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Area forecast discussion 
National Weather Service Grand Rapids Michigan
323 PM EDT Thursday Jul 31 2014

Latest update...
synopsis/short term/long term/Hydro/marine

issued at 258 PM EDT Thursday Jul 31 2014

The upper low that has been centered over Ontario the past couple
of days will shift east. This will allow for a moderating trend to
the temperatures for the end of the week here in Michigan. A few mainly
afternoon thunderstorms could develop Friday and Saturday...otherwise
the weather will be mainly dry. The more seasonable temperatures
will persist into early next week.


Short term...(this evening through Saturday night)
issued at 258 PM EDT Thursday Jul 31 2014

The main challenge in the short term deals with the potential for
showers and thunderstorms each day. The storms in Wisconsin are
expected to dissipate as they try to Cross Lake Michigan. Surface
based parcels are stable with should cause the convection to
weaken. Satellite loops show the cumulus organizing from near Big
Rapids to Lansing and down to Battle Creek. We could see a couple
of showers develop in this region over the next hour or two. Given
the greater than 1000 j/kg...a thunderstorm cannot be ruled out
either. The most likely region for this to happen would be east of
a Big Rapids to Kalamazoo line.

The combination of low level warm air advection and middle level cool
air advection support a higher potential for thunderstorms Friday
afternoon. Better than 1000 j/kg surface based cape develops. Deep
layer shear will be weak. Thus any convection that develops should
be pulse in nature. Will keep the thunder risk going.

Instability develops again on Saturday. Winds look rather good surface based heating expected. The lake breeze
could be focusing mechanism for storms Saturday afternoon. Will
maintain the low pop.

Long term...(sunday through thursday)
issued at 258 PM EDT Thursday Jul 31 2014

Forecast concerns continue to center around the middle of next week.
A weak cold front will slip south across Lake Superior Monday. A
weak wave of low pressure will may generate a shower or storm middle
day Monday. The main issue with the front is that it is forecasted to
stall over the middle of the County Warning Area Monday afternoon due to a deeper
developing low over the northern plains pushing warmer air northward
on the west end of the front. Several short waves are forecasted to move
along the boundary in general northwest flow aloft and each wave will bring
a chance of precipitation. As the main low moves east Wed-Thu...heavier rain
is possible across Wisconsin and central lower Michigan. Both the GFS and
European model (ecmwf) have been showing this signal for a few runs now. Low level jet ramps up
across Wisconsin late Wednesday ahead of the low and as a
result...shear values increase substantially. Main opportunity for
severe weather looks to be in the Wednesday/Thursday time frame.


Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 137 PM EDT Thursday Jul 31 2014

VFR weather expected this afternoon. Eastern taf sites will see more cloud
coverage this afternoon. A shower or brief thunderstorms and rain is also possible
and covered with a vcsh. Fog may be an issue at kmkg Friday
morning due to proximity near the lake where colder lake temperatures
will cause surface temperatures at kmkg to come closer to dewpoint.


issued at 258 PM EDT Thursday Jul 31 2014

The combination of warming surface temperatures and the arrival of
warmer water should support a decreasing trend to the fog this
afternoon. Muskegon glerl observation showed a rise in the surface
temperature of 3 degrees from roughly 17z to 18z. Cams show the
fog persisting though. Will hang onto the headline for now.

Much less in the way of fog is expected for Friday as the warm
water advection alters the fog setup for the nearshore waters.

Weak pressure gradient will keep the winds under 20 knots...and
thus wave will remain low through the weekend.


issued at 258 PM EDT Thursday Jul 31 2014

Basin average quantitative precipitation forecast stays minimal through the end of the week. Thus
not significant river rises expected. Isolated storms could
locally produce up to a half inch of rain.


GRR watches/warnings/advisories...
Lm...dense fog advisory until 9 PM EDT this evening for lmz846>848.



short term...mjs
long term...93

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