FXUS64 KMRX 190714
Area Forecast Discussion
National Weather Service Morristown TN
314 AM EDT Tue Mar 19 2019
.SHORT TERM...(Today and Tonight)...
A ridge of high pressure will produce dry and cool conditions
through tonight. Main concern will be the low afternoon relative
humidity. Have included this concern in the Fire Weather Forecast.
Will continue freeze warning for the southern plateau and valley
through mid-morning. Temperatures have dropped to the lower 30s
across much of the area.
For tonight, a few locations will drop to near freezing in the
same areas, but not widespread enough to issue another freezing
warning. Dry conditions will limit any frost development.
.LONG TERM (Wednesday through Monday Night)...
The extended range fcst period tips off on Wednesday morning amidst
a fairly active H5 pattern highlighted by a potent shortwave
advancing eastward across the Central Plains into the Mid MS and
Lower OH Valleys, while zonal flow prevails out ahead over the
East/Southeast CONUS. At the surface, high pressure prevails over
the Eastern Seaboard in lee of the Appalachians, beneath weak
confluent flow aloft. Pattern evolution through the extended range
will feature the aforementioned shortwave traversing the OH/TN
Valleys Wendesday night, while the left exit region of an upper
jetmax moves along the I10 corridor region of GA/FL promoting
surface cyclogenesis along the Carolina coastline. By midday
Thursday, the primary shortwave axis should be crossing the
Appalachians setting up deep nwly flow atop the region, while the
East Coast Cyclone races north toward New England. As for impacts
associated with this wave across the TN Valley and Southern
Appalachians, profiles ahead of the system suggest a rather dry
airmass given minimal preceding return flow. However, the wave
itself does look to advect modest midlevel moisture into the region
on Wendesday night, sufficient to support showers. Likewise, on
Thursday amidst the developing nwly flow, cannot rule out some
residual focusing of light precipitation along the favored upslope
regions, possibly with a few light snow showers at the highest
elevations of east TN and southwest VA into Friday morning as snow
levels fall, before all precipitation moves out.
Beyond that moving into Friday, sharp and nearly full latitude H5
ridging sets up across the Central CONUS, while the Eastern CONUS
trough slowly shifts east. Rising heights into Saturday will be
accompanied by another region of dry high pressure advecting
southward across the OH Valley into Central/Southern Appalachians.
On Sunday the upper ridge begins to deamplify as troughing deepens
and moves east setting up a zone of baroclinicity over the Plains
and MS Valley, as well as a return to weak sly waa across the
southeast. At this range guidance tends to diverge a bit with regard
to the details, but it looks like a deepening H5 low will initiate
surface cyclogenesis across the Midsouth in that late Sunday to
early Monday timeframe, with a potent frontal passage and associated
convection to traverse across the TN Valley Monday evening into
As for temperatures throughout the period, expecting at or below
normal levels to dominate through the remainder of the work week. As
the aforementioned upper ridge builds into the region on Saturday
and weak waa initiates on Sunday, moderation should commence allowing
temperatures to return to and exceed normal levels by periods end.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 57 37 60 44 / 0 0 10 30
Knoxville McGhee Tyson Airport, TN 54 35 57 43 / 0 0 0 30
Oak Ridge, TN 55 35 59 43 / 0 0 10 40
Tri Cities Airport, TN 52 30 56 40 / 0 0 0 30
TN...Freeze Warning until 9 AM EDT /8 AM CDT/ this morning for
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