Area Forecast Discussion
Issued by NWS Grand Rapids, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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

000
FXUS63 KGRR 211643
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1143 AM EST Wed Feb 21 2018

LATEST UPDATE...
Update

.SYNOPSIS...
Issued at 308 AM EST Wed Feb 21 2018

The area of precipitation that has been over our area since Monday
afternoon will finally exit the area this morning. The
precipitation will change to freezing rain, sleet and snow on the
back edge for around two hours at any one location. Some minor
accumulations of snow are possible mostly west of Grand Rapids.
A large high pressure system will track east across Michigan
tonight into Thursday. This will bring partly cloudy skies and
cooler temperatures. A wave on the front to our south will track
northeast toward Indiana and Ohio on Friday bringing some light
precipitation to the area. That will likely start as light
freezing rain and sleet then change to rain during the day.
Precipitation amounts are expect to be light. Another high
pressure system moves across the area Saturday but then a stronger
storm moves into the Great Lakes Sunday with more precipitation.

&&

.UPDATE...
Issued at 1143 AM EST Wed Feb 21 2018

Increased max temp forecast for today as some clearing is
expected through the afternoon. The clearing will be most notable
north of I-96.

&&

.SHORT TERM...(Today through Friday)
Issued at 308 AM EST Wed Feb 21 2018

The big question for me this morning is will there be enough
frozen precipitation to issue a Winter Weather Advisory. There is
little question the below freezing surface temperatures will reach
at least the western CWA before the precipitation ends by mid
morning over the western CWA and late morning over the eastern
CWA. In fact at 3 am Holland Airport is reporting freezing rain at
33 degrees (dew point is 30). I expect a narrow band of freezing
rain that will end as sleet and snow between 5 am and 8 am near
and west of US-131. It is possible some areas north and west of
GRR could see as much as an inch of snow. The real question though
is will there be enough freezing rain to cause significant road
hazards? Given how warm it has been, and that air temperatures
are not expected to fall below 30 degrees, I am thinking this will
not be a big issue. More than likely we will issue and SPS for
this once it gets going.

The dry air surges in behind the system at low to mid levels this
afternoon. That should end the precipitation and bring at least
partial clearing to the area by late this afternoon. The large
surface high crossing the area tonight into Thursday should keep
it dry into Thursday evening. However it should be pointed out
that the entrance region to a 180 knot jet core (over upper
Michigan this afternoon) is causing our precipitation now and that
is not east of our area until midday Thursday. That means we will
have nearly overcast high clouds into Thursday morning.

Since the longwave trough is west of us, is anchored over the
western CONUS into next week, we will continue to see shortwaves
coming out of the Southwest CONUS for awhile yet. The next one is
currently moving into the base of the trough over CA and NV and
will move out into the southern plains Thursday. This has enough
energy to create and 130 to 140 knot jet exit region over
northern Michigan Thursday night but the surface front stays south
of I-80 Friday. Most of the precipitation with that system will
be near and south of I-80. However since the jet core is north of
here we will still see some light precipitation. It will be warm
enough between 750 mb and 950 mb to make the precipitation mostly
rain. Still we could see some sleet and freezing rain at the onset
during the mid morning hours. Precipitation amounts should mostly
be less than a quarter inch so this should not add much to our
flooding problems.

.LONG TERM...(Friday night through Tuesday)
Issued at 308 AM EST Wed Feb 21 2018

Forecast concerns revolve around the potential for more rain over
the weekend.

Both the gfs and ecmwf show a similar storm track for the weekend
event, but the gfs is 25 mb deeper with the low and thus paints much
more precipitation. The gfs has stronger upper support, but the 00z
ecmwf is beginning to develop the upper way a little bit more than
previous runs which may hint at it coming on board with a stronger
sfc low in future model runs. We`ve have high pops in the grids
Saturday night and Sunday and much of the precipitation is rain,
which isn`t really good given how much is currently falling over the
cwa. However, we`re looking at another third of an inch and some of
it may mix with wet snow Saturday night. If the deeper gfs verifies,
Sunday could be fairly breezy.

Mainly dry weather is expected after that as high pressure builds
into the region. Above normal temperatures are expected through the
period with highs in the 40s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 618 AM EST Wed Feb 21 2018

IFR/MVFR to VFR by 16z at most if not all TAF sites.

The area of precipitation is moving will be out of the area by 15z
or so. The last hour or two features 1 to 2 hours of freezing rain
just before the precipitation end. I did not put freezing rain at
JXN as the air should be able to warm up enough so that will not
be a problem there. The precipitation as already ended at MKG and
GRR and will shortly end at AZO, BTL and LAN.

The low clouds will move out in the 16z to 18z time frame then
there will just be a broken to overcast cirrus cloud deck into
Thursday morning.


&&

.HYDROLOGY...
Issued at 329 PM EST Tue Feb 20 2018

Very little has changed in the last 24 hours. Widespread rainfall
amounts of 1 to 2 inches fell overnight Monday into Tuesday morning.
These amounts, in addition to snowmelt and frozen surface layer,
resulted in rapid feedback on area streams and rivers. All rivers
are being impacted by some magnitude of river rise and/or flooding.

Most notable impacts are along the Looking Glass River near Eagle.
Emergency management reported several roads closed in Watertown and
Eagle Twp, various road along the river, flooding in Wacousta Park
and homes threatened and/or impacted in/near Grand Ledge and Fowler.
The river is forecast to continue to rise overnight, possibly
achieving record levels of around 10.5 feet late Wednesday evening.
Given record event type levels, reference data is limited to the
type of impacts that could occur beyond previous events. All
residents should continue to heed advice from local official, while
maintaining vigilant to river levels and keep up with latest
forecasts.

The Grand River basin will also take on plenty of water from smaller
streams and tributaries. Several sites along the Grand River will
reach moderate flood level, while Comstock Park could reach over 17
feet, which is slightly below 2013 levels.

Additional rainfall this evening through early Wednesday morning is
expected to generally range from 1 to 2 inches. Embedded storms
could result in periods of heavy rain, possibly enhancing localized
rainfall totals. The greatest totals are likely to fall over
Southern Lower Michigan, in places already impacted by last night`s
heavy rain. River rises will continue through the end of the week
with larger rivers cresting over the weekend. Areas away from
rivers, such as low lying, flood prone locations, will also run the
risk of minor flooding, at least until rain exits Wednesday.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

UPDATE...JK
SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...04
AVIATION...WDM
HYDROLOGY...JAM



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