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Area forecast discussion 
National Weather Service Grand Rapids Michigan
326 PM EDT Tuesday Apr 21 2015

Latest update...
synopsis/short term/marine

issued at 325 PM EDT Tuesday Apr 21 2015

It will be cold with some rain and snow showers through Thursday.
Below normal temperatures will continue into next week with only
scattered light precipitation expected.


Short term...(this evening through Thursday night)
issued at 325 PM EDT Tuesday Apr 21 2015

Primary forecast issues in the near term are precipitation type and
extent of frost and freezing temperatures in the central and
southern part of the forecast area where the growing season has

We will continue to see wind gusts around 40 miles per hour through early
evening and could touch 45 miles per hour at times across the south where
there will be some deeper mixing.

For tonight...scattered rain and snow showers continues as upper
low spins in place north of the lakes with lobes of vorticity
pivoting around it in cyclonic flow. As colder air advects in
tonight...there could be light snow accums across the High Ground of
the northern forecast zones from tonight through tomorrow night
otherwise no impacts expected.

We do expect frost and freezing temperatures both Wednesday night
and Thursday night across all of the forecast frost or
freeze headlines will likely be needed for where the growing
season has started.

Long term...(friday through tuesday)
issued at 223 PM EDT Tuesday Apr 21 2015

Clearly no warming trend is seen in this time frame. Curiously
through very little in the way of precipitation is expected until
Tuesday and that would only happen of the 00z run of the European model (ecmwf)
turns out to be correct.

The current closed upper low that will keep southwest lower
Michigan colder than normal most of this week gets lifted out late
this week as another strong Pacific storm heads into the Gulf of Alaska.
That strong Pacific storm kicks out the system currently there.
That system helps kick the upper low over the southwest Continental U.S. East
into the Central Plains over the weekend but the trailing edge of
the system currently over this area keeps that south of Michigan
so we should have a dry weekend.

Where it gets interesting is that system that is kicked out of the
Gulf of Alaska has a hard time crossing the western upper ridge
but finally it does make it through. The European model (ecmwf) has a much stronger
and deeper system in the Gulf of Alaska early next week. That
causes the kicked out system to deepen farther west...which in
turn brings a significant storm into the Great Lakes by Tuesday.
The GFS with a weaker system in the Gulf of Alaska does allows the
lead Pacific system to head to the East Coast before developing.
That would result an a dry period into the middle of next week.
Either way it stays colder than normal.


Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 223 PM EDT Tuesday Apr 21 2015

The cyclonic flow around the deep storm centered over southern
Canada...just north of the central Great Lakes will keep VFR ceilings
with occasional showers going through most of Wednesday. For the
most part expect VFR ceilings and visibility. However during the
early morning hours of Wednesday a shortwave moves through the
area and it should result in a period of showers at most of the
taf sites. Since by then it will be cold enough to snow at all taf
sites I brought a 2 to 3 hour period of snow at most of the taf
sites. It may become briefly IFR in snow around 8 am tomorrow
morning if this really does happen.


issued at 325 PM EDT Tuesday Apr 21 2015

Will keep the Small Craft Advisory unchanged. Winds and waves will
begin to diminish Wednesday afternoon and evening as high pressure
gradually builds in.


issued at 1248 PM EDT Tuesday Apr 21 2015

Hydro concerns over the next week are minimal. Scattered light
rain and snow will be possible at times this afternoon through
Wednesday with precipitation amounts less than a quarter inch. Mainly dry
weather is expected Thursday through the weekend...with just a
slight chance for some light rain across Southern Lower Michigan
late Friday night into Saturday.


GRR watches/warnings/advisories...
Lm...Small Craft Advisory until 6 PM EDT Wednesday for lmz844>849.



short term...ostuno
long term...wdm

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