Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Memphis Tennessee
721 am CDT Wednesday Sep 17 2014
Updated for the 12z aviation discussion.
Previous discussion... /issued 340 am CDT Wednesday Sep 17 2014/
Infrared satellite showing patchy cloudiness across the midsouth this
hour...with more clouds over the northern counties. Upstream
convective clouds were crossing eastern Kansas and Missouri with a
few storms forming. Also noted across the midsouth was a large
range in temperatures...with a cool 50f in Paris Tennessee...and
66f observed in Aberdeen Mississippi. Winds were generally
northeast at around 5 miles per hour.
For today and tomorrow...weak disturbances in an upper northwest
flow will bring increased cloudiness and the threat for elevated
convection to the area. Best chances for rain timing will be
tonight into early Thursday. Most favorable area will be across
the west...closer to a stationary front in central Arkansas.
Temperatures this period will run a degree or two below normal.
Friday and Saturday...the only change from the previous thinking
was to lower fridays temperatures slightly as lingering Northeast
Boundary layer winds slow the start of low level warm air advection. By Saturday
though the low level flow will veer more southerly as the ridge
axis passes overhead. This should take highs to near 90f for many
locations. The period will be dry with comfortable humidity.
Sunday through Tuesday...a more active period expected...at least
for Sunday and Monday. The ridge will shift east...while the
combination of Odile remnants and a deepening Great Lakes trough
drive a cold front south. For now have leaned more with a wetter
European model (ecmwf) solution with regards to both precipitation amounts and
timing. Believe the GFS is just to dry and fast with the
Dewpoints will increase to the upper 60s ahead of the front by late
Sunday...giving the additional lift associated with Odile plenty
of moisture to work with. The Euro solution also lingers activity
into most of the day Monday as a second shortwave in the Ohio
Valley slows the front across Mississippi. With this setup Euro
quantitative precipitation forecast amounts of 1 to 2 inches during the period sounds much more
reasonable...though any additional slowing would make these
initial amounts to conservative. In response to these changes have
increased probability of precipitation over the area Sunday night and into Monday
morning...with drier air working into the north beginning Monday
afternoon. Post frontal Canadian airmass will settle into the
entire midsouth by Tuesday with highs cooling to widespread 70s.
12z taf cycle
VFR ceilings are expected today at kmem...kmkl...and ktup. MVFR ceilings
have developed into kjbr this morning but will slowly lift through
late morning to VFR. A few vicinity showers and thunderstorms will
be possible late this morning into early afternoon at kjbr and
kmkl with a decaying thunderstorm complex now over Missouri. This
complex should diminish by early afternoon.
Latest model guidance suggests that renewed mesoscale convective system storm development
will occur late this afternoon and impact kjbr through this
evening with reduced ceilings and visibilities. Elsewhere VFR ceilings will
persist through the evening with only vicinity storm coverage.
MVFR ceilings will eventually redevelop at kjbr...kmem...and kmkl
towards midnight with some patchy fog as well. Ktup should
maintain low end VFR ceilings but MVFR visibility reductions in fog.
Winds will be mainly light northeast this morning veering to to
southeast and fairly light through the evening hours. Winds should
go back to east northeast later tonight behind convection.