Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 112029
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
330 PM EST Wed Jan 11 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Hydro/Marine

.SYNOPSIS...
Issued at 330 PM EST Wed Jan 11 2017

A low pressure system will move through the Great Lakes region
tonight and bring a wintery mix of precipitation. Fair weather
will return late Thursday through Friday as a high pressure ridge
builds in. Cooler temperatures will briefly return Friday into
Saturday before a moderating trend of temperatures occurs again
late in the weekend into next week.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 330 PM EST Wed Jan 11 2017

Primary short term fcst concerns involve determining potential for
snow/freezing rain late today through tonight into Thursday.

A consensus of latest short range guidance suggests that light
snow will develop across our northern fcst area late this
afternoon and evening as a 1000 mb low currently over northern
Missouri moves northeast to near Toronto by 06Z. Snow
accumulations of around an inch or two are expected across our far
northern fcst area tonight with locally higher amounts to 3 inches
possible.

A polling of 12Z model fcst soundings and higher resolution short
range/sref probabilistic guidance all suggest that pcpn from
around KMKG/KLDM ene to KRQB/KMOP will become mixed with or change
over to a several hour period of fzra this evening. Up to a tenth
of an inch of ice accumulation is possible. For the aforementioned
reasons which will result in hazardous travel conditions we have
issued a winter wx advisory for most of our northern fcst area.
Thx for coord on fcst/headline decisions APX/DTX.

Near to south of I-96 we expect rain to develop tonight. Pcpn
along the I-96 corridor may become mixed with or changeover to
a very brief period of sleet or very light freezing rain just prior
to ending prior to daybreak. Isolated convection should stay
south/se of our area tonight as we do not believe there will be
sufficient enough instability or forcing for convective initiation
to occur.

Tranquil wx will return beginning Thursday afternoon through
Friday as a high pressure ridge builds in.

.LONG TERM...(Saturday through Wednesday)
Issued at 330 PM EST Wed Jan 11 2017

A zonal flow upper pattern is in place throughout the long term. The
zonal flow of air will lead above normal temperatures during the
long term period. We are looking at highs in the 30s over the
weekend with readings pushing into the 40s early to mid next week.

There is one main feature to key on in the long term and that is a
cut off low that is forecast to be over the Baja of California
Saturday morning. The upper low pivots to the Texas panhandle Sunday
evening and is forecast to move into the western Great Lakes early
next week. This low will bring a southerly push of warmer air into
our region.

Surface high pressure will keep the weekend dry it appears for the
most part. We may see a little light snow late Sunday night on the
initial fringes of the precipitation shield of the low lifting north
through the plains. The bulk of the precipitation is expected on
Monday and Tuesday as the low moves northward near Lake Michigan.
850mb temperatures from 12z Monday into Tuesday evening, the main
time frame of precipitation, are above 0 C. Both the operational
ECMWF and GFS have us pushing towards +8C, so it mainly looks like a
rain event outside of some light snow mixing in possible on the lead
edge.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 106 PM EST Wed Jan 11 2017

VFR weather is in place across the bulk of the area at 18z, but
conditions are going to deteriorate rapidly late this afternoon
and evening. Lower ceilings and visibilities will develop from the
south after about 21z. By 01z this evening IFR and LIFR conditions
will be fairly widespread. Rain showers will move through the
area this evening, with the potential for a bit of freezing
drizzle or freezing rain at the northern TAF sites (KMKG, KGRR and
KLAN) overnight (05z to 12z). Low ceilings will persist into
Thursday morning.

The low ceilings and precipitation are associated with a frontal
boundary sagging into the area from the north and a low moving
northeast along the front.

Bottom line, conditions trending rapidly to IFR and LIFR this
evening and remaining at those levels into Thursday morning.


&&

.MARINE...
Issued at 330 PM EST Wed Jan 11 2017

A small craft advisory remains in effect through early this
evening. Wind speeds and wave heights will subside somewhat this
evening and overnight.

&&

.HYDROLOGY...
Issued at 330 PM EST Wed Jan 11 2017

Rivers are running above normal across the area due to rain, melting
snow and ice jams. The Looking Glass River at Eagle and the Grand
River at Comstock Park have warnings active, as they are expected to
reach flood stage. A watch is out on the Grand River at Robinson
Township due to ice jam potential. Multiple sites also have
advisories active. A period of colder than normal temperatures today
through the weekend may allow river ice to redevelop.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 8 PM this evening to 10 AM EST
     Thursday for MIZ045-046-050-051.

     Winter Weather Advisory from 6 PM this evening to 10 AM EST
     Thursday for MIZ037>040-043-044.

LM...Small Craft Advisory until 7 PM EST this evening for LMZ844>849.

&&

$$

SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...Duke
AVIATION...Duke
HYDROLOGY...63
MARINE...Laurens



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