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Area forecast discussion 
National Weather Service Grand Rapids Michigan
636 am EDT Tuesday Jul 28 2015

Latest update...

issued at 330 am EDT Tuesday Jul 28 2015

Another sunny and hot day with temperatures near 90 can be
expected before a cold front brings a period of clouds with
scattered showers and thunderstorms late tonight and Wednesday.
Slightly cooler and less humid weather will follow behind the
front on Thursday along with plenty of sunshine.


Short term...(today through thursday)
issued at 330 am EDT Tuesday Jul 28 2015

The main focus is on precipitation potential with the incoming front
late tonight and Wednesday as well as the chance for a few stronger
storms. It has been over a week now with any substantial rainfall so
we could use some rain.

Unfortunately this system does not appear to have much to offer in
terms of areal coverage of heavier rainfall amounts. The showers
will be scattered at best and most locations will see less than one
quarter inch of rain. That said the precipitable water values along
and ahead of the front will be near two inches which does support
the possibility of some localized heavy downpours.

Upper support will be seriously lacking with this system as the middle
level shortwave passes well to our northwest... tracking from the
northern plains northeast toward Hudson Bay. This results in deep layer
shear values of less than 20 kts...greatly limiting the potential
for any organized severe storms.

The thing to watch will be extent of destabilization Wednesday
before frontal passage as mu cape forecasts show near 2000 j/kg south and east of
GRR Wednesday afternoon. This could support a few isolated stronger
storms around jxn before developing low level westerly flow pushes
convection completely out of the area.

Expect high temperatures today very similar to yesterday with upper
ridge/subsidence still firmly in place and limited cloud cover. The
Lakeshore should be as warm or warmer than inland areas again with
southeast low level flow. A weak lake breeze is expected to develop
this afternoon which should cool the beaches a bit.

Long term...(thursday night through monday)
issued at 330 am EDT Tuesday Jul 28 2015

The trend for the long term over the past 24 hours is for a delay in
solid precipitation chances to Sat night and beyond.

The chance of rain for Friday is not zero...however it looks to be low
enough to leave out of the forecast for the time being. A weak front
does look to drop through the forecast area during the day on Friday as
upper troughing begins to take a better hold on the area. The issue
with precipitation with this front is that the upper energy stays north of
the area...and there is little moisture return with the low level
flow from the W/NW. The wrly flow will also limit precipitation chances being
downwind of the cooler waters of Lake Michigan.

Sat looks to be dry across the area now with the weak front coming
through on Friday and the next system not expected to arrive until Sat
night/sun. Temperatures do not look to be that much cooler on Sat behind
the front. H850 temperatures drop only a couple of degrees and remain in
the middle teens. This will continue to support highs in the 80s.

Sun and Monday do continue to look somewhat unsettled with occasional
chances for rain each of the days. There is a little better chance that we
will see waves close enough to give precipitation chances a boost. In
addition...there looks to be a better surge of moisture coming in
from the Gulf of Mexico. We could be looking at some potential for
stronger storms with better wind fields aloft helping shear
values...and some potential instability ahead of these waves. Plenty
of time to monitor the trends.


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 635 am EDT Tuesday Jul 28 2015

Patchy MVFR/IFR ground fog will lift by 13z otherwise VFR weather
expected today and tonight. Some patchy fog may develop again
late tonight after 06z although increasing high clouds at or above
12,000 feet may limit that potential.

Some lower ceilings around 4000 feet and a few showers may approach mkg
toward 12z Wednesday. A thunderstorm cannot be ruled out either but
the probabilty is too low to have in the taf at this time.


issued at 330 am EDT Tuesday Jul 28 2015

Increasing south winds ahead of the cold front late tonight/early
Wednesday will build waves... but probably only to 1 to 3 feet north
of Holland. The westerly flow and slight cold advection behind the
front late Wednesday into early Thursday could lead to a period of 2
to 4 footers.


issued at 149 PM EDT Monday Jul 27 2015

River levels are falling and are well below bankfull. With under
an inch of precipitation expected through the week... these
conditions should continue.


GRR watches/warnings/advisories...


short term...Meade
long term...njj

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