Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Morristown Tennessee
333 PM EDT Wednesday Mar 12 2014
Short term (today and tonight)...
a cold front is exiting to the east...and gusty winds have developed
across the area as the deepening surface low tracks into the central
Appalachians. Several observation sites are showing winds above advisory
criteria...and this is expected to continue through the evening. The
current end time of 03z for the advisory looks good.
Temperatures are falling rapidly behind the front as strong cold advection
spreads into the area. Light showers over eastern Kentucky will spread into SW
Virginia through the rest of the afternoon...changing over to snow this
evening as midlevel temperatures drop. Steep low level lapse rates will
help maintain scattered to numerous snow showers in northern areas
overnight...with a 30-40 knots northwest flow from 925-850 mb enhancing
amounts in higher elevations. Moisture depth appears adequate for
accumulations between 00z and 06z...after which time precipitation should
taper off. 1-3 inch amounts appear reasonable in elevations above
2500 feet...will less than 1 inch below that level for SW Virginia and NE
Tennessee. Will maintain the Winter Weather Advisory as is.
Morning clouds will give way to sunshine tomorrow afternoon...but
high temperatures will only reach into the 40s in most spots...with 30s
north and in the mountains. Went a bit below MOS temperatures as this is an
anomalously cold air mass for this time of year.
Long term (thursday night through wednesday)...
a quiet start to the long term with a potentially wet weekend
followed by a return of quiet weather through the rest of the
High pressure is expected to continue building over our area
Thursday night through most of the day on Friday. Clear skies on
Thursday night will give way to increasing clouds through the day on
Friday as an upper level trough begins to swing across the Ohio
River valley. Thursday night will once again be cold with lows in
the upper 20s to lower 30s. Friday temperatures rebound back into middle/upper
50s and low 60s. The low pressure center associated with the upper
level trough is north of the Great Lakes so whatever trailing energy
sweeps across our area on Friday night/Saturday morning will be very
weak and should keep US mostly dry but will drop temperatures a few degrees
as the front moves through. By Saturday morning models are showing a
weak wave over the Texas Panhandle and another stronger wave moving
into the Pacific northwest. The weaker wave will move east and give
US a slight chance for some light precipitation through the day on
Saturday. This is where pattern becomes a little messy.
Saturday night into Sunday...the aforementioned wave across the
Pacific northwest drops down into Texas along with the developing
trough...but strong ridging off the Baja California peninsula forces that wave
down into Mexico instead of on a continued eastward track across the
southern U.S. The models want to show the approaching trough
catching up to the first weaker wave...now located around the
Mississippi River valley...and phase these two features
together...resulting in a strengthening system. When/where/if they
phase will greatly impact our weather during the Saturday night
through Monday period. Both the European model (ecmwf) and GFS show colder air
getting pulled into our area on Sunday night into Monday on the back
side of the developing low pressure system...which means that if
there is enough moisture still around we could see some snow Sunday
night into Monday. Still way too early for any type of snow amounts
due to the uncertainty with this system. Both models show the trough
exiting to our east on Monday with clearing conditions thereafter.
High pressure builds back in for Tuesday with another system
possible on Wednesday.
Preliminary point temps/pops...
Chattanooga Airport, Tennessee 30 50 32 64 / 10 0 0 0
Knoxville McGhee Tyson Airport, Tennessee 28 44 32 62 / 30 0 0 0
Oak Ridge, Tennessee 27 44 32 62 / 30 0 0 0
Tri Cities Airport, Tennessee 23 40 26 58 / 50 10 0 0
NC...Wind Advisory until 11 PM EDT this evening for Cherokee-Clay.
Tennessee...Winter Weather Advisory until 4 am EDT Thursday for Blount Smoky
Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
Mountains-southeast Carter-southeast Greene-southeast
Wind Advisory until 11 PM EDT /10 PM CDT/ this evening for
Anderson-Bledsoe-Blount Smoky Mountains-Bradley-Campbell-
Claiborne-Cocke Smoky Mountains-east Polk-Grainger-Hamblen-
Marion-McMinn-Meigs-Morgan-NW Blount-north Sevier-northwest
Carter-northwest Cocke-northwest Greene-northwest Monroe-
Rhea-Roane-Scott Tennessee-Sequatchie-Sevier Smoky Mountains-
southeast Carter-southeast Greene-southeast Monroe-Sullivan-
Unicoi-Union-Washington Tennessee-west Polk.
Virginia...Winter Weather Advisory until 4 am EDT Thursday for wise.
Wind Advisory until 11 PM EDT this evening for Lee-Russell-Scott-