856 
fxus64 kmeg 211458 
afdmeg 


Area forecast discussion 
National Weather Service Memphis Tennessee 
958 am CDT sun Mar 21 2010 


Update... 
updated for falling temperatures and extended mix of rain and snow 
into portions of north central Mississippi...and stronger winds 
across northeast Arkansas. 


&& 


Discussion... 
temperatures continue to fall behind the front across southwest 
Tennessee...eastern Arkansas...and northern Mississippi. Rain has 
quickly changed to snow in Calhoun City on the very backside of 
main rain band where temperatures are in the middle 30s. A mix of rain 
and snow showers will remain possible this afternoon across most 
of northern Mississippi and eastern Arkansas. Northeast winds are 
also stronger across portions of northeast Arkansas in vicinity of 
the surface low center. 


Jab 


&& 


Previous discussion... /issued 715 am CDT sun Mar 21 2010/ 


Update... 
updated to add 12z aviation discussion. 


Previous discussion... /issued 413 am CDT sun Mar 21 2010/ 


Discussion... 


A 1005 mb surface low pressure system was currently positioned 
over eastern Arkansas with a cold front stretching southward from 
the low across eastern Arkansas into southwest Mississippi. Ahead 
of the front...temperatures were still in the low to middle 50s. 
Behind the front across southern Arkansas into northern Louisiana 
temperatures have dropped into the middle and upper 30s. Widespread 
rain continued over much of the middle south early this 
morning...with patchy light precipitation now mixing with or 
changing to light snow showers to our southwest across southern 
Arkansas and northern Louisiana. 


A strong upper level low pressure was still located over 
northeast Texas early this morning. This feature will continue to 
strengthen as it moves east from the arklatex this morning and 
across north-central Mississippi tonight. As this occurs...the 
surface low pressure should become fully occluded to the north of 
the upper low. Colder air associated with this upper low will 
advect across the region from the southwest to the northeast. 
Therefore expect temperatures to first fall across portions of 
northwest Mississippi this morning...then points further northeast 
through the afternoon and overnight. A middle level dry slot noted on 
water vapor imagery early this morning over eastern Louisiana will 
rotate northeastward across the middle south through the day. This 
will help to diminish the intensity and limit the overall coverage of 
precipitation from south to north through the day. Light rain 
showers over northwest Mississippi may mix with light snow showers 
later this morning into this afternoon as temperatures fall into 
the upper 30s. Further north and east...temperature profiles 
should remain warm enough in the warm occlusion zone to keep 
precipitation type as all rain. 


Colder air will spread from southwest to northeast tonight 
allowing for areas southeast of a line from Union City Tennessee 
to Wynne Arkansas to have the potential for light rain showers to 
mix with or change to light snow showers. Deeper moisture and lift 
should return as well tonight in association with the strong upper 
level low pressure moving across southern portions of our forecast 
area. Areas further northwest...including northeast Arkansas and 
the Missouri bootheel will actually remain in the warm occlusion 
area and will likely see precipitation types remain as all rain. 
Any precipitation amounts tonight should remain light and across 
areas where snow does fall...expect temperatures above freezing 
and warm soil temperatures to limit or prevent snow accumulations. 
If snow were to fall at a heavier rate than currently 
expected...then light snow accumulations would be possible. At 
this time this does not appear likely. 


The upper level low pressure will move east of the middle south on 
Monday. Lingering light rain or snow showers early in the morning 
will change to all rain by late morning into the afternoon hours 
as the cold core low pulls east and low-middle level temperatures 
warm. Light rain showers should end from west to east through the 
day. 


High pressure both at the surface and aloft should build over the 
middle south on Tuesday and persist into the day Thursday. Rapidly 
rising heights and return low level southerly flow should allow 
temperatures to quickly rebound back to above average levels for 
Tuesday through Thursday. An upper level disturbance and 
associated cold front will move across the area Thursday evening 
through Friday. This system will be accompanied by a round of 
showers and thunderstorms. Considering several days of return flow 
off the Gulf of Mexico will need to watch for potential strong 
storms as dewpoints attempt to surge back into the upper 50s. This 
system is still several days away with plenty of time to monitor 
storm intensity and potential. Temperatures behind the end of the 
week front should remain mild with no big cool Downs expected 
through the extended forecast period. 


Jlh 


Aviation... 
12z taf cycle 


Occluded low moving through lower Mississippi Valley as of 12z taf 
issuance...producing MVFR and occasional IFR conditions. 
Conditions expected to improve to MVFR by this afternoon as 
rain briefly comes to an end. Additional precipitation and IFR 
ceilings are anticipated tonight as wrap around moisture around 
the low moves through all sites. Did not include snow in tafs as 
confidence/impacts too low to justify mention in forecast. Winds 
will veer south/southwest this morning and gradually veer 
west/northwest by tonight. 


Cjc 


&& 


Preliminary point temps/pops... 
mem 47 34 54 46 / 100 60 40 0 
mkl 52 34 50 42 / 100 50 40 10 
jbr 48 38 54 42 / 100 80 40 0 
tup 50 34 50 44 / 100 50 30 0 


&& 


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


$$