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Displaying AFOS PIL: AFDGRR Received: 2018-02-13 08:09 UTC

FXUS63 KGRR 130809

Area Forecast Discussion
National Weather Service Grand Rapids MI
309 AM EST Tue Feb 13 2018

Synopsis/Short Term/Long Term

Issued at 308 AM EST Tue Feb 13 2018

High pressure will bring fair weather today and into Wednesday. 
Low pressure will track south of Lower Michigan on Thursday with 
rain changing to snow by Friday.


.SHORT TERM...(Today through Thursday)
Issued at 308 AM EST Tue Feb 13 2018

Only forecast issue in the near term is for precip type late
Thursday across the northern forecast area as colder air filters
back in. Model soundings continue to show the moisture is shallow
on Wednesday with the DGZ unsaturated and even drizzle appears to
be a long no POPs in the forecast until Wednesday night.

Model consensus is that the northern and southern streams remain
separate through Thursday with Lower Michigan on the northern
periphery of the precip shield of a sfc low tracking across the
Ohio Valley. Bulk of the precip looks to remain south of the
Michigan border and light rain showers across the forecast area,
with a change to snow beginning in the afternoon across the 
higher elevations of the northern tier.

.LONG TERM...(Thursday night through Monday)
Issued at 308 AM EST Tue Feb 13 2018

A cold front will push through Thursday night.  There will be a 
strong surge of cold air behind this system.  So rain will switch 
over to snow overnight.  This will be followed by a brief period of 
lake effect snow mainly Friday morning.  It will wind down mid day 
Friday as a surface high builds in.  This brief period of snow may 
put down an inch or less of accumulation mainly along the lakeshore 

It will stay cold Friday into Saturday, but then we will see another 
warming trend starting Saturday night and continuing into early next 
week as we get on the backside of the surface high.  There could be 
some very light snow Saturday on the leading edge of the warm 

The models are not in good agreement with the timing of next system 
that arrives Sunday into Monday.  The operational GFS is quicker 
than it's ensembles, and the ECMWF is leaning toward a slower 
solution too.  So I also leaned toward the slower solution which 
will allow for temps to remain warmer longer, and give the region a 
chance of rain initially, starting Sunday afternoon/evening. 

Difficult forecast by late Sunday night into Monday given the models 
differences and attempting to forecast pcpn type.  The front may 
slow even further Monday as low pressure moves along the front.  For 
now will expect the rain changing to snow across Central Lower late 
Sunday night and continuing into Monday.  However if the front does 
stall, areas along and south of I-96 may stay all rain into Monday. 
We have time to iron this out with future model runs and as we 
monitor timing trends.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1220 AM EST Tue Feb 13 2018

VFR conditions will prevail through the next 24 hours. Southerly
winds will increase to around 10 knots along the lakeshore by mid
day and continue into the evening. Elsewhere it will remain 


Issued at 150 PM EST Mon Feb 12 2018

A warmup will be underway as the week progresses, with highs 
reaching the 40s by Wednesday. Up to a quarter inch of rain is 
possible Thursday into Thursday night. These events should cause 
river ice to partially melt and shift toward the end of the week, 
and could lead to ice jam formation as temperatures fall back 
below freezing toward the weekend.

A flood advisory remains in effect for the Looking Glass River near 
Eagle due to elevated levels of water/ice from an ice jam. River 
levels in the vicinity of ice jams will continue to fluctuate by 
several feet until the ice breaks free.