Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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 50

589
FXUS63 KGRR 181140
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
640 AM EST Sat Jan 18 2020

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 300 AM EST Sat Jan 18 2020

- Snow transitioning to mix this morning, then back to snow by this
evening

- Some lake effect snow showers Sunday and Sunday night

- Another system with mixed precipitation possible late Wednesday
into Friday

&&

.DISCUSSION...(Today through next Friday)
Issued at 300 AM EST Sat Jan 18 2020

-- Snow transitioning to mix this morning, then back to snow by this
evening --

Things are progressing as expected so far with this event. We will
be holding on to the Winter Weather Advisory as is this morning.
Amounts thus far have been generally around 2 to 3 inches across the
area. We are looking at the best burst expected with this event over
the next 4-6 hours. This is evident in the regional radar with more
intense and convective elements over Illinois. This coincides well
with the nose of the low level jet/moisture transport coming through
at that time.

Much of the precipitation will be snow, but we still expect a
transition to a mix, then rainfall through mid afternoon. We expect
a warm layer aloft to move close to the I-94 counties over the next
few hours that could bring a couple of hours of some sleet or
freezing rain. This should not be much of a problem with the layer
of snow on the roads already, and with the limited duration
expected. Precipitation should then change over to some rain from I-
96 and south by mid morning as the warm air aloft and surface
temperatures rising above freezing move in briefly ahead of the
surface low.

The surface low and colder air will move east through the area by
early evening, and change any residual precipitation back over light
snow. This colder air will be ushered in quickly by wind gusts
approaching 40-45 mph from the west. Precipitation will then
transition to some lake effect snow showers.

-- Some lake effect snow showers Saturday night through Sunday
night --

Lake effect parameters are all sufficient for some additional
accumulations of snow Saturday night through Sunday night, however
there are a couple of factors that look to limit additional
accumulations from being a lot.

The ingredients that are favorable for lake effect include the area
being on the cyclonic side of the upper jet, delta t`s in the mid to
upper teens C, and moisture/inversion heights up to around 7k feet
or so. However, a lack of direct impact by short waves over the
area, and strong winds displacing the bands inland a bit into Sunday
will limit lake effect accumulations. Then, lake effect should move
mostly offshore by daybreak on Monday as the flow goes offshore.
That will essentially end lake effect chances with this event.

-- Another system with mixed precipitation possible late Wednesday
into Friday --

We will see a break in the unsettled weather then from Monday, until
Wednesday afternoon with some sunshine possible at times.
Precipitation chances could arrive as early as Wednesday afternoon
up north as return flow with a Gulf connection could bring enough
moisture in ahead of a weakening front coming in from the NW by
then.

The better chance of precipitation will then come Thursday night
into Friday. This will be the result of a better short wave and
associated surface low approaching the area from the west. This will
have a chance to interact with the lingering Gulf feed to bring some
precipitation.

Precipitation type with this could be rain or snow with sufficiently
warm enough air expected to be in place.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 640 AM EST Sat Jan 18 2020

Snow continues across most of the area, with some freezing rain
mixing in along the I-94 terminals. We will see these conditions
continue, with some mixture becoming possible over the next couple
of hours for the I-96 terminals. As the back edge of the
widespread precipitation moves through this morning, precipitation
should change over to drizzle as temperatures rise to above
freezing. Can not rule out a little freezing drizzle if
temperatures take a little longer to warm above freezing. Fog will
also become more of an issue with the surface low coming through.

The drizzle and fog will persist through the heart of the day,
until the low and colder air move east through the area from
around 20-24z. Precipitation will then change over to light snow,
and then will scatter out to lake effect snow showers. Ceilings
and visibilities will increase as the low and cold air comes in.
This will be ushered in by wind gusts around 35-40 knots from the
west. Snow showers will then persist through 12z at the western
terminals.

&&

.MARINE...
Issued at 300 AM EST Sat Jan 18 2020

Winds are up a bit this morning, but not producing many impacts with
the flow being offshore. Winds will switch to the SW this afternoon,
and will ramp up significantly to around 40 knots. The worst winds
will be centered from about 20z to 03z, with the highest waves
lagging a little. We still anticipate a fair amount of lakeshore
flooding and erosion with up to 14 foot waves coming in directly to
the lakeshore. Winds and waves will ease up a little later tonight
and Sunday, before coming down better for Monday.


&&

.HYDROLOGY...
Issued at 330 PM EST Thu Jan 16 2020

All rivers have crested from the heavy rain last weekend. Two flood
warnings remain, both on the Grand River, at Comstock Park and also
at Robinson Township, where it will probably be early next week
before these spots fall below flood stage.

With cold temperatures expected late this weekend and next week, the
rivers should have a chance to drop down below bankfull at all
locations. However, cold temperatures also bring the growth of river
ice, so some freezeup ice jam issues are possible next week,
especially in some of the most favored areas such as on the Muskegon
River downstream of Big Rapids.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Warning until 7 PM EST Sunday for MIZ037-043-050-
     056-064-071.

     Winter Weather Advisory until 7 AM EST Sunday for MIZ037>040-
     043>046-050>052-056>059-064>067-071>074.

LM...Heavy Freezing Spray Warning from 4 PM this afternoon to 1 PM
     EST Sunday for LMZ844>849.

     Gale Warning until 10 AM EST Sunday for LMZ844>849.

&&

$$

SYNOPSIS...NJJ
DISCUSSION...NJJ
AVIATION...NJJ
HYDROLOGY...AMD
MARINE...NJJ



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