Severe Thunderstorm Warning 50, NWS Morristown, TN

Area Forecast Discussion
National Weather Service Morristown TN
329 PM EDT Thu Jun 20 2019

.SHORT TERM...(Tonight and Friday)...

The main concern for the short term period is convective potential
through the evening hours. SHRA/TSRA ahead of a front has
developed across middle Tennessee in a moist and unstable
environment. LAPS analysis shows SBCAPE values in excess of
2000j/kg with dewpoints in the upper 60s. The HRRR has shown this
coverage well and continues to develop scattered convection this
evening. Further north across southern Kentucky and northern
Tennessee, convection is developing along the front where better
moisture convergence in occurring.

Given the convective parameters, and increased shear due to an
upper level jet, strong to severe storms are still possible
through the afternoon and evening. Main threats will be damaging
winds, and hail. With the shortwave trough exiting the area
tonight, convection will exit as well. Drier air filtering in
behind the front should begin to clear skies overnight. Friday, a
surface ridge will bring tranquil weather conditions to the area.
A lifting warm front will move into parts of the area by Friday
afternoon. As a result high temperatures should be a couple
degrees warmer with daytime highs in the mid to upper 80s over
most of the area.

.LONG TERM...(Friday night through Thursday)...

The extended period kicks off on Friday evening amidst deep ridging
across the southeast states with the ridge axis centered over the
MidSouth region, thus favoring weak nwly flow aloft into the TN
Valley and Southern Appalachians.  Guidance continues to suggest
multiple rounds of MCS activity firing across the Kentuckiana region
along the theta-e ridge.  Models (GFS/ECMWF) seem to be in better
agreement with regard to mean layer flow suggesting one or more of
these MCSs tracking across KY into east TN, southwest VA, and
eventually southwest NC.  The first of these MCSs looks to arrive
mid/late morning Saturday which depending on heating/instability,
could favor a round of strong/severe convection, which is supported
by fcst soundings with steep lapse rates and thus large/deep cape
profiles.  Given this scenario playing out, would expect elevated
chances for damaging winds and large hail. The second MCS looks to
move in from the northwest overnight into Sunday morning, which
based on timing would suggest a less unstable environment for deep
convection.  That said, confidence is still marginal as the NAM
continues to suggest abundant subsidence amidst the deep ridge
keeping the vast majority of any MCS activity generally confined
across extreme northeast TN and southwest VA, therefore essentially
just glancing the forecast area.  Because of this, kept pops in the
mid/high chance range for much of the area on Saturday with only low
end likely pops featured over the above noted regions.  Into Sunday,
once again pops are highest across northeast TN and southwest VA
given the most favorable model MCS forecast tracks, but confined to
only mid/high chances at best.

Pops will taper late Sunday into Monday morning as the upper ridge
axis slides east atop the region, eventually moving over the
Carolinas by mid/late day.  Meanwhile, a northern stream trough will
eject from the Rockies into the Plains with cyclogenesis to occur
beneath, and a surface cold front draped southward across the
mid/lower MS and OH Valleys.  At this point the operational guidance
tends to diverge a bit as the GFS favors a more progressive track of
the upper wave into the Midwest and eventually the Great Lakes into
Tuesday, thus surging the cold front into the TN Valley Monday
evening.  This solution would support a fairly wet pattern for
Monday.  On the other hand, the ECMWF features slower progression of
the upper trough leading to a delayed fropa (relative to the GFS)
Tuesday afternoon/evening, thereby favoring only diurnal prefrontal
convection on Monday.  All said, the start of the work week looks
somewhat active therefore the fcst will generally feature mid/high
chance pops.  Beyond that for Wednesday/Thursday, am expecting at
least 1-2 drier days amidst nwly flow and high pressure.
Temperatures through the entire period will generally be near a
category above normal levels, especially by next week.&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             70  90  72  89 /  30  10  30  50
Knoxville McGhee Tyson Airport, TN  68  86  69  86 /  30  10  40  50
Oak Ridge, TN                       67  88  69  86 /  30  10  40  50
Tri Cities Airport, TN              64  81  63  83 /  50   0  50  60

&&

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

AD/CDG

Hazardous Weather Outlook
National Weather Service Morristown TN
308 PM EDT Thu Jun 20 2019

NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-
005-006-008-211915-
Cherokee-Clay-Scott-Campbell-Claiborne-Hancock-Hawkins-Sullivan-
Johnson-Morgan-Anderson-Union-Grainger-Hamblen-Northwest Cocke-
Cocke Smoky Mountains-Northwest Greene-Southeast Greene-
Washington-Unicoi-Northwest Carter-Southeast Carter-Roane-Loudon-
Knox-Jefferson-Northwest Blount-Blount Smoky Mountains-
North Sevier-Sevier Smoky Mountains-Sequatchie-Bledsoe-Rhea-Meigs-
McMinn-Northwest Monroe-Southeast Monroe-Marion-Hamilton-Bradley-
West Polk-East Polk-Lee-Wise-Russell-
308 PM EDT Thu Jun 20 2019 /208 PM CDT Thu Jun 20 2019/

This Hazardous Weather Outlook is for portions of southwest North
Carolina...east Tennessee and southwest Virginia.

.DAY ONE...This Afternoon and Tonight

Showers and thunderstorms will occur over much of the forecast
area again this afternoon and evening. While widespread severe
weather isn't expected, a few strong to severe storms could occur.
Damaging winds would be the main threat with these storms.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

...Round of Strong to Severe Storms Possible late Friday Night
and Saturday....

For late Friday and Friday night, an area of storms is expected
to develop across the mid-west and then move southeast into east
Tennessee valley and southern Appalachians by Saturday morning.
Some of these storms could be strong to severe producing damaging
winds, hail up to quarter size, and heavy rainfall. Localized
flash flooding is possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required this evening and possibly
Saturday. Reports of flash flooding, storm damage, or heavy
rainfall amounts will be appreciated this week.

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