Area Forecast Discussion
Issued by NWS Nashville, TN
FXUS64 KOHX 041636
Area Forecast Discussion
National Weather Service Nashville TN
1036 AM CST Sun Dec 4 2016
FOR 18Z AVIATION DISCUSSION.
Ongoing rainfall has continued overnight, and looks to impact most
of the mid state through the morning hours. Models have most of
the precip over the eastern portion of the CWA by this afternoon.
KCSV ASOS has been reporting unknown precip with temperatures
holding around 37, so the potential is still there for areas north
of there along the Plateau to see some snow mix in this morning.
Radar shows the melting layer to be around 7500 ft above that
area, but Pickett and Fentress Counties might be just cold enough
before sunrise to see some snowflakes mix with the rain.
Chances for rain will linger into this evening as well, and for
the overnight hours mainly have slight chances for the Plateau
before the next shortwave moves in from northern Mexico/Texas
Tuesday morning. Precip chances will increase from the south
during the day on Monday, with the entire mid state seeing rain by
the late evening. Kept in mention of thunder from late Monday
afternoon through Tuesday morning as 100-400 J/kg of MUCAPE as
well as 50-70 knots of 0-6km shear still exist between the models.
The upper shortwave trough will also be overhead or nearby
depending on which model you choose, so all those factors will be
in place to continue to leave in mention of thunder for now.
Besides the chances for thunderstorms, ongoing rain will continue
Monday night into Tuesday morning as the fast paced upper
shortwave heads to the northeast. Precip chances will linger in
the morning before most of the mid state sees a break from precip
by Tuesday afternoon. Kept late Tuesday night and Wednesday dry
for now even though the GFS has some scattered precip over the mid
state. Other models are keeping things dry, so backed off pops a
Thursday is when things get a little interesting. The GFS and
ECMWF have further separated themselves and are making the
forecast a bit more difficult. The GFS has moved the broad upper
trough across the Midwest faster than the ECMWF, is now much
drier, and much colder. The ECMWF is a little slower by about 18
hours, remains warmer than the GFS, and has increased its QPF
output over the area. Since the GFS is drier, all we will see if
the GFS pans out is some light rain late Wednesday and maybe some
flurries after the cold front moves through Thursday night. The
ECMWF will have more rainfall starting overnight Wednesday and
switch over to mainly snow by Thursday afternoon. Went with a
consensus and persistence forecast and mainly kept Thursday
unchanged, leaving in mention of a rain snow mix for most of the
mid state overnight Wednesday and into Thursday morning.
Thursday night through most of the day Saturday dry conditions
return as CAA dominates the region and zonal flow returns aloft.
Warm air will work its way into the region Saturday, but before
then, we will see winter arrive with lows Friday morning mainly in
the teens and highs Friday only in the low to mid 30s. With some
weak WAA highs will be in the upper 30s to low 40s Saturday ahead
of the next trough moving in from the Great Plains on Sunday. The
GFS and ECMWF are a bit different on this trough, with the ECMWF
being warmer and bringing more rain, while the GFS is more
aggressive with the cold air and gives us some backside snowfall
behind the cold front. For now, again went with a consensus blend
and have mention for a rain snow mix Saturday night and Sunday
night with rain during the day on Sunday.
18Z TAF DISCUSSION.
BNA/CKV/CSV...An inverted trough attached to a low centered off
the Gulf Coast is currently stretching into West Tennessee, with a
broad area of drizzle, fog, and MVFR/IFR ceilings covering Middle
Tennessee. Expect these conditions to remain largely unchanged
until this evening when the trough passes through and winds shift
to the NW. However, improvement will be gradual, and we likely
won`t see VFR wx again until after 12Z.