Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 281056
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
556 AM EST Mon Nov 28 2016

.AVIATION...

Inbound corridor of VFR showers will steadily deteriote upon entry
through the first half of the day, but will present at least a
chance for some reduction in ceiling heights within any activity.
Otherwise, simply a thickening canopy of mid cloud with an
increasing southeast wind through the early afternoon period. Deeper
moisture will surge northward by late afternoon/evening.
Accompanying reduction into MVFR as widespread rain overspreads the
region, with an eventual lowering to IFR/LIFR through the overnight
period.  Strong southeast winds emerge just off the surface for
tonight.  Stability will dictate whether these winds translate into
gusty conditions at the surface /20 to 25 knots/ or becomes more a
low level wind shear issue /40 to 50 knots at 2000 ft/.

For DTW...Brief window for weakening rain showers mid morning with
an accompanying reduction of CIGS below 5000 ft.  Otherwise, favor
clear skies across the lowest 5000 ft until widespread rain shifts
north beyond 20z.  A period of LIFR possible overnight.  Firm
southeast flow through the daylight period. Potential low level wind
shear and/or gusty conditions /20 to 25 kts/ tonight.

//DTW Threshold Probabilities...

* Moderate for ceiling 5000 feet briefly this morning. High for
  prevailing cig less than 5000 ft by late this afternoon through
  tonight.

&&

.PREV DISCUSSION...
Issued at 250 AM EST Mon Nov 28 2016

DISCUSSION...

Subtropical jet is hauling across the southern tier of the US as a
consequence of the expansive cyclonic flow regime taking shape over
the middle of the country. Deep occluded cyclone currently sits over
the northern Great Plains and will act as a wave guide for the
potent shortwave digging into AZ/NM early this morning as it ejects
toward the Ohio Valley and Great Lakes tonight.

In the short term, the band of showers translating east over Lake
Michigan this morning will provide a low chance of rain for SE
Michigan through midday. This will mainly be supported by a waning
segment of the low-level jet and will dry up substantially as it
encroaches on the dry profile noted in the 00z DTX sounding.

The southwest US shortwave will strengthen as it propagates along
the cyclonic side of the powerful subtropical jet. Strong dynamic
lift will elicit a secondary cyclogenesis response over the western
Great Lakes along the triple point of the aforementioned occluded
cyclone this afternoon into this evening. Rapid amplification of the
downstream ridge will support several hours of a coupled jet
structure directly overhead leading to strong sustained divergence
aloft and supportive of the modeled 80+kt low-level jet response
over the Ohio Valley. Surface winds should have no problem hovering
around 20 knots through tonight with mechanical mixing forcing the
occasional 30 kt wind gust in spite of the unfavorable nocturnal
timing. For today, expect blossoming clouds to the south to steadily
expand into the area. Precip will follow suit over
Arkansas/Missouri/Kentucky this morning into this afternoon, pushing
into southern parts of the forecast area around 21z. Sided toward
the faster guidance given the strong dynamic setup. Rainfall amounts
will likely range from a half inch to one inch.

The long residence time of the jet over the central US yields high
confidence in an effective dry slot for Tuesday. Embedded height
rises in the wake of the departing wave and persistent descent along
the cold side of the jet axis will effectively scour out moisture
through the column. Continued southerly flow as the filling occluded
cyclone remains parked upstream will advect 925mb temps into the
upper single digits during Tuesday. High degree of insolation ought
to support temps approaching 60 degrees.

Tricky forecast for Wednesday as a strong push from the Pacific
forces the broad low toward the Great Lakes. At the same time, there
is strong NWP consensus that a shear max will lift into the area
along the eastern periphery of the circulation. Antecedent
conditions are expected to be a carryover from Tuesday. Thus, there
will be plenty of dry air to contend with. At the same time,
decreasing static stability through the column may still support an
overachieving response in the lower troposphere. No complaint with
chance pops for now as any rain threat remains uncertain and the
surface response will likely be transient anyway as the wave sweeps
by.

MARINE...

Steady increase in southeast winds today as a large low pressure
system organizes and increases intensity over the Plains states.
Additional strengthening tonight will result in a period of gale
force winds throughout the Lake Huron basin, as well as the Michigan
waters of Lake Erie.  Peak gusts during the overnight period
reaching near 40 knots across northern and central sections of the
lake.  The long southeast fetch will also support extensive wave
growth, with waves potential peaking near 20 feet.   Small craft
advisories are in effect today for outer Saginaw Bay and southern
Lake Huron as the system ramps up.  Wind conditions are projected to
improve Tuesday night into Wednesday as direction shifts to the
southwest bringing milder air and more stable conditions over the
region.

HYDROLOGY...

Abundant supply of gulf moisture will lift northward in advance of a
warm front over the next 24 hours.  This will result in a high
probability for rainfall throughout Southeast Michigan tonight.
Total rainfall amounts around a half inch are expected across the
region during this time. This is an above normal amount of rainfall
for this time of year but it is not expected to result in any
flooding hazards.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Warning from 7 PM this evening to 4 PM EST Tuesday FOR LHZ363-
     421-422-441-462.

     Gale Warning from 7 PM this evening to 10 AM EST Tuesday FOR LHZ361-
     362-442-443-463-464.

     Small Craft Advisory until 7 PM EST this evening FOR LHZ421-441>443.

Lake St Clair...Small Craft Advisory from 7 PM this evening to 10 AM EST Tuesday
     FOR LCZ460.

Michigan waters of Lake Erie...Gale Warning from 7 PM this evening to 10 AM EST Tuesday FOR LEZ444.

&&

$$

AVIATION.....MR
DISCUSSION...JVC
MARINE.......MR
HYDROLOGY....MR


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