Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Memphis Tennessee
1131 PM CST Sat Dec 20 2014
updated for 06z aviation discussion below.
Previous discussion... /issued 844 PM CST Sat Dec 20 2014/
Currently...temperatures have already fallen quickly into the low and middle
30s across much of middle Tennessee and upper 30s to low 40s
across northern Mississippi. With a surface ridge nosing into the
midsouth...near ideal conditions exist for a significant
radiational component to the cooling tonight. The exception to
this is across eastern Arkansas where a scattered to broken cloud
deck exists. Guidance isn't consistent in its handling of this
deck but it should be enough to prevent these areas from cooling
as rapidly. A quick warmup is expected tomorrow morning after
sunrise but a cold morning is expected early.
Previous discussion... /issued 231 PM CST Sat Dec 20 2014/
Discussion...surface analysis this afternoon places a 1025 mb
ridge of high pressure over the lower Mississippi Valley this
afternoon. Residual low level moisture trapped below a
subsidence inversion has resulted in partly sunny sunny skies
north of I-40...while areas to the south have remained mostly
sunny. As of 2 PM CDT...temperatures are in the 40s to lower 50s
across the middle south.
Short term...(tonight through tuesday)...surface high pressure
will bring precipitation free weather to the middle south tonight.
This area of high pressure will gradually move east Sunday and
Sunday night with southerly return flow on the backside of high
pressure and southwest upper level flow returning to the middle
south. Rain chances during the day Monday appear to be minimal and
went with slight chance at best for now. Better chances for
showers and perhaps a thunderstorm or two will come Monday night
and especially Tuesday as an upper level trough over the plains
begins to move into the Mississippi Valley. Best chances for
thunderstorms at this time appears to be better over northeast
Mississippi where better instability and steeper lapse rates will
reside. A cold front will pass through the area Tuesday. Some
residual moisture associated with an upper level low will produce
a potential for some rain showers and/or snow showers across the
middle south Wednesday morning.
Long term...(christmas day through saturday)...long term models
suggest surface and upper level ridging will build back in across
the lower Mississippi Valley on Wednesday night and persist across
the area through Christmas night. Another cold front is expected
to pass through the region Friday into Saturday...bringing another
potential of precipitation back to the middle south.
MVFR ceilings may edge in an out of the jbr vicinity overnight...near the
eastern edge of an elevated stratus deck over the Ozark Plateau.
Otherwise...VFR and light winds will prevail over the midsouth taf
sites through the next 24 hours.