000
FXUS63 KGRR 181740
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
140 PM EDT Wed Apr 18 2018

LATEST UPDATE...
Aviation/Hydro

.SYNOPSIS...
Issued at 330 AM EDT Wed Apr 18 2018

Low pressure will move from Missouri this morning to Pennsylvania by
Thursday morning. As the low moves south of the Great Lakes
precipitation will spread into Lower Michigan this afternoon and
continue into Tonight. The precipitation will start off as mainly
rain this afternoon as temperatures warm into the 40s. Tonight
however, readings will cool into the 30s and the precipitation will
switch over to snow. Light accumulations of snow are certainly
possible with a dusting to possibly around 1 inch of new snow
forecast in many areas. Dry weather will return for Thursday and
continue right through the upcoming weekend as high pressure settles
into the Great Lakes region. After highs in the 40s today and
Thursday, readings will warm into the 50s on Friday, possibly
hitting 60 over the weekend.

&&

.SHORT TERM...(Today through Friday)
Issued at 330 AM EDT Wed Apr 18 2018

A compact fast moving shortwave can be seen in water vapor imagery
moving east across Nebraska. Rain and snow is currently falling
beneath this upper system with some embedded lightning as well. We
are not expecting the lightning, but we will see the rain and snow.
The instability currently in place with the system over NE/IA will
erode before it gets to our area.

Expecting rain to spread into Western Lower Michigan this afternoon,
possibly mixed with some light snow across Central Lower Michigan.
The rain will change over to all snow this evening as the
precipitation cools the column and air temps drop off with
nightfall. The upper system will be forced to the south tonight by a
developing northerly flow aloft. Therefore, the heaviest
precipitation should be across southern portions of the state.
Precipitation will range from less than a tenth of an inch up along
U.S. 10 to near a third of an inch along I-94. In regard to
snowfall, thinking a dusting to an inch of snow is possible tonight
for most areas.

The DGZ appears to become unsaturated at times tonight given a
weakening and somewhat shallow moisture depth. Would not be
surprised to see a little drizzle or freezing drizzle tonight. At
this point not confident in this occurring, so left it out of the
forecast. With the snow and temperatures falling to below freezing
late in the night it could be another slick morning commute on
Thursday.

Weather concerns are low from Thursday through Friday with surface
ridging building in. Mainly clear with temperatures moderating.

.LONG TERM...(Friday night through Tuesday)
Issued at 330 AM EDT Wed Apr 18 2018

High pressure will keep dry and quiet weather over the area through
at least Monday night. Shortwave energy dropping through the Great
Lakes will bring an increase in cloud cover on Saturday, but skies
will otherwise be mostly sunny/clear. Upper trough will swing
towards the area by late Tuesday, but chances for precipitation
through the day still looks very low with the frontal boundary still
well upstream. Temperatures will gradually warm each day Saturday
through Tuesday, with highs finally reaching close to normal by
Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 140 PM EDT Wed Apr 18 2018

VFR conditions this afternoon and evening will transition to MVFR
and IFR as rain moves in by 00Z and transitions to snow later this
evening. The steady snow will taper off around 06Z and some
partial clearing is possible late with VFR conditions expected to
return after 12Z Thursday.

East winds around 10 knots will go northeast this evening then
north on Thursday with some gusts to 20 knots.

&&

.MARINE...
Issued at 330 AM EDT Wed Apr 18 2018

North winds will be on the increase from tonight, lasting into
Thursday night. Winds of 15 to 30 knots are expected, which will
build nearshore waves into the 4 to 7 foot range. We have hoisted a
Small Craft Advisory from midnight tonight through midnight Thursday
night to account for the increase in wind and waves. The wind
increase is in response to a tightening pressure gradient between a
low moving through the Ohio Valley and a high situated across the
Northern Plains. Winds and waves will be much tamer for Friday and
Saturday as high pressure builds in from the west. Expect foot or
less wave action from Friday into Saturday.

&&

.HYDROLOGY...
Issued at 140 PM EDT Wed Apr 18 2018

Lowland flooding near riverbanks will be ongoing over the next
several days as water from last weekend`s mixed precipitation event
moves through the river basins. About 0.2 inches of rain/snow are
expected tonight in the Grand and Kalamazoo basins. Since no heavy
rain events are anticipated through early next week, river levels
will gradually crest then subside. The exception may be the Muskegon
and Chippewa Rivers, which still have a fair amount of surface water
locked up as snow/sleet. That snowpack will gradually melt with
warmer temperatures this weekend, so flood concerns are limited
though river levels will remain elevated.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory from midnight tonight to midnight EDT
     Thursday night for LMZ844>849.

&&

$$

SYNOPSIS...Duke
SHORT TERM...Duke
LONG TERM...HLO
AVIATION...Ostuno
HYDROLOGY...CAS
MARINE...Duke