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Area forecast discussion 
National Weather Service Grand Rapids Michigan
816 PM EDT Tuesday Jul 29 2014

Latest update...

issued at 330 PM EDT Tuesday Jul 29 2014

Unseasonably cool weather will linger a few more days but will
rebound to near normal for the end of the week and over the weekend.
Widely scattered showers and thunderstorms are expected each day
this week... particularly in the afternoon and evening and inland
from Lake Michigan.


Short term...(this evening through Thursday night)
issued at 330 PM EDT Tuesday Jul 29 2014

Scattered diurnal convection has developed east of Highway 131
underneath upper trough/cold pool aloft and will continue through
sunset with an overall eastward drift before dissipating.

While the Lakeshore counties have been spared of any diurnal
activity due to the stable onshore flow... this area is still at
risk for some showers after 7-8 PM this evening as the convection
currently developing in northern Wisconsin slides southeast across
Lake Michigan in a decaying Mode.

The probability/coverage of showers and thunderstorms on Wednesday looks
less than today as models continue to show best surface convergence
along and south of I-94. Will have chance probability of precipitation south and east of
GRR... decreasing west and north of GRR.

While the coverage/intensity of convection will certainly be less
late at night into middle morning over the next 72 hours... feel some low
probability of precipitation may still be warranted outside of pk heating time. Models/water
vapor imagery show several weak shortwaves/vorticity maxes rotating
around the Hudson Bay vortex. Any one of these features could still
touch off a few showers at any time as they slide southeast through
the Great Lakes region... even without the diurnal component.

Long term...(friday through tuesday)
issued at 330 PM EDT Tuesday Jul 29 2014

Overall the same general weather pattern will persist through the long
range forecast period featuring a persistent upper level trough over
the Great Lakes region in response to the high amplitude ridge out
west. The upper trough will be most amplified over our region Friday
through the weekend. However temperatures should average close to normal in
spite of that.

Instability due to daytime heating and with cold air aloft under the
upper trough may lead to a few diurnally driven showers and perhaps
a few isolated storms during the afternoon and early evening hours.

There will still be some influence from the upper trough into early
next week. However the upper trough axis and pool of colder air
aloft should shift NE to Quebec. Temperatures will continue to average
quite close to normal early next week.


Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 816 PM EDT Tuesday Jul 29 2014

The bottom line to the forecast is VFR through Wednesday. Winds
will mostly be less than 10 knots too.

The convection associated with the shortwave is currently moving
out of the Lansing and Jackson area and the convection over
eastern Wisconsin...while making it to Middle-Lake does not appear as
through it will get much farther east than it already has. All of
that should be south of our taf sites by 02z for sure. I put VFR
ceilings in the tafs since there as there is a shortwave north of Lake
Superior that should bring those VFR ceilings in as this moves into
lower Michigan by 06z. So while currently there are no clouds with
ceiling below 12000 feet over northern lower Michigan to actually
move in I do believe they will by 06z or so. The shortwave should
be through the area by middle morning Wednesday. That would deal to
clearing skies by late morning. There is not nearly as much
instability Wednesday afternoon as there was today so I do not
think we will be seeing convection Wednesday afternoon like we did


issued at 330 PM EDT Tuesday Jul 29 2014

Two north flow upwelling/overturning events in the last week has
resulted in very cold water temperatures in the 40s developing along the
coast per buoy readings. This is actually resulting in some patchy
dense fog as shown on the Muskegon web cam despite a cool and
relatively dry air mass.

Surface dew points however are in the middle 50s which over 40 degree water
with winds 10 kts or less is promoting some fog. Have added this
threat to the nearshore forecast over the next few days. Periods of
stronger winds in the afternoon and early evening may mix the fog
out at times. Confidence in coverage and persistence of the fog is
low... so will not issue a marine dense fog advisory.

No significant winds/waves expected over the next few days which
would necessitate small craft advisories.


issued at 330 PM EDT Tuesday Jul 29 2014

No Hydro concerns at this time given widely scattered nature of
the convection over the next few days. Some brief locally heavy
downpours with small hail may occur in any of the healthier cells.


GRR watches/warnings/advisories...


short term...Meade
long term...Laurens

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