Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Nashville Tennessee
911 am CDT Wednesday may 27 2015
Update...for morning discussion.
With the current trends in the latest hi-res guidance and activity
upstream from the mid-state...a fairly substantial bump in daytime
probability of precipitation looks warranted. An expanding complex of showers and
thunderstorms on the Arkansas-MS state line line...currently spreading
northward into northern MS and soon...west Tennessee...will close in on
our southwestern counties late this morning. By this afternoon...
this activity should spread across the rest of middle Tennessee bringing
widespread showers and ts to the whole area. The question is...how
strong will they become. Dew points are firmly in the upper 60s
and this will not change...but the current cloud cover could
hamper much of the destabilization we could realize. Still...
1500-2000 j/kg is a likely number for US. Coupled with the dry air
that was being shown on the 12z ohx sounding...the wind threat
will likely be a little higher than it was yesterday.
I think the bigger thing we will need to pay attention to is the
slow moving nature of these storms. Along with the dry air
aloft...this morning's sounding is also showing only 13 kts of
forward motion. While our flash flood guidance is a little higher
than most of our surrounding weather forecast offices...rain rates of 1 to 2 inches an
hour with slow motion could produce a localized flash flood
threat this afternoon that we will need to monitor.
Updates are already out.
Aviation...12z taf discussion.
Upper trough axis down through western Missouri into eastern
Oklahoma with convection firing in Missouri this morning along
Interstate 44 corridor with another complex down in Louisiana.
Models take Missouri convection into southern Illinois keeping it
well north of the middle state. New development of convection takes
place in north Mississippi after 14z and expands northward into
western Tennessee as we go through the morning. Around 18z showers
and isolated thunderstorms break out along Interstate 65 corridor
and begins to work eastward while new convection develops across
western middle Tennessee and back toward the Mississippi River.
All in all looking for LIFR ceilings at times during the day with
best shower and storm chances at terminals from about 18z through