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

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FXUS64 KMRX 170706

Area Forecast Discussion
National Weather Service Morristown TN
306 AM EDT Wed Jul 17 2019

.SHORT TERM...(Today through Tomorrow)...
The remnants of Barry will finally begin to move through the area
today, bringing widespread showers and thunderstorms. Currently
precipitation is occurring over AL/Middle Tennessee and is expected
to continue moving eastward. It A few scattered showers may form
ahead of the main bulk of precipitation, but the more widespread
rain will move into the Cumberland Plateau in the late morning
hours, and is expected to last into the evening hours. Another weak
mid/low level trough will move through Wednesday night behind the
main round of rain during the day. Will continue precipitation
chances Wednesday night and into Thursday as this secondary, but
weaker, system moves through.

Biggest concern with the upcoming storms will be the threat of
flooding. Precipitable water values around 2 inches with a tall
saturated column will help warm rain processes. Expect some of the
stronger storms to be able to produce quick heavy rainfall, but they
will also be moving eastward at a decent clip as well. So while the
storms will be capable of creating heavy rain, they (hopefully)
won`t be over any one location for very long. SREF models are
relatively consistent with each other of most places seeing about
0.5 - 1.0 inches of rain today and tonight and almost all of the
members showing storm total QPE of less than 1.5 inches. Luckily
we`ve been relatively dry across the area for the past few days, so
hopefully the rivers and low lying areas are able to handle much of
this rain. With the quick moving storms the threat for widespread
flooding looks relatively low at this time so at this time have no
plans to issue any flood related watches... HOWEVER, it is still
VERY possible that some isolated locations get a few heavier storms
over them and experience flash flooding. So the main message of the
day is turn around, don`t drown.

High resolution models are indicating that there may be an area of
heavier precipitation somewhere in Middle Tennessee towards the
Cumberland Plateau (with QPF amounts closer to 2 inches). Areas
along and near higher terrain are more likely to see heavier
rainfall as these storms move through.

With the secondary trough moving in later tonight expect there to be
some additional storms capable of producing brief heavy rain, but
coverage of storms should be much lower compared to earlier today.

.LONG TERM (Thursday night through Tuesday)...
Overall, GFS and ECMWF are in good agreement with the extended
forecast. An upper ridge will develop over the Ohio Valley and
central/southern Appalachians for Thursday night through Saturday.
For Sunday, ridging weakens with upper trough becoming established
for Monday and Tuesday over the eastern third of the nation. A
frontal boundary moves into the Tennessee valley and southern
Appalachians early next week. Now for the particulars.

For Friday and Saturday, upper ridge across the region, but moisture
and instability remains and expect mainly diurnal convection each
day. Greatest coverage over the higher elevations. Typical summer-
time air-mass with MLCAPEs 1500-2000 J/Kg, PWs of 1.6-1.9 inches
(highest south), and DCAPEs of 700-1000 J/Kg. These values will
produce isolated strong storms producing strong/gusty winds, heavy
rains, and frequent lightning.

For Sunday, upper ridge breaks down allowing for greater coverage of
convection over the region. Same as Friday/Saturday, isolates strong
storms likely.

For Monday and Tuesday, upper trough develops over the eastern third
of the nation pulling a frontal boundary southward into the
Tennessee valley and southern Appalachians Monday night and Tuesday.
Again, some strong storms are anticipated for Monday afternoon and
evening. High pressure will build into the are Tuesday with slowly
drier air advecting into the northern sections during the day.


Chattanooga Airport, TN             87  74  91  75 /  70  40  40  20
Knoxville McGhee Tyson Airport, TN  86  72  90  72 /  70  50  40  30
Oak Ridge, TN                       85  72  90  73 /  70  50  40  20
Tri Cities Airport, TN              85  69  89  69 /  70  60  50  20




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