Winter Weather Advisory 4, NWS Grand Rapids, MI

Area Forecast Discussion
National Weather Service Grand Rapids MI
320 AM EST Tue Jan 19 2021

LATEST UPDATE...
Synopsis/Discussion/Marine

.SYNOPSIS...
Issued at 320 AM EST Tue Jan 19 2021

-Lake effect flare up this afternoon and evening

-Windy later Wednesday into Thursday; dry and milder

-Light snow possible Friday, better chance Sunday and Monday

&&

.DISCUSSION...(Today through next Monday)
Issued at 320 AM EST Tue Jan 19 2021

--Lake effect flare up this afternoon and evening--

We are issuing a Winter Weather Advisory for Ottawa, Allegan, and
Van Buren Counties from 3 PM this afternoon through 4 AM tonight.

A potent shortwave dropping southeast from MN later today brings a
period of deeper moisture/lift that should significantly enhance the
westerly flow lake effect over the sw corner of Lwr MI, squarely
during the evening commute time.

Total accumulations this afternoon and evening in the advisory
area expected to be roughly 2-4". Intensity of some of the snow
showers with sfc temps in the mid to upper 20s will likely create
some travel impacts due to reduced visibilities and slick roads.

One concern we have is that some of the more intense snow bands
later today could extend well inland, possibly impacting srn
Kent, Barry and Kalamazoo Counties. If HiRes model updates trend
more in this direction we may have to add a few counties to the
advisory.

RAP and NAM3km fcst soundings at South Haven are fairly impressive,
especially between 21Z and 03Z, showing no inversion aloft, deep
moisture and omega to 15K ft, and a pretty good looking DGZ/Omega
"crosshairs" signature.

Snow showers diminish overnight after shortwave pulls away, but
some NW flow L.E.S. may persist near and west of Hwy 131 with some
additional light accums.

--Windy later Wednesday into Thursday; dry and milder--

Shortwave ridging moving in for Wednesday leads to a dry day, but
the sfc pres gradient tightens up quickly. Southwest winds may
begin gusting to 40 mph already in the afternoon especially at
the lakeshore. Winds remain up Wednesday night into Thursday while
veering more westerly, with temps rising into the 30s to perhaps
40 degrees. Still looking at a fairly good chance of seeing some
sunshine on Thursday, especially over southern sections.

--Light snow possible Friday, better chance Sunday and Monday--

The period of milder air is short-lived as a cold front drops
south through the state Thursday night and Friday. Some light NW
flow lake effect may set up for a time later Thurs night and
Friday before a sfc high arrives in MI on Saturday.

Longer range guidance is similar in showing a warm advection/
overrunning pattern shifting toward Lwr MI on Sunday and
continuing into Monday. This occurs as longwave troughing sets up
over the wrn U.S. and deep southwest flow sets up downstream into
the GrtLks Rgn. At least light snow accumulations appear
possible, and we'll have to watch for the potential of a more
organized system approaching from the southwest next Monday
night/Tuesday as ensemble guidance has been suggesting.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1205 AM EST Tue Jan 19 2021

Primarily MVFR conditions are expected overnight and Tuesday due
to extensive low cloud cover and occasional light snow showers and
flurries. A burst of heavier snow is expected Tuesday evening at
our southern terminals which will cause conditions to deteriorate
to IFR/LIFR there from around 00Z through 06Z Wed.

&&

.MARINE...
Issued at 320 AM EST Tue Jan 19 2021

Brisk westerly flow today and tonight will create hazardous
conditions for small craft. A further increase in winds and waves,
out of the southwest, is expected on Wednesday. Gales are
possible Wednesday afternoon into Thursday and will issue a Gale
Watch for that possibility.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 3 PM this afternoon to 4 AM EST
     Wednesday for MIZ056-064-071.

LM...Gale Watch from Wednesday afternoon through late Wednesday night
     for LMZ844>849.

     Small Craft Advisory until 1 PM EST Wednesday for LMZ844>849.

&&

SYNOPSIS...Meade
DISCUSSION...Meade
AVIATION...Laurens
MARINE...Meade

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