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fxus63 kiwx 220001 
afdiwx 


Area forecast discussion 
National Weather Service northern Indiana 
700 PM EST Friday Nov 21 2008 


Aviation... 
winds to slacken/back significantly as surface based inversion quickly 
develops across snowpack. Little more than high thin cirrus in advance of eastern 
South Dakota shortwave. This wave to dampen considerably into Saturday with 
lowering middle deck clouds. 


&& 


Short term... 
lake effect snow event winding down across Northwest Indiana and 
southwest Michigan. Overnight dominant band through Berrien... 
LaPorte...St Joseph...and into Starke counties responsible for 
heaviest snow degraded earlier this morning as flow backed more 
westerly becoming more multi banded as it shifted NE into early 
this afternoon. Shorter fetch along with reduced lake induced 
instability as warmer air aloft lowered eql heights near bottom of 
growth zone has resulted ni just widely scattered snow showers 
ongoing with coverage continuing to decrease. Expect a rapid end to 
showers as drier warmer air continues to move in and completely 
shuts down the process early this evening. Radar trends at press 
time indicate this is currently ongoing with redevelopment upstream 
over/near the lake falling off significantly in the last hour. 


Overnight lows will be tricky over areas with fresh snow cover as 
flow is expected to be light with surface ridging moving along just to 
our south. Any areas free of cloud cover with heavy snowpack could 
cool rapidly and have gone below guidance in areas receiving the 
most snow as well as SW County Warning Area closer to center of ridge. Temperatures warm 
slightly Saturday afternoon with return flow around west side of 
ridge but will be tempered over snow cover and under incoming clouds 
in the afternoon associated with weakening middle level shortwave. Temperatures 
Saturday night somewhat warmer as southerly flow overspreads the 
County Warning Area. 


&& 


Long term... 
active pattn still in place west/strong SW trough off Washington coast this 
afternoon. This system will flatten short amplitude ridge over the northern 
rockies early Sat and amplify quickly southeastward sun/Sun night. Still 
some degree of uncertainty west/regard to how fast rtn moisture plume 
advtg off Gomex gets entrained into this deepening system but by all 
accounts...12z models across the board quicker to entrain sig moisture 
into this system and faster at breaking out precipitation lt Sun night. 
Secondary concerns lie west/how fast lls warm out ahead west/initially 
pronounced thermal ridging breaking down quickly as deep layered 
ascent develops along west/increasing diabatic cooling. Prior mixed 
mention was retained lt Sun night into Monday am before going west/an all 
snow mention after that. 


Otherwise another lake enhanced snow likely Monday night/Tuesday as deep upper 
trough develops through the Ohio Valley but not expected to be as intense as 
this past event per prognosticated 850mb temperatures which at this point are 
considerably warmer. However long axis fetch within deep cyclonic follow 
and deep synoptic scale moisture in the least warrant expanding and 
upping going probability of precipitation across County Warning Area. 


Moderating temperatures short term into sun ahead of this system before cooling back 
down Monday/Tuesday and then near normal into Thanksgiving. 


&& 


Iwx watches/warnings/advisories... 
in...none. 
Michigan...none. 
Ohio...none. 
Lm...Small Craft Advisory until 8 am EST Saturday for lmz043-046. 


&& 


$$ 


Short term...Ludington 
long term...holsten 
aviation...Ludington