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Area forecast discussion 
National Weather Service Memphis Tennessee
525 am CST Sat Dec 27 2014

Update...

Updated aviation discussion for 12z tafs

&&

Discussion... /issued 425 am CST Sat Dec 27 2014/

A deep positively tilted upper level trough axis was stretched
from the upper Mississippi Valley southwestward into The Four
Corners region early this morning. At the surface...a slow moving
cold front was progressing eastward and was located from southwest
Missouri into northwest Arkansas back through the arklatex region.
Deep moisture continues to advect northward ahead of the front and
with large scale ascent increasing in association with the
approach of the upper trough...scattered showers and a few
thunderstorms have developed and are moving across the middle south
this morning. Coverage of showers and a few thunderstorms should
increase later today with most locations picking up anywhere
between one quarter and one half of an inch of rainfall by days
end. Elevated instability should be sufficient across the southern
two thirds of the forecast area to support thunder but not
expecting anything in the way of severe weather.

As an initial shortwave ejects northeast into the Mississippi
Valley later today...surface low pressure is expected to develop
along the frontal boundary along the Upper Texas coast. This
surface low will lift northeast along the front into northeast
Mississippi tonight. This may help to focus heavier rainfall and
thunderstorms across this region where a couple of additional
inches of rainfall will be possible beginning later this evening
and continuing into Sunday morning. There may be a temporary lull
in the rainfall later Sunday morning into early afternoon...but
this should be shortlived as a secondary shortwave ejects from
northeast Texas towards the middle south. By Sunday evening...the
front will have moved southeast of the entire area...but another
surface low pressure system will move northeast along the front
and bring another round of rain into northeast Mississippi Sunday
evening through Sunday night. Anywhere between 2 and 3 inches of
rainfall will be common across portions of northeast Mississippi
from this evening through Sunday evening...with isolated higher
amounts. Considering the potential for thunderstorms in this area
and heavy rainfall amounts...have issued a Flash Flood Watch from
00z Sunday through 00z Monday across portions of northeast
Mississippi.

Rain should come to an end areawide by Monday morning with high
pressure building over the middle south with dry conditions and
seasonably cool temperatures. An Arctic cold front moving south
across the plains states Monday will move through the middle south on
Tuesday. Limited moisture should allow the front to pass through
mostly dry...but this will usher in a much colder airmass for the
middle of next week.

Medium range model guidance continues to suggest an active
southern stream towards the end of next week with another strong
upper low lifting northeast from the Desert Southwest. This should
help to advect moisture and lift northward into the middle south by
Thursday night. As the residual Arctic airmass remains in
place...a wintry mix of precipitation will be possible. Warmer
temperatures should eventually work northward across the region
from south to north on Friday...with wintry precipitation
gradually transitioning to all rain areawide by Friday evening.
Rain chances will continue into next weekend as the upper low
moves into the area. There remains plenty of time to work through
the p-type issues with this system. Stay tuned to the latest on
this storm system and potential impacts as we move into early next
week.

Jlh

Aviation...

12z taf cycle

Scattered showers have been moving across or near all terminals
early this morning with rainfall only expected to increase through
the day. Conditions will rapidly deteoriorate through MVFR to
possibly IFR by afternoon on Saturday as ceilings lower to between 700
and 1000 feet. Also of concern is the development of a few
thunderstorms at mem and tup...generally after 15z at mem and
later toward 20z at tup. Lightning strikes will not be extremely
widespread but enough elevated instability exists for at least a
mention. Guidance is very strongly suggesting that once IFR
conditions develop...they will remain there through the taf valid
period as this system will be very slow to move out.

Tvt

&&

Meg watches/warnings/advisories...
Arkansas...none.
MO...none.
MS...Flash Flood Watch from this evening through Sunday afternoon for
Calhoun-Chickasaw-Itawamba-Lee MS-Monroe-Pontotoc-Prentiss-
Tishomingo.

Tennessee...none.
&&

$$

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