Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Morristown Tennessee
315 am EDT Sat Apr 18 2015
Short term (today and tonight)...
satellite trends show decreasing clouds from west to east. This
should result in some patchy fog in areas where clearing will take
place. With mostly sunny skies through the morning and a downslope
southeast flow aloft intensifying in the afternoon...we should see the
warmest temperatures in the northern Tennessee Valley...with highs around 80 in
the Tri-Cities area. Greater cloud cover in the south will keep
highs in the upper 70s in that area. Afternoon heating should
provide a little instability...especially in the mountains...and
will have a slight to low chance pop in the afternoon.
More organized precipitation associated with an upper level jet and
shortwave trough will move in from the south tonight. Categorical
probability of precipitation will gradually spread north through the night...and with good
upper level divergence acting in conjunctino with on marginal
elevated instability...a chance of thunderstorms will be mentioned.
Southern areas should see at least a half inch of quantitative precipitation forecast before
12z...while downslope winds will suppress quantitative precipitation forecast north for most of the
Long term (sunday through saturday)...
Sunday morning continues the widespread precipitation associated
with the low moving north along the Arkansas/Tennessee border. Some
of the heaviest rain will likely be Sunday midnight through around
Sunday at noon as precipitable water values are generally near or
above 1.5 inches. Could see widespread rainfall of near 1 inch of
late Sunday afternoon with potentially higher amounts in some
localized areas. We will then need to turn our attention to some
potential strong to severe storms Sunday night. Will have to be
watching storms as they form across far eastern Texas into far
western Tennessee along a pre-frontal trough associated with an
upper level trough moving across the eastern half of the United
States. Could see isolated storms congeal into a line as they move
east across the State of Tennessee. At this point think that the
storms will lose a lot of their punch overnight, but won't rule out
the chance that a few strong storms could make their way into our
County Warning Area.
Will still have a few showers and maybe some thunderstorms lingering
around the area during the day on Monday as the cold front makes
it's way through the area. We will clear out overnight leading to
mostly sunny skies by Tuesday. Precipitation chances stay away through the
middle part of the week behind the front. A few ripples of energy
move across the region at the end of the work week leading to some
slight chances of precipitation. European model (ecmwf) is starting to come more in
line with the GFS towards the end of the forecast period for the
next round of widespread rain. Right now the details are fuzzy, but
we could be in for a wet start to next weekend.
Preliminary point temps/pops...
Chattanooga Airport, Tennessee 76 62 76 61 / 40 100 90 60
Knoxville McGhee Tyson Airport, Tennessee 78 61 76 61 / 20 100 90 60
Oak Ridge, Tennessee 77 62 75 60 / 20 100 90 60
Tri Cities Airport, Tennessee 80 58 75 56 / 20 70 90 60