FXUS64 KMRX 290735
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
335 AM EDT Fri May 29 2020
.SHORT TERM...(Today and Tonight)...Aloft, deep troughing is
currently across much of the Ohio and Tennessee valley with deep
moisture transport from the western GoM northward into the region.
Closer to the surface an area of low pressure exists north of the
Great Lakes with a cold front extending from the low southward
into the Ohio river valley into through the Midsouth.
Current radar imagery indicates a few showers still lingering
around the southern valley. These could linger for a couple more
hours but generally expect dry conditions through the rest of the
morning. Area observations show low dewpoint depressions of around
1-3 degrees from southwest Virginia to near or just south of the
Knoxville area. This along with light winds, and recent rainfall
is allowing fog to develop rapidly. Fog should further expand
across areas that saw rainfall yesterday.
As the cold front continues to progress through the area, an
increase in showers and embedded thunderstorms are expected
especially in the afternoon hours during peak heating. Overall
strong storm threat remains low with the lack of appreciable
forcing and lower instability. The front will advance out of the
area Friday night with a decrease in showers and thunderstorms.
.LONG TERM...(Saturday through Thursday Night)... A significant
change in the overall synoptic pattern is expected in the expected
period. Upper trough that has dominated the weather the last several
days will move east of the area with building surface ridging
ushering in much drier airmass into the Tennessee valley and
southern Appalachians for this weekend. Pleasant warm days and cool
nights will be the main story for Saturday through Monday. A few
showers possible early Saturday in the mountains areas, otherwise
dry and stable airmass anticipated.
For Tuesday, surface ridge moves east of the Appalachians allowing
for gradually return flow of southerly moist winds into the region.
Upper ridging will build into the mid-section of the nation as well
with warmer conditions. Instability may be enough to produce
isolated showers and thunderstorms across the mountains of southwest
Virginia and far east Tennessee.
For Wednesday, upper ridge strengthens some producing warm and
increasingly muggy afternoons. The gradual increase in moisture and
warmer afternoon will allow for greater coverage of mainly terrain
showers and storms.
For Wednesday night into Thursday, a short-wave will move across the
Great Lakes into the northeast/mid-atlantic states with a trailing
cold front approaching late. Upper ridge weakens with plenty of
instability to produce a greater coverage of showers and
thunderstorms. Some of these storms Thursday afternoon may be strong
to severe with the main concern being damaging winds and hail.
06Z TAF DISCUSSION.
Diurnal convection has waned for the most part this evening with
only a few showers to the south and west of CHA. Expect much of
the rest of the night to remain quiet with fog likely setting in
at all TAF sites. This is already starting at TRI where
visibilities have dropped to one and a half miles or less. Given
the recent rainfall at the TAF sites, would expect fog to continue
and develop at TYS and CHA through the morning hours. IFR/LIFR
conditions are possible with a TEMPO to highlight this potential.
Fog will begin to mix out after 13Z.
A cold front will continue to approach the area today. Showers
and embedded thunderstorms will occur along this boundary.
Confidence on timing remains a bit low and as a result will
include PROB30 groups for all TAF sites to mention -TSRA. This
activity will push out of the area after 00Z with VFR conditions
prevailing Friday night.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 83 63 81 59 80 / 60 50 10 0 0
Knoxville McGhee Tyson Airport, TN 83 62 80 57 77 / 50 50 20 0 0
Oak Ridge, TN 82 61 80 56 77 / 60 50 10 0 0
Tri Cities Airport, TN 81 60 77 53 73 / 50 50 30 0 10
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