Scientific Forecaster Discussion
fxus63 kdtx 251648
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
1148 am EST Sat Feb 25 2017
Westerly cold advection and deep mixing allowing for wind gusts up
around 30 knots this afternoon, with the low levels slowly drying
out. Cold flow off Lake Michigan will attempt to slow the process
(flurries this afternoon), with good subsidence kicking in early
this evening behind mid level cold pool exiting east. Will maintain
low VFR/possible high MVFR ceilings for much of tonight underneath
subsidence inversion, but low level warm advection kicking in by
sunrise should allow for a quick dissipation in the low clouds, with
mid/high clouds spreading in during Sunday. Once again, winds look
to be strong tomorrow afternoon ahead of a cold front, with gusts
around 30 knots, but out of the southwest direction.
For dtw... westerly wind gusts around 30 knots will continue this
afternoon, helping to dry out the low levels, with just flurries
expected as Lake Michigan activity struggles to reach the terminal.
Banking on just enough moisture to become trapped underneath
strengthening low level inversion this evening to support low
VFR/borderline MVFR ceilings, with clearing taking place sometime in
7-11z time frame.
//Dtw threshold probabilities...
* moderate for ceiling 5000 feet or less through 7z, then low.
* Low for exceeding westerly cross wind threshold today.
issued at 353 am EST Sat Feb 25 2017
Our recent run of record warmth will end today as colder air surges
into the Great Lakes during the early morning. Temperatures quickly
fell from the 50s into the 30s and lower 40s Post front leaving
midnight readings as the high temps for this calendar day. The
report of 57 at Detroit Metro Airport is long gone and pushing the
upper 30s at press time. Temperatures will now require all the
diurnal help possible to hold steady in the mid to upper 30s through
the afternoon against a west wind gusting to near 35 mph by late
morning and a chance of light rain/snow mix or flurries. These
conditions are a considerable turn from yesterday but much closer to
normal for late February.
The colder air flowing into Southeast Michigan will follow the front and
parent low pressure that continues to deepen and mature over
Northern Lake Huron during the early morning into northern Ontario
during the afternoon. Satellite and radar composites indicate the
upper level trough axis still over the western Great Lakes which is
supporting an area of snow forced by mid level deformation. The 00z
model package has a good handle on current conditions and projects
the trough axis to become more neutral to negatively tilted while
moving through lower Michigan today. This process will direct the
stronger deformation forcing to our north and leave the Saginaw
Valley and northern thumb to have the best chance of any measurable
snow through the day.
Dry conditions will follow tonight in between the departing system
and the next short wave due through the northern Great Lakes during
Sunday. The notable aspect of conditions tonight will be the
persistent moderate gradient flow remaining gusty as model soundings
indicate the low levels remaining well mixed up to about 825 mb.
This will continue through Sunday and increase a notch as the
northern stream wave increases the gradient between it and broad
high pressure over the southeast states. Model soundings indicate
gusts near 40 mph will be possible in the Tri Cities area by mid
afternoon. The system will otherwise bring just a weak and moisture
starved pattern of mid level isentropic ascent that will struggle to
produce a light mix of rain and snow. The strong southwest flow will
scour out enough cold air to lift Max temps to around 40.
The departure of the northern stream wave Sunday night will leave
rising 500 mb height and low level thickness warming to start next
week. A broad area of high pressure off the Atlantic coast and Lee
side troughing over the plains will support light south low level
flow over the Great Lakes. This will start another warming trend
through mid week that is projected to lift temperatures into the 40s
Monday and 50s Tuesday. Low pressure moving into the Midwest by
Tuesday will support the southerly flow of warmer air and also the
next chance of rain Tuesday into Wednesday.
Low pressure over Northern Lake Huron during the early morning will
continue to deepen as it moves into Ontario today. This will produce
westerly gales through this evening. Gale warnings and small craft
advisories remain in effect for all marine areas for the wind and
resulting hazardous waves. The wind will ease below headlines
tonight but then increase again during Sunday as the next wave of
low pressure moves across Lake Superior. Cold air lingering over the
region in the low levels will support unstable conditions over the
water as southwest flow strengthens and likely produce another
period of gales through Sunday afternoon and evening. This will
mainly affect outer Saginaw Bay and the central sections of Lake
Huron. A gale watch is in effect for this time segment. Wind and
wave conditions will then become more favorable to start next week.
Lake Huron...gale watch from Sunday morning through Sunday evening for lhz362-
Gale Warning until 10 PM EST this evening for lhz363-421-441>443-
Gale Warning until 4 am EST Sunday for lhz361-362.
Small Craft Advisory from 4 PM this afternoon to 10 PM EST this
evening for lhz422.
Gale Warning until 4 PM EST this afternoon for lhz422.
Lake St Clair...Small Craft Advisory until 10 PM EST this evening for lcz460.
Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EST this evening for lez444.