Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 260730

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 AM EDT THU MAY 26 2016

Synopsis/Short Term/Long Term/Marine

Issued at 330 AM EDT Thu May 26 2016

Warm and humid weather with periodic showers and thunderstorms will
continue through at least Sunday. A cold front late in the holiday
weekend may bring dry and less humid weather for Memorial Day.


.SHORT TERM...(Today through Saturday)
Issued at 330 AM EDT Thu May 26 2016

Shortwave responsible for overnight rain will exit early this
morning leaving a window of predominately dry weather this morning.
However low chc pops are warranted for this afternoon as instability
builds and fuels scattered diurnal convection.

Sfc Dew pts near 65 will lead to SB Capes near 2500 J/KG inland from
Lk MI. Current water vapor imagery shows another shortwave/several
vorticity maxima upstream across MN/IA/MO. The arrival of this
shortwave should be a trigger for afternoon convection, in
additional to wk sfc convergence along the lk breeze front.
Coverage is expected to be scattered.

The next feature of interest is a shortwave which rounds the base of
the trough in the srn plains later friday, and heads slowly
northeast, reaching Wisconsin by 12Z Sunday. Models indicate a 30-40
kt low level jet developing ahead of this wave, which becomes aimed
at Sw Lwr MI for a prolonged period from Friday afternoon through
Saturday night. PWATs of 1.5 to 1.75 are progged during this time,
with deep unidirectional flow and continued MU Capes over 1000
J/KGpossibly leading to a heavy rain threat. The severe weather
threat remains quite low however since deep layer shear values
generally remain under 30 kts.

.LONG TERM...(Saturday night through Wednesday)
Issued at 330 AM EDT Thu May 26 2016

As we work through the holiday weekend the dominate ridge that has
been parked over the eastern seaboard should gradually weaken.  This
will allow an upper trough and cold front to push across the Great
Lakes late Sunday or Sunday night.  This will not only bring more
risks of showers and storms, but it will also bring less humid air
into the region to end the holiday weekend.  Memorial Day and into
the mid portion of next week should be very pleasant, not as warm
and less humid.

The models rebuild the ridge in the east toward mid week, but
surface high pressure does not slide by until about Tuesday
afternoon, so the warmer southerly breezes won`t move in until
Wednesday at the earliest.

I tweaked the Sunday night min down a bit as we should be in the
cooler air mass by then.  Minimal rain chances finally move in by
Sunday night and linger until Tuesday night or Wednesday.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 152 AM EDT Thu May 26 2016

An area of thunderstorms was moving across southern MI early this
morning. This will pass through with a lull in the thunderstorm activity
through much of Thursday. We could see more storms arrive toward
the end of this forecast period (06Z Friday).

Where it has rained tonight we will likely see IFR fog develop by
daybreak Thursday. This is not expected to last long, but a 2-4
hour period of IFR could be seen at any site. Otherwise VFR
weather will prevail with a light southerly wind.


Issued at 330 AM EDT Thu May 26 2016

Dew points over 60 have arrive which support a fog threat over lk
mi. However the flow is 10 to 20 kts out of the south which may help
keep things mixed just enough to limit the fog threat. Will maintain
areas of fog in the nearshore fcst for the next 48 hours, but
confidence too low for any fog advisories due to the wind speeds.


Issued at 314 PM EDT Wed May 25 2016

The rivers are certainly in a position to handle a half inch to an
inch of rain through the weekend with little impact other than
mainly within bank rises. Locally heavier rainfall could potentially
cause quicker rises on smaller creeks and streams, but the basin
average QPF should not be high enough to warrant flooding on main
stem rivers or even tributaries. Nevertheless, local trends will be
monitored as storms occasionally develop across the region for the
next several days.


.GRR Watches/Warnings/Advisories...


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