Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 250353

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1153 PM EDT MON OCT 24 2016


A ridge of Canadian surface high pressure is now expanding into the
western and central Great Lakes. Northwesterly flow aloft remains
strong enough to keep a light, mixed northwesterly wind at the TAF
sites. Stratocumulus continues to stream southeastward from northern
Lower Michigan but is largely east of TAF sites over Saginaw Bay and
Lake Huron. Otherwise, SKC skies and flat diurnal cumulus at 3.5 kft
agl by late Tuesday morning.

//DTW Threshold Probabilities...

*  High confidence in SCT cigs aob 5kft by late Tuesday morning.


Issued at 247 PM EDT Mon OCT 24 2016


Lake enhanced diurnal cu field is beginning to erode over southwest
Lower Michigan in response to building high pressure. Although NW to
NNW flow will persist through tonight, 1032mb high pressure becoming
centered over southern Lower combined with the loss of a diurnal
heating component will limit overnight clouds to nothing more than a
few stray filaments supported by Superior-Michigan. Diminishing
wind, particularly over the SW half of the CWA will allow for
favorable diurnal cooling into the low 30s. Further east and north,
increased cloud potential and a stronger gradient further from the
center of the high may keep temps slightly elevated, but still in
the 30s.

Diurnal cu-up by Tuesday will be substantially reduced with low-
level high pressure firmly in place. The lack of lake enhancement
and the entrance of upstream cirrus advecting in from the front
range will suppress mixing and keep temperatures in the upper 40s
and low 50s once again.

Attention late Tues night through Wednesday turns to the evolution
of the PV anomaly off the Baja Peninsula today and eventual
interaction with energy breaking off the Pacific NW cyclone. Strong
consensus among NWP that height falls and strengthening right
entrance dynamics will aid a healthy LLJ response over the upper MS
valley Tues night/Wed. Although confidence in the track of the low
as simulated by the high-res runs is low at this time (per usual),
their depiction of strong system relative fgen along the encroaching
theta-e gradient is quite impressive. Isentropic ascent will be
prolonged and will exist through a deep layer before moisture even
arrives. This will work against an initially dry sounding and
increasingly strong reinforcing dry easterly flow in the low-levels.
Thinking is that forcing will be strong enough to at least support a
mesoscale band of showers along the elevated warm front between 09-
18z Wed. Event then transitions to an overrunning scenario for the
remainder of Wednesday. Strong continuity with the EC and decent
agreement from the GFS suggest a surface low track near the
Michigan/Ohio border during Wednesday. Strong easterly gradient and
impressive dynamics reinforced by a persistent LLJ running
perpendicular to the elevated frontal zone all but guarantee an
unpleasant Wednesday afternoon. Expect widespread stratiform rain
from at least 8 Mile northward with temperatures in the low to mid
40s and wind gusts in excess of 20 mph.

Low pressure situated over the eastern Great Lakes will bring the
chance for additional rain showers Thursday morning into the
afternoon hours, with chances for precipitation dwindling by the
evening hours. High pressure building into the region Friday
morningwill keep us dry for the first half of the day. However, this
period of dry conditions will be short-lived as a second low
pressure system, centered over the north central Great Plains Friday
at 12Z, pushes southeastward over Michigan by Saturday at 12Z. A
cold front ahead of the low will bring another round of rain
starting Friday night and continuing into Saturday morning


Cold northwest flow will maintain unstable conditions across the
lakes tonight. High pressure will weaken northwest flow Tuesday
while veering winds to the southeast by Wednesday morning in advance
of an approaching storm system. Southeasterly flow will increase
Wednesday and become more easterly as a rain shield will overtake
the lakes late Wednesday afternoon into Thursday.


Lake Huron...Small Craft Advisory until 11 AM EDT Tuesday FOR LHZ421-441>443.

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



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