324 
fxus64 kmeg 211750 
afdmeg 


Area forecast discussion 
National Weather Service Memphis Tennessee 
1150 am CST Sat Nov 21 2009 


Update... 


Updated aviation discussion for 18z tafs. 


&& 


Discussion... 


/issued 1051 am CST Sat Nov 21 2009/ 


Update...an upper level low and associated surface low are 
located across the Texas/Louisiana coast this morning. Regional 
WSR-88D radar trends/metar observations indicate no precipitation 
reaching the ground thus far across the middle south. 12z WRF/GFS 
short term models indicate most of the forecast area will remain 
dry this afternoon. Will add a slight chance of rain showers 
across the southern two tiers of counties across east Arkansas 
south of I-40 and across north Mississippi as isentropic ascent 
will increase across these areas...especially towards early 
evening. Will make slight adjustments to other forecast elements 
as needed. Otherwise...forecast in good shape. 


Updated grids will be published shortly. 


Cjc 


&& 


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... 


18z tafs 


At kmem...kmkl...and kjbr...VFR conditions are expected through 
18z Sunday with east winds. Ceilings will develop and slowly 
lower. -Ra may get close to kmem and kmkl after 11z...but think 
most -ra will stay south and east of these sites...so did not 
mention in tafs. MVFR ceilings may get close to kmem and kmkl 
after 16z...but chose to keep out of taf for now thinking these 
lower ceilings will move into these sites after 18z. 


At ktup...VFR conditions are expected through 06z...then 
deteriorating conditions can be expected...especially 06-15z as 
-ra moves into this site. MVFR conditions will develop 07-10z. IFR 
conditions are possible anytime after 09z...but did not mention in 
tafs at this time with low confidence of occurrence. 


Mbs 


&& 


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


&& 


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


$$