Debate de meteorólogos científicos
Area forecast discussion
National Weather Service Morristown Tennessee
320 PM EST Thursday Dec 5 2013
Short term (tonight through saturday)...cold front will move into
the northern Cumberland Plateau and extreme SW Virginia tonight. The upper
jet core and the colder surface temperature will remain northwest of the
area. Southwesterly layer shear continues to increase tonight. Precipitable water
values in excess of 1.50 are well above normal. Ongoing convection
will move into the east Tennessee Valley tonight. This activity will likely
train or redevelop along the frontal boundary. The frontal boundary
moves little on Friday with periods of showers and thunderstorms.
Localized flooding becomes possible...especially along the
Cumberland Plateau and areas south of Knoxville. A strong upper jet
segment will move NE through middle Tennessee by Friday afternoon. This feature
will likely enhance convective development with a low chance of
strong to severe storms Friday afternoon and evening. The cold front
begins to move back southeast by Friday evening. The shallow and much
colder air will move into the area late Friday night. The back end
of the tapering convection will likely see sleet and freezing rain
before ending Sat morning. Some ice accumulation is possible across
SW Virginia and the northern plateau. Tree limbs and power lines will
likely see some accretion. Temperatures will be frontal position
dependent. Leaned toward a warmer solution southeast of the front.
Long term /Saturday night through Thursday/...this period begins
Saturday evening with the next system approaching from the
southwest...with a cold air mass in place at the surface. Aloft a
strong and deep southwesterly flow streams over the region...between
a trough in The Rockies and a ridge over the western Caribbean.
There are two issues with this next wave of precipitation...first is
the threat for any freezing/frozen precipitation through about 15z
Sunday...when the warmer air should win-out...and the second issue
is how heavy the rain will get.
The pattern pretty much stays unsettled for the first 3 days of this
period...until the trough axis finally clears the area...roughly
late Tuesday. So from 00z Wednesday through the end of the forecast will
keep it dry.
Getting back to Saturday night...looks like most of the area will
just get a cold rain...but concerned about northwestern areas that
will have upslope northerly low level flow...such as Jellico and
Oneida...that the cold air mass may be locked into place longer and
there will be a better chance of freezing rain...but only expecting
a few hundredths of accrual...so at this time...not anticipating
many problems. Also am mentioning parts of wise and Russell Virginia
counties for light freezing rain...but precipitation should be lighter
For Sunday through Monday night...precipitation should be rain...then as
cold air returns on Tuesday...will likely have some snow showers on
the back end of the system.
In the second wave of precipitation...from Saturday night through
Sunday...we have precipitation of about 1/2 inch to an inch across the
area. There will be more rain on Monday...that will be addressed in
Preliminary point temps/pops...
Chattanooga Airport, Tennessee 58 73 39 47 39 / 100 100 100 20 80
Knoxville McGhee Tyson Airport, Tennessee 54 72 38 48 36 / 80 100 100 20 60
Oak Ridge, Tennessee 52 69 36 44 34 / 100 100 100 20 70
Tri Cities Airport, Tennessee 49 71 38 47 33 / 80 100 100 20 50