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

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FXUS64 KMRX 270756

Area Forecast Discussion
National Weather Service Morristown TN
356 AM EDT WED JUL 27 2016

.SHORT TERM...(Today and Tonight)...Upper level ridging refusing to
budge along the southeast US coast into the Tennessee Valley today.
Some convection was continuing overnight across northern middle
Tennessee possibly along an outflow boundary and this may spread
into the northern plateau before sunrise. Otherwise the beginning
of the day will be mostly sunny with a few areas of patchy fog
early. Fog not widespread enough to put in forecast. Weak frontal
boundary stays to the north over the Ohio Valley today.
Temperatures were again very warm yesterday in the mid and upper
90s. With current temperatures early this morning in the lower 70s
northeast and mostly upper 70s south and central. Another hot day
is in store. GFS brings in more convection south and NAM northeast.
Think GFS is trying to cool temperatures down too much so will go
closer to warmer NAM with highs again mid 90s in most lower
elevations. Hopefully a couple degrees cooler than Tuesday as there
should be a little better coverage of showers and storms. Weak mid
to upper level low over lower Mississippi Valley begins to move
east overnight and should bring a surge of moisture west toward the
forecast area late wednesday night into Thursday. Will keep rain
chances up overnight and then increase in the west late. Models now
not showing as much coverage or as much rainfall late tonight so
lowered pops some from earlier forecast.

.LONG TERM...(Thursday through Tuesday)...Middle level low over
the MS Delta tonight continues to drift northward around the
western periphery of the Atlantic subtropical ridge. Guidance in
good agreement on this low merging with the Westerlies N of the
subtropical ridge over West TN by Thursday morning, then drifting
E over Middle TN by Thursday night. This break in the subtropical
ridge will allow for ample deep layer moisture to flow northward
out of the Gulf Of Mexico into the East TN Valley on Thursday with
PWS reaching to near 2 inches over the Southern and Central
portions of the area. Combination of slow moving middle level
trough and ample deep moisture will bring good rain chances to the
area on Thursday with prospects of some locally heavy and sustained
rains for portions of the area in need of it. With SFC-6KM shear on
the order of 20-25 kt and MLCAPE values of 1000-1500 J/Kg, there is
a possibility that some of the tstm activity may be strong to
severe. Given precipitation and cloud cover expected, temperatures
should fall back to near climatological normals for Thursday.

As the broad middle level trough remains over the area through the
weekend, a series of weaker middle level disturbances will propagate
through bringing increased rain chances during maximum daytime
heating. First of these shortwaves looks to move through the area on
Friday. Although deep layer moisture will be cut off by that time,
there is still enough instability, particularly over the southern
half of the area to generate diurnal shower and thunderstorm

Trough then begins to shift East on Monday and Tuesday with
decreasing chances for pcpn and a return to slightly above normal
temperatures across much of the area. Building middle level ridge
begins to shift E over the Ohio Valley by late Tuesday.


Chattanooga Airport, TN             95  74  89  73 /  30  40  70  50
Knoxville McGhee Tyson Airport, TN  94  73  88  72 /  30  40  70  50
Oak Ridge, TN                       93  73  86  72 /  30  40  70  50
Tri Cities Airport, TN              93  70  87  69 /  30  30  70  50




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