071
FXUS63 KGRR 172022
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
422 PM EDT Sat Aug 17 2019
LATEST UPDATE...
Marine
.SYNOPSIS...
Issued at 322 PM EDT Sat Aug 17 2019
- Multiple chances for thunderstorms exist through mid week. Strong
storms are possible.
- Dangerous swimming conditions are expected Sunday.
- Cooler temperatures prevailing into next weekend.
&&
.DISCUSSION...(This evening through next Saturday)
Issued at 322 PM EDT Sat Aug 17 2019
The main forecast concern is the potential for thunderstorms into
mid week, as zonal flow brings multiple weak waves over the area.
Ridging will then form in the west by Wednesday and move toward
Lower Michigan forcing the waves to the north of the region.
Therefore, the second half of the week into the weekend should be
more tranquil. Due to the uncertainty in timing of the waves and
the location of the convection as they react with meandering
fronts, confidence remains low for the first half of the forecast.
The wave moving by the area today will move away late this
evening, only to be followed by a stronger wave Sunday and a
weaker pulse Sunday night. Looking like strong thunderstorms are
possible Sunday with hail and gusty winds as the main hazards. The
additional waves, Tuesday through Wednesday, appear to again be
weaker and should result in non severe weather with some
thunderstorms.
Besides the thunder threat, patchy fog is expected late tonight
with locally dense fog possible. Fog could also be a problem into
mid week, as the forecast rainfall and atmospheric moisture could
lead to fog any night as temperatures cool off.
Temperatures will be above normal into mid week, then fall to
below normal into the weekend. Normal highs this time of year are
around 80 degrees and normal lows are around 60 degrees.
&&
.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 114 PM EDT Sat Aug 17 2019
Two chances for storms during the period. The first is later this
afternoon and will mainly affect the southern TAF sites. An area o
showers/storms is moving east from Chicago and will move along
I-94 mid to late afternoon. The second chance arrives closer to
12z. Confidence is moderate that we`ll see some storms after 12z
and these should affect all of the TAF sites.
MVFR cigs expected overnight, especially along I-94 where moisture
from recent rain will enhance fog/low cig chances.
&&
.MARINE...
Issued at 420 PM EDT Sat Aug 17 2019
Winds and waves Sunday on Lake Michigan should reach Small Craft
Advisory levels (SSW winds of 15 to 25 knots and 3-5 foot waves), so
an Advisory was issued from 8 AM to 8 PM. Winds and waves will
increase in the morning resulting in longshore currents and waves
topping piers given the high water levels. A Beach Hazard Statement
will also be issued for Sunday. Calmer conditions are expected to
start the workweek.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from Sunday morning through Sunday
evening for MIZ037-043-050-056.
LM...Small Craft Advisory from 8 AM to 8 PM EDT Sunday for LMZ846>849.
&&
$$
SYNOPSIS...63
DISCUSSION...63
AVIATION...04
MARINE...63
NWS GRR Office Area Forecast Discussion
