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

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FXUS64 KMRX 202032

Area Forecast Discussion
National Weather Service Morristown TN
332 PM EST Fri Jan 20 2017

.SHORT TERM (Tonight and Tomorrow)...
Visible satellite imagery indicating more breaks in cloud cover this
afternoon as the deep moisture has exited NE of the area. With
these breaks, temperatures have been able to climb into the upper
60`s over southern two-thirds of the area, with Chattanooga
currently at 70 degrees and within a degree of tying a record of 71
set in 1929.

We will continue to experience a break in pcpn overnight tonight ahead
of the next active weather period. Given residual low level moisture,
we may see some localized areas of patchy fog by late tonight into
the morning hours. Otherwise, overnight lows from the upper 40`s
to middle 50`s will be about 15-20 degrees F above late January

For tomorrow, middle level ridge axis extends N to S along the east
coast. A shortwave trough will ride NE along the western periphery
of this ridge across our area during the day. This coupled with
increasing instability and the return of significant moisture to
the lowest 300 mb of the atmosphere will help to generate shower
activity that is expected to push from SW to NE across the area
through the day. Overall rainfall amounts with this round of pcpn
do not look to be that impressive given continued middle level dry
air holding on for most of the day. Would expect most areas to see
less than 0.25 inches in shower activity. However, the combination
of increasing instability coupled with the shortwave energy and
favorable 0-3 km directional shear fcst for the latter portion of
the period, strong to possibly severe convection could develop and
would produce locally higher rainfall amounts. Threat for strong to
possible severe looks to be mainly over the southern third of the
area during the afternoon and evening hours with greatest threat
expected to be wind, hail, and possible localized flooding.

.LONG TERM (Tomorrow Night through Friday)...
The active weather pattern continues through the long term with a
strong short wave driving northeast across the Southern
Appalachians Saturday night into Sunday, followed by a deep upper
level low Sunday into Monday. Probability will be in the
categorical range for much of the area during this period for
showers. However, strong dynamics and instability with this system
will require thunderstorms to be included in the forecast. Some of
the storms may be rather strong late Saturday night into Sunday.
The main threat with the storms will be strong and gusty winds. The
showers will taper off from slowly from west to east Monday night
into Tuesday as the deep upper low shifts northeast into the
Northeastern U.S. Some colder air will build in behind this system
and the precip may end as brief period of light snow across the
highest terrain in the Smoky Mountains. Due to the broadbrushed
nature of the superblend protocol, the only period in the remainder
of the long term with no pops will be Tuesday night as drier air
and ridging build into the region. The next upper trough and
surface cold frontal system will move across the area Wednesday
into Wednesday night in the form of rain showers. However, it will
be turning colder as a deepening upper trough develops over much of
the nation and there may be opportunities for orographically driven
snowfall as perhaps as many as three shorter wavelength features
build across the Southern Appalachians in this predominant
northwest flow regime.



Chattanooga Airport, TN             54  67  54  64 /  20  70  90  80
Knoxville McGhee Tyson Airport, TN  53  67  53  64 /  10  50  80  90
Oak Ridge, TN                       52  66  53  63 /  10  50  80  80
Tri Cities Airport, TN              47  65  50  62 /  10  40  70  80



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