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000
FXUS64 KMRX 031120
AFDMRX

AREA FORECAST DISCUSSION
National Weather Service Morristown TN
720 AM EDT Mon Aug 3 2020

.UPDATE...
FOR 12Z AVIATION.

&&

.SHORT TERM (Today and Tonight)...

Current radar imagery indicates showers/storms to the east of the
southern Appalachians in the Carolinas along on old frontal
boundary. Current water vapor and RAP upper air analysis indicates a
broad trough that extends from the Great Lakes southward into the
Gulf of Mexico. Water vapor imagery indicates dry air extending from
central Kentucky southward across Middle TN into the northwestern
Gulf Of Mexico. Due to this dry air approaching, PW values vary a
great deal across the forecast area from 1.7-19 inches across east
Tennessee into southwest Virginia with values of 1.0-1.2 inches
across the Cumberland Plateau. The RAP indicates that a couple of
shortwaves will traverse the area today. This first is forecast in
the 12-15z timeframe. The forecast area will also be in the favored
right entrance region of an elongated 50-70 kt 300mb south to north
jet streak. All of these factors, would support convective
initiation some time around daybreak or shortly after for areas
generally to the east of I-75. Due to the early natures of the CI,
instability will not be overly impressive, somewhere in the
500-1000 J/Kg. However, 0-6 km bulk shear will be a respectable
35-45 kts due to the jet streak. Overall, expect most storms will
remain well below severe limits this morning but could not rule
out a stronger storm or two with gusty winds.

This first shortwave trough should lift out of the area late this
morning into the early afternoon before another races through the
region in the 21z-00z timeframe. By this time, it appears the best
jet dynamics will be a bit further to the north and east. However,
SBCAPE values will be a little higher with daytime heating and once
again could not rule out a stronger storm or two with gusty winds
being the main threat. Overall, think temperatures will stay on the
cooler side of guidance today with the early CI and persistent cloud
cover from this activity early in the day. High temperatures will
range from the low to mid 80s for most locations. Additionally,
expect the PoP gradient will be tight today with much lower chances
to the west of I-75 as drier air moves in from the west.

Decreasing PoPs are forecast overnight as Isaias races northwards
across the eastern Carolinas. A front will approach the area from
the west as another shortwave trough dives into the Ohio River
Valley by daybreak. The location of the upper level jet, subsidence
around the outer edge of the tropical system, and low PW values will
not be favorable for PoPs overnight. The southern Appalchians will
be in the left entrance region of a 70-90 kt 300 mb south to north
jet. The location of the jet will favor upper level convergence. PW
values will drop down into the 1.2-1.4 inch range areawide. which is
around to slightly below average for early August. Therefore, expect
a decreasing trend in precipitation chances overnight. Overnight lows
will generally be in the 60s.

MA

.LONG TERM (Tuesday through Sunday)...

For the bulk of this forecast period the eastern U.S. will be
under the influence of a broad trough. Expect diurnal showers and
thunderstorms each day throughout this period. A few isolated
stronger storms could produce strong wind gusts and locally heavy
rain particularly on Tuesday afternoon. No widespread severe
weather is expected for the remainder of the week/weekend. A
pattern change begins to occur starting on Friday as the upper
high begins building eastward -setting the stage for more much
warmer daytime temperatures.

AC


&&

.AVIATION...
12Z TAF DISCUSSION.

VFR conditions currently across the terminals. Current radar
imagery indicates showers/storms along the spine of the
Appalachian Mountains as the CAM`s forecast. These showers and
storms will drift down into the valley later this morning. With
the close proximity of TYS to the ongoing activity, went ahead
and started with VCTS there. This first shortwave is forecast to
move through the area this morning into the early afternoon.
Expect the possibility of a break in the coverage late this
morning into the early afternoon before the next shortwave trough
rotates through later in the afternoon. Coverage with this
shortwave may not be as widespread but kept VCTS in all the
terminals to account for any activity. Convection should come to
an end around 00z with patchy fog possible late in the TAF cycle.

MA

&&

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

$$