Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Nashville Tennessee
728 am CDT Sat Apr 18 2015
12z taf discussion.
Patchy fog will bring MVFR/IFR visible early in the taf period.
Otherwise...VFR conditions are anticipated through 19/03z when
-shra along with MVFR ceilings/visible spread into the area from the
southwest. Light northeast winds this morning will increase and
become southeasterly Saturday night.
Previous discussion... /issued 335 am CDT Sat Apr 18 2015/
Another relatively quiet night across the middle state tonight. Some
fog has developed thanks to partial clearing skies and lingering
surface moisture from all of the precipitation this week. Winds
are also calm...which is adding to the potential for fog
development. Visibilities across the area are showing as low as
quarter mile up to around 5 miles for sites reporting fog. The fog
potential should continue into middle morning or so as temperatures
warm up a bit.
The trough moving up from the southwest will start to impact the
region with precipitation this afternoon. Some models are placing a bit
of quantitative precipitation forecast on the plateau earlier this morning...but continued with
the trend and kept probability of precipitation for the afternoon. Bumped probability of precipitation a bit this
afternoon as models also are bringing precipitation in a bit earlier.
Main bands of precipitation should move in later this evening and
overnight...with rain totals around a half inch to an inch or more
A brief break in the precipitation moves in Sunday morning as the surface
low travels northward and the middle state is under the clear slot
in the warm sector. Severe parameters havent changed much since
yesterdays forecast...with MUCAPE values around 1000-1500 j/kg and
0-6km shear in the 35-45 knot range. Storm Prediction Center outlook still has the
region in a slight risk for severe weather as well. There is a
chance that some isolated cells will be ahead of the cold front in
the warm sector...however there is a better chance for a more
linear convective Mode with the approaching cold front. This
should cause the main impact with severe potential to be damaging
winds...but hail can not be ruled out especially with any cells
out ahead of the main line.
Drier weather still looks to be in place on Tuesday and Wednesday
before some subtle disturbances in the upper flow and a cold front
from a Great Lakes upper low move in. The GFS and European model (ecmwf) still
differ slightly on their solutions for the end of next
week...however by next Saturday both models are showing a good
amount of quantitative precipitation forecast over the region. Ran with higher probability of precipitation at the end of
the extended to reflect this.