Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Nashville Tennessee
517 am CST Sat Dec 3 2016

Update...
for 12z aviation discussion.

&&

Discussion...

A short period of dry weather looks to come to an end this
afternoon, and chances for precip will remain in the forecast
through next Thursday. Precip looks to move in from the southwest
with the approaching shortwave during the late morning to early
afternoon for areas near the Tennessee/Alabama border and the southern Tennessee
River valley. Precip should cross the Nashville area during the
late afternoon and evening hours, and become widespread across the
area overnight into Sunday morning. A few models still indicate
there will be some chances for mixed precip along the northern
plateau early Sunday morning, but again looks to be just warm
enough to keep all precip rain when comparing the majority of model
data.

Rain will continue Sunday morning for most of the area and
continue to mainly impact eastern zones Sunday afternoon. A trough
moving across the Midwest will help kick out the precip chances
Sunday night into early Monday morning. However the shortwave
trough moving in from northern Mexico/Texas as mentioned in
previous discussions will start to impact the mid state by Monday
afternoon and evening. The trough will be very fast paced, and
will move across the southeast US up the East Coast by Tuesday
evening. The GFS and European model (ecmwf) are in very good agreement still on the
placement of the upper trough, and have it over the region Tuesday
morning. Instability is a little bit less than what was seen
yesterday, but the 0-6km shear still looks to be between 50-70
knots. Left in mention of thunder from Monday afternoon through
Tuesday morning to reflect the dynamic upper trough combined with
low instability and high shear as it passes overhead.

Rain will continue on Tuesday, but as the low quickly moves out to
the northeast, conditions look to be primarily dry overnight
Tuesday and during the day Wednesday. Models disagree slightly on
some backside precip chances, so left in mention of slight chance
pops until better agreement shows up. Another large trough will
move across the Great Plains and bring more precip chances in
Wednesday night into the day Thursday. This trough will be a bit
different than the others as it brings in a shot of Arctic air
behind it. The GFS is just a bit faster with the precip and colder
air, while the European model (ecmwf) is slower and slightly warmer at first. With
the uncertainty of low to mid level temps, put in chances for rain
and snow over the mid state mainly for the overnight and early
morning hours on Thursday. If the European model (ecmwf) solution turns out to be
correct, the backside precip will mainly be flurries and will
likely have no accumulation. The GFS has a bit more quantitative precipitation forecast associated
with the below 0c temps at 850mb, but not very much, so some
areas may see some light accumulation if the GFS pans out. Right
now, however, the uncertainty is high and model agreement is not
high enough to put in any accumulation.

Precip should move out Thursday afternoon, and cold air advection will be very
strong behind the cold front bringing in Arctic air. Lows on
Friday morning will be mainly in the teens across the mid state,
with much of the area not getting above freezing on Friday for
high temps. 850mb temps between the models are still around -12c
to -16c, so if that pans out would not be surprised to see highs
in the low to mid 30s on Friday. Temps will warm a bit Saturday as
some warm air advection moves in ahead of the next trough, with more precip
chances moving in on Sunday with the next cold front.

&&

Aviation...
12z taf discussion.

VFR conditions expected most of the taf period as cirrus continues
to thicken and gradually lower through the day. Light rain
expected to spread northeastward across airports Saturday evening
and continue into Sunday. Late in the current taf period,
cigs/visibility will continue to lower down to MVFR levels. Light
northeast to east winds are anticipated through the taf period.

&&

Ohx watches/warnings/advisories...
none.

&&

$$

Discussion......Barnwell
aviation........shamburger

National Weather Service Glossary of Abbreviations