Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KGRR 180729

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 AM EDT Wed Apr 18 2018

Synopsis/Short Term/Long Term/Marine

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

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


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 131 AM EDT Wed Apr 18 2018

MVFR ceilings are favored overnight as low-level moisture remains
locked in place under an inversion, which will continue to lower
slightly towards daybreak as weak ridging expands into Southwest
Michigan. Flow will turn off the lake by 08-10Z, which could allow
some breaks to develop. Confidence in ceilings scattering out is
low. Low pressure tracking through the Ohio Valley will spread
precipitation and lower clouds into the area by late afternoon and
evening. Rain is expected to move into the area between 20-22Z,
then change to snow after sunset (about 01Z). This should drop
ceilings vis to MVFR or IFR. Northeast winds will also begin to
gust up to 20 knots in the evening.


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.


Issued at 1122 AM EDT Tue Apr 17 2018

River levels are above normal in Southern Lower Michigan and around
normal in Central Lower Michigan. The significant precipitation over
the weekend has led to rising river levels across the area. With
only a few tenths of precipitation expected Wednesday into Wednesday
night and nothing else until next week, rises are still expected to
continue for the next several days. Minor flooding near river banks
is still possible.


LM...Small Craft Advisory from midnight tonight to midnight EDT
Thursday night for LMZ844>849.



MARINE...Duke is the U.S. government's official web portal to all federal, state and local government web resources and services.