National Weather Service Raw Text Product

Displaying AFOS PIL: AFDGRR Received: 2017-12-07 08:29 UTC


559 
FXUS63 KGRR 070829
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
329 AM EST Thu Dec 7 2017

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

.SYNOPSIS...
Issued at 304 AM EST Thu Dec 7 2017

A reinforcing shot of arctic air moves in today leading to
unseasonably cold temperatures and lake effect snow showers.
Slick travel conditions will be possible. An area of high pressure
builds up the Ohio Valley for tonight into Friday diminishing the
snow showers. A widespread accumulating snow event is expected 
for Friday night into Saturday as an area of low pressure tracks 
through.

&&

.SHORT TERM...(Today through Saturday)
Issued at 304 AM EST Thu Dec 7 2017

The leading edge of a reinforcing shot of arctic air was pushing 
through the forecast area at this time. As this front sinks 
southeast over the next couple of hours...the steadier snow 
showers ahead of it will track through Kalamazoo and Battle Creek.
A northwesterly flow was setting up behind this front where lake 
effect snow showers were strengthening. The northwest flow then 
persists through the day supporting the steadiest snow showers 
where we have the headlines out. We will need to monitor the 
Interstate 94 corridor for possible expansion further inland of 
the headlines due to the potential for stronger snow showers 
today.

A more significant wave of low pressure tracks southeastward
through the CWA Friday night and Saturday. Widespread impacts are
becoming more likely with this event. The combination of deep
moisture...favorable lift and lake enhancement supports an
increased potential for more than 4 inches of snow for western
parts of the forecast area.





.LONG TERM...(Saturday night through Wednesday)
Issued at 304 AM EST Thu Dec 7 2017

The long term begins with a deep upper trough moving across eastern 
Michigan and a sfc low over Ontario. Snow from this system will be 
winding down and most locations will probably be dry Saturday night 
through Sunday evening. 

A clipper is progd to move southeast from Manitoba to southern 
Ontario Sunday evening and dragging a cold front through the cwa 
Monday. Light snow is likely with this system. Lake effect snow that 
develops behind it as h8 temps fall to -17c will be limited to the 
lake shore and perhaps the far eastern cwa if boundary layer winds 
can get enough of a easterly component off of Lake Huron to bring a 
few bands through Mid Michigan. 

Another clipper is shown by both the ecmwf and gfs to move from 
northern Minnesota southeast across Chicago Tuesday night. This 
should bring light synoptic snow to the cwa during this time leading 
to some minor accumulations. 

Highs through the period will range from the upper 20s to mid 30s. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1157 PM EST Wed Dec 6 2017

A cold front moving through the state will create in increase in
snow showers as colder air moves south over the lake. That in turn
will result in some MVFR conditions through mid afternoon. Snow
showers will diminish by late in the day and VFR conditions will
return. 


&&

.MARINE...
Issued at 304 AM EST Thu Dec 7 2017

Small craft advisory conditions continue throughout the nearshore
area. The cold airmass will persist as west to northwest flow
lingers into Friday as high pressure builds up the Ohio
Valley...keeping the conditions hazardous.

&&

.HYDROLOGY...
Issued at 329 PM EST Wed Dec 6 2017

Several rounds of snow are expected over the next week due to a 
combination of lake effect processes and passing low pressure 
systems. The first round of more widespread snow will occur late 
today through Thursday afternoon, bringing several inches of snow to 
counties near the lakeshore. Total liquid equivalent (melted snow) 
through Thursday evening will be below one-quarter of an inch for 
most locations, but locations in Allegan, Van Buren, and Kalamazoo 
counties could see locally higher totals up to one-half inch. No 
issues with flooding or rivers are expected. Another round of more 
widespread snow is expected to start mid-day Friday and last through 
Saturday afternoon. This looks to bring another tenth to one-quarter 
of an inch of liquid equivalent, and again not cause any issues 
aside from accumulating snowfall.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 4 PM EST this afternoon for MIZ037-
     038-043-050-056-064-071-072.

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

&&

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...04
AVIATION...04
HYDROLOGY...HLO
MARINE...MJS