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Area forecast discussion 
National Weather Service Grand Rapids Michigan
648 am EST Friday Dec 26 2014

Latest update...

issued at 328 am EST Friday Dec 26 2014

A pleasant Friday is in store with some sun in the morning followed
by increasing clouds later in the day. A weak area of low pressure
will slide northeast across the Great Lakes region on Saturday. This
will result in light rain on Saturday with highs climbing into the
middle to upper 40s. Much colder air arrives Saturday night with a
reinforcing shot of Arctic air on Tuesday. Highs will only be in
the 20s for most of next week. Fairly dry weather is expected
Sunday through the middle part of next week.


Short term...(today through sunday)
issued at 328 am EST Friday Dec 26 2014

A very mild beginning to the weekend is expected along with some
light rain showers on Saturday before colder air arrives Saturday night.

The chance for light rain will increase early Saturday morning and
persist through the day. Flurries could begin to mix in with
drizzle Saturday evening before the deeper moisture moves off to
the northeast overnight. A weak low pressure system will eject
northeast out of the plains from the upper level western US
trough. The surface low is expected to track just off to our north
and west across Lake Michigan and northern lower Michigan. Warmer air and
moisture will advect in via the warm conveyor belt ahead of the
surface trough. Only weak isentropic ascent is expected over
southwest lower with light rain and drizzle at times on Saturday.

Temperatures drop quickly Saturday night behind the cold front and
there is a slight chance for some lake effect snow.
accumulations are expected due to very shallow
unsaturated dgz...and anticyclonic flow.

Otherwise...Friday will be quite mild with some sun possible
mainly in the morning. Colder on Sunday behind the front with
highs in the lower to middle 30s.

Long term...(sunday night through thursday)
issued at 328 am EST Friday Dec 26 2014

Overall the period is looking colder than normal with less than
normal precipitation.

Cold air advection will be underway Sunday night and Monday as the
cold front pushes into New England. The low level flow veers from
the north to northeast as we go through Sunday night. The northeast
flow persists into Tuesday. Thus...while it will be cold enough
for lake effect...the flow suggests limited potential for
accumulations. I will keep probability of precipitation low for now.

Later Tuesday a reinforcing shot of Arctic air arrives from the
north. Onshore flow does develop. However the flow is mostly
divergent behind the front. Also...with the low level flow backing
to the west...upstream seeding from Superior will not exist. Plus
the flow will be relatively fast due to the tight pressure
gradient. Thus continued limited potential for measurable
precipitation will exist into the middle part of next week.

Plenty of baroclinicity appears to exist across the central U.S. As
a stronger middle level wave tracks out of The Rockies for the end of
next week. This could wind up a stronger storm for the Great Lakes
region or the Ohio Valley.


Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 643 am EST Friday Dec 26 2014

MVFR clouds near kmkg will persist for a few hours this morning
before southerly winds lift them northward. VFR weather should
then prevail for much of southwest lower Michigan through the day.
Overnight we will see moisture increasing from the southwest. This
will act to cause the ceilings to lower back down to MVFR. Rain
will arrive later tonight...and enhance the risk for IFR
conditions which are now forecasted.


issued at 328 am EST Friday Dec 26 2014

Winds and waves on Lake Michigan will remain hazardous to small
craft through Friday afternoon. South winds 15 to 25 knots tonight
will diminish to southwest 10 to 20 knots Friday. Waves of 3 to 6
feet are expected.


issued at 328 am EST Friday Dec 26 2014

River flood advisories remain on the Sycamore Creek at Holt and
the Maple River at Maple Rapids. The Sycamore Creek at Holt has
slightly exceeded its banks but is currently cresting and should
begin a slow fall on Friday. The Maple River will continue to rise
slowly. No significant precipitation is expected to have an impact
on area rivers this weekend.


GRR watches/warnings/advisories...
Lm...Small Craft Advisory until 10 PM EST this evening for lmz844>849.



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

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