Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
320 PM EDT Sat Mar 15 2014
Short term...this evening and tonight
An extension of the eastern Canadian polar low now rotating across northern
Ontario will advance into Quebec tonight...while surface high pressure
/1038 mb/ builds across the upper MS valley and northern Great Lakes in
its wake. Yet another late season Arctic air intrusion has been
infiltrating the region ahead of this strong surface high. Despite the
ongoing low level cold air advection...a middle March sun angle has
been effectively holding temperatures in the 30s this afternoon.
The approach of some middle and high clouds will act to temper the
radiational cooling during the first half of the night. These clouds
are resulting from deep layer frontal forcing extending from Iowa
into southern Wisconsin...within the entrance region of an upper jet
streak. Intensification of the upper streak streak tonight will lead
to a deep layer of frontogenetical forcing overspreading the Ohio
Valley and southern Great Lakes. The lack of good middle level instability
and significant low level dry air advection through the night will
be large limiting factors for precipitation development across Southeast Michigan. These
factors remain supportive of the current dry forecast tonight. The
thicker clouds will slowly advance to the south during the overnight
as the better low-middle level fgen becomes focused south of the state.
The clouds and persistent north-NE gradient will limit the opportunity
for good radiational cooling potential tonight. This supports
holding min temperatures on the warmer side of MOS /teens in metropolitan Detroit
and points south and single digits to the north where skies will be
Long term...Sunday through Friday
Strong surface high pressure over Manitoba will weaken as it sinks
down into the Great Lakes Sunday and Sunday night. The high should
become centered over Michigan by tomorrow evening...keeping dry and
quiet weather around for the second half of the weekend. Cold dome
of high pressure will however keep the colder air around...and even
reinforce it with h850 temperatures diving to between -10 and -18 c.
At the surface...this should translate to maximum temperatures primarily in the
20s tomorrow...with only upper teens forecast in the northern thumb.
These numbers are a little above MOS given the recent trend of
overachieving on maximum temperatures under the middle-March sun. There will be
some high clouds around tomorrow however...possibly a little thick
near the Michigan/Ohio border as a low pressure system tracks to our
south. Low maximum temperatures will be threatened tomorrow at mbs (24) and fnt
(27)...but we should get above the record of 19 at dtw. Overnight
lows will be quite chilly...although increasing high clouds again
overnight ahead of the next upper wave lends some uncertainty to the
forecast. Time of arrival and thickness of these clouds could have a
big impact on the temperatures...and will stay conservative for now
until we get a better feel for these parameters with forecast mins
in the single digits to slightly below zero. Record low for March 17
at mbs is 1...which could be challenged.
A warm front will lift across Michigan late Monday and Monday
night...with a secondary warm front advertised by models to arrive
on Tuesday as the big low off the British Columbia coast shears and
moves east into the northern and Central Plains. Isentropic ascent
along each of these boundaries looks weak across Southern Lower
Michigan per NAM/GFS analysis...and should have little moisture to
work with. Forecast is therefore dry through Tuesday. The approach
of this system will however usher in a pronounced warmup for
Tuesday...with 850mb temperatures climbing back up above zero. Did raise
maximum temperatures into the upper 30s to low 40s by Tuesday.
Middle latitude cyclone looks to mature over the Great Lakes region on
Wednesday with the general medium range model consensus tracking
the low mke-glr. Temperatures trend closer to normals for the
period. Any quick/weak clippers or shortwaves will bring the
opportunity for rain/snow mix for the rest of the extended period as
mins dip below freezing each night. The next organized chance for
precipitation will be late Friday night...but models still quite
High pressure sinking down into the central Great Lakes from
Manitoba will bring a decreasing trend to winds tonight and Sunday.
The exception will be over Western Lake Erie where easterly winds
will increase tonight through early Sunday as low pressure tracks
across the Tennessee Valley. Gusts are expected to remain under 25
Fairly light winds are expected across all marine areas Sunday night
as high pressure remains in control. A low pressure system will then
lift towards the area by middle-week bringing an increase in winds an a
chance for rain and snow showers.
Aviation...issued 104 PM EDT Sat Mar 15 2014
Satellite trends over the last couple hours have been supportive of
an increase in clouds as a result of diurnal heating within a plume
of moisture streaming in from northwest lower Michigan. These clouds should
decrease this evening under persistent low level dry air advection
and loss of daytime heating. While some low stratus development is
possible off Lake Huron under north-NE flow overnight...the degree of
dry air and building surface ridging make the probability too low to
mention a low ceiling in the tafs at this time.
For dtw...an added downslope component into metropolitan Detroit under west-northwest
winds this afternoon lessons the chances and duration of a broken
strato cumulus field in comparison to locations farther north. Some
slight decrease in the west-northwest winds is expected this afternoon as the
gradient relaxes a bit. Winds will continue to diminish this evening
as they veer to the north amidst building surface high pressure.
//Dtw threshold threats...
* low confidence in ceilings at or below 5000 feet this afternoon.
Lake St Clair...none.
Michigan waters of Lake Erie...none.
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at www.Weather.Gov/Detroit (all lower case).