Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Memphis Tennessee
115 PM CDT Monday may 25 2015
Previous discussion... /issued 1050 am CDT Monday may 25 2015/
morning update. Its been a busy Monday morning...but things are
finally settling down across the midsouth. The break may prove to
be short lived as we are rapidly destabilizing across the region.
East Arkansas already has convective available potential energy in excess of 1000k/kg with lifted indice's
between -2 and -4c. We should see at least partial clearing today
helping US to destabilize even further this afternoon. However
with dew points in the middle to upper 60 and an approaching
shortwave...dynamic energy may be sufficient to result in another
round of strong to severe thunderstorms even if we did not have
the thermodynamic support.
Previous discussion... /issued 644 am CDT Monday may 25 2015/
updated to add 12z aviation discussion.
Previous discussion... /issued 453 am CDT Monday may 25 2015/
A large upper level low pressure system continues to move slowly
east into the western High Plains this morning. A lead shortwave
is currently lifting northeast and away from the middle south early
this morning. Widespread showers and thunderstorms across areas
mainly along and east of the Mississippi River will continue to
diminish in coverage and intensity this morning. Most locations
will dry out temporarily later this morning through middle afternoon
as a pronounced middle level dry slot rotates across the region.
There will likely be breaks in the cloud cover during this period
and decent surface heating should occur and help to destabilize
the atmosphere again by later this afternoon. High temperatures
should range from near 80 degrees across eastern areas to the
middle 80s across the Mississippi Delta areas.
Another distinct shortwave over southwest Texas early this morning
will eject northeastward today across the Southern Plains and into
western portions of the middle south later this evening. There
remains some differences in timing among the latest model guidance
with the GFS and NAM/WRF runs suggesting an earlier arrival
compared to the latest European model (ecmwf). At this time...it appears that an
earlier arrival falls in line with the overall daily model run to
run continuity along with the latest high resolution hrrr output.
This should support redevelopment of showers and thunderstorms
this evening mainly along and west of the Mississippi River which
should eventually consolidate into a line and move slowly east
across areas east of the Mississippi River through Tuesday
Latest preferable model output with earlier timing suggests that
the atmosphere will again destabilize this afternoon...especially
areas along and west of the Mississippi River with SBCAPE values
rising to between 1500-2500 j/kg by 00z Tuesday. In addition...as
the shortwave approaches this evening expect 0-1 srh to increase
to between 200-300 m^2/s^2 as low level winds remain backed to the
southeast with a veering profile with height. Low level jet winds
on the order of 40-50 kts will overspread western areas during the
evening hours and persist through the night. Large scale ascent
with the shortwave should allow numerous showers and thunderstorms
to develop quickly by middle afternoon across the arklatex and spread
quickly northeast as a quasi linear convective system (qlcs) into
areas west of the Mississippi River this evening. Latest high
resolution models also suggest the potential for thunderstorm
development in advance of this line. The potential will exist
again for a few severe thunderstorms beginning this evening and
continuing into early Tuesday morning mainly along and west of the
Mississippi River. The primary severe weather threats will again
be damaging winds and a few tornadoes.
The threat for heavy rainfall will also continue with the
potential for localized amounts between 2 and 4 inches. There may
be a few isolated higher amounts. These rainfall amounts if
realized will lead to areas of flash flooding. Therefore...have
continued and extended the Flash Flood Watch for the entire middle
south through 18z Tuesday.
As the shortwave lifts northeast of the region Tuesday
morning...the area will be left under an area of broad upper
troughing associated with the approaching upper low to our
northwest. Showers and thunderstorms will likely continue across
the region through Tuesday but should become increasingly
unorganized through the day as focused lift diminishes and deep
layer wind fields weaken through the day.
The upper level pattern will become less amplified late in the
week but with a continued tropical airmass in place combined with
daytime heating should lead to mainly diurnally forced convection.
A few pulse strong to severe thunderstorms will be possible each
afternoon with the potential for wet microbursts as strong
instability develops but with weak wind fields. Any storm will be
slow moving and could also produce localized heavy rainfall.
Temperatures will warm back to near or slightly above seasonal
averages along with continued high humidity levels.
Another upper level trough will approach from the west by early
in the weekend and move slowly across the middle south through the
weekend into early next week. This will bring a continuation and
increased chances for showers and thunderstorms across the area
through the end of the extended forecast period. Temperatures will
remain seasonably warm with humid weather continuing through the
Aviation...18z taf cycle
Southerly winds should continue through the period, pick up
this afternoon with associated gusts. Showers and thunderstorms
will pick up this afternoon. A more organized group of severe storms
will come through tonight.
Arkansas...Flash Flood Watch through Tuesday afternoon for Clay-Craighead-
MO...Flash Flood Watch through Tuesday afternoon for Dunklin-Pemiscot.
MS...Flash Flood Watch through Tuesday afternoon for Alcorn-Benton MS-
Tennessee...Flash Flood Watch through Tuesday afternoon for Benton Tennessee-