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fxus63 kgrr 072116 
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Area forecast discussion 
National Weather Service Grand Rapids Michigan 
410 PM EST Wednesday Jan 7 2009 


Latest update...all but long term... 


Synopsis...(410 PM EST Wednesday Jan 7 2009) 
low pressure east of Michigan will produce periods of light snow 
tonight and Thursday before pulling away from the region. West winds 
off the warmer waters of Lake Michigan will result in some 
enhancement to the snow south and west of Grand Rapids tonight. 


A low pressure system tracking southeast from the northern plains 
will bring the threat of widespread accumulating snow Friday and 
Friday night. 


&& 


Short term...(410 PM EST Wednesday Jan 7 2009) 
(tonight through Friday night) 
deep and moist cyclonic flow over the region will result in a 
continuation of periodic light snow tonight. Additional 
accumulations will be generally on the light side at only an inch or 
less... with the exception of where lake enhancement produces 
heavier snow bands. 


Nam12 has been indicating a flare up of lake effect this afternoon 
and evening west and south of GRR... which has now come to fruition 
per recent radar trends and surface observation. Azo and biv have both been down 
to 1/2 visible under these heavier bands. BUFKIT overviews from biv to 
azo and btl show strong upward vertical velocity/S from 00z to 12z below about 8k feet 
tonight... with the dgz located in roughly the 5-8k feet layer. No 
inversion is present in the forecast soundings either. Will call for 
localized 3 to 6 inches through Thursday morning. 


Also of concern is fact that models crank up the winds in this same 
area tonight which will likely result in some lower visibilities in 
blowing snow. Believe the heaviest part of this event will end 
around 12z Thursday... but will have the lake effect Snow Advisory 
run until 11 am just in case it GOES beyond that time. We can always 
cancel early. 


As far as the event for Friday and Friday night... closely followed 
the GFS for guidance as it is in close agreement to the European model (ecmwf) and 
the global Gem. The NAM does not appear to be handling this system 
well and have discarded it/S slower and farther north solution. At this time 
it looks like a potential 3-6 inch snowfall over the central and southern 
portions of the County warning forecast area... with lesser amounts in the northern County warning forecast area. 


&& 


Long term...(302 PM EST Wednesday Jan 7 2009) 
(saturday through wednesday) 
the long term is going to be rather snowy and cold. The main concern 
deals with the Arctic blast expected Monday evening. The European model (ecmwf) and 
GFS are in decent agreement showing an Arctic blast moving in behind 
a clipper Monday evening. The clipper will likely bring some light 
snow and then More Lake effect will follow. 1000-500 mb thickness 
around 485dm and 800 mb temperatures near -27c mean very cold air moving into 
lower Michigan. Expect highs in the teens Tuesday with single digits 
possible in the northeast County Warning Area. Wind chills will be in the 10 to 20 
below range. The Arctic air will last into Wednesday. 


In addition to the cold weather...the extended period looks snowy too. 
The European model (ecmwf) and GFS are in disagreement in the track of a low moving 
through the region Saturday. The the NAM is the farthest north. Am 
leaning toward the European model (ecmwf)/GFS at this point which takes the low south 
of the County Warning Area and means both synoptic snow and lake effect snows 
Saturday and lake effect snow showers Sunday. Snow showers will 
continue into middle week...although snowfall accums are hard to pin 
down. The Arctic air will push the dgz down to near the surface and 
limit the depth. I suspect the Crystal size will be small which will 
limit the accums. 


&& 


Marine...(410 PM EST Wednesday Jan 7 2009) 
northwest flow will be increasing tonight and continuing Thursday... 
especially south of mkg where models are showing 30kts at 925mb. 
Arrival of the surface ridge on Thursday night should allow conditions 
to settle back down below Small Craft Advisory criteria. 


&& 


Aviation...(410 PM EST Wednesday Jan 7 2009) 
light snow is expected to continue during the next 24 hours... 
although some heavier lake effect bands may impact azo and btl at 
times tonight and early Thursday. Visibilities generally in the 2-4sm range 
and ceilings around 1.5k feet... although azo and btl may briefly drop to 
1/2sm or less in heavier lake bands. 




&& 


Hydrology...(410 PM EST Wednesday Jan 7 2009) 
no immediate Hydro concerns for the next couple of days as all 
precipitation will be in the form of snowfall. The biggest concern 
will be the colder weather pattern shaping up over the course of the 
next week. This colder weather will likely produce some ice jams at 
the normally favored locations. This will be something that will be 
monitored. 


&& 


GRR watches/warnings/advisories... 
Michigan...Lake effect Snow Advisory in effect until 11 am EST Thursday 
for Ottawa Allegan Barry Van Buren Kalamazoo Calhoun cos. 
Lm...Small Craft Advisory through Thursday from St. Joe through 
Manistee. 


&& 


$$ 


Synopsis: Meade 
short term: Meade 
long term: 93 
marine: Meade 
aviation: 93/Meade 
hydrology: njj/Meade