of any meaningful precip chances through the
weekend.

MARINE...

A brief lull in wind strength occurs this morning as the center of
high pressure slides through the Ohio Valley. However, another low
pressure system will be quick to drop into the northern Lakes and
the resultant gradient will bring an uptick in southwest winds
across central Lake Huron this afternoon and evening. SW flow is
usually warm and stable heading into early March however the
departing air mass is cold and well mixed over central Lake Huron
which adds confidence in frequent gusts reaching 35 to 40 knots. A
new round of Gale Warnings and Small Craft Advisories are now in
effect from noon until 10 PM Tuesday night. The associated cold
front moves through by Wednesday morning and will be much weaker
than the past Sunday evening and Monday cold fronts. It will open
the door for an extended period of NW to N winds for the mid to late
week that look to remain below headline criteria.

&&

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

     Small Craft Advisory until 10 PM EST this evening for LHZ421-441.

Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
-- End Changed Discussion --
&&

$$

AVIATION.....SS
DISCUSSION...SC
MARINE.......TF/BT


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