265 
fxus63 klmk 191925 
afdlmk 


Area forecast discussion 
National Weather Service Louisville Kentucky 
325 PM EDT Friday Mar 19 2010 


Short term (tonight and saturday)... 


More clouds Sat but still warm...about 10 degrees above the mean. 


Central rockies trough will evolve to an upper low on its southeastward track into 
the Southern Plains by the end of the period. Surface ridge axis across the eastern Ohio 
Valley will shift to the Middle Atlantic States by Sat morning while 
cold front...at this time from northern Illinois to north central MO...moves southeastward to central 
in...southern Illinois and southeast MO. Model time height cross sections show mainly 
increasing low-middle level moisture Sat...preceding front...but a 
broad dry layer above and a relatively dry layer from 900 mbs down. 
Bottom line for Sat clouds...mostly sunny in the am and partly sunny 
in the PM. 


Temperatures tonight in our lowest lying areas/river valleys... 
especially in our southeastern most counties...will be several degrees 
cooler than the rest of our forecast area...with the greatest decoupling of 
wind there. In general...lows should be in the Lower/Middle 40s. Sat 
temperatures should be similar to today...perhaps a degree or two cooler in our 
northwestern forecast area...where clouds will be most invasive/opaque. 


Long term (saturday night - friday)... 


Saturday night through Tuesday night... 


Latest model runs continue to be in pretty good agreement through 
this portion of the forecast period. In terms of model trends...the 
current set of solutions seems to be a bit slower with the arrival 
of precipitation Saturday night. All of the models show a deep 500 mb 
cutoff low digging through the lower MS valley area. With this 
solution...precipitation will be delayed by about 6-8 hours with 
showers moving into the western sections of the area early Sunday 
morning. Rain coverage should begin to quickly increase Sunday 
morning with the best chances of rain coming Sunday afternoon and 
evening as the frontal occlusion moves east through the region. 
While the models do not show any surface based instability...there 
continues to be some hint of elevated instability that may be enough 
for some isolated rumbles of thunder across the region. Rain 
showers are expected to continue through Sunday night and much of 
Monday. Was a bit concerned about these systems producing enough 
cold air due to the cold core aloft for some mixed precipitation issues. 
However...the latest runs continue to keep the boundary layer 
sufficiently warm enough for all rain late Sunday night and Monday 
morning. As the upper low and surface low move east Monday 
night...clearing will commence in the west Tuesday morning and 
gradually work eastward during Tuesday afternoon. 


Lows Sunday morning will drop into the upper 40s to the lower 50s 
with highs on Sunday topping out in the middle to upper 50s in the west 
and upper 50s to around 60 in the east before frontal passage. Lows 
Sunday night should drop into the upper 30s with highs on Monday in 
the lower to middle 40s. A potential freeze looks possible for 
Monday night and early Tuesday depending on cloud cover. For now 
have adjusted temperatures down a bit in the northwest/west with lower to 
middle 30s. 


Wednesday through Friday... 


Long range model solutions agree that decent middle-level ridge axis 
will be centered across the middle Ohio Valley Wednesday morning. This 
ridge will slowly transition eastward Wednesday night and Thursday 
keeping the forecast area dry and mild through the period. By late 
Thursday...both the GFS and Euro solutions bring a stronger 
middle-level wave through the central United States. Both models try 
to close off the wave but are not successful and the wave looks to 
remain open as it crosses the Ohio Valley around the Friday time 
frame. In the recent trends...the GFS is slightly stronger with its 
wave and has a further south surface solution than the Euro run. Even 
with that said...it appears that a decent rain chance exists on 
Friday and will raise probability of precipitation here quite a bit given the good model 
agreement. 


Temperatures will be mild through the period with highs in the lower 
to middle 60s in the north and upper 60s in the south for Wednesday and 
Thursday. With additional clouds and precipitation expected for 
Friday...temperatures should be about 10-15 degrees cooler with highs in 
the lower to middle 50s. Overnight lows look to be in the lower to middle 
40s. 


&& 


Aviation (18z taf issuance)... 


VFR through the period. 


Upper level trough across the central rockies will reach the southern/Central 
Plains during the period. Associated cold front...from northern Illinois to central MO 
at this time...will extend from southern in to southern Illinois to southeast MO by Sat afternoon with 
clouds...but no precipitation preceding it. Light SW/S winds will precede 
front as well. 


&& 


Lmk watches/warnings/advisories... 
Kentucky...none. 
In...none. 
&& 


$$ 


Short term........dk/11 
long term.........Mj 
aviation..........dk/11