Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 051931

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


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

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.



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.


Issued at 1144 AM EST Mon Dec 5 2016


MVFR dominates through the daylight hours as moisture remains
trapped beneath the strong inversion noted on the 12z DTX sounding.
Building upper ridge and approaching high pressure has been forecast
to scour out cigs from south to north around 00z this evening.
However, given the strength of the inversion and short residence
time of the upper ridge there is some concern that subsidence may
not make it all the way to the surface. Will hint at the potential
for lingering low cloud for now with a SCT group at all locations.
By 08z, easterly flow off of Lake Erie will raise concerns for
lake stratus to infiltrate the Detroit area sites.

For DTW...East flow increasing to around 10-15kts will cause noise
abatement issues in the 08z-20z time frame. Dry air likely to lead
to virga as rain moves in from the southwest...precip timing focused
18-00z. Ptype will be rain.

//DTW Threshold Probabilities...

* High for cigs aob 5kft thru 00z. Low 00z-08z. Moderate after 08z.


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



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