acus01 kwns 191942
Storm Prediction Center ac 191940
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0240 PM CDT sun may 19 2013
Valid 192000z - 201200z
..there is a MDT risk of severe thunderstorms from central OK to western MO...
..There is a slight risk of severe thunderstorms surrounding the MDT risk from
north central Texas to central Minnesota...
..there is a slight risk of severe thunderstorms from parts of middle Tennessee into
..few strong tornadoes possible across MDT risk area...
Strong heating across western OK has removed the cap along the
dryline...per deepening cumulus from the Red River near Special Weather Statement...northward across
Caddo County into scntrl Kansas over Harper County where lightning is
now observed with deepest convection. With temperatures continuing
to rise there is reason to believe scattered supercells will emerge
along the dryline...especially north of I-40 into eastern Kansas where very
moist/buoyant airmass currently resides. Vertical shear profiles
are such that long-lived supercells are expected...and if sufficient
coupling with moist boundary layer occurs a few strong tornadoes may
be noted across the MDT risk into the evening hours...especially
in vicinity of old outflow boundary that was draped across northestern OK/southeastern Kansas.
Although it has lost its identity...boundary layer winds are backed
a bit across this region and this may serve to enhance low level
..ern Tennessee...Northestern Alabama/northwestern Georgia...
Have opted to increase severe probs across parts of eastern Tennessee into northestern
Alabama/northwestern Georgia to account for northwest-southeast oriented convective cluster that
should propagate southward across this region. Locally damaging winds may
accompany this upward evolving complex of storms before diurnal
cooling results in weakening.
Earlier thoughts regarding deep convection remain and only minor
changes have been made to 1630z forecast.
Previous discussion... /issued 1115 am CDT sun may 19 2013/
A deep layer cyclone appears likely to continue to evolve through
this forecast period over the middle Missouri Valley region. In
association with this feature...mid/upper flow has already
strengthened across the Texas/Oklahoma Panhandle region through the
Central Plains and upper Mississippi Valley...in a belt curving
cyclonically out of the intermountain region. Within this
regime...a series of short wave impulses/speed maxima have and will
continue to emerge from the intermountain west...while additional
perturbations continue to dig into the Great Basin.
East of The Rockies...mid-level lapse rates remain very steep over a
broad area...from the Central Plains and middle Mississippi Valley
southward to Gulf coastal areas. Atop a relatively moist boundary
layer...this will contribute to substantial convective instability
and sizable cape across a broad area of the plains and Mississippi
Valley region. This is expected to be accompanied by considerable
thunderstorm activity...including another outbreak of severe
weather...particularly across parts of eastern Kansas and Oklahoma
into parts of Missouri.
Additionally...on the western periphery of a weak cyclonic belt of
flow developing eastward across the South Atlantic coast
region...lift and steepening middle-level lapse rates associated with
Lower/Middle tropospheric warm advection will maintain a risk for
thunderstorm activity from parts of the Tennessee Valley into
Georgia and northern Florida. Marginally severe wind and hail do
not appear out of the question in stronger storms...particularly
with additional heating ahead of an organizing storm cluster now
advancing west through south of Atlanta Georgia.
One short wave impulse is currently in the process of turning
northeast of the Central Plains into the upper Mississippi Valley.
This feature is aiding increasing storm development across parts of
northeast Missouri into west central Illinois. Some severe
hail/wind potential may exist with this activity... but a more
substantive severe weather risk may await further boundary layer
destabilization and weakening inhibition across Iowa northward into
parts of Minnesota and Wisconsin later today.
The primary severe weather potential is expected to develop in the
wake of this initial impulse...as another continues to pivot east of
the Central High plains this afternoon. This seems most likely to
become focused along/south and east of a remnant convectively
generated boundary that currently curves from the Missouri Ozarks
into northern Oklahoma. A northward retreat of this boundary into
southern Kansas is still expected...and latest high resolution rapid
refresh appears reasonable suggesting initiation of storms along the
intersection of this boundary and an eastward advancing
dryline...across north central Oklahoma or south central Kansas...by
Aided by forcing in the exit region of a middle-level speed maximum
nosing northeastward across the south Central Plains...upscale
convective growth into a substantial mesoscale convective system is
expected late this afternoon and evening. In the presence of strong
deep layer shear...40-50 knots southerly 850 mb flow near and south of
the convective boundary will contribute to sizable clockwise curved
low-level hodographs supportive of the risk for tornadoes. Highest
probabilities for tornadoes...some possibly strong...may be
supercells on the southern flank of the evolving convective
system...across southeast Kansas into parts of west
central/southeast Missouri...as well as with storms initiating and
advancing northeastward off the dryline...across northeastern
Oklahoma. Further strengthening of the 850 mb jet across eastern
Oklahoma into southwest Missouri will maintain tornadic potential
well into the evening hours...with one or two long-lived tornadic
acus11 kwns 191955
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 191955
Mesoscale discussion 0700
National Weather Service Storm Prediction Center Norman OK
0255 PM CDT sun may 19 2013
Areas affected...W-cntrl and southern Georgia...far northern Florida
Concerning...Severe Thunderstorm Watch 179...
Valid 191955z - 192030z
The severe weather threat for Severe Thunderstorm Watch 179
Summary...strong-svr winds may continue to accompany S-southeastward
propagating thunderstorm cluster across southern Georgia and perhaps into far northern Florida.
Local offices may clear counties from ww 179 in its wake...where the
boundary layer has stabilized.
Discussion...radar trends indicate a thunderstorm cluster over west-central Georgia
has become less organized over the past 1-2 hours...with a diminishing
comma head structure. Propagation now appears to be occurring
parallel to an outflow boundary accompanying earlier convection over
east-central Georgia. Although the downstream environment remains sufficiently
unstable to maintain convection /I.E. 1300-1800 j/kg MLCAPE per rap
objective analysis/...weak deep-layer flow suggests that this
cluster may continue struggling to organize. However...a
strong-marginally severe wind threat may still exist given the degree
of instability present and steep low-level lapse rates.
..please see www.Spc.NOAA.Gov for graphic product...
Latitude...Lon 32638260 30958158 30498145 30078157 30108238 29858252
30008285 30308371 30588411 30718473 31068496 31798492
32488490 32768373 32638260