074 
fxus64 kmeg 210527 
afdmeg 


Area forecast discussion 
National Weather Service Memphis Tennessee 
1127 PM CST Thursday Nov 20 2008 


Discussion... 
updated for 06z aviation discussion. 


&& 


Previous discussion... /issued 941 PM CST Thursday Nov 20 2008/ 


Update... 


Very cold air is pouring into the middle south this evening on gusty 
north winds. The winds are generally 15 miles per hour with gusts to around 
30 miles per hour at some places. Temperatures are steadily dropping despite the 
wind with readings ranging from the lower 30s north to around 40 
south. As a result of the wind and cold temperatures wind chills have 
fallen well into the 20s. Expect low temperatures by morning to range 
from the low 20s north to upper 20s south with northerly winds 
still at 10 to 15 miles per hour. Meanwhile some stratocu associated with the 
cold airmass continues to move across mainly west Tennessee. This 
cloudiness will clear out late tonight. Will update the forecast to 
increase winds and to adjust sky cover for west Tennessee. 


Sjm 


Previous discussion... /issued 328 PM CST Thursday Nov 20 2008/ 


Discussion... 


A polar airmass continues to filter southward into the forecast 
area this afternoon behind a strong cold front that moved through 
early this morning. Strong low level cold air advection will 
continue through tonight as a 1044mb surface high pressure system 
currently positioned over the Dakotas moves southward. The strong 
cold air advection and associated tightened pressure gradient 
should keep winds brisk and gusty until well after midnight. These 
winds and scattered cloud cover over northern sections will 
prevent temperatures from dropping too low...although with that 
said it should still be a cold night with wind chills becoming an 
issue after sunset. Overnight lows will still average several 
degrees below normal. 


The cold winterlike temperatures will persist into the weekend as 
strong high pressure settles over the middle south. Skies should 
remain clear to mostly clear through Saturday night with high 
temperatures on Friday struggling to reach the middle 40s south and 
the upper 30s over northern sections. These temperatures will be 
15 to 20 degrees below normal. A very cold morning is expected 
Saturday morning as high pressure moves directly over the middle 
south and ideal radiational cooling conditions set up...with the 
atmosphere decoupling. This will allow temperatures to drop into 
the middle and upper teens along the Tennessee River valley in west 
Tennessee and far northeast Mississippi to the low and middle 20s 
elsewhere. Cool temperatures along with an increase in clouds can 
be expected on Sunday ahead of the next approaching storm system. 


By Sunday night...surface high pressure will slowly retreat east 
as a rather potent shortwave and associated cold front approach 
from the west. The flow in the low levels should turn 
southwesterly and help to advect deeper moisture northward and 
overtop of the stable low level airmass which will still remain in 
place. This overrunning scenario should help to eventually moisten 
the atmosphere suffiently later Sunday night to support some light 
rain...especially over areas along and west of the Mississippi 
River. The airmass should start out rather dry in the low 
levels...so it may take several hours before the airmass supports 
precipitation. Isentropic lift along with frontal lift will 
support chance to likely probability of precipitation over much of the middle south on 
Monday. Although probability of precipitation will increase...still not expecting more 
than just some light rain...keeping quantitative precipitation forecast values around a third of 
an inch or less. The cold front will move east by Monday evening 
bringing an end to any rainfall. 


High pressure will build back over the middle south for the middle of 
next week with a return of dry weather and continued slightly below 
average temperatures. 


Jlh 


&& 


Aviation... 
for 06z taf cycle 


Gusty north winds continue to blow mainly over the eastern half of 
the forecast area with some scattered clouds around 4000 feet. The 
clouds and gusty winds should continue until around 11z. Skies 
should remain clear after 11z with less gusty north winds. 


Ars 


&& 


Preliminary point temps/pops... 
mem 30 44 26 51 / 0 0 0 0 
mkl 24 40 18 46 / 0 0 0 0 
jbr 25 41 22 50 / 0 0 0 0 
tup 29 45 22 51 / 0 0 0 0 


&& 


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


$$