Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
1153 PM EST Tuesday Feb 9 2016
Adequate moisture to sustain pockets of light snow showers or
flurries within an extensive MVFR stratus through the morning
period. Brief disruptions to visibility /IFR/ remains plausible
during this time...additional accumulation at a half inch or less.
Diurnal boost to coverage by midday Wednesday...again perhaps
favoring a window for periodic fluctuations down to IFR during the
afternoon. Lower confidence at this stage in providing a more
definitive outlook on timing/location of possible higher intensity
snow showers Wednesday.
For dtw...minor disruptions to visibility early this morning as
light snow showers linger. General MVFR conditions outside of any
heavier snow showers through the morning period.
//Dtw threshold probabilities...
* high for ceiling at or below 5kft through Wednesday.
* High for snow as precipitation type.
Previous discussion...issued 841 PM EST Tuesday Feb 9 2016
Impressive long duration snowfall event...particularly for areas
from The Thumb down into portions of the Saginaw/Flint
corridor...finally showing signs of easing per latest radar
trends. The slow general downturn in both coverage and intensity
prompted by the gradual eastward release of the residual trowal
like structure and attendant moisture feed off Lake Huron...as the
parent middle level circulation drifts into southern Ontario.
Perpetuation of light snow likely to continue over the next
several hours as this process unfolds...but of considerably lower
impact now as frequency/duration of higher snowfall rates continue
to lessen. Additional accumulation now at a half inch or less into
the early morning period. With that in mind...plan to allow all
headlines to expire at 9 PM. Ribbon of higher moisture now
shifting from eastern Wisconsin into Lake Michigan embedded within
the elongated height falls of an inbound shortwave. This moisture
plume augmented by the increasing moisture flux off Lake Michigan
will slip into Southeast Michigan 10z-13z. Weak large scale support
/DCVA/ points toward seeing an increase in snow shower coverage
during this time...will await the response as this plume exits
Lake Michigan overnight before calling for anything more than a
few tenths/dusting of accumulation for the morning commute.
Previous discussion...issued 344 PM EST Tuesday Feb 9 2016
Current radar imagery indicates that snow will continue through the
evening hours as the upper level low continues to pivot over the
Great Lakes region. With the heaviest band of snow still expected
across The Thumb region...the Winter Storm Warning will remain in
effect through this location through 9 PM. Winter storm advisories
will also remain across the rest of the Saginaw Valley and down to
Oakland County. We will continue to assess the snow this evening to
determine if warnings/advisories need to be extended or if they can
be expired early. At this time...though snow does not show any signs
of letting up and therefore current thinking is that snow will
continue into the evening and slowly begin to taper off in a
southwest to northeast fashion as drier air filters in and the low
starts to track eastward around 9 PM. A surge of colder Arctic air
will result in noticeably colder temperatures starting Tuesday
night. Low temperatures will be in the upper teens to low 20s Tuesday
night...nearly 10 degrees cooler than the previous night.
Snow chances continue into Wednesday as strong northwest winds flow
over Lake Michigan and kick up some lake effect snow showers. These
showers could accumulate another half inch to one inch across the
entire County Warning Area through the day tomorrow. Colder air continues to filter
in resulting in high temperatures in the middle 20s with low
temperatures on Wednesday night in the low teens with areas in The
Thumb region dropping into the upper single digits. As winds
diminish Wednesday night...snow will also come to an end. Flurries
are expected on Thursday...however little to no accumulations are
expected. Another cold day is in store for Thursday as highs are
expected to only reach into the low 20s.
Remainder of the forecast will continue to highlight potential for
bitterly cold temperatures Friday into the weekend. Deterministic
models and ensemble systems have been very stable and in good
agreement in the progression of the Arctic closed low into southeast
Canada and New England over the weekend. While this will leave the
coldest air to our east...850 mb temperatures are likely to reach the
vicinity of -25c. At the surface...an Arctic front is likely to pass
through Southeast Michigan on Friday...accompanied by snow showers. Low-level
Post-frontal flow turns to the north-northwest with cold advection ensuing.
Current forecast calls for lows around 5 degrees either side of zero
Friday night...highs in the single digits and lower teens
Saturday...and lows below zero in most locations Saturday night as
surface high pressure builds in. In addition to the cold...low-level
flow trajectories may result in lake effect snow activity along the
Huron shoreline Friday night and Saturday.
A nearly stationary low pressure system over Southern Lake Huron will
finally release eastward...reaching Lake Ontario overnight. As the low
moves further east...winds will become northwesterly across the region
with a surge of Arctic air advancing in. This will result in elevated
winds tonight through Thursday with waves heights building along the
shoreline of The Thumb. A long duration Small Craft Advisory continues
for these winds and waves. In addition...the elevated winds and snow
bands will encourage snow squalls over the eastern lakes. Conditions
will become increasingly more favorable for freezing spray on
Wednesday...and heavy freezing spray Wednesday night thus a heavy
freezing spray headline has been issued. The wind will diminish later
Thursday through Friday while Arctic air maintains a hold on the region
into next weekend.
Lake Huron...heavy freezing spray warning from 7 PM Wednesday to 7 am EST
Thursday for lhz362-363-441>443-462>464.
Small Craft Advisory until 4 PM EST Thursday for lhz441>443.
Lake St Clair...none.
Michigan waters of Lake Erie...none.
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