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

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FXUS64 KMRX 210710

Area Forecast Discussion
National Weather Service Morristown TN
310 AM EDT Mon May 21 2018

.SHORT TERM...(Today and Tonight)...

Another mild start this morning with temperatures in the mid 60s
to low 70s at 3am. Already seeing a few reports of patchy fog and
expect this will continue to increase towards sunrise with
dewpoints in the mid to upper 60s. For now, not expecting fog to
be as widespread as yesterday morning. Current water vapor imagery
and RAP upper air analysis indicates a weak closed low along the
northeastern Gulf of Mexico with another shortwave trough across
the Mid-Mississippi River Valley. Closer to home, there is a weak
ridge overhead but this will begin to breakdown today. At the
surface, an E-W boundary stretches from a surface low in Missouri
to the east to the Mid-Atlantic.

For today, the ridge will breakdown with PW values increasing into
the 1.4-1.6 inch range. These values are near the 90th percentile
for mid to late May. With the atmosphere nearing saturation, mid-
level lapse rates will be near moist adiabatic and expect SBCAPE
values will be less than 1500 J/Kg with 0-6 km bulk shear values
less than 10 kts due to weak flow aloft. Therefore, not expecting
there will be any organized updrafts for any strong to severe
storms. Models do indicate that the E-W boundary to the north may
slide south slightly. Regardless, there will be increased low
level convergence across Northeast Tennessee and Southwest
Virginia and this is where the highest PoPs are for this
afternoon. With elevated PW values and recent rainfall, there
could be some localized areas of flooding, especially in areas of
poor drainage. PW values do not drop off overnight and a weak
shortwave trough from the south moves northward over the Southern
Appalachians. Models are not overly impressive with QPF values
overnight but did continue with at least a slight chance to chance
PoPs during the overnight period. Highs will range from the upper
70s to mid 80s with lows in the upper 50s to mid 60s.

.LONG TERM...(Tuesday through Sunday)...

Ridge will still be over us on Tuesday, but the main focus for the
weather will be a frontal boundary that should be moving into the
area. Models have had a tough time figuring out where this front
will end up stalling out, but with this latest run most of them have
it pushing through by Thursday and stalling out south of Tennessee.
As it moves through we should see some showers and thunderstorms
developing along and ahead of it. But once it`s able to move through
towards the end of the week we will dry out and see more sunshine
across the area.

As the front stretches and fizzles out over us the southerly winds
pick back up at the end of the work week. This will means we will
see an increase in shower and thunderstorm activity as we head into
the weekend. These precipitation chances will remain through much of
the weekend as potential low in the Gulf helps to funnel in moisture
and more unstable air into the forecast area.



Chattanooga Airport, TN             83  67  81  67 /  30  20  50  40
Knoxville McGhee Tyson Airport, TN  83  65  81  65 /  40  20  50  30
Oak Ridge, TN                       84  65  81  66 /  40  30  50  30
Tri Cities Airport, TN              82  62  81  62 /  50  30  50  40




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