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

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FXUS64 KMRX 240709

Area Forecast Discussion
National Weather Service Morristown TN
309 AM EDT Sat Mar 24 2018

.SHORT TERM...(Today and Tonight)...Models in reasonable agreement
with the track of the approaching low pressure system that moves
into our area tonight.  Isentropic lift out ahead of this system
already is bringing some light rain.  The precipitation will
continue to increase and then should shift north during the day with
the southern areas missing much of this action.  Precipitation type
is still problematic across the extreme northeastern parts of our
area, with model soundings showing a deep near isothermal layer
close to freezing for a period at the beginning of the
precipitation.  Will include some snow and sleet in these areas, but
how long it will last will have a big impact on how much snow
accumulation will occur.  Still considerable uncertainty, but right
now it looks like previous forecast of an inch or two across mainly
higher elevations looks reasonable. Will keep the SPS going for
these areas.  Rain will increase again across southern/central areas
later this afternoon into tonight before decreasing again from west
to east late.  There appears to be enough elevated instability
across southern areas for a few rumbles of thunder so will keep
mention in the forecast. Will not stray far from MAV temps.

.LONG TERM...(Sunday through Friday)...A few lingering showers
may be present on Sunday as this first weather system keeps slowly
moving off to the East. Ridging and a warming trend then begin
through the first half of the week. Models are still struggling a
bit with how to handle a semi-stationary boundary to our south. If
it moves into our southern counties we should see precipitation,
but if it keeps further to the south then we might remain just out
of reach of the rain.

A better chance for rain will come during the middle of the week as
a low/trough over the 4-corners region begins to swing to the east.
Ahead of it a frontal boundary will sweep through the southeastern
states. Strong low level winds out of the southwest will pump a lot
of moisture into the area leading to high PWAT values and a
potential for heavy rainfall over parts of the area. During the
middle/second half of the work week widespread rain will likely
occur with the highest chances and rainfall totals likely in
Southeast Tennessee/Southwest North Carolina. Current QPF forecast
show a possibility of some locations seeing 3+ inches of rain mid to
late next week. However there will likely be a sharp gradient where
rainfall totals drop off, and if the jet is a bit weaker than
currently forecasted the higher rainfall totals may stay outside of
our area. This system will be one to keep an eye on and see how the
models evolve as future runs and higher resolution models begin to
take hold of it.


Chattanooga Airport, TN             63  53  68  46 /  60  90  30  30
Knoxville McGhee Tyson Airport, TN  53  45  58  41 /  90 100  30  20
Oak Ridge, TN                       52  46  59  44 / 100 100  20  20
Tri Cities Airport, TN              45  38  51  34 / 100 100  30  10




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