000 FXUS63 KGRR 162343 AFDGRR  Area Forecast Discussion National Weather
Service Grand Rapids MI 743 PM EDT Tue Aug 16 2022  LATEST UPDATE...
Aviation  .DISCUSSION...(This evening through next Tuesday) Issued at 244
PM EDT Tue Aug 16 2022  ...Risk for a few showers/storms this evening... 
Surface and 100 mb mixed layer instability has developed this
afternoon...mainly east of of a line from KMOP to KJXN. A few showers and
thunderstorms have developed in this region. They were drifting southwest
with time. The forecast instability for the remainder of the afternoon into
the evening suggests that the instability will struggle to build west.
Aloft a weak shortwave was noted over eastern Lower MI. That feature is
predicted to remain there through sunset.  We will hold onto a low risk for
showers and/or a storm mainly for eastern zones into this evening. Along
the lake breeze near Little and Big Sable Points a second area of
instability has developed. PWAT values are lower over the western parts of
the CWA...so moisture may be a limiting factor for storm development there.
However...there may be enough ingredients there to lead to a shower or
storm along the lake breeze.  ...Increasing chances for Showers/Storms over
the weekend...  A series of mid level waves drop in from the northwest over
the weekend. As a result we see steady height falls during this time. At
the same time...PWAT values are shown to climb up to around 1.5 inches by
Sunday. Down low...a warm front is indicated near Kalamazoo and Jackson
during the day on Sunday. Also on Sunday...models are showing a 250 mb
speed max just south of the MI border which is shown to track east during
the day. Upper level diffluence is noted here in MI. So given all the above
ingredients...we will feature the highest pops of the period on Sunday.
Deep layer shear is not supportive of severe weather then...so impacts if
any would be hydro related. 

NWS GRR Office Area Forecast Discussion