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

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FXUS64 KMRX 121850

National Weather Service Morristown TN
250 PM EDT Mon Apr 12 2021

.SHORT TERM...(Tonight through Tuesday)...

Key Messages:

1. Dry and windy this afternoon with above normal temperatures.

2. Dry and above normal on Tuesday with slight chances for showers
in the afternoon.

Shortwave upper ridging continues to build in from the west across
the TN Valley and Southern Appalachian region, all working to
reinforce surface high pressure along the central Gulf Coast.
Elevated PGFs between said high and the departing northeast CONUS
low pressure system continue to favor gusty wly/nwly winds across
the region, generally in the 20-25mph range.  These winds will
gradually subside through the overnight, with light nwly flow to
prevail.  Otherwise, dry with mostly sunny skies yielding highs
nearly 7-10 degrees above normal with mixed dewpoints allowing for
RH in the 20s to lower 30s.  Tonight am expecting gradually
increasing sky cover as mid level moisture builds from the west
thanks to the approach of a weak H5 impulse riding atop the
shortwave ridge.  Low temperatures tonight will generally be 5-7
degrees above normal. Moving into/through Tuesday, as noted sky
cover will increase as the H5 wave approaches from the west, perhaps
with rain showers possible in the afternoon along/north of I40.
However, given how weak the synoptic ascent regime looks amidst
stable profiles, kept pops at slight chance levels.  Highs on
Tuesday will once again top out well above normal levels.


.LONG TERM...(Tuesday Night Through Monday)...

By Tuesday night the the low to our north will be slowly moving it`s
way through the Great Lakes Region and a broad ridge will be set up
across the southern half of the U.S. Clouds will begin to increase
on Wednesday as moisture rides around the northern edge of the ridge
and moves into the region. Precipitation chances will increase on
Wednesday as strengthening jet overhead allows for some vertical
movement closer to the surface. Models are showing a weak front
expected to push through on Wednesday which could act as the focal
point for some early morning showers on Wednesday. But, think better
chances will hold off until later in the day on Wednesday when
better jet structure develops over the area. Forecast soundings
still show relatively meager instability on Wednesday, but there
should be enough that a few storms are able to develop lighting,
with the highest chance for thunderstorms generally south of I-40.
They also keep indicating a moderate amount of shear in the mid and
low levels, enough that a couple of strong storms could develop, but
the threat of widespread severe weather still looks low at this time.

Precipitation should leave the area by Thursday morning and the sun
will make a return. Winds will remain generally out of the northwest
to north, and this will help keep daytime high temperatures in the
60`s through the rest of the work week.

Clouds and precipitation chances make a return over the weekend as a
shortwave moves over the area coming out of the Plains States. Still
some timing discrepancies on when this shortwave will move into the
eastern Tennessee Valley this weekend with the GFS being faster and
the ECMWF holding it off till the end of the weekend. But confidence
is increasing that there will be showers and thunderstorms at some
point during the weekend. Have kept precipitation chances in through
much of the weekend, but should hopefully be able to trim down the
temporal coverage of PoPs when models come into better agreement.




VFR through the period as high pressure dominates amidst mostly
clear skies and gusty wly/nwly winds. Winds will weaken overnight
with loss of mixing. Moisture will increase from the west early on
Tuesday as a weak upper impulse advects east, therefore introduced
mid level clouds/cigs. Winds on Tuesday will remain wly, albeit



Chattanooga Airport, TN             53  80  55  72  46 /   0  10  20  40  20
Knoxville McGhee Tyson Airport, TN  49  74  52  70  45 /   0  20  10  40  30
Oak Ridge, TN                       48  73  52  69  44 /   0  20  20  50  20
Tri Cities Airport, TN              45  67  49  68  43 /   0  20  20  50  40



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