Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 172250
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
650 PM EDT Thu Oct 17 2019


.AVIATION...

There remains a shallow broken to overcast strato cu deck across Se
Mi based primarily between 4k and 5k feet. During the course of the
night, the low level flow will become increasingly more anticyclonic
as high pressure nudges into the area from the west. Latest model
soundings suggest this will allow a gradual clearing to take hold,
especially after 4 or 5 UTC. Given the degree of strato cu still in
place across the region and with model soundings still holding onto a
relatively deep inversion into Friday, there is a concern that these
clouds may hold together a little longer than anticipated. The
current forecast will maintain a clearing trend between 03 and 05Z.
Observational trends will continue to be monitored through the
evening with adjustments made to sky cover if needed.


DTW THRESHOLD PROBABILITIES...

*  High for cigs aob 5000 feet into the evening.

&&

.PREV DISCUSSION...
Issued at 357 PM EDT Thu Oct 17 2019

DISCUSSION...

Gusty NW wind reinforces cool temperatures this afternoon before the
wind diminishes quickly around sunset. A generous coverage of
diurnally supported stratocu fades with sunset as well and the
clearing trend feeds back into wind decoupling due to quick
establishment of the surface based inversion. All of these elements
combine to organize the radiational cooling scenario for later
tonight as high pressure builds in from the Midwest. A few streamers
of lake induced stratocu are possible but a 330/NW wind below 700 mb
is favorable for maintaining minimal cloud coverage through the
night. There is some mixed signals in model output in terms of cloud
potential however NW flow and incoming high pressure supports
leaning the forecast toward lower coverage. Model soundings that
favor clear sky then indicate a surface temperature dropping into
the upper 20s across interior sections of Lower Michigan with a
shallow moisture profile that makes surface dewpoint vulnerable to
being carried lower by strong radiational cooling. This results in
widespread frost and warning worthy freezing temperatures across SE
Michigan as high pressure becomes centered over the region by
sunrise Friday.

Temperatures recover from the cold start to reach highs in the lower
to mid 50s Friday afternoon. This occurs under full sun as high
pressure is in full control of conditions will drifting east across
the central Great Lakes. The eastward drift represents displacement
of the low level thermal trough that continues through Friday night
and leads to moderation of low temperatures by Saturday morning.
Development of light SE wind and some increase in high clouds also
help support low temperatures in the upper 30s to lower 40s.

Low pressure moving across central Canada has a cold front trailing
southward into the Plains and Midwest Saturday. This initial affect
of this system is an additional increase of south wind over SE
Michigan during which further boosts the warming trend. High
temperature guidance in the upper 50s to lower 60s is finally back
up around normal for mid October although readings are muted
slightly by increasing clouds ahead of the cold front. The moisture
return is respectable as the 12Z models generally agree on 850 mb
dewpoint rising to around 10C in the warm sector. The limiting
factor for showers is the weakness in the front itself so far south
of the parent low centered over Hudson Bay by Saturday night. A
chance POP for scattered shower coverage looks reasonable at this
point in the forecast.

Amplifying ridge ahead of a developing system across the
Central Plains will move over the Great Lakes with surface high
pressure allowing for dry conditions on Sunday. General south to
southwest flow in the lower levels will draw warmer air into the
region to close out the weekend allowing high temperatures on
Sunday to climb into the 60s under mostly sunny skies.

The surface low will undergo cyclogenesis as it lifts into Minnesota
during Monday morning pulling a warm front northward through Lower
Michigan by Monday afternoon. This will bring one more day in the
60s before widespread precipitation chances arrive late Monday
evening into Tuesday. Strong dynamics will support this rainfall
within the corridor of higher theta-e being drawn northward ahead of
the cold front. Post frontal conditions will be much cooler with
troughing over the Midwest ushering in 850 mb temperatures of around
0C by Tuesday evening. This will bring high temperatures back down
into the 50s for Tuesday and through the middle of next week.

MARINE...

Strong and cold northwest flow over Lake Huron will continue to
slowly diminish tonight, but waves in excess of 4 feet will continue
across the southern Lake Huron basin. Winds becoming light tomorrow
over the Central Great Lakes as high pressure arrives. This high
will be slow to push east over the Weekend, and thus winds remaining
light into Saturday. Southeast winds then ramp slowly ramp on Sunday
and Monday, with gusts at or above 30 knots over Lake Huron by
Monday evening ahead of the next strong cold front. Strong winds
then persist into Tuesday behind the cold front, but post
frontal wind speeds look to remain below Gales at this time.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning from 2 AM to 8 AM EDT Friday for MIZ047>049-053>055-
     060>063-068>070-075-076-082-083.

     Lakeshore Flood Advisory until 4 AM EDT Friday for MIZ049.

Lake Huron...Small Craft Advisory until 4 AM EDT Friday for LHZ421-441>443.

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

$$

AVIATION.....SC
DISCUSSION...BT/AA
MARINE.......SF


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