Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Memphis Tennessee
827 am CDT Thursday Jul 2 2015
updated for reduced probability of precipitation this morning.
Satellite and radar indicating complex of storms waning with
warming cloud tops and decreased intensity/coverage. So this
morning shifted likely probability of precipitation to west of I-55...and reduced probability of precipitation to
the east. Clouds will linger into early afternoon with
destabilizing expected later in the afternoon and throughout the
evening. Also adjusted morning temperatures down a few degrees.
Previous discussion... /issued 638 am CDT Thursday Jul 2 2015/
updated for 12z aviation discussion below.
Previous discussion... /issued 438 am CDT Thursday Jul 2 2015/
Discussion...surface analysis this morning places a quasi-
stationary boundary stretching from southeast Kansas through east
central Missouri and southwest Illinois. Meanwhile...water vapor
satellite/regional WSR-88D VAD wind profiles indicate a mesoscale
convective system /MCS/ located over southern Missouri. As of 4
am CDT...showers and embedded thunderstorms are beginning to enter
the northern third of the middle south with some warm advection rain
showers occurring south of I-40. Strong to severe thunderstorm
potential into tonight and potential for heavy rainfall are the
concerns in this morning/S forecast.
Leading stratiform showers and thunderstorms associated with a
weakening mesoscale convective system will continue to push south across the middle south
this morning...especially along and north of I-40. At this
time...think the early morning convective activity may stabilize
the boundary layer perhaps at least through middle afternoon. Short
term models indicate the quasi-stationary boundary over Missouri
will begin to move south into the lower Mississippi Valley tonight
into Friday with a potential for the atmosphere to recover later
this afternoon into this evening. Surface based cape values
between 2000-4000 j/kg combined with 0-6 km bulk shear between 30-35
kts...and somewhat favorable winds aloft suggest a potential for
strong to severe thunderstorms to develop during this period.
Precipitable water values around 2 inches will pose a threat for
localized heavy rainfall and possible flash flooding. Damaging
winds would be the primary threat for any thunderstorms that can
reach severe limits. Models have struggled with mesoscale trends
over the past 24 hours and this morning/S convective activity
does raise some uncertainty with the overall coverage of the
severe weather potential later this afternoon into tonight.
Forecast trends will be monitored throughout the day and any
potential hazards adjusted if needed.
Models indicate this boundary will become quasi-stationary across
the middle south Friday into the Fourth of July. This boundary
combined with several shortwave troughs embedded within northwest
flow aloft and a warm...moist and unstable atmosphere will result
in several chances for showers and thunderstorms. This surface
boundary is anticipated to begin lifting north Sunday into next
week as an upper level ridge over the Southern Plains tries to
build into the lower Mississippi Valley. The middle south appears to
be on the eastern periphery of the ridge axis and isolated to
scattered shower and thunderstorm chances will exist during this
period...especially during the afternoon and evening hours each
day. Strong to severe thunderstorms along with localized heavy
rainfall may be possible each day.
Decaying convective system that dropped southeast from the Ozarks
early this morning will present a limited chance for thunder at
jbr. Otherwise... -shra possible this morning with VFR / isolated
MVFR at the other midsouth taf locations.
Afternoon destabilization / location of best low level convective
development remains the forecast challenge. Hrrr and NAM models
have struggled struggled in handling daytime convection following
nocturnal airmass modification from nighttime rains. That said...
today/S late afternoon thunderstorms and rain chances may get a boost from a shortwave
that was entering northwest Kansas at discussion time...1130z. If this
scenario plays out...late afternoon would could see a late afternoon
bump in thunderstorms and rain chances...followed by reduced late evening thunderstorms and rain chances
behind the exiting shortwave.