A strengthening pressure gradient developed over the Southern Appalachian region during the day as a deepening low pressure system moved northeast along the Ohio Valley. The tight gradient resulted in strong southerly winds across the region.
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The episode as NWS MRX wrote it up.
A strengthening pressure gradient developed over the Southern Appalachian region during the day as a deepening low pressure system moved northeast along the Ohio Valley. The tight gradient resulted in strong southerly winds across the region.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Morristown, TN wrote its last area forecast discussion before the first event at Dec 31, 3:12 PM EST, 18 minutes earlier.
Area Forecast Discussion
National Weather Service Morristown TN
312 PM EST Mon Dec 31 2018
.SHORT TERM (Tonight and Tuesday)...Warm day ahead of approaching
convective line. Strong winds aloft are associated with this
weather system, hence the mountain wind event ongoing, but we can
also see strong winds brought down to the surface by the
convection as it enters the westernmost portion of the forecast
area before dark. As darkness falls, so does the risk of severe
storms, but the Plateau and southern valley are included in a
Marginal Risk area until evening, and this seems appropriate. The
system is moving quick enough so as to not become a flooding
scenario even with the wet soils, but rivers will experience rises
following the rain. The system moves east and out of the area
during the morning hours, leaving us with a mostly fair and mild
New Years Day.
.LONG TERM (Tuesday Night through Monday)...
The long term period will begin with an elongated upper
trough/cutoff low over the four corners region, with broad west to
southwest flow over the lower Mississippi River Valley and
southeastern United States, and broad upper troughing within the
polar jet flow over the upper midwest to New England regions. A
shortwave trough within the northern branch flow will dive southeast
out of Canada and across Minnesota during the day Wednesday, which
will allow the four corners low to begin to move slowly eastward,
finally reaching eastern Tennessee during the day Friday.
Surface high pressure will build across the central plains Tuesday
night, for dry conditions locally Tuesday night and into the day
Wednesday. As the western upper low begins to shift east, an active
subtropical jet and increasing isentropic lift well to its east
should allow some showers to develop by Wednesday evening, but
especially Wednesday night into Thursday morning. Temperatures will
continue to run above normal during this time thanks to warm
southerly flow, with highs into the 50s across much of the area Wed
and lows in the 40s Wed night.
Shortwave upper ridging east of this approaching low may actually
shut precipitation off completely on Thursday. However discrepancies
with respect to how strong this ridging is ahead of the low, as well
as how quickly the low moves east, prevent me from dropping rain
from the forecast completely on Thursday. Best chances for a lull in
rainfall would be Thursday afternoon as the downstream ridge axis
moves overhead. It makes little difference however as rainfall
becomes widespread again Thursday night as the best forcing arrives.
Previous forecasts featured rainfall turning to snowfall at higher
elevations Thursday night however newer model runs feature a slower
progression of this system, thus delaying any drop in temperatures
aloft. Do have some rain/snow mix in for higher elevations beginning
during the afternoon hours on Friday and lasting into Saturday
morning as the upper low shifts east along the TN/VA border. Hard to
say what to expect with regard to accumulations. Suspect some
accumulating snow will be possible at higher elevations, but how
much depends on how quickly the upper low pulls away to the east and
that is a source of some inconsistency in the models at this time.
In any case, any snow comes to an end during the day Saturday, with
a drier pattern with ridging building into the Tennessee Valley
thereafter.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 54 63 43 51 / 80 10 0 50
Knoxville McGhee Tyson Airport, TN 52 61 42 51 / 80 10 10 30
Oak Ridge, TN 51 61 41 50 / 80 10 10 30
Tri Cities Airport, TN 50 59 41 51 / 80 10 0 20
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...Wind Advisory until midnight EST tonight for Johnson-Southeast
Carter-Southeast Greene-Southeast Monroe-Unicoi.
High Wind Warning until midnight EST tonight for Blount Smoky
Mountains-Cocke Smoky Mountains-Sevier Smoky Mountains.
VA...None.
&&
GC/CDHazardous Weather Outlook National Weather Service Morristown TN 315 PM EST Mon Dec 31 2018 NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002- 005-006-008-012015- Cherokee-Clay-Scott TN-Campbell-Claiborne-Hancock-Hawkins- Sullivan-Johnson-Morgan-Anderson-Union-Grainger-Hamblen- Northwest Cocke-Cocke Smoky Mountains-Northwest Greene- Southeast Greene-Washington TN-Unicoi-Northwest Carter- Southeast Carter-Roane-Loudon-Knox-Jefferson-NW 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-Scott-Russell-Washington- 315 PM EST Mon Dec 31 2018 /215 PM CST Mon Dec 31 2018/ This Hazardous Weather Outlook is for portions of Southwest North Carolina...East Tennessee and Southwest Virginia. .DAY ONE...This Afternoon and Tonight Showers and possibly a few thunderstorms can be expected later today into tonight as a cold front approaches and moves through. Strong gusty winds can be expected ahead of this cold front, with the greatest threat for damaging winds in the mountains of East Tennessee. Some localized damaging wind gusts may also occur with the main band of heavier showers and possible storms that will move in late this afternoon or evening, especially in the south and plateau. Two problems may arise due to the already very wet soils. First, localized flooding will be possible in areas that experience the heaviest rainfall. Second, trees may be more prone to toppling beneath strong wind gusts. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday A storm system will move across the Tennessee Valley and Southern Appalachians during the latter half of the week. This system has the potential of producing moderate to heavy rainfall from late Wednesday through Thursday night. Colder temperatures will move into the region changing the rain to snow showers for Friday and Friday night. Snow accumulations are possible over the higher elevations. Confidence is relatively high for another round of moderate to heavy rain, but low on the potential of snowfall. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated at this time. However, reports of flooding or wind damage are encouraged.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MORRISTOWN TN
315 PM EST MON DEC 31 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1115 AM NON-TSTM WND GST 2 S CAMP CREEK 36.06N 82.77W
12/31/2018 M50 MPH GREENE TN MESONET
GUST REPORTED AT CAMP CREEK MET TOWER.
&&The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
A tree and some power lines were reported down at 8001 Clinton Highway approximately two miles west of Powell.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Tennessee in 2018Every state in 2018This day in weather historyWarnings in Tennessee, December 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 793009.