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

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FXUS64 KMRX 280912

Area Forecast Discussion
National Weather Service Morristown TN
412 AM EST Tue Feb 28 2017

.SHORT TERM /Today and Tonight/...
A warm front will move northeast into the region, coinciding with
a weak shortwave trough/ripple tracking across the Ohio/Tennessee
Valleys later this afternoon. This feature will bringing with it
a warmer/moist air mass in it`s wake as well as opportunities for
scattered to numerous showers and thunderstorms from the late
morning through the evening hours (supported by the latest runs of
the RAP/HRRR). The best chance for precipitation will be during
the afternoon, with the highest PoPs favoring the Plateau and
Southern/Central Valleys. Strong downsloping winds along the
mountains will lessen coverage and QPF amounts along the immediate
mountains and foothills. Low instabilty will significantly limit
any severe threat for today, other than a couple strong storms
along the Plateau later in the afternoon.

Overnight, a 850 mb jet will begin to intensify as it moves into
the region ahead an amplifying trough and it`s associated cold
front to the west. These strong southerly winds will result in
advisory level concerns along the Great Smoky Mountains late
tonight and across the entire region on Wednesday (addressed in
the section below). The winds will also help to maintain the warm,
moist air mass in place, setting the for a potential severe
weather outbreak on Wednesday (Also addressed below). Main impact
overnight will be with temperatures as lows will remain in the mid
50s to lower 60s, with similarly high dewpoints. Strong/severe
storms will fire along the cold front along the Mississippi River,
with some remnants of which may approach the Plateau late
tonight, so have higher PoPs and a thunder mention there.

.LONG TERM /Wednesday through Monday/...
Biggest weather event of concern will be the chance for severe
weather as a trough moves across the northern plains and a surface
low moves through the Great Lakes Region with it, and this system
drags a cold front through our area on Wednesday. We could have some
ongoing convection Tuesday night into Wednesday morning which could
help stabilize the atmosphere and alter the chances for severe
weather. Soundings suggest that any ongoing convection would be
pretty weak and could wain in the overnight hours as dry air in the
mid levels hinders convection, and we could get some cloud clearing
during the day. If this hindrance does occur then the atmosphere
should be primed for much stronger storms as we roll into Wednesday
and the front moves closer to our area. Best timing for the
strongest storms still seems to be the afternoon hours till a bit
after sunset. During this time mid level jet will put us in the
favored region for some upper level support and the low level jet
will be cranking from early in the morning until the front moves
through. Low level jet speeds of 50-60+ knots will help create
strong shear as well as strong pre-frontal winds on Wednesday.
Forecast models indicate the possibility of 500-1500 J/kg of CAPE
depending on the model and location in our forecast area. This
combined with strong 0-1km and 0-6km shear will lead to a good
possibility to see damaging winds from a line of severe
thunderstorms. In addition with this set up we could also see large
hail and a few tornadoes as well.

As the front exits overnight we will cool down quite a bit as drier
air pours into our area. Highs on Thursday will be about 20 degrees
cooler than they will be on Wednesday before the front moves
through. These colder temperatures will last through the end of the
week and into the weekend and overnight lows on Thursday night and
Friday night will likely get below freezing. These temperatures will
be unfortunate for some of the plants out there that have started to
bloom due to the recent extraordinarily warm February we
experienced. Ridging will build back in over the area and a warming
trend will begin over the weekend and into next week, with another
chance for precipitation coming at the tail end of the 7-day


Chattanooga Airport, TN             68  61  74  41 /  70  50  80  40
Knoxville McGhee Tyson Airport, TN  70  60  74  39 /  60  40  90  50
Oak Ridge, TN                       67  59  75  39 /  70  40  90  30
Tri Cities Airport, TN              69  54  73  38 /  50  40  90  60


NC...Wind Advisory from 7 AM Wednesday to midnight EST Wednesday
     night for Cherokee-Clay.

TN...Wind Advisory from midnight tonight to 7 AM EST Thursday for
     Blount Smoky Mountains-Cocke Smoky Mountains-Sevier Smoky

     Wind Advisory from 7 AM EST /6 AM CST/ Wednesday to midnight EST
     /11 PM CST/ Wednesday night for Anderson-Bledsoe-Bradley-
     Campbell-Claiborne-East Polk-Grainger-Hamblen-Hamilton-
     Morgan-NW Blount-North Sevier-Northwest Carter-Northwest
     Cocke-Northwest Greene-Northwest Monroe-Rhea-Roane-Scott TN-
     Sequatchie-Southeast Monroe-Sullivan-Union-Washington TN-
     West Polk.

     Wind Advisory from 7 AM Wednesday to 7 AM EST Thursday for
     Johnson-Southeast Carter-Southeast Greene-Unicoi.

VA...Wind Advisory from 7 AM Wednesday to midnight EST Wednesday
     night for Lee-Russell-Scott-Washington-Wise.



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