465 
fxus64 kmeg 211148 
afdmeg 


Area forecast discussion 
National Weather Service Memphis Tennessee 
548 am CST Sat Nov 21 2009 


Update... 


Updated for 12z taf discussion. 


&& 


Previous discussion... /issued 329 am CST Sat Nov 21 2009/ 


Discussion... 


Main forecast concerns through the period are rain chances today 
through Sunday and how cold the extended may get. 


Today through Sunday...models have been trending back on precipitation 
chances through this weekend with each run. Forecast soundings 
indicate quite a bit of dry air near the surface across the County Warning Area 
through this afternoon. There is so much dry air in fact that I 
was able to remove all probability of precipitation. Model quantitative precipitation forecast through 00z is a hundredth 
or less...and along the southern border of the County Warning Area. Highs today 
are a bit tricky given the potential for clouds to keep them lower 
than guidance indicates...but with a reduced threat for rain and 
925 mb temperatures of +10 to +11c...low to middle 60s seems like a good 
bet and is close to MOS. 


Isentropic lift increases tonight and the lower levels of the 
atmosphere will attempt to saturate as low pressure over the 
northwestern Gulf tracks east to the Florida Panhandle. Models 
have shunted the best quantitative precipitation forecast south of the area and this trend may 
continue if the low stays offshore. Was not confident to continue 
the categorical probability of precipitation...so trimmed them back to likely over the 
south and tapered them off quickly to slight chance just south of 
kmem. Some rain will linger through Sunday over the southeast... 
with mostly cloudy conditions elsewhere. 


Sunday night through next week...high pressure builds in Sunday 
night into Monday night. Forecast soundings indicate a lot of low 
level moisture trapped under an inversion around 5 kft. The result 
may be a lot of residual cloudiness. 


The next system to watch develops over the northern plains Monday 
and rapidly becomes negatively tilted by Tuesday near Iowa. This 
will cause a rather potent cold front to swing through Tuesday or 
Tuesday night. The GFS and European model (ecmwf) are at odds with timing...so will 
account for this and keep probability of precipitation going Tuesday and Tuesday night. It 
does not appear the front will have a lot of moisture to work with 
and it will be moving rather quickly...so rainfall amounts will be 
light. 


A cool northwesterly flow will settle in for Thanksgiving with 
highs likely remaining only in the 40s...especially north of I-40. 


It should be noted that if Memphis misses the rainfall today 
through Sunday as expected...and rainfall amounts remain light 
Tuesday...they will have a very good chance at breaking the record 
for driest November on record. It is very unusual to have a record 
wet month followed immediately by a record dry month for sure. 


Borghoff 


&& 


Aviation... 


12z taf cycle 


Middle and high level cloud cover will continue to overspread the middle 
south through the day...but VFR conditions will prevail. Light 
rain will likely develop tonight at tup towards midnight with MVFR 
conditions developing. Elsewhere...rainfree conditions should 
continue tonight with VFR ceilings and visbys expected. Winds should 
remain light (< 7 kts) through the period. 


Jlh 


&& 


Preliminary point temps/pops... 
mem 67 49 63 45 / 10 20 10 10 
mkl 66 45 60 41 / 10 10 10 10 
jbr 65 44 62 41 / 10 10 10 0 
tup 63 48 57 46 / 10 70 30 10 


&& 


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


$$