Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Morristown Tennessee
229 am EST Wednesday Dec 18 2013
Short term...(today and tonight)...
surface high pressure was building into the region early this
morning. The surface pressure gradient over SW Virginia and along the
Tennessee/NC mountains should begin to relax as the morning GOES on...so
expect less wind as the day progresses. Maximum daytime and overnight
low temperatures today and tonight will be slightly below seasonal
Long term...(thursday through tuesday)...
a ridge off the Atlantic coast will provide a mild SW flow to the
area for the rest of the week...with temperatures rising well above
normal. Outside of some increasing high clouds Thursday night...the
column remains quite dry until Friday. Positive Theta-E advection
and isentropic lift will bring a chance of showers starting on
Models appear to be in generally good agreement with the system for
the weekend. The SW flow pattern remains nearly stationary through
Friday night...and the strong lift stays to our west through
Saturday. Will begin to slowly edge probability of precipitation upward in the plateau on
Saturday...a bit slower than previously forecast. The pattern
becomes more progressive once the southern stream low merges with
the northern stream trough Saturday night. We will begin to see some
strong lift associated with a dynamic jet and good low level
convergence late Saturday night. 850 mb Theta-E values around 330k
suggest a chance of thunderstorms is warranted through Sunday. A
threat of some severe storms cannot be ruled out either as the low level jet
in the GFS is 60-70 kts.
Surface frontal passage occurs Sunday night...but with the positively-tilted
upper trough...there is not a strong surge of cold air behind it.
Monday and Tuesday should be dry and mostly sunny as dry air and
high pressure build in...with temperatures close to normal.
Preliminary point temps/pops...
Chattanooga Airport, Tennessee 50 30 58 41 61 / 0 0 0 0 40
Knoxville McGhee Tyson Airport, Tennessee 45 28 57 38 62 / 0 0 0 0 40
Oak Ridge, Tennessee 45 29 57 39 60 / 0 0 0 0 40
Tri Cities Airport, Tennessee 41 23 56 33 62 / 0 0 0 0 20