Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Nashville Tennessee
529 am CST sun Feb 14 2016
Today through Tuesday night.
Our main concern is winter weather potential today and
tonight...generally along and north of Interstate 40. Not much
change from the previous forecast. The only changes to the winter
weather advisories included the addition of Van Buren County...and some
minor adjustments to the timing and grouping of counties.
Regional radar shows bands of light snow already getting started
to our northwest. With cold air in place...the precipitation development
this morning over our northwest counties...and midday to afternoon
farther eastward...will be mainly light snow. We have a start time
of 9 am for our first advisory segment. This looks good for
Stewart County...and a few hours on the early side for Nashville
metropolitan...but did not want too many County groups. The air mass is
quite dry...so it may take a little while for any measurable snow
to begin after it develops on radar. The light snow should
gradually expand to the plateau by middle afternoon...while our far
southern counties having just a chance for light rain.
Later this afternoon into tonight...strong warm advection will
transition the snow over to a wintry mix...and then all rain.
This process will go generally from southwest to northeast.
Nashville metropolitan should be pretty much liquid and above freezing
from 6pm Onward. Areas from Dover to Springfield may keep some
surface cold air...meaning a little longer period of sleet or
freezing rain into the evening there. The full transition to rain
will reach the upper Cumberland toward daybreak Monday...so the
upper Cumberland region shows the greatest snow potential...and
the greatest ice potential late tonight. A few spots near the Kentucky
border and across the upper Cumberland could be over achievers in
terms of snow and ice...but given the expected strong atmospheric
warming...and relatively short duration of significant travel
impacts...we believe a Winter Weather Advisory will suffice at
this time rather than upgrading to a warning.
What could go wrong? Well...any winter weather forecast in middle Tennessee has
the potential to fail. This event is classic for middle Tennessee...with our
area in the transition zone between snow to the north and rain to
the south. The most likely way the forecast could go wrong will
be the strong warm advection aloft bringing a change to rain more
quickly...thus cutting down snow amounts. As mentioned
earlier...the forecast could be a little conservative for some
spots along the Kentucky border and upper Cumberland...where there could
still be enough cold air late today...when precipitation rates are
increasing...to give a burst of moderate snow or freezing rain.
Overall...we hope our forecast represents the most reasonable
approach...but updates and adjustments should be expected. The
main impacts from this system will be on travel for areas north of
I 40...and those impacts will disappear quickly with the warming
and precipitation transition.
On Monday...the main feature will be a surface low pressure
system that will lift from the lower MS valley across Tennessee. This
track will focus rainfall over the middle state...with some moderate
rain at times. 1 to 2 inches of rainfall will be common on Monday.
This system will move out Monday night...perhaps a few snowflakes
along the back edge...but no issues.
Another wave will come through on Tuesday with scattered light
Wednesday through Saturday.
There's a slight chance of a lingering light rain/snow mix along
the upper Cumberland early Wednesday. However, after that,we can
kiss the possibility for wintry precipitation goodbye for a while. Mean
upper trough pushes off the East Coast during late week, as upper
ridge builds across the Tennessee Valley. The result will be warmer
temperatures, and by Friday afternoon we'll be looking at highs in
the lower and middle 60s!
A weak cold front drops down into our neck of the Woods by late
Friday, but has little umpf with it and becomes quasi-stationary
near the Ohio River valley by Saturday. As a result, we stay in a
mild and moist southwest flow of air, with at least a small chance
for showers continuing all the way from Friday night through
Saturday night, as moisture funnels up from the western Gulf of
Mexico up across the lower Mississippi and Tennessee valleys.
A potent shortwave drops in from the northwest into the Central
Plains and middle MS valley late in the extended, increasing the
chance for showers by next Sunday.
12z taf discussion.
Flying conditions will deteriorate today as a winter storm moves
in from the northwest.
Although area terminals will start off with VFR conditions early
today, expect conditions at ckv and bna to deteriorate to MVFR by
late morning, in snow, along with occasional IFR conditions during
the afternoon. IFR conditions will prevail at bna and ckv
throughout the night, with snow changing to rain during the
At csv...expect MVFR conditions to develop by middle-afternoon and
continue for the remainder of the forecast period, along with the
possibility for periods of IFR. Snow this afternoon will then mix
with freezing rain and ice pellets during the evening and continue until about 10z,
when precipitation is expected to transition to rain.
Winter Weather Advisory from noon today to 6 am CST Monday for
Winter Weather Advisory from 9 am this morning to midnight CST
tonight for Cheatham-Davidson-Dickson-Houston-Humphreys-