Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 210723

Area Forecast Discussion
National Weather Service Grand Rapids MI
324 AM EDT Wed Jun 21 2017

Synopsis/Short Term/Long Term/Marine

Issued at 324 AM EDT Wed Jun 21 2017

We`ll have several opportunities for showers and thunderstorms
during the next few days. Thunderstorms are expected late tonight
and again Thursday night ahead of a cold front. Thursday will be the
warmest day with highs in the mid 80s, and then a slow cooling trend
will result in highs in the lower 70s by Sunday.


.SHORT TERM...(Today through Friday)
Issued at 324 AM EDT Wed Jun 21 2017

Forecast concerns deal with convective trends through the period. A
sunny day is expected with highs in the mid to upper 70s. A
northward moving warm front will be the focus for mcs development
tonight near the MN/WI border as a strong low level jet intersects
the front. Thickness patterns would take any mcs southeast across
Wisconsin and eventually Lower Michigan. Like the idea of the 3km
NAM as it is a bit farther south with the mcs than the ecmwf/gfs.
Looking at a arrival around 08z. Moderately strong shear around
50kts suggests the potential for a few strong storms.

Much of Thursday may actually be dry. By Thursday evening, another
round of strong/severe storms are possible as a cold front moves
south through the state. Once again, strong shear is progd and a few
of the expected storms could be strong/severe. The cold front
doesn`t actually clear the cwa until late Thursday night, so frontal
timing may act to decrease the severity of the storms.

Skies will clear Friday as the front moves southeast and pcpn moves
out of the cwa.

.LONG TERM...(Friday night through Tuesday)
Issued at 324 AM EDT Wed Jun 21 2017

After a quiet start to the long term, we are looking at a cool and
somewhat unsettled period similar to the last few days with small
periodic chances for rain as weak waves of low pressure pass through.

The only period in the long term with higher confidence that it will
be dry is Fri night. We will remain under the influence of ridging
sandwiched between the departing cold front to our south, and the
next trough to our northwest. Saturday has the potential to be dry
also, although this is not totally certain. This is due to the
differences in the models as to how far south the next wave dives.
If it dives a bit further south like the GFS, there will be a chance
of afternoon showers and perhaps a storm.

We do have fairly good confidence that the period from Sunday
through Tuesday we will see small chances for showers along with
cooler temperatures. This is due to the long wave trough
establishing itself over Ern Canada and the NE quadrant of the
CONUS. We will see short wave troughs dive in from the NW, similar
to the pattern of the last few days. There will be a diurnal boost
to pcpn with any short wave that moves through. The better rain
chances will be determined by the exact track of each wave.

Temperatures will average a bit cool for the period with the NW flow
in place. This will result in highs mainly in the 70s and lows in
the 50s.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 135 AM EDT Wed Jun 21 2017

Fog is our initial concern for the first few hours of the
forecast. There is a good chance for fog tonight with the rain
that fell this afternoon/evening and with winds becoming light. We
have gone with IFR conditions everywhere. The I-94 terminals are
expected to be worst as the rain lingered longer and there was
less drying before sunset.

Fog will dissipate quickly with the early sunrise for the
solstice. We will then see some diurnal cumulus develop toward
afternoon away from Lake Michigan. This should all be VFR so
limited impacts expected. Winds will likely stay under 10 knots
with a light gradient remaining in place.

Some mid clouds will stream in late in the period, ahead of
showers/storms that are expected to develop over WI. These storms
will likely hold off moving in until after this forecast period.


Issued at 324 AM EDT Wed Jun 21 2017

Wave will generally be below 2 feet today. Thunderstorms will pose a
threat to small craft tonight.


Issued at 203 PM EDT Tue Jun 20 2017

Rivers levels are around to a little above normal for this time of
year. The Flat River near Smyrna may reach bankfull over night, but
is the only site expected to do so. Scattered showers and a few
thunderstorms will be possible today with less than a tenth inch
of rain expected on average. Additional heavier rains will be
possible Wednesday night through Friday and should lead to
additional rises on area river systems.




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