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Area forecast discussion
National Weather Service Morristown Tennessee
325 PM EST Fri Feb 24 2017

Short term...
upper level low centered over central Iowa this afternoon will
lift NE toward the Great Lakes overnight tonight. At the surface,
associated 995 mb low centered over central Illinois will also
lift NE into the eastern Great Lakes by Saturday morning.
Associated cold front moving toward the Mississippi Valley this
afternoon will push east across Tennessee tonight before moving east of
the area Saturday morning.

Ahead of the front, an intensifying low level jet will move across the
plateau and into the Tennessee Valley during the overnight hours.
Over the plateau, ml cape of 700-900 j/kg coupled with bulk shear
values of 45-60 kts will allow the line of convection to remain
organized with the real possibility of some strong to severe
storms as it pushes through the area during the overnight. Timing
looks to be a little more delayed than previous model runs with
both hires hrrr and rap13 indicating that convection will push
through the area during mainly the midnight to 6 am time frame.
This agrees well with the NAM that has also slowed the progression
of this front as well. With presence of the near unidirectional
wind profiles, strong to severe straight line winds look to be the
dominant threat with this event. Any overnight severe weather
event poses an additional risk. Given that people are not as
connected to latest weather information as they typically are
during normal waking hours, people should be extra diligent to
ensure they have access to the latest watch and warning
information from the National Weather Service.

Further east of the front tonight in the eastern portions of the
cwa, a tightening pressure gradient is expected to increase winds
for areas of the smoky mtns above 3000 ft in Cocke, Sevier, and
Blount counties. These winds will decrease with the frontal
passage on Saturday morning. A Wind Advisory has been issued for
the those areas from 7 PM tonight until 7 am on Saturday.

As the front moves out on Saturday conditions should gradually
improve through the afternoon. Gusty west winds and a daytime high
in the lower to middle 50s that will slowly drop during the day
will make it feel a bit more like winter. Especially after the
record breaking late week warmth we have been experiencing. With
the gusty winds tomorrow, consideration was given to a Wind
Advisory behind the front, but 850 mb winds weaken precipitously
by afternoon. However, do expect to see marginal advisory level
gusts, particularly near mid-day and a Special Weather Statement
may be necessary by morning to alert users to the winds gusting 25
to 35 mph behind the front.

Long term...the long term forecast
will follow the slower European model (ecmwf) modeling rather than the quicker GFS
suggestion of a frontal passage for the week ahead. Dry and cold
advection brings an end to the precipitation Saturday night with a
zonal westerly flow regime gradually becoming southerly again ahead
of another amplified long wave mid America trough at mid week. In
this scenario, isentropic lift with a moist, southerly component
will lead to the development of showers Monday into Tuesday. The
atmosphere will be destabilizing in the moistening pattern by
Tuesday and so some thunderstorms could be part of the mix at this
time. But the better chance for convection will be Tuesday night
into Wednesday ahead of another relatively strong cold front due in
the southern appalachian region later Wednesday afternoon and
evening. Kept the remainder of the long term dry behind this system
with a prevailing west to northwesterly flow building in with higher
surface pressure. The new week's temperature forecast features
another most pleasant warm up into mid week with highs back in the
upper 60s and lower 70s followed by a return to more typical early
March weather.

$$



&&

Preliminary point temps/pops...
Chattanooga Airport, Tennessee 50 56 31 57 / 70 20 0 0
Knoxville McGhee Tyson Airport, Tennessee 50 53 29 53 / 80 40 0 0
Oak Ridge, Tennessee 49 52 27 53 / 80 30 0 0
Tri Cities Airport, Tennessee 50 55 26 49 / 80 60 10 0

&&

Mrx watches/warnings/advisories...
NC...none.
Tennessee...Wind Advisory from 7 PM this evening to 7 am EST Saturday for
Blount Smoky Mountains-Cocke Smoky Mountains-Sevier Smoky
Mountains.

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