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

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FXUS64 KMRX 300724
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
324 AM EDT Sun Apr 30 2017

.SHORT TERM (Today through Monday)...

Another summer-like day forecast across the area. Temperatures at
3 am are still in the upper 60s to mid 70s across the area.
Current water vapor and RAP upper air analysis indicates a closed
low spinning across the Southern Plains with a ridge just off the
Carolina coast. At the surface, a low pressure center is currently
near Tulsa, Oklahoma with a warm front stretch to the east along
the Ohio River Valley and a cold front extending southward into S
Texas. IR satellite imagery shows a large area of showers and
storms ahead of the cold front across Arkansas and stretching
southwards into SE Texas.

Expect a few areas of patchy fog to start off the day that will
quickly mix out shortly after sunrise. Model soundings suggest that
the CAP will be stronger today and a bit more elevated in the 750-
650 mb range. Therefore, not expecting any shower or storms outside
of the higher elevations. Winds will begin to increase as the
pressure gradient tightens from the approaching front. Winds in
the mountains late in the day could approach wind advisory
criteria but have decided to hold off on an advisory for now.
Temperatures will once again top out well above normal for late
April with highs in the 80s for most locations.

Models have come into pretty good agreement with the timing of the
system overnight tonight into Monday morning. Expect the line of
shower/storms will be weakening as they move into a more stable and
capped environment. Model soundings indicate the atmosphere will
saturate late tonight but SBCAPE values are generally less than 500
J/Kg with some weak capping continuing throughout the overnight
hours. The low level wind field is very impressive with an 850 mb
jet of around 55-60 kts. Expect a couple of storms will be strong
enough to transport these winds down to the ground despite the
limiting factors. Therefore, the main threat with these storms will
be damaging straight line winds. The low-level shear profile is
generally uni-directional and the storms will be weakening as they
move into the forecast area and think the chance for a tornado is
very low. Flooding should not be an issue with the line of showers
and storms moving through the area rather quickly. The main
timeframe for strong to severe storms will be from around
midnight to 8 am Monday morning.

Clearing conditions are expected by Monday afternoon with cooler
temperatures behind the front. Highs on Monday will be much more
pleasant in the upper 60s to mid 70s as cold air advects in behind
the departing system.

.LONG TERM (Monday Night through Saturday)...

A cold front and associated shower and thunderstorm activity will
be pulling away from the area Monday night for generally dry
conditions. However...850MB winds will remain elevated and
breezy...gusty winds will continue over the region through the
night. These breezy winds will bring in cooler near normal
temperatures. Surface high pressure and zonal flow aloft on
Tuesday will provide a quiet and dry weather day. Then...we will
quickly move into an active weather pattern Wednesday through the
end of the period. Model consistency isn`t great but there is some
general agreement. The basic pattern appears to be a weak warm
front lifting through around Wednesday... followed quickly by a
cold front Thursday and the upper low slowly moving across the
area around the Friday/Saturday time frame. This general scenario
will keep at least chance pops in place through the end of the
extended with the best chance of convection expected on around
Thursday.


&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             86  63  73  53 /  10 100  70  10
Knoxville McGhee Tyson Airport, TN  87  66  73  50 /  10  60  80  10
Oak Ridge, TN                       87  64  72  50 /  10  70  80  10
Tri Cities Airport, TN              85  66  73  48 /  10  30  60  10

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&

$$

MA/MJB



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