Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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213
FXUS63 KGRR 271732
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
132 PM EDT FRI MAY 27 2016

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 327 AM EDT Fri May 27 2016

Memorial Day weekend will see occasional showers and a few
thunderstorms along with temperatures in the upper 70s to lower
80s most days.

&&

.UPDATE...
Issued at 1233 PM EDT Fri May 27 2016

An enhanced warm advection wing convergence zone has developed
from Wisconsin extending southeast across Lake Michigan into
northern Indiana. A modest low level jet nosing into the Chicago
area is advecting in higher dewpoint air at H850. This boundary
will be the main source of lift this afternoon.

Scattered showers and storms are expected on the northwest to
southeast oriented boundary this afternoon. Favorable instability
for thunder has developed rapidly today in the clearing ahead of
the advection wing cloud band. Deep layer shear is marginal with
upper ridging still in place over the region. Effective bulk shear
is currently a bit more favorable across the northern forecast
area at 30-35 kts. Storms this afternoon could produce gusty
winds, small hail, and brief heavy rain.

&&

.SHORT TERM...(Today through Sunday)
Issued at 327 AM EDT Fri May 27 2016

Weak sfc low tracks from Southern Plains to north of Lake Superior
the next few days with Michigan in moist southerly flow, but not a
strong focus for convection. Lifted indices are are progged to be
in the minus 2 to 5 range this afternoon and evening so we expect
diurnal enhancement for coverage of storms that will persist into
the evening then decrease overnight.

Similar pattern expected for Saturday as set up is the same. A
weak cold front coming through on Sunday afternoon could also
bring an enhanced coverage of showers and thunderstorms.

.LONG TERM...(Sunday night through Thursday)
Issued at 327 AM EDT Fri May 27 2016

Good agreement in the models showing a cold front coming through
Sunday evening.  With this agreement I increased pops for Sunday
evening across central lower as the best dynamics should remain to
the north.

Behind this front the area should be largely dry late Sunday night
through Tuesday as a drier and slightly cooler air mass moves in.
The upper ridge that was so dominate much of this past week over the
far eastern U.S. should become reestablished as we move into the
middle of next week. This will help bring gulf moisture back into
the Great Lakes.  The ECMWF races another cold front east that could
come through Wednesday evening.  But the GFS is much slower and
still has this front to our west through Thursday.  I like the look
of the slower GFS given the building ridge over the eastern
seaboard. We could start seeing more showers and storms as early as
Tuesday night, but it seems more likely to hold off until Thursday.

Expect rather uniform and pleasant temps through the long term with
daytime highs from the mid 70s to lower 80s...and nighttime lows
mainly in the 50s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 128 PM EDT Fri May 27 2016

The atmosphere has become unstable. Showers were developing at
this time. They should grow into thunderstorms over the next hr or
so. Thus Tafs sites mostly feature a thunderstorm for the next hr
or two...then VCTS for the remainder of the afternoon into the
evening hrs.

Low level winds will increase tonight. This may lead to some
turbulence. I did not go with LLWS...but it was a close call. This
increase in winds could also trigger thunderstorms...especially
Saturday morning.

&&

.MARINE...
Issued at 327 AM EDT Fri May 27 2016

Some areas of fog will be around this morning but tend to lift in
the afternoon as winds and showers increase. Winds and waves
should remain below small craft advisory conditions through the
weekend.


&&

.HYDROLOGY...
Issued at 108 PM EDT Fri May 27 2016

River levels across the area are near to just above their expected
values for this time of year. Precipitation of up to an inch is
possible over the next week. Convection through the weekend will
produce localized heavy rainfall. Rises will mainly be confined
to smaller creeks and streams and should not reach flood levels.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...None.
&&

$$

UPDATE...EBW
SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...JK
AVIATION...MJS
HYDROLOGY...63
MARINE...Ostuno



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