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Area forecast discussion 
National Weather Service Grand Rapids Michigan
931 PM EST Thursday Feb 11 2016

Latest update...

corrected at 442 PM EST Thursday Feb 11 2016

Scattered light snow showers are expected overnight with little in
the way of accumulation but lows will be cold... mostly between 10
and 15 above. An Arctic front comes through Friday and it will
bring snow showers and increased winds. Most areas will see
measurable snow by evening. As the Arctic air comes in Friday
night...bringing in the coldest air of the Winter... Lake effect
snow showers will be heavy at times along the Lake Shore with
areas south of Holland and west of US-31 seeing the heaviest snow
with considerable blowing and drifting snow. The wind and snow along
the Lake Shore subside by Saturday evening but temperatures will be
very cold with highs between 10 and 15 degrees.

A series of weak systems will move through the area between Monday
and Wednesday bringing some additional snow... but temperatures will
warm to near freezing.


issued at 928 PM EST Thursday Feb 11 2016

No changes to the headlines. The Arctic front is currently just
north of Lake Superior and will continue to move south tonight.
Convergence ahead of the front will likely result in some snow
formation Friday morning with more substantial lake effect snow
showers behind the front.


Short term...(this evening through Saturday night)
corrected at 442 PM EST Thursday Feb 11 2016

I have issued a Winter Storm Warning for Allegan and Van Buren
counties from Friday morning through Saturday afternoon with over a
foot of snow possible locally accompanied by gusty winds causing
blowing and drifting snow. I have also issued a Winter Weather
Advisory for the rest of the Lake Shore counties for the same time
period but snowfall there will be more in the 4 to 8 inch range.
For the second row of counties inland... I issued a Winter Weather
Advisory for the snow showers with the Arctic front since both the
morning and evening commutes will be impacted by it.

With the surface high moving south of the area this evening and
the trough associated with the Arctic front starting to drop
southward into northern lower Michigan... the lake effect snow will
move inland and dissipate. However snow will quickly reform as
southwest to west winds over Lake Michigan in combination with the
trough moving in create surface convergence near I-96. None of this
will accumulate to much though. More like nuisance light snow

Once the Arctic front gets into southwest Michigan Friday the
inversion heights jump to 8000 feet while the dgz increases in depth
to nearly 6000 feet. With the lift associated with the Arctic front...
the deep moisture and deep dgz it would seem we should see a period
of at least moderate snow just ahead of the Arctic front. Hence the
Winter Weather Advisory for the second row of counties inland during
the day tomorrow.

Behind the Arctic front we have 8000 feet inversion heights through a
good part of Friday night into Saturday morning. Theta-E decreases
with height to 8000 feet while there is up to 200 j/kg of cape as the
coldest air of the winter crosses Lake Michigan on north northwest
winds. This will set up a dominant snow band from near South Haven
to around Bloomingdale ( more or less) that will remain nearly
stationary a good part of the night. I expect heavy snowfall with
gusty winds during this time... hence the warning.

All of this slowly diminishes Saturday but it will remain cold.

Long term...(sunday through thursday)
issued at 328 PM EST Thursday Feb 11 2016

High temperatures will rebound to reach the upper teens to lower 20s Sunday
afternoon after a very cold start to the day with temperatures ranging from
5 below to 5 above zero across most of our forecast area early Sunday
morning with high pressure and clearing skies setting up excellent
radiational cooling conditions.

Several weak low pressure systems and upper level disturbances will
move through Sunday night through the early to middle portion of
next week bringing several chances for light snow. Temperatures will
moderate and return to near normal for this time of year for most of
next week.

It is noted that the 12z European model (ecmwf) develops a more significant low
pressure system along the Gulf Coast region Monday and takes it
northeast to the middle Atlantic region while also indicate this system
could strengthen. A consensus of latest medium range guidance
including the global Gem... UKMET and GFS all continue to suggest
that this system should stay well southeast of our region.

However if the upper level trough over the eastern Great Lakes
region early next week deepens with phasing of the northern and
southern streams then there would be potential for that
strengthening system to impact lower Michigan. So we will need to monitor
the evolution of that system and medium range guidance trends
closely as 12z operational European model (ecmwf) guidance indicates that this system
could potentially impact far south to southeast lower Michigan Monday


Aviation...(for the 00z tafs through 00z Friday evening)
issued at 649 PM EST Thursday Feb 11 2016

Scattered light snow showers continue to wind down this
evening...but is resulting in very spotty MVFR. The prevailing
conditions will be VFR through the rest of the night.

Snow showers will redevelop between 11-15z Friday...and conditions
will gradually deteriorate to MVFR once again. IFR will be
possible as well at kmkg due to heavier snow. Winds will become
westerly Friday morning and increase to 10-15 kts with gusts to
20-25 kts. Winds will turn northwesterly by Friday evening.


issued at 203 PM EST Thursday Feb 11 2016

A Small Craft Advisory continues in effect through 1 PM Friday and
is followed by a gale watch for Friday afternoon through Saturday
morning. Wave heights will gradually build particularly on Friday
due to strong northwest winds that could potentially reach gale
force and the cold air advection. Freezing spray will also develop
with the strong northwest flow cold air advection and falling temperatures behind the Arctic
cold front.


issued at 1216 PM EST Thursday Feb 11 2016

Not much has changed in the last 24 hours. The downward trend
continues at Maple Rapids...which has allowed US to drop the
advisory at that location.

This mornings observations on the Grand River at Robinson TWP show
small...thin pieces of ice flowing in the river. A few river
gauges throughout southwest lower Michigan are beginning to show
signs of being affected by ice. At this point it is not an issue.
However...temperatures will only continue to get colder through
the weekend. This will support additional ice formation through at
least Sunday morning with overnight temperatures in the single
digits. Something to consider is that we are late in the winter
season and water temperatures are low enough that ice development
could occur fairly quickly with long periods of sub-freezing air.

Overall precipitation amounts are still low through the next 7
days. Aside from any local heavy lake effect snowfall that
occurs...overall amounts will be fairly light. Even this will not
be realized until melting takes place. The main concern will be
river fluctuation due to ice in the event that thick ice develops.


GRR watches/warnings/advisories...
Michigan...Winter Storm Warning from 7 am Friday to 4 PM EST Saturday for

Winter Weather Advisory from 7 am to 7 PM EST Friday for miz044-

Winter Weather Advisory from 7 am Friday to 4 PM EST Saturday
for miz037-038-043-050-056-072.

Lm...gale watch from Friday afternoon through Saturday morning for

Heavy freezing spray warning from 7 PM Friday to 7 am EST
Saturday for lmz844>849.

Small Craft Advisory until 1 PM EST Friday for lmz844>849.



short term...wdm
long term...Laurens

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