Scientific Forecaster Discussion
fxus63 kdtx 191951
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
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
County Warning Area 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
Low pressure traveling northeast from Iowa/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 European model (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.
issued at 1258 PM EST Fri Jan 19 2018
VFR conditions will prevail through this evening under scattered to broken
high clouds streaming over Michigan. Southwesterly winds with a few
gusts up to 20-25 kts will be possible through this afternoon before
winds calm down by early evening. Potential MVFR conditions enter
the forecast by around 12z tomorrow as a push of warm air advection
with a warm front will lift across the terminals.
/Dtw threshold probabilities...
* moderate for cigs aob 5kft by around 12z tomorrow morning.
Lake St Clair...none.
Michigan waters of Lake Erie...none.