Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS64 KMRX 030748

Area Forecast Discussion
National Weather Service Morristown TN
248 AM EST Sat Dec 3 2016

.SHORT TERM (Today through Sunday morning)...
The low pressure trough over the Rockies and Desert SW tonight will
split into a southern stream closed low that will slowly track east
into northern Mexico, and a more progressive northern stream trough
that will move into the MS Valley on Sunday. The southern stream
low will spread a deep flow of moisture across the Southeast today,
with isentropic lift increasing in our southern sections this
evening as the northern stream trough approaches. Lift continues
to strengthen as the 850 mb low moves into West TN Sunday morning,
with a convergence zone extending east across the southern TN
border. Will have POPs in the categorical range from late tonight
through noon Sunday. As the precip spreads in tonight, temperatures
in the northern mountains and SW VA may support a little snow,
mainly at or above 3000 ft. With initial QPF amounts in the
northern half being light while temperatures are cold enough, there
should be little accumulation before warm advection raises
temperatures Sunday morning.

.LONG TERM (Sunday through Friday)...
Rain chances will continue through the day on Sunday as the
atmosphere remains relatively moist. The better chances for
precipitation on Sunday will be in our Southern counties closer to
the boundary near the Gulf of Mexico. Models are in some
disagreement with when/if the precipitation will end before our
next round begins. GFS wants to move the precipitation south of us
by Monday morning and slowly bring in the low pressure system from
Mexico/Texas by Monday night. The ECMWF looks to hold on to rain
chances a bit longer and keep the precipitation present in our
southern counties through Monday. The European solution is also a
bit faster in bringing in precipitation from the low Monday

Regardless of which solution you believe they both are producing
decent widespread rain chances Monday night into Tuesday morning,
and hopefully helping us erase some of the rainfall deficit we`ve
seen this year.

The majority of the rain leaves the area with the low pressure
system by Wednesday morning. A cold front quickly moves in behind
and will usher in some of the coldest temperatures we`ve seen this
season. Highs will barely reach the 40`s in most places Thursday and
many places won`t even get above freezing on Friday. Along with this
front there will be some precipitation chances, but models vary
largely with how much will be present. Will go with a blend between
the GFS/ECMWF in this regard. If widespread precipitation does occur
with this system and temperatures stay cold enough we could see some
snow showers behind the front. However... due to past model
performance and current disagreement with this latest run,
confidence is very low on what might occur at the end of the work


Chattanooga Airport, TN             55  43  48  45 /  10 100 100  50
Knoxville McGhee Tyson Airport, TN  50  40  46  43 /   0  90  90  50
Oak Ridge, TN                       51  40  47  43 /   0  80  80  50
Tri Cities Airport, TN              47  35  45  40 /   0  50  80  50




DGS/ABM is the U.S. government's official web portal to all federal, state and local government web resources and services.