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Area forecast discussion 
National Weather Service Grand Rapids Michigan
610 am EST Sat Dec 27 2014

Latest update...

issued at 328 am EST Sat Dec 27 2014

We will see the last of the mild weather today with intermittent
light rain and drizzle. Colder air moves in tonight with a second
wave of Arctic air Monday night through Wednesday. Highs only in the 20s
are expected during the middle portion of the week and may
struggle to reach 20 degrees on Wednesday...especially north of Grand
Rapids. Snow accumulations also appear possible Monday night into
Wednesday. Temperatures will moderate slightly toward the end of
the work week before another surge of Arctic air next weekend.


Short term...(today through monday)
issued at 328 am EST Sat Dec 27 2014

Temperatures had risen into the middle 40s mainly along and south of
I-96 as of this writing. Temperatures and dewpoints will continue to
creep up this morning. 06z hrrr continues to indicate periods of
light rain and drizzle today...the first after 10z or so.

The weak surface low is forecast to deepen to around 1008 mb over
northern lower Michigan by 18z. The cold front then moves through
followed by a veering of the winds during the afternoon. Surface
temperatures are expected to remain above freezing at 00z this
evening...and moisture quickly bails after 00z. The onshore flow
is also slightly divergent. Forecast thinking has not
changed...little if any snow tonight.

Quiet weather expected on Sunday. A very strong 1057 mb high
develops over western Canada and an extension of this high
pressure system turns low level flow northeasterly by Monday.
Thinking partly sunny for now with highs in the low to middle 30s.

Long term...(monday night through friday)
issued at 328 am EST Sat Dec 27 2014

Models are in decent agreement in showing a deepening upper low over
Hudson Bay as we head through the extended period. This will result
in a colder than normal period through the long term period.

The Arctic air will arrive in waves. Monday night through Wednesday
will feature cold air advection. The low level thermal trough
pushes through on Wednesday. Highs on Wednesday may struggle to
reach 20 degrees...especially north of Grand Rapids. Wind will
accompany this Arctic airmass and sub zero wind chills will occur at
times. Also models have been trending toward more moisture in the
dgz Monday night into Wednesday. Thus we may end up with some
accumulations. I did trend probability of precipitation upward based on the trends.

Temperatures are likely to moderate slightly Thursday into Friday as
warm air advection develops on the backside of the departing
high. They are expected to still average out below normal.

Another surge of Arctic air will likely push in over next weekend.
This is when the southern rockies low kicks out into the plains and
tracks to the central Appalachians. As this wave tracks
impressive surge of Arctic air sinks south through the Great Lakes
region. There is a risk for snow associated with the arrival of
this next reinforcing shot of Arctic air. Overall models have come
into better agreement of the timing and duration of this next Arctic


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 607 am EST Sat Dec 27 2014

The main challenge in the aviation forecast deals with the
potential for impact ceilings and visibilities.

While delayed...the IFR is developing over in Indiana and
Illinois...and has now moved into the kbeh region. This low level
moisture will be tracking northward into southwest lower Michigan this
morning. The low conditions will then persist through much of the
afternoon. Improving conditions are forecasted for later today as
the wind veers with time allowing a colder/drier airmass to arrive
from the west.


issued at 328 am EST Sat Dec 27 2014

A Small Craft Advisory has been issued for 11 am today through 11
am Sunday. As the surface low approaches...southerly winds will
increase to 15 to 25 knots today. Winds will veer west to 30 knots
late this afternoon and evening. Waves will build to 4 to 8 feet
north of Holland and 3 to 5 feet south of Holland. West winds will
veer northwesterly tonight.


issued at 328 am EST Sat Dec 27 2014

Around a tenth of an inch or less of rainfall is expected
today...with slightly higher amounts possible toward Ludington.
This light rainfall is not expected to have a significant impact
on rivers. All river flood advisories have been canceled.


GRR watches/warnings/advisories...
Lm...Small Craft Advisory from 11 am this morning to 11 am EST Sunday
for lmz844>849.



short term...ebw
long term...mjs

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