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Area forecast discussion 
National Weather Service Grand Rapids Michigan
1141 PM EDT Tuesday Mar 31 2015

Latest update...

issued at 337 PM EDT Tuesday Mar 31 2015

Mainly dry conditions are expected tonight through Wednesday evening
as weak high pressure drifts through the area. An approaching cold
front will bring chances for showers and even a few thunderstorms to
the area late Wednesday night into Thursday. There will be periods
of moderate rain as showers and a few thunderstorms move through the
region. Cooler air will filter back into the region for late in the
week and into next weekend after mild weather Wednesday and Thursday.


Short term...(this evening through Thursday night)
issued at 337 PM EDT Tuesday Mar 31 2015

Main item of note in the short term is the frontal passage on
Thursday and the chances for showers and storms associated with
stretching from Wednesday night into Thursday evening. Showers and
embedded thunderstorms will press into the area from the west after
midnight on a surge of 850mb moisture transport. A strong low level jet
located upstream Wednesday evening will Bend into the area overnight
a lose a bit of punch/speed. Instability is not all that impressive
with mu cape values on the order or 500 j/kg. Enough instability
though to keep storms in the forecast...nothing severe.

On Thursday the showers and storms will likely undergo a diurnal
fade in the morning...trying to reintensify during the afternoon.
Showers and a few storms will become prevalent once again Thursday
afternoon...especially across Southern Lower Michigan. Feel severe
threat is minimal once again given weak instability. Rainfall
amounts should be on the order of 0.25 to 0.75 through the course of
the nothing too heavy.

Otherwise...a few flurries will be possible later this evening
across central lower Michigan associated with a weak shortwave
moving through the northern lakes.

Long term...(friday through tuesday)
issued at 337 PM EDT Tuesday Mar 31 2015

The long term portion of the forecast will feature a return to cooler
conditions in the beginning...with a trend toward unsettled
conditions from late in the weekend through the first portion of
next week.

We have added the threat for precipitation back into the forecast for the Friday and
Friday night time frame. There is good agreement amongst the models
that the upper wave that has been prognosticated to lift NE from The Four
Corners region...will bring the surface wave along the front close
enough to the area to bring precipitation chances to the area. Enough warm
enough air will remain in place early on Friday to keep precipitation rain. We
do expect a change over to some snow by Friday evening as cold air is
drawn south from Canada behind the wave.

There is a small chance of some rain or snow showers later on Sat after
a brief break late Friday night and Sat morning. This comes with a cold
front that will brush the area. The better chance of precipitation will come
back on sun as the front returns north and moisture returns.

There is quite a bit of uncertainty with the details from Monday
through Tuesday for the area. The front that returns north on sun will
become stalled out as it becomes parallel with a zonal upper flow
over the region. This will be the focus for occasional waves of precipitation
along we have chances of precipitation in for Monday and Tuesday. Some of the
precipitation initially could end up being a wintry mix at times with a surface
high to our north funneling in cooler and drier air.

Precipitation will eventually become all rain with warmer air coming in late
in the period and beyond as a western trough digs and the flow becomes
more southwesterly over the area.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1136 PM EDT Tuesday Mar 31 2015

Fog and stratus has been holding offshore and latest trends
suggest that it will only make a close approach to kmkg. New
forecast will reflect keeping the IFR west of kmkg.

High pressure will be largely in control of the weather for
Wednesday. This will likely result in lighter winds and VFR weather.


issued at 337 PM EDT Tuesday Mar 31 2015

Will hold off on a Small Craft Advisory at this point...but it looks
like one may be needed Wednesday night. It is into the 3rd
period...and there is some question as to how much wind will mix
down in a warm air advection setup. Thinking 3 to 5 foot waves at
this point...with south winds to 30 knots. Until that time...fairly
quiet conditions given light winds.

Expecting marine fog to continue to mix out as we head through the
remainder of the evening.


issued at 1120 am EDT Tuesday Mar 31 2015

Rivers continue to remain well below advisory levels with only small
and momentary responses noted from recent precipitation. Northern
sections of the forecast area will see slower responses due to
snow melt with last nights snowfall.

We will see a rather active pattern set up through the next 7
days. Much of this comes in two Thursday then the
second very late in the weekend and into the next work week. General
amounts on total precipitation through the period are around one
inch or so. This is fairly evenly divided between the two waves
which should be favorable for response times. No flooding is
expected at this time. However...the heavier rain that is
anticipated to our south through the Ohio Valley should be watched
in the event that any adjustments are needed in precipitation


GRR watches/warnings/advisories...


short term...Duke
long term...njj

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