Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 052022
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
322 PM EST Tue Dec 5 2017

.DISCUSSION...

Strong PGF and and a well-mixed environment courtesy of ongoing cold
advection has supported sustained winds of 20 to 30 mph and wind
gusts of 35 to 45 mph this afternoon. A peak gust of 54 mph was
observed at MBS at 1754z. Most locations have fallen short of
achieving advisory criteria, so the 4pm forecast package will
contain of most of the headline based upon the latest obs. Even as
the parent low over Ontario lifts away, energy embedded within the
broad cyclonic flow regime will sustain the the existing pressure
gradient through tonight. Winds of 15 to 20 kts will persist with
mechanical mixing sufficient to maintain an element of gustiness
through the tonight. The relatively warm NAM12 was strongly weighted
in tonight`s low temperature forecast of 25 to 28 degrees areawide
as its radiation scheme tends to handle mixed nocturnal boundary
layers well.

Prolonged stretch of quiet weather in store for the foreseeable
future as deep longwave trough axis stays positioned near the Great
Lakes. Flow will be predominantly confluent and NW to occasionally
WNWLy leaving little room for embedded disturbances to amplify over
the Great Lakes region. As a result, expect episodic light snow
showers and occasional low-impact lake effect over the next several
days. To drive home the point, 10-Day run-total snow accum on the
12z ECMWF averages about 2 inches over the CWA. Most noteworthy
snowfall may be Thursday, when slightly better moisture pivots
across the Great Lakes allowing for some eastward extension of LES
and possibly widespread flurries/snow showers during the day. There
is some concern for the potential of an inch or two of accumulation
in a portion of Lenawee County, but there is still noteworthy spread
in model depictions of moisture quality with no clear answer. Given
background forcing, went with chc pops everywhere, with borderline
likely in Lenawee. Left any accums under 0.5 inches for now.
Persistent troughing will keep temperatures suppressed below through
mid-December.

&&

.MARINE...

We are in the midst of a long duration gale event across the Great
Lakes as a strong low pressure system lifts toward James Bay. The
low is just about at it`s forecast deepest pressure, and should
begin to fill back in after 00Z. In spite of this, winds currently
across Lake Huron range from 35 to 45 knots with some potential for
gusts approaching 50 knots over a portion of central Lake Huron for
the next few hours. These gales will persist through Wednesday as
continued cold air advection within a tight westerly pressure
gradient keeps unstable conditions over the waters. Slightly lower
wind speeds across Lake St Clair and Lake Erie being farther removed
from the low thus a small craft is in effect for Lake Erie along
with a low water advisory. Current gale warning for Lake St Clair
should drop off this evening, but will likely need a small craft in
it`s place for the rest of the night through Wednesday. Colder air
moving in mid to late week will also increasing coverage of lake
effect snow squalls to further hinder marine conditions.

&&

.PREV DISCUSSION...
Issued at 1231 PM EST Tue Dec 5 2017

AVIATION...

Strong southwesterly winds continue to be the predominate threat to
aviation as a deepening low pressure system and cold advection
affect the region. Gusts should peak this afternoon as daytime
mixing maximizes, potentially bringing gusts of 35 to 40 knots with
highest gusts expected near MBS closer to the low. Boundary layer
will remain mixed through the overnight keeping winds elevated with
only a slight drop off in gusts from this evening. Gusts will become
renewed on Wednesday as mixing depths yet again increase bringing
down higher wind speeds. Increased mixed layer depth will keep
ceilings primarily VFR although a couple MVFR observations may
linger after 18Z this afternoon as mixing depths are in the process
of increasing. Dry airmass will likely bring a period of SCT sky
cover tonight with BKN returning Wednesday.

For DTW...Strong southwesterly winds will be the main concern
through the taf cycle. Expect gusts to remain at or above 20 knots
through the overnight as well mixed layer remains in place. CIGS
will be VFR as they slowly rise to near 5kft this afternoon. Though
presently in a pocket of SCT sky cover, BKN skies should return
shortly as diurnal mixing peaks.

//DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less this afternoon. Low tonight.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory until 7 PM EST this evening for MIZ047>049-053>055-
     060>062-068.

Lake Huron...Gale Warning until 4 PM EST Wednesday for LHZ361-362-421-422-
     441>443-462>464.

     Storm Warning until 7 PM EST this evening for LHZ363.

     Gale Warning from 7 PM this evening to 4 PM EST Wednesday for
     LHZ363.

Lake St Clair...Gale Warning until 10 PM EST this evening for LCZ460.

Michigan waters of Lake Erie...Low Water Advisory until 4 AM EST Wednesday for LEZ444.

     Small Craft Advisory until 4 PM EST Wednesday for LEZ444.

&&

$$

DISCUSSION...JVC
MARINE.......DRK
AVIATION.....DRK


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.



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