Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 060112
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
812 PM EST Mon Dec 5 2016

.UPDATE...

Clearing skies this evening have allowed for a fast drop in
temperature. As a result, forecast min temps for tonight were
lowered. Expect mins in the mid 20s to be reached by midnight-2AM
timeframe before leveling off or even starting to rise slightly as
winds turn east off the Great Lakes and allows for an increase in
low clouds.

&&

.PREV DISCUSSION...
Issued at 658 PM EST Mon Dec 5 2016

AVIATION...

MVFR cigs over the Ohio Valley and far southern Michigan have been
eroding as a 925mb warm front lifts through the area and with the
loss of diurnal heating. Expect to see a scattering out of ceilings
from DTW-FNT over the next few hours. MBS looks to hold onto this
low celling longer as the front stalls and washes out per latest
model data. High pressure moving east will allow winds to turn east
late tonight in advance of low pressure lifting towards the Ohio
Valley. This will pull low-level moisture off Lake Erie, and then
Lake Huron, and filter it into the Southeast Michigan terminals late
tonight. The moisture should allow MVFR ceilings and potentially
visibility to develop at the Detroit-area terminals, with IFR
ceilings developing further north at FNT and MBS. Diurnal mixing
should allow conditions to improve by mid-morning before rain shield
and lower clouds spread into the area as low pressure lifts through
the Ohio Valley.

For DTW...MVFR ceilings have scattered out at DTW. Expect VFR
conditions through the remainder of the evening and early tonight
before moisture arriving off Lake Erie allows MVFR ceilings and
potentially visibility to develop after about 06Z. Ceilings should
lift around 14Z, while stronger east-northeast winds 9-14 knots
develop on the north side of low pressure lifting into Ohio.
Precipitation looks to begin at DTW around 18Z.

//DTW Threshold Probabilities...

* Low for cigs below 5000 feet through 06Z. Moderate after 06z. High
  after 18Z Tuesday.

* High confidence precipitation Tuesday will be rain.

PREV DISCUSSION...
Issued at 231 PM EST Mon Dec 5 2016

DISCUSSION...

Upper low pressure within southern stream will open as it lifts from
the Rio Grande Valley today to the Tennessee Valley midday Tuesday.
The separation of this system from main northern stream energy now
digging into the Dakotas will limit the degree of phasing between
the streams, so while abundant moisture will be pulled northeast
from the Gulf of Mexico over the next 24-36 hours as the southern
stream system ejects into the eastern CONUS, much of the rainfall
that results will pass southeast of the forecast area.

That said, 12z model cycle still suggests that weak deformation
associated with this system will brush the southeast portion of the
forecast area on Tuesday afternoon and bring a period of light rain
showers. Inverted troughing between this low pressure and the main
northern stream low well to the northwest will then pivot northeast
through the region Tuesday evening and bring the small chance of
additional scattered light showers to parts of the area.

As southern stream shortwave lifts into the northeast CONUS and
eventually dissipates, deepening upper low over the northern plains
and upper midwest will shift gradually east into the northern Great
Lakes by Wednesday. During the time frame, a full latitude upper
trough intensifies to cover much of North America. This upper level
pattern evolution will usher in the beginnings of a notably colder
period of weather with the first step down occurring Wednesday as
high temperatures only reach the 30s (as compared to lower 40s on
Tuesday).

Slight chance for flurries/light isolated snow showers exists
Thursday into Friday as a series of upper-level disturbances pushes
through the region. Bottom half of the atmosphere remains fairly
saturated throughout Thursday, with 1000-500 mb RH values ranging
between 60 - 80% throughout the day, drying out slightly by late
Friday. The main story will continue to be the advent of cold air,
as westerly winds keep temperatures capped in the upper 20`s
Thursday - Saturday, with a shot as returning to the freezing mark
by Sunday. Next potential for significant precipitation accumulation
returns Sunday into Monday as a weak low from the Central Plains
pushes into the Great Lakes region. Both the GFS and ECMWF vary in
the nature of the thermal profile and placement of the low, so both
the extent and type of precipitation cannot be derived with
confidence. Additional details will be supplemented with future
model runs.

MARINE...

Winds will transition to southeasterly on Tuesday at 15 to 20 knot
as two surface low pressure systems advance into the central United
States for the middle of the week. A cold front will push across the
area Tuesday opening the door for fresh to strong westerlies with
gusts to near-gales over the open waters of Lake Huron. Unsettled
and gusty conditions set in for the remainder of the week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

UPDATE.......99
AVIATION.....HLO
DISCUSSION...DG/AM
MARINE.......JVC


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at www.weather.gov/detroit.



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