Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KDTX 281045
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
645 AM EDT Wed Oct 28 2020


.AVIATION...

Drier low level air will continue to work into the area this morning
with remaining MVFR to patchy IFR cigs dissipating/shifting east in
the first hour or two of the forecast for the I-94 corridor. Partly
to mostly clear skies are then expected much of today into tonight
before some increasing upper level clouds begin to lift north into
the area with developing low well to the south. Very late in the
forecast period, north/northeast flow will develop and bring some
lake effect/enhanced cloudiness late tonight into Thursday morning.

For DTW...Brief period of MVFR cigs early with some potential again
by early Thursday morning. In between, VFR conditions will dominate.

.DTW THRESHOLD PROBABILITIES...

* Medium for ceilings at or below 5000 ft through 13z or so, low
  after 12z Thursday morning.

&&

.PREV DISCUSSION...
Issued at 314 AM EDT Wed Oct 28 2020

DISCUSSION...

PV anomaly and jet streak that helped generate a rainy/drizzley day
yesterday continues to slide eastward into the Northeast. As these
features exit the central Great Lakes, high pressure will overspread
SE MI this morning ushering in a drier airmass helping to clear out
this persistent cloud cover. Increased insolation will allow highs
to rise back to closer to average for this time of year, albeit
still a bit below normal in the low to mid 50s. Mixing depths
subsequently increase allowing the 25-30kt winds aloft over the
Thumb and Saginaw valley and 20-25kt winds aloft over the Metro area
to mix down toward the surface. As a result, expecting a bit
breezier of a day with gusts up to around 20mph for the majority of
the area with the slightly stronger wind gusts up to around 25mph
over the Saginaw valley and Thumb.

Main focus is the track of the conglomeration of Zeta and a closed
low coming out of the desert southwest. Timing has remained fairly
consistent in the closed low ejecting out of the Southwest into the
southern Plains daytime Wednesday as Zeta makes landfall late
Wednesday in eastern LA. These systems look to partially merge, at
least in respect to their precipitation shields, with models still
trying to show two distinct low centers in the mid-levels. Zeta`s
track rides the Appalachians in VA with the closed low lagging behind
sliding into the southern Ohio/Tennessee Valleys Thursday. These
tracks keep the broad precip shield to our south with perhaps only
the southern sliver of Lenawee and Monroe having any shot of seeing
some rain. This chance doesn`t look to be high with the best
potential for rain from Toledo-south so have only a slight chance PoP
for those areas. Due to the southerly track of these systems,
moderate northeast low level flow develops advecting moisture from
Lake Huron over SE MI Thursday. This will allow for the chance of
scattered lake-effect rain, particularly over the Saginaw Valley and
Thumb. This shallow layer of moisture will reside below the dendritic
growth zone keeping this all rain with perhaps only a few melting
snowflakes mixed in given a 1500-2000ft freezing level and highs in
the mid to upper 40s.

High pressure then builds in from the east late Thursday into Friday
reinforcing the northerly flow allowing for colder air out of Canada
to spill south over SE MI. 850mb temps fall over the course of
Friday with -6C to -8C temps overhead by the afternoon resulting in
much below normal temps with highs only in the low to mid 40s. The
one positive will be this drier airmass should help to erode cloud
cover over the region allowing for a fair amount of sun. Surface high
pressure quickly moves east residing over the Northeast by Saturday
morning setting up southerly return flow. This will allow for a
slight rebound in temperatures with highs Saturday reaching near 50.

MARINE...

As high pressure settles into the Ohio valley, marine conditions
give way to low pressure moving across northern Ontario tonight.
This results in moderate SW flow between systems over Lake Huron and
lower Michigan through Wednesday. A Small Craft Advisory remains in
effect for Saginaw Bay to Harbor Beach tonight until wind diminishes
by Wednesday afternoon followed by waves shortly after. Gale
potential remains limited to a few entry level gusts in the central
to northern Lake Huron open waters through the morning. Forecast
temperature profiles continue to reflect instability over the water
mixing into some 35 knot wind in a couple of the stronger model
solutions mainly for a few hours around sunrise before the wind
pattern diminishes. Gradient flow weakens as the cold front settles
southward from the low into the north third of Lake Huron by
Wednesday night. The front then washes out as high pressure
approaches from the Midwest and as the remnants of Zeta move through
the Tennessee valley. A period of moderate NE wind occurs between
the systems Thursday and Friday likely producing high waves on the
south half of Lake Huron to finish the week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ421-422-
     441.

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

$$

AVIATION.....DG
DISCUSSION...KDK
MARINE.......SS


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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.