159 
fxus64 kmeg 211109 
afdmeg 


Area forecast discussion 
National Weather Service Memphis Tennessee 
509 am CST Friday Nov 21 2008 




Previous discussion... /issued 332 am CST Friday Nov 21 2008/ 


Discussion... 
upper level pattern will remain progressive through the next 7 
days...typical for late November. 


09z surface map showed Arctic high pressure centered over 
northeast Kansas...with the associated cold front driven several 
hundred miles off the Gulf shore. Temperatures over the midsouth averaged 
near 30f...while upstream temperatures over central and northern Iowa were 
in the single digits. The Arctic airmass was typically very 
dry...as noted by dewpoints near 10f as close as southern MO. 


By late afternoon...surface pressure gradient over the midsouth will 
relax...as the high pressure center moves into the Ozarks. Cold 
advection will only be partially offset by full Sun. Afternoon 
temperatures will average 15 to 18 degrees below normal. Despite the 
cold temperatures...minimum relative humidities will drop below 30 
percent in most locations. By tonight...the lax pressure 
gradient...very low dewpoints and clear skies will allow for 
prime radiational cooling conditions. GFS MOS guidance appears 
several degrees too warm and will undercut accordingly. 


Saturday will see the surface high pressure center move to northern 
Georgia...allowing light surface return flow to commence over the 
midsouth. A midlevel shortwave will drop through Ohio Valley 
Saturday afternoon...but will be moisture starved and have little 
impact. 


Sunday will see low level Gulf moisture lift into East Texas...in 
advance of a sharpening midlevel trough dropping into the MS River 
Valley Sunday night. The models have been very consistent in 
lifting the low level moisture axis east into the midsouth late 
Sunday night. Expect the subcloud layer to eventually saturate...given 
the moisture advection and synoptic lift moving into the midsouth 
late Sunday/early Monday. 


The rain will clear the midsouth by Monday afternoon...in the wake 
of the departing upper trough. The remainder of the week will see 
upper level riding lift from Texas into the MS River Valley by 
Thursday...moderating temperatures. Both GFS and European model (ecmwf) models develop 
deep strengthening temperature and moisture advection by 
Thursday...in advance of an upper level trough. GFS is slightly 
faster than the European model (ecmwf) with this trough. A compromise solution would 
bring scattered showers into the midsouth late Thursday... 
continuing through Friday. 


Pwb 


&& 


Aviation... 
for 12z taf cycle 


VFR conditions expected over next 24 hours. Northerly winds have 
died down over the last couple of hours. However...expect an 
increase in speeds after sunrise. Winds will quickly subside after 00z 
as the high settles over the County Warning Area. 


Krm 


&& 




Preliminary point temps/pops... 
mem 43 27 52 34 / 0 0 0 0 
mkl 43 15 49 24 / 0 0 0 0 
jbr 42 19 49 27 / 0 0 0 0 
tup 45 22 53 26 / 0 0 0 0 


&& 


Meg watches/warnings/advisories... 
Arkansas...none. 
MO...none. 
MS...none. 
Tennessee...none. 
&& 


$$