530 
fxus64 kohx 202324 
afdohx 


Area forecast discussion 
National Weather Service Nashville Tennessee 
624 PM CDT Sat Mar 20 2010 


Update...for 00z tafs. 


&& 


Aviation... 


VFR expected through 12z with light south wind becoming southeast. 
Conditions will deteriorate rapidly from 12z-18z. Arrival of deep 
moisture with approaching low pressure will result in rain showers 
with MVFR ceilings and visibilities at bna by 16z and csv around 18z. 
Embedded convection (downpours) will cause periods of IFR late in 
the taf period (sunday afternoon). 


13 


&& 


Previous discussion... /issued 557 PM CDT Sat Mar 20 2010/ 


Update... 
with radar depicting light showers moving into and across 
locations generally along and west of I-65...have introduced a 
slight chance of showers across this area. Most of the rain 
will not be reaching the ground however...as boundary layer 
conditions expected to remain dry this evening across these 
locations and surface relative humidity values presently in the middle 20s to middle 
40s will climb only slowly during the evening hours also. 


31 


Previous discussion... /issued 253 PM CDT Sat Mar 20 2010/ 


Discussion...surface map at 19z shows trough of low pressure 
lying just across the Ohio and Mississippi rivers, west/ visible 
satellite showing broken cumulus field across middle Tennessee. 
Temperatures were a bit sluggish earlier, but latest readings are 
primarily in the middle to upper 60's, with dew points still in the 
30's. 


Am not introducing any pop's until after midnight, and even then 
mainly in the west. GFS drags the surface cold front across middle 
Tennessee from late morning through late afternoon, with the low 
pressure center clipping the northwest corner of middle Tennessee 
during the afternoon. 


System is not vertically stacked, so the upper low won't come 
across until Monday. Since the upper low passes just to our south, 
middle Tennessee will find itself on the cold side of the low. 
With temperatures dropping significantly once the Post-frontal air 
mass enters the middle state, we'll see 850 temperatures drop to -6c 
to -8c by 12z Monday, with snow developing aloft. Looking at 
various model soundings, believe boundary layer temperatures 
will stay just above freezing, so am looking for a rain/snow 
mixture late Sunday night and early morning morning. 


Am not forecasting any freezing surface temperatures, and with the 
recent warm spell, believe ground and Road temperatures won't 
allow for any accumulation. 


Temperatures will make a quick recovery from monday's cool 
readings, with 60's back in the forecast by Tuesday. 


Look for high pressure to dominate our weather pattern during the 
middle part of the week, with the next weather system affecting 
the middle state Thursday and Friday. 


Rose 


&& 


Preliminary point temps/pops... 
Nashville 49 63 38 48 / 20 90 70 40 
Clarksville 47 61 35 47 / 30 90 70 40 
Crossville 48 61 33 44 / 10 80 80 50 
Columbia 49 60 37 47 / 30 90 50 40 
Lawrenceburg 50 57 36 46 / 40 90 50 40 
Waverly 48 60 35 47 / 40 90 60 40 


&& 


Ohx watches/warnings/advisories...none. 


&& 


$$