Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 260552

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


Issued at 314 PM EDT Wed May 25 2016

Weak low pressure moving across Lower Michigan this evening will
cause scattered storms to develop, some of which may contain gusty
winds. A warm and humid air mass will remain in place through the
weekend. High temperatures will continue to be 5 to 10 degrees above
normal through the middle of next week. Isolated to scattered
showers and thunderstorms are possible through the weekend.


.SHORT TERM...(This evening through Friday night)
Issued at 314 PM EDT Wed May 25 2016

Forecast concerns deal with convective trends through the period.

Latest radar imagery shows developing showers and storms across the
northern cwa in the vicinity of a washed out frontal boundary. Also
a few more were noted near the lake breeze. Mesoanalysis reveals
sbcape around 1000 j/kg across the western cwa and we`ll likely see
continued develop through the afternoon and early evening until
instability diminishes. However, by then, the approach of a weak
short wave may provide a boost to the convection that will carry
overnight. Thus, we`ve got likely pops across much of the cwa.
Precipitable water values increase to around 1.5 inches tonight
suggesting the potential for locally heavy rain in one of the
stronger storms.

From tonight through Friday night there isn`t much change to the
synoptic features. Southwest flow aloft will provide an avenue for
weak short waves to travel across the Great Lakes and provide a
catalyst for a few storms to develop. Overall, I think the threat
for precipitation has decreased a bit from earlier model runs and we
went a bit below guidance mainly due to the lack of a focusing
mechanism. The warm and humid air mass will continue through Friday
night and so instability will be sufficient for thunderstorm
development. At this point severe storms aren`t anticipated due to
shear values remain aob 25 knots.

.LONG TERM...(Saturday through Wednesday)
Issued at 314 PM EDT Wed May 25 2016

The warm and rather humid pattern will continue into the holiday
weekend with deep sw flow continuing. Weak to potentially moderate
instability will develop Saturday and Sunday afternoon and any upper
level disturbance moving in from the southwest may trigger
development of a few showers and thunderstorms Saturday through
Sunday.  However dry conditions will prevail the vast majority of
the time this weekend.

A somewhat drier and less humid airmass will move in Memorial Day
and through the early to middle portion of next week. Some mid to
upper level ridging should also tend to build in by Tuesday and

Although the airmass next week will be less humid it should remain
quite warm with temperatures expected to average around 5 to 10
degrees above normal through the long range forecast period.


.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 314 PM EDT Wed May 25 2016

The pressure gradient remains weak so winds and waves should be
fairly tame. As low level moisture increases, fog may become an
issue due to the relatively cold lake. It`s possible that the fog
may become dense at which point a marine dense fog advisory would
be needed.


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...


LONG TERM...Laurens
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