Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 171005
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
605 AM EDT Sun Oct 17 2021

.AVIATION...

Pockets of VFR stratocumulus track across the region early this
morning as a weak surface trough moves through. Westerly wind will
veer to west-northwest and become breezy by this afternoon with
gusts on the order of 20 to 25 kt. Redevelopment of SCT to
occasional BKN coverage of diurnal cumulus this afternoon with cloud
bases around 5 to 6 kft. Loss of daytime heating brings a decreasing
trend to cloud cover and wind magnitude during the evening.

For DTW... Wind out of 280-290 degrees peaks around 22 kt between
19z and 00z this afternoon but is expected to remain below crosswind
threshold.

.DTW THRESHOLD PROBABILITIES...

* Low for wind gusts to exceed 25 knots from 290 degrees this
  afternoon.

* Medium for ceiling at or below 5000 feet today.

&&

.PREV DISCUSSION...
Issued at 337 AM EDT Sun Oct 17 2021

DISCUSSION...

Prototypical mid October conditions will exist to finish the weekend
period. Southeast Michigan still immersed within deeper layer
northwest flow defining the back end of a gradually recovery upper
height field as the mean trough axis clears the great lakes. This
process lends some degree of airmass modification to a rather
seasonable resident thermal profile. High degree of early day
insolation potential before standard diurnal cu expansion commences
within a steepening lapse rate environment. This yields a high
temperature right at average - around/just above 60 degrees.
Moderately mixed profile again translates into gusty conditions -
wind magnitude within the boundary layer supporting gusts of 25 to
30 mph.

Deep layer stability held firm within confluent mid level northwest
flow and general low level ridging ensures benign weather conditions
Monday. The depth and magnitude of dry air translates into full
insolation. The underlying increase in mean thicknesses as upper
heights steadily build will nudge daytime temperatures above average
- readings of low to mid 60s. Similar environmental conditions in
place Tuesday as the inbound upper ridge axis anchors overhead.
Advent of modest warm air advection as low level flow backs to
southwesterly offers a noted boost to the warming trend, supporting
highs near 70 degrees.

Latest deterministic model solution space and ensemble guidance
indicate a lower height anomaly will organize across the western
conus early in the week, before migrating eastward with time toward
the great lakes mid-late week. Standard downstream response as
strengthening southwest flow offers meaningful moisture advection
within a burgeoning warm sector. This moist ascent currently
projected to arrive locally invof of the Wed night period - precip
potential increasing accordingly. This nocturnal timing would afford
another mild/dry daylight period Wednesday - targeted highs again
around 70 degrees. This pattern evolution projects unsettled
conditions then on Thursday as the mean trough or closed mid level
circulation and accompanying cold frontal boundary pivot through.

MARINE...

An upper trough axis will move east of the Central Great Lakes
region today helping drive a colder air into the region. This is
resulting in increased over-lake instability bringing gusty winds
across all marine zones along with scattered rain showers. Shower
activity will be mainly across the favored northwest flow areas
across central and northern Lake Huron. A chance of waterspouts
remains for today with this activity. The over-lake instability with
a tight pressure gradient will keep peak winds in the 20 to 30 knot
range. Thus, a Small Craft Advisory remains in effect for all
nearshore zones through today. A period of dry weather with a
warming trend is expected Monday into Wednesday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422-
     441>443.

Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444.

&&

$$

AVIATION.....TF
DISCUSSION...MR
MARINE.......AA


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