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1 2 3 4 Severe Storm Outlook Narrative (AC)
000
acus01 kwns 200602
swody1
spc ac 200600
day 1 convective outlook
nws storm prediction center norman ok
0100 am cdt mon may 20 2013
valid 201200z - 211200z
... there is a mdt risk of svr tstms across portions of ok/southeast
ok/southern mo/northwest ar...
... there is a slgt risk of svr tstms from the southern plains to the
midwest/great lakes region...
... synopsis...
yet another active/relatively widespread severe weather day is
likely across portions of the southern plains to midwest today and
tonight. a prominent central conus upper trough will continue a
general eastward advancement through tonight ... with a lead/closed
upper low pivoting over the dakotas/upper midwest. a southern stream
shortwave trough/moderately strong polar jet will eject
east - northeastward over the southern rockies to the southern
plains/ozarks ... with severe tstms increasingly likely by peak
heating and continuing into tonight.
meanwhile ... a lingering upper low over the coastal southeast states
will contribute to another day of widely scattered to scattered
tstms over the region ... some of which may again be strong or severe.
... southern plains/ozarks/middle ms valley...
under the influence of broad/moderately strong cyclonic flow
aloft ... the airmass is expected to again become quite unstable
across much of the region by the afternoon beneath an elevated mixed
layer extending across the southern plains into parts of the ozarks
and lower/middle ms valley. middle/upper 60s and some lower 70s f
surface dewpoints will be quite common within a spatially broad warm
sector ahead of a cold front extending from an eastern dakotas/mn
surface low southwestward to near the kansas city area/eastern ks
and western ok ... and ahead of a dryline extending from southwest ok
southward into western north tx/west - central tx.
outflow remnants from overnight/early day convection across the
ozarks/middle ms valley will likely be a factor into this
afternoon ... possibly as a renewed focus for severe tstm
redevelopment ... with the most aggressive heating/destabilization on
the western fringes of this activity across the southern plains and
perhaps lower mo valley just ahead of the true synoptic cold front.
severe tstms capable of hail/damaging winds and some tornado threat
will be possible along this frontal zone across eastern ks/northern
mo into the upper ms valley ... with a persistent/east - northeastward
developing severe threat into the evening.
that said ... the most intense/most probable severe storms are
anticipated a bit farther south - southwest across the southern
plains/ozarks by mid/late afternoon into tonight. this includes a
portion of the synoptic front and/or outflow across far southeast
ks/southwest mo ... areas roughly parallel and northwest of the i - 44
corridor ... but especially south - southwestward into much of the
middle part of ok /potentially including okc metro/... to near the
heat - aided surface low and southward - extending sharpening dryline
into the western part of north tx/west - central tx. in this
corridor ... mlcape values are likely to exceed 2500 - 3000 j/kg by
afternoon within the warm sector across ok and
west - central/north - central tx ... and perhaps into parts of southeast
ks and mo. with broad/moderately strong cyclonic mid - high level flow
/50+ kt at 500 mb/ over the region ... 40 - 50 kt of effective shear
will coincide with the majority of the effective frontal zone and/or
dryline across ok/extreme north tx into southeast ks and the ozarks.
the degree of shear and moisture/instability within the warm sector
will favor scattered to numerous supercell structures ... at least
through mid - evening of the convective cycle. very large hail and
tornadoes are possible with supercells ... with an early evening peak
tornado threat /perhaps a couple of strong tornadoes/ boosted by a
nocturnally strengthening southerly low level jet and associated
low - level hodograph enlargement. ultimately ... one or more mcs/s
should evolve along nose of strengthening low level jet over ok and
eventually into the ozarks by late evening/overnight. damaging wind
potential will likely increase in association with mcs development
this evening.... aside from a severe hail and continued tornado
risk ... but on an increasingly isolated basis into late
evening/overnight.
... upper midwest/great lakes...
mid - level shortwave trough/speed max will pivot northeastward over
the upper midwest/upper ms valley during the afternoon ... with
associated forcing for ascent overspreading a relatively
moist/unstable boundary layer to the south of a warm front extending
from the eastern dakotas/mn surface low eastward to northern
portions of the great lakes region.
two general scenarios for severe tstm development seem probable this
afternoon. one being parts of ia/upper ms valley on the eastern
periphery of the upper low and upper jet exit region as it coincides
with the synoptic front. meanwhile ... farther east ... propagation of
remnant outflow /even subtle remnants into afternoon/ are a
plausible influence for renewed tstm development into a very
unstable airmass across the great lakes region. overall ... this
includes potential for some supercells aside from sustained linear
structures ... with bouts of damaging winds/severe hail and a couple
of tornadoes all possible across the region.
... southeast states/fl...
the airmass should strongly destabilize this afternoon ... especially
in areas near and west - southwest of the appalachians ... with
diurnally increasing/intensifying tstm development further aided by
a persistent upper low over the region. bouts of damaging winds and
some hail will be possible as storms generally drift southward
through the afternoon/early evening hours.
.. guyer/mead.. 05/20/2013
000
acus01 kwns 200602
swody1
spc ac 200600
day 1 convective outlook
nws storm prediction center norman ok
0100 am cdt mon may 20 2013
valid 201200z - 211200z
... there is a mdt risk of svr tstms across portions of ok/southeast
ok/southern mo/northwest ar...
... there is a slgt risk of svr tstms from the southern plains to the
midwest/great lakes region...
... synopsis...
yet another active/relatively widespread severe weather day is
likely across portions of the southern plains to midwest today and
tonight. a prominent central conus upper trough will continue a
general eastward advancement through tonight ... with a lead/closed
upper low pivoting over the dakotas/upper midwest. a southern stream
shortwave trough/moderately strong polar jet will eject
east - northeastward over the southern rockies to the southern
plains/ozarks ... with severe tstms increasingly likely by peak
heating and continuing into tonight.
meanwhile ... a lingering upper low over the coastal southeast states
will contribute to another day of widely scattered to scattered
tstms over the region ... some of which may again be strong or severe.
... southern plains/ozarks/middle ms valley...
under the influence of broad/moderately strong cyclonic flow
aloft ... the airmass is expected to again become quite unstable
across much of the region by the afternoon beneath an elevated mixed
layer extending across the southern plains into parts of the ozarks
and lower/middle ms valley. middle/upper 60s and some lower 70s f
surface dewpoints will be quite common within a spatially broad warm
sector ahead of a cold front extending from an eastern dakotas/mn
surface low southwestward to near the kansas city area/eastern ks
and western ok ... and ahead of a dryline extending from southwest ok
southward into western north tx/west - central tx.
outflow remnants from overnight/early day convection across the
ozarks/middle ms valley will likely be a factor into this
afternoon ... possibly as a renewed focus for severe tstm
redevelopment ... with the most aggressive heating/destabilization on
the western fringes of this activity across the southern plains and
perhaps lower mo valley just ahead of the true synoptic cold front.
severe tstms capable of hail/damaging winds and some tornado threat
will be possible along this frontal zone across eastern ks/northern
mo into the upper ms valley ... with a persistent/east - northeastward
developing severe threat into the evening.
that said ... the most intense/most probable severe storms are
anticipated a bit farther south - southwest across the southern
plains/ozarks by mid/late afternoon into tonight. this includes a
portion of the synoptic front and/or outflow across far southeast
ks/southwest mo ... areas roughly parallel and northwest of the i - 44
corridor ... but especially south - southwestward into much of the
middle part of ok /potentially including okc metro/... to near the
heat - aided surface low and southward - extending sharpening dryline
into the western part of north tx/west - central tx. in this
corridor ... mlcape values are likely to exceed 2500 - 3000 j/kg by
afternoon within the warm sector across ok and
west - central/north - central tx ... and perhaps into parts of southeast
ks and mo. with broad/moderately strong cyclonic mid - high level flow
/50+ kt at 500 mb/ over the region ... 40 - 50 kt of effective shear
will coincide with the majority of the effective frontal zone and/or
dryline across ok/extreme north tx into southeast ks and the ozarks.
the degree of shear and moisture/instability within the warm sector
will favor scattered to numerous supercell structures ... at least
through mid - evening of the convective cycle. very large hail and
tornadoes are possible with supercells ... with an early evening peak
tornado threat /perhaps a couple of strong tornadoes/ boosted by a
nocturnally strengthening southerly low level jet and associated
low - level hodograph enlargement. ultimately ... one or more mcs/s
should evolve along nose of strengthening low level jet over ok and
eventually into the ozarks by late evening/overnight. damaging wind
potential will likely increase in association with mcs development
this evening.... aside from a severe hail and continued tornado
risk ... but on an increasingly isolated basis into late
evening/overnight.
... upper midwest/great lakes...
mid - level shortwave trough/speed max will pivot northeastward over
the upper midwest/upper ms valley during the afternoon ... with
associated forcing for ascent overspreading a relatively
moist/unstable boundary layer to the south of a warm front extending
from the eastern dakotas/mn surface low eastward to northern
portions of the great lakes region.
two general scenarios for severe tstm development seem probable this
afternoon. one being parts of ia/upper ms valley on the eastern
periphery of the upper low and upper jet exit region as it coincides
with the synoptic front. meanwhile ... farther east ... propagation of
remnant outflow /even subtle remnants into afternoon/ are a
plausible influence for renewed tstm development into a very
unstable airmass across the great lakes region. overall ... this
includes potential for some supercells aside from sustained linear
structures ... with bouts of damaging winds/severe hail and a couple
of tornadoes all possible across the region.
... southeast states/fl...
the airmass should strongly destabilize this afternoon ... especially
in areas near and west - southwest of the appalachians ... with
diurnally increasing/intensifying tstm development further aided by
a persistent upper low over the region. bouts of damaging winds and
some hail will be possible as storms generally drift southward
through the afternoon/early evening hours.
.. guyer/mead.. 05/20/2013