Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 241847
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
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
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.
Issued at 1232 PM EDT Mon OCT 24 2016
Strong northwest flow between departing low and advancing high
pressure is producing lake effect enhanced diurnal bkn-ovc deck
generally in the 3-4k ft range. Sheared out vort max embedded in
mid level flow also helping in generating pockets of mainly sprinkles
mainly north of a DTw-FNT line. Clouds will dissipate towards evening
as diurnal heating ends. High pressure will maintain a northwest
flow through Tuesday with mostly clear skies tonight and some
scattered diurnal cu by early afternoon Tuesday.
//DTW Threshold Probabilities...
* High confidence in cigs aob 5kft through evening.
Lake Huron...Small Craft Advisory until 11 AM EDT Tuesday FOR LHZ421-441>443.
Small Craft Advisory until 10 PM EDT this evening FOR LHZ422.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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