Weather

471 
fxus64 kmeg 060115 
afdmeg 


Area forecast discussion 
National Weather Service Memphis Tennessee 
715 PM CST Monday Jan 5 2009 


Discussion... 


Lots to consider late this afternoon into early evening. Mesoscale 
observations around the middle south indicate temperatures hovering 
around the freezing mark roughly along and north of a Paris to 
West Memphis to West Helena line. Pockets of much colder air 
reside where the Ice Storm Warning has been posted which includes 
Wynne to Jonesboro...Blytheville...the Missouri bootheel and 
northwest Tennessee. Temperatures here were in the upper 20s and 
will likely remain well below freezing. 


Rain beginning to increase over southern Arkansas spreading 
northeast toward the forecast area. This precipitation moving into 
the colder region will pose the most significant threat overnight. 
Ice accumulations over one quarter inch are likely over the Ice 
Storm Warning outlined above. 


In the meantime...temperatures hovering around 32 degrees mainly 
along and south of Interstate 40 will begin to warm slightly. By 3 
am enough warm air should move in and bring an end to the freezing 
rain. However...rain will persist through the day Tuesday. Heavier 
rain still a possibility so the Flash Flood Watch continues over 
parts of north Mississippi. 


Ac 


&& 


Previous discussion... /issued 351 PM CST Monday Jan 5 2009/ 


Discussion... 
very complex forecast for the short term. Knqa radar showed 
widespread light to moderate precipitation containing over the 
midsouth at discussion time. 21z surface map showed the freezing 
line running roughly along a Helena Arkansas...to Midtown Memphis to 
Huntington Tennessee. North MS was mild by comparison...with 
temperatures in the upper 40s to lower 40s. This warmer region was where 
radar was showing stronger returns around 40 dbz. Will continue 
the inherited Flash Flood Watch to the south of Memphis...with 
additional moderate to occasionally heavy rain expected later 
tonight. 


For the evening...expect the status quo until the warmer air from 
MS filters north late in the evening and early overnight. Nam12 
1000mb to 950mb thicknesses increase overnight...with the 408 meter 
thicknesses confined to the higher elevations of northeast 
Arkansas...northwest of Jonesboro. Accounting for some model 
error...have maintained the Winter Weather Advisory over all of 
northeast Arkansas...the MO bootheel and northwest Tennessee through 9 am 
Tuesday. Evening shift will monitor for ice accumulations 
exceeding one quarter inch to the west and northwest of Memphis. 
For now...best quantitative precipitation forecast appears will be east of this area...in the 
warmer air overnight. 


Rain should exit the midsouth late Tuesday night...but some light 
rain and snow mix will be possible mainly north of Memphis early 
Wednesday morning. Thereafter...dry northwest flow aloft will 
prevail through Friday. GFS forecasts some low level moisture return 
ahead of a cold front Saturday morning. Temperatures should be warm 
enough for prefrontal precipitation to remain liquid Saturday morning... 
but it may be close. Followed a GFS/European model (ecmwf) blend for the latter half 
of the week. 


Pwb 


&& 


Aviation... 


00z taf cycle 


Busy weather at the terminals tonight with widespread 
precipitation sheild primarily southeast of a Obion to Cherry 
Valley line as of 00z. Expect that another upper level disturbance 
will reintensify the warm advection regime aloft and allow heavier 
precipitation to redevelop across the northern taf 
sites...including mem and jbr by 03z. Precipitation should 
continue through the night at the mkl and tup sites with little in 
the way of breaks. The next issue is ptype at mem and jbr. The 
freezing line remains positioned at 00z from Helena to Memphis to 
north of Jackson. Don't see much of a reason for a significant 
northward shift of the freezing line tonight as low level winds 
will remain northeasterly and there remain a lack of a strong 
pressure system. At mem...think that ptype will remain liquid with 
temperatures hovering just above freezing. Think that at jbr...once 
precipitation redevelops...should fall as -fzra as temperatures should remain 
below freezing tonight. Slow warmup tomorrow may try to change 
lingering precipitation to liquid at jbr by middle day tomorrow but 
confidence still low. 


Jlh 


&& 




Preliminary point temps/pops... 
mem 34 46 38 47 / 100 90 60 10 
mkl 35 46 36 42 / 100 90 80 20 
jbr 29 42 33 46 / 100 70 40 10 
tup 40 53 41 46 / 100 100 90 20 


&& 


Meg watches/warnings/advisories... 
Arkansas...Winter Weather Advisory until 9 am CST Tuesday for Clay-Greene- 
Lawrence-Randolph. 


Winter Weather Advisory until 3 am CST Tuesday for Crittenden- 
Lee AR-Phillips-St. Francis. 


Ice Storm Warning until 9 am CST Tuesday for Craighead-cross- 
Mississippi-Poinsett. 


MO...Ice Storm Warning until 9 am CST Tuesday for Dunklin-Pemiscot. 


MS...Flash Flood Watch through Tuesday afternoon for Calhoun- 
Chickasaw-Coahoma-Itawamba-Lafayette-Lee MS-Monroe-Panola- 
Pontotoc-Prentiss-Quitman-Tallahatchie-Tishomingo-Union- 
Yalobusha. 


Tennessee...Winter Weather Advisory until 3 am CST Tuesday for Carroll- 
Chester-Decatur-Fayette-Hardeman-Haywood-Henderson-Henry- 
Madison-Shelby-Tipton. 


Ice Storm Warning until 9 am CST Tuesday for Crockett-Dyer- 
Gibson-Lake-Lauderdale-Obion-Weakley. 


&& 


$$