Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 142353
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
653 PM EST Tue Nov 14 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 326 PM EST Tue Nov 14 2017

Clouds will be on the increase this evening, with rain showers
increasing from the Northwest overnight and Wednesday morning as a
frontal system moves in. Rain will then gradually come to an end
late Wednesday as the front passes East of the area. A few lingering
rain showers may mix with/change over to some snow Wednesday night
and Thursday morning before ending.

We will see a break in the unsettled weather from later Thursday and
early Friday. Rain showers will then move back in over the area
later on Friday and last into Saturday. Colder air will filter in on
Saturday behind the front, bringing some snow showers to the area.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 326 PM EST Tue Nov 14 2017

Our main focus of the forecast is on the incoming system that will
be coming in later tonight and Wednesday. We need to determine
timing of the rain, and then snow shower potential on the back side
of the system.

Rain is sure bet tonight into Wed as the front moves into the
region. We will see the strong forcing out ahead of the supporting
upper wave approach the area tonight, and move through the state on
Wed. The sfc low is strengthening some as it moves in, and there is
a moisture feed becoming established from the Gulf. This looks like
simply a good soaking rain that will progress through the area. The
atmosphere is warm enough that mixed pcpn should not occur. Thunder
potential is almost zero, and not enough to justify mentioning at
this time.

Rain will diminish in the afternoon as the cold front pushes
through, and as the main short wave with the long wave trough does
late in the afternoon. Cold enough air will arrive Wed evening to
help to at least mix snow in with the residual rain showers, if not
change over to light snow showers entirely. The snow showers hold on
some with the next short wave diving in from the NW. Temps are not
forecast to drop below freezing at many locations, so snow
accumulations will be quite limited.

The shower activity will then end gradually on Thursday. We will see
the long wave trough lift out Thu afternoon. Moisture depth will
become more shallow as this occurs, and the dgz will not really be
saturated anymore. The mean low level flow also veers offshore,
sending most of the clouds and any sprinkles/flurries out over the
lake. We should then clear out by Thu night.

.LONG TERM...(Friday through Tuesday)
Issued at 326 PM EST Tue Nov 14 2017

Medium range guidance looks to be converging on a solution of taking
the sfc low across southern lower MI on Saturday then deepening it
Saturday night as it moves east-northeast through southern Ontario.

This is a farther south solution than we had seen 2-3 days ago with
a delayed deepening of the sfc low, which should result in less
impact in terms of winds and snow showers on the back side than
previously suggested. It will still be breezy however later Saturday
into Sunday morning on the back side of the deepening low.

While some scattered lake effect snow showers still look to be a
good bet on Saturday night and Sunday, little or no accumulation is
expected since the boundary layer looks too warm and the sfc low
pulls away rapidly on Sunday.

On the front side of this system, much of Friday may end up dry as
all models except the speedier GFS hold off most of the warm
advection rain until after 00Z Saturday. Will have chc pops in the
afternoon on Friday but even this may be too pessimistic. The bulk
of the rain comes on Friday night into Saturday morning and will
carry high pops during this time, with a slight chance for a rumble
of thunder south and east of GRR - closer to the warm sector of the
developing cyclone.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 654 PM EST Tue Nov 14 2017

VFR conditions this evening will become MVFR as rain moves in
later tonight with IFR developing Wednesday morning and persisting
into the afternoon. Winds will be southerly around 10 knots this
evening then going southwest and increasing later tonight with
some gusts to 20 knots through Wednesday afternoon.

&&

.MARINE...
Issued at 326 PM EST Tue Nov 14 2017

We are hoisting a Gale Warning for the entire nearshore immediately
following the Small Craft Advisory that is in effect until Wed
afternoon. Winds are on their way up this afternoon, and will
stabilize a bit around 25-30 knots through much of Wed ahead of the
front. Once the front comes through, the colder air moving in and
better winds aloft will mix down some Gales. These will last into
Thu morning before gradually coming down as high pressure moves in.


&&

.HYDROLOGY...
Issued at 108 PM EST Tue Nov 14 2017

Model QPFs with the Wednesday cold front have trended up, with
widespread amounts near 0.50 now expected. This should bring an
end to the current slowly receding river levels and probably bring
about some slight/minor rises. The system for Friday and Saturday
could produce around an inch of rain, and that may lead to more
notable rises in the days following. At this time, it appears the
Kalamazoo and St. Joseph rivers would be most susceptible.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 4 PM EST Wednesday for LMZ844>849.

     Gale Warning from 4 PM Wednesday to 8 AM EST Thursday for
     LMZ844>849.

&&

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...Meade
AVIATION...Ostuno
HYDROLOGY...Meade
MARINE...NJJ



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