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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 181049
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
649 AM EDT Thu Apr 18 2024

.KEY MESSAGES...

- Dry today with showers moving in late this evening along a cold
front. A few rumbles of thunder cannot be ruled out.

- Showers exit Friday morning with drier and cooler weather heading
into the weekend.

&&

.AVIATION...

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MVFR to lower VFR ceilings will clear out this morning, leaving some
degree of cirrus this afternoon into evening. Additional MVFR cigs
will arrive overnight tonight as an area of showers accompany a cold
front. Some potential for IFR as well. Winds will vary considerably
this forecast backing from WSW this morning to S this afternoon to E
tonight and then WNW late as the cold front cross the area. While a
rumble of thunderstorm is not out of the question, low probability
does not warrant a mention in forecast as instability is marginal at
best.

.DTW THRESHOLD PROBABILITIES...

* High for ceiling aob 5000 ft through this morning, then high again
  after 04z-06z tonight.
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&&

.PREV DISCUSSION...
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Issued at 340 AM EDT Thu Apr 18 2024

DISCUSSION...

Brief window of ridge amplification occurs across the Great Lakes
today, in between the shearing upper low to our northeast and an
expansive stacked low that is located to our west over central
Canada. Increasing cyclonic influence of the inbound low leads to a
quick return of warm advection to support highs today in the mid to
upper 60s. Wrap around moisture on the western flank of the
departing system has slowly blanketed the cwa with a low stratus
deck that will linger this morning. There is increasing support for
a window of at least partial clearing this afternoon for the
southern half of the cwa, but upstream lee cyclogenesis and return
flow quickly advect the next round of moisture aloft.

A stray shower or two will be possible as early as this afternoon
across the Tri Cities and Thumb as a 700mb wind maximum around 50
knots initiates strong theta-e advection immediately following the
ridge axis. Standard lag in low level moisture advection affords low
coverage of any shower activity, favoring broader coverage of virga
and cloud cover until low level moisture transport ramps up late
this evening. Forcing will be maximized invof a lengthy baroclinic
zone/cold front that originates from the Canadian low and extends
into the Texas panhandle, so expecting a broken line of showers and
embedded thunderstorms to track through between roughly 03z-12z
(11pm-8am local). The cyclogenesis mentioned above yields a surface
low that will track northeast along the boundary, which effectively
keeps the warm sector and instability axis well south of the state
line. Elevated thunderstorms do remain possible however, with mean
HREF MUCAPE of 100-250 J/kg (some CAMs up to 500 J/kg), but severe
weather is not expected. Progressive nature of this system keeps
widespread QPF totals between a quarter to localized half inch by
Friday morning.

This cold front will draw in a notably colder and drier airmass
Friday morning, evident as H8 temperatures drop below zero which
locks daytime highs Friday-Sunday in the 50s, just a few degrees
below climatology. Will see a gradual eastward drift to the
governing Canadian low through the weekend which will maintain
elevated boundary layer winds to support breezy conditions both
Friday and Saturday. Otherwise, benign conditions expected through
the weekend as high pressure expands across the eastern half of
CONUS. Ensemble mean 500mb height anomalies give a strong signal for
the upper low to stall over Hudson Bay early next week, with
deterministic runs consistently steering a glancing shortwave toward
the Great Lakes Tuesday.

MARINE...

A brief period of ridging expands over the central Great Lakes
keeping westerly winds and subsequent waves to a minimum throughout
today. Another cold front sags through the region late tonight into
the first half of Friday bringing another shot at widespread showers
as well as a slight chance for a couple non-severe thunderstorms
over the southern Great Lakes. Upper level troughing settles over
the Great Lakes following the frontal passage and will hold overhead
through Sunday. Main impact is cooler air spilling back south
creating a more favorable overlake thermal environment to support
moderate west turning northwesterly winds through this weekend. Peak
winds look to occur daytime Saturday though holding sub-gales
instead topping out around 30kts over northern Lake Huron- 20-25kt
gusts favored over the rest of the region.
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&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....DG
DISCUSSION...MV
MARINE.......KDK


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