Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KDTX 200501

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1201 AM EST Sat Jan 20 2018


An amplifying longwave ridge over the central United States and
increasing stability aloft will maintain relatively quiet weather
throughout the period. Models are having a difficult time
forecasting the amount of saturation that will occur in the near
surface layer Saturday morning as there is some projected low level
moisture advection from the south. With snowpack in place, model
boundary layer schemes are very suspect and low confidence exists.
Have used the Rap as a guideline and instead, will call for a
prevailing MVFR HZ at all sites around/after daybreak with MVFR cig
heights taking hold throughout the day.


* Moderate to High for cigs aob 5kft after 12Z Saturday.


Issued at 251 PM EST Fri Jan 19 2018


Upper level ridge spilling over into the Great Lakes region today.
12Z Minneapolis sounding revealed very warm air/near record, as 850
mb temp checked in at 11 C, and this narrow axis of warm air will be
sliding through southeast Michigan this evening as a dry cold front
slides through the northern Great Lakes tonight. Sufficient
mixing/elevated southwest surface winds through the night expected
to hold temperatures around 30 degrees.

Remnant/weak 850-700 MB theta-e ridge axis sliding south through the
CWA on Saturday, with renewed 850 mb moisture/theta-e coming out of
the Midwest late in the day. Maxes will be determined by amount of
low clouds around tomorrow, as there is a major difference between
12z NAM/GFS 925 mb moisture/temps vs 12z Euro/Regional GEM. Could
see maxes ultimately end up anywhere from the mid 30s to mid 40s.
Preference will be to lean toward partly sunny skies and milder temps
(lower 40s), as ARW is not nearly as bullish with the 925 MB

Low level jet (925-850 MB) over the Ohio Valley Saturday night
veering, and becoming a bit more west-southwest, and thinking the
low level moisture sufficient to generate drizzle/light rain will
struggle to make much inroads across the southern Michigan border
through Saturday Night. None-the-less, if a sufficient depth of
saturation occurs, with temperatures flirting around freezing mark,
a slight chance of light freezing rain/drizzle appears warranted
along/south of M-59. Higher dew pts coming over the frozen ground on
Sunday will likely result in some fog, but dew pts only expected to
be in the mid 30s, probably not high enough to support dense fog,
prefer values closer to 40 degrees, but also the amount of snow cover
remaining, if any, will factor in as we head into Sunday evening.

Aggressive height falls spreading into the Plains on Sunday, and
over the Midwest/Iowa by Monday Morning. Strengthening surface high
over northern Ontario (1036-1038 MB) with the tightening low level
baroclinic zone over Lower Michigan will present a better
opportunity for freezing rain along/north of M-46 late Sunday night
as drier sfc-925 mb easterly flow undercuts the moisture/warm
advcection above.

Low pressure traveling northeast from IA/MO into Michigan Monday 12Z
to Tuesday 12Z will bring the likely chance for precipitation
throughout both days. There are slight discrepancies regarding the
track of the low as it traverses across Michigan, with the GFS/GEM
taking the low over northern lower Michigan, while the ECMWF run
places the low across central lower Michigan and into the thumb.
Despite the discrepancies, 850 mb temperatures averaging 4 - 6 C and
surface temperatures peaking in the low to mid-40s will support rain
for precipitation seen throughout Monday. As the low continues to
push northeast into Ontario, cold Canadian air will quickly wrap
around the western side of the low, dropping 850 mb temperatures
down to an average of -5C by 12Z Tuesday. As a result, precipitation
is expected to transition from rain, to a rain snow mix, and
eventually all snow throughout the Tuesday morning hours. Light snow
will be possible throughout Tuesday, before tapering off by early
Wednesday as low pressure pushes into the New England.

Temperatures will return to season to slightly above seasonal norms
behind the low, with daytime highs peaking in the mid to upper-30s
through the mid-week period. Surface high pressure and ridging aloft
will help keep conditions dry through this time, with a late week
developing low pressure system bringing the next chance for
precipitation by Saturday.


High pressure centered over the southeastern US will dominate the
weather over the Great Lakes for the next couple days. Southwesterly
flow on the northwestern edge of the high pressure will persist
through today with winds staying generally around 30 knots or less.
Winds will back to the south/southeast by Sunday afternoon and
evening as the next low pressure system approaches and also brings
increased chances for rain to close out the weekend. Rain chances
continue on Monday with winds becoming elevated as the center of low
pressure system enters the Great Lakes region. Anticipate winds to
be somewhat tempered by the warm air advection with this system
through the weekend, but winds could pick up out of the southwest
when cold air rushes in on the back side of the system.


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



You can obtain your latest National Weather Service forecasts online
at is the U.S. government's official web portal to all federal, state and local government web resources and services.