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Area forecast discussion 
National Weather Service Grand Rapids Michigan
658 am EDT Wednesday Sep 17 2014

Latest update...
aviation

Synopsis...
issued at 217 am EDT Wednesday Sep 17 2014

A weakening area of high pressure over the Ohio Valley will keep
the weather here in southern Michigan dry through today. A weak
cold front will slip southward through the region tonight. A high
pressure system will strengthen as it drops southward from Ontario
on Thursday. This fair weather system will keep conditions dry and
cool into Friday. Some frost will be possible for early Friday morning.

&&

Short term...(today through friday)
issued at 217 am EDT Wednesday Sep 17 2014

The main challenges in the short term deal with the precipitation
potential tonight with the cold frontal passage and also the frost
risk Thursday night.

Overall the risk for precipitation looks low tonight. The moisture
remains below the dgz and very little in the way of lift is seen.
We will see a wind shift along the the arrival of some clouds
mainly below 5000 feet. Those clouds will linger into Thursday. If any
precipitation does fall out of these clouds...it will be drizzle.

A stronger high pressure system moves in from the north Thursday into
Thursday night. After a cool day with some clouds the skies will clear
out supporting better radiational cooling especially as the
pressure gradient weakens. Temperatures under this high in Manitoba are
in the 20s right now. Guidance for Thursday night here in Michigan are
generally in the low 40s. It appears that the models are too warm
with the temperatures Thursday night. This forecast reflects much lower
values and the possibility of frost has been expanded. We may need
headlines for parts of southwest lower Michigan Thursday night for frost.

After a cool start Friday...temperatures will start to rebound as
a south to southwest flow develops.

Long term...(friday night through tuesday)
issued at 217 am EDT Wednesday Sep 17 2014

Unseasonably warm weather is anticipated Friday night and Saturday
in strong SW flow warm air advection in advance of approaching low pressure and the
cold front. Scattered showers and thunderstorms are anticipated in
the warm air advection pattern Friday night and forcing from the approaching cold
front will bring potential for some thunderstorms Saturday through
Saturday night. Temperatures will average around ten degrees above normal
for this time of year Friday night through Saturday.

A significantly cooler airmass will move in behind the front
beginning Sunday and especially for Monday and Tuesday when temperatures
will likely average around 5 to 10 degrees below normal. Maximum temperatures
by next Monday/Tuesday will struggle to reach the upper 50s to lower 60s
with min temperatures generally ranging from the middle to upper 30s up
north to the middle 40s south.

We will maintain a dry forecast for now for early next week. However if
more amplified medium range guidance solutions verify that feature
cyclonic flow... upper level troughing and 800 mb temperatures down around 0 c
then there would be potential for lake effect showers next Mon/Tue.

&&

Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 653 am EDT Wednesday Sep 17 2014

Patchy fog located over Southern Lower Michigan will likely impact
kazo to start the forecast period with IFR and lower conditions. This
fog appears shallow so I am not expecting it to last past 13z. I
did not include the fog for other nearby taf sites like kbtl and
kjxn as the risk appeared lower...but will need to monitor trends
closely.

VFR weather prevails through the day however on the backside of a
late night cold frontal passage we may see MVFR ceilings arriving.

&&

Marine...
issued at 217 am EDT Wednesday Sep 17 2014

Winds and waves could become hazardous to small craft late tonight
mainly for the little and Big Sable Point region. Increasing
northeast flow behind a southward sinking front may lead to these
conditions. Not confident enough to go with a headline yet as the
setup is marginal at this point.



&&

Hydrology...
issued at 217 am EDT Wednesday Sep 17 2014

No major changes to the river levels are expected through the end
of the week. We will need to monitor the weekend system closely
with the possibility of some heavier rain in places.

&&

GRR watches/warnings/advisories...
Michigan...none.
Lm...none.
&&

$$

Synopsis...mjs
short term...mjs
long term...Laurens
aviation...mjs
hydrology...mjs
marine...mjs

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