Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 170731
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
331 AM EDT MON OCT 17 2016
Upper ridge positioned over the Central Great Lakes will shift east
this morning as the upper trough over the West Coast begins to phase
with the strong upper wave over the northern plains as it progresses
eastward. Meanwhile...the frontal boundary that settled into
northern IL/IN and central Ohio yesterday will lift back northward
as a warm front during the late morning and early afternoon with the
increase in southerly flow ahead of the approaching trough. Fog and
stratus that developed overnight will gradually scour out from south
to north as the front lifts through, with at least low clouds
lingering into the late morning over the Saginaw Valley and Thumb.
Low coverage of showers expected early this morning as the front
lifts northward, with better coverage expected north of I-69 after
8AM as an upper shortwave zips across northern Lower Michigan and
over the top of the warm front as it lifts through. Negative
showalter indices will maintain potential for thunderstorms. Chances
for showers and thunderstorms will end from south to north today as
warmer air arrives behind the warm front and provides a cap, and we
see subsidence behind the upper shortwave by late afternoon.
Southerly winds will become a bit breezy as we mix into stronger
winds aloft. Expect to see wind gusts in the 25 to 30 mph range.
Temperatures remain a bit tricky today with some uncertainty
surrounding how long morning stratus will linger. Surface
temperatures should respond quickly as mixing increases behind the
front and skies clear in-part over the far southern portion of
Michigan. Expecting max temps to range from mid-70s over the thumb
to the low 80s from Detroit southward.
Energy from the upper trough will push into the Western and Central
Great Lakes tonight and Tuesday, with height falls and left exit
region forcing helping to intensify surface low pressure as it lifts
across the U.P. of Michigan and towards St James Bay. Models still
differ with how much the low will deepen, lending some uncertainty
to how strong wind speeds will get tonight and early Tuesday.
Forecast soundings from the NAM/GFS suggest enough mixing overnight
to support gusts in the 35 to 40 mph range from early to mid-
morning. Well-mixed boundary layer and mild airmass (20C at H925)
will keep temperatures very warm overnight in the mid to even upper
60s. This is way above normal lows in the upper 30s to low 40s. (May
not break low-min temps for Oct 18 however as cooler air rushes in
late Tuesday and drops temps before midnight.)
Cold front will drop through the area Tuesday behind the exiting
low, with limited moisture providing only a very low chance of a
shower or thunderstorm. Winds will slowly subside through the
afternoon and early evening as surface ridging expands in from the
south. High temperatures will again be tricky and be largely
dependent on frontal timing. Given very warm start to the day, feel
comfortable with maxes in the low to upper 70s (graduated from
northwest to southeast with the timing of the frontal passage).
Next notable weather-maker will be an upper trough passing through
the region early Thursday through Friday. This will provide a chance
for rain showers and reinforce cooler air over the region. Max
temperatures by Friday are expected to only run in the mid 50s, with
low temperatures Friday night dropping back down into the 30s.
A warm front will lift north through the area today with easterly
flow gusting to 30 knots near the Straights this morning in advance
of this front. As the front lifts further north, southerly winds of
15 to 20 knots or so will develop for all marine areas from late
this afternoon into this evening. Small craft advisories will be
issued starting late this evening as gusts climb to 25 knots.
South to southwest winds will increase further late tonight into
Tuesday as a rapidly deepening low moves into Ontario and forces a
strong cold front through Central Great Lakes. A Gale Watch will
continue for the northern two thirds of Lake Huron as southwest wind
gusts approach gale force early Tuesday morning and quite possibly
reach gale force by midday Tuesday as winds veer to the west in the
wake of the cold front and initially stable conditions over the
waters ease and allow for more gust potential. Winds will quickly
diminishing Tuesday Night, and remaining light on Wednesday as a
ridge of high pressure builds into the area.
Issued at 1155 PM EDT Sun OCT 16 2016
Moist low level environment will sustain a combination of low
stratus and fog through the early and mid morning period. Areas from
PTK northward already at or near LIFR conditions and expect these
locations to remain locked at these restrictions right through this
time. Trends not nearly as evident across the Detroit corridor, but
still favor a window for LIFR or near LIFR in stratus/fog during the
early morning period. Gradual improvement off these conditions by
late morning/early afternoon as a warm front lifts through. Light
southwest wind tonight will strengthen as mixing deepens behind the
warm front on Monday. Gusts reaching into the 25 knot range by
For DTW...Low stratus holds firm through at least mid morning,
before mixing out beyond 14z. Component of fog also expected to
emerge heading into the early morning period. However, confidence
in dense fog development resulting in visibility restrictions below
1 mile remains low given the presence of low stratus. Maintaining a
forecast of LIFR highlighting CIGS below 500 ft 09z-13z.
//DTW Threshold Probabilities...
* High in ceilings below 5000 ft through mid morning Monday, then
low thereafter through the afternoon.
* Low for ceilings below 200 feet or visibility below 1/2 mile
through Monday morning.
Lake Huron...Gale Watch Tuesday morning FOR LHZ363-421-441-462.
Small Craft Advisory from 10 PM this evening to 4 PM EDT Tuesday
Small Craft Advisory from 10 PM this evening to 6 AM EDT Tuesday
Gale Watch from Tuesday morning through Tuesday afternoon FOR
Small Craft Advisory from 10 PM this evening to noon EDT Tuesday
Lake St Clair...Small Craft Advisory from 10 PM this evening to 4 PM EDT Tuesday
Michigan waters of Lake Erie...Small Craft Advisory from 10 PM this evening to 4 PM EDT Tuesday
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