Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 220725
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
325 AM EDT SAT OCT 22 2016
Slow release of the existing mid level cyclonic flow within the
trailing section of the departing mean trough periphery will leave
SE Michigan under generally benign northwest flow today. Cloud
trends the primary challenge through the daylight period. A
gradually drying north-northwest gradient this morning promoting a
slow clearing process of the existing stratus, although satellite
trends still present a mixed signal as to exactly how much clearing
will commence yet this morning. Model evidence then continues to
point toward the eventual eastward expansion of the residual lake
Michigan moisture plume now tucked closer to the coastline. This
advective process occurs in response to general backing of the mean
flow toward the west with time, with this moisture capitalizing on a
sufficiently steep lapse rate environment as diurnal heating takes
hold. Increasing upper heights will yield a natural increase in mid
level temperatures relative to yesterday, but expect lower levels to
respond more slowly. Highs arrive in close proximity to yesterday,
with readings in the vicinity of 50 degrees. There will be a noted
diurnal uptick in northwest winds as well, with a gust component
into the 25 mph range this afternoon.
Pocket of higher mid level moisture will lift across the region
tonight, as the surface ridge slips through and mid level flow
briefly transitions to weakly anticyclonic. Presence of at least
some degree of cloud cover and the eventual emergence of a light
southwest flow will cap the cooling potential. Coldest locales
could potentially achieve the mid 30s /thumb/ should a greater
window of clear sky develop, but generally favor lows in the upper
30s/near 40F for many locations.
Pattern of weak low level warm air advection develops on Sunday,
existing low level southwest flow increasing immediately downstream
of an inbound cold front. Mixing potential perhaps compromised some
as mid level warm air advection remains stronger, but the noted
warming across the lowest levels should still support readings into
the 60 to 65 degree range. Compact shortwave will quickly track
from the Upper MS Valley Sunday morning into central/southern Lake
Huron by early Sunday night. Model response remains rather muted
as this wave clips across central lower Michigan 21z-04z Sunday
evening/night. Best response locally tied to the attendant cold
frontal boundary, with frontal convergence increasing with time as
trailing stronger height falls eventually catch the boundary. A
simple chance pop mention still warranted for areas mainly M-59
northward during this time.
Cooler post-frontal environment will define conditions Monday under
prevailing northwest flow. Little expectation for the ambient
airmass to moderate much heading into the midweek period.
Extended guidance projects the development of low level easterly
flow locally, downstream of a dynamic system organizing across the
Plains. This tends to limit the diurnal response, particularly if
an increasing coverage of cloud cover further caps an already
meager mixing profile. This points to below normal temperatures
across the Monday to Wednesday period. Dry conditions through at
Tuesday under confluent mid level northwest flow and high pressure
at the surface.
Northerly winds mostly in the 20 to 25 knot range over Lake Huron
will become northwest Today, with just a slow diniminishing trend
Tonight. Small craft advisories remain in effect for the nearshore
waters of southern Lake Huron, including Saginaw Bay. Winds will
decrease to 15 knots or less on Sunday as the gradient finally
relaxes across the region. This will be brief however as another
push of cold air will support a reintesification of the northwest
winds by Monday, with gusts around 30 knots over the open waters
of Lake Huron.
Issued at 1125 PM EDT Fri OCT 21 2016
Mid cloud stratus has been eroding quickly this evening. Still
expecting patches of cloud to hold on during much of night with the
cold cyclonic flow and the trough axis overhead. However, guidance
is unanimous in showing clearing after 09Z tonight. Rolled back the
cloud for Saturday morning. Remnant Lake Michigan theta e plume will
advect into southeastern Michigan during the late morning and
afternoon. VFR stratocumulus is expected to become broken by the
For DTW...Cyclonic flow and a lack of strong dry air advection
supports continued cloud through 09Z. Expecting clearing trend
through the morning before daytime heating develops cloud by the
//DTW Threshold Probabilities...
* High ceilings at 5000 ft this evening and tonight. Low Saturday
morning. Moderate to high Saturday afternoon.
MI...Frost Advisory until 8 AM EDT this morning FOR MIZ047>049-053>055-
Lake Huron...Small Craft Advisory until 10 PM EDT this evening FOR LHZ421-422.
Small Craft Advisory until 4 AM EDT Sunday FOR LHZ441>443.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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