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acus01 kwns 231253
swody1
Storm Prediction Center ac 231251
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0751 am CDT Wednesday may 23 2012
Valid 231300z - 241200z
..there is a slight risk of severe thunderstorms across southwestern Minnesota/western Iowa/southeastern
South Dakota/southern and eastern Nebraska/northwestern and north-central Kansas...
..there is a slight risk of severe thunderstorms across portions of the
Carolinas and far southeastern Virginia...
...
A large trough over the western half of the Continental U.S. Will dig southeastward as
middle-level height falls overspread the central/southern rockies and Central
Plains...with a belt of strong middle-level flow within the broad base
of the trough. An associated surface cold front extending south-southwestward from the
ND/Minnesota border to a low over the Kansas/Colorado border will gradually progress
ewd/sewd. Broad/mostly weak middle/upper-level cyclonic flow will be
found from the northern Gulf of Mexico extending northeastward across the southeastern
states into the middle Atlantic.
..swrn Minnesota/western Iowa/southeastern South Dakota/southern and eastern Nebraska/northwestern and north-central Kansas this
afternoon into tonight...
as a plume of the elevated mixed layer is advected into the region
by the enhanced middle-level flow accompanying the amplifying
trough...steep middle-level lapse rates will overlay a corridor of
modest boundary-layer moisture near and east of the cold front. With
warm-sector boundary-layer dewpoints in the 50s to perhaps around
60f -- limited by vertical mixing and distance from substantially
Richer low-level moisture -- 1000-2000 j/kg of MLCAPE will likely
develop this afternoon. And...with increasing large-scale
ascent/diurnal heating contributing to the erosion of the initially
strong eml cap...sfc-based storms will likely develop in vicinity of the
front by late afternoon.
The combination of moderate instability and moderate to strong deep
shear -- strongest behind the front -- will support organized storms
including bowing line segments and possible supercells. This
activity will be capable of producing large hail...especially with
sustained supercell structures...along with severe wind...particularly
with surface-based convection.
Low-level shear may be sufficient to support the threat for a
tornado or two into the evening...though limited low-level moisture
and eventual frontal undercutting/upscale convective growth should
limit the overall tornado threat.
..nern Colorado this afternoon into early evening...
Modestly moist upslope flow beneath strong middle/high-level flow will
support isolated to scattered thunderstorms with a threat for severe
hail/wind. Only marginal destabilization should prevent a more
substantial severe threat from evolving.
..southeast states/Carolinas/sern Virginia this afternoon into early
evening...
a zone of cool middle-level temperatures /-14c to -17c at 500 mb/ will
overlay areas of strong surface heating and a north-northeast-SSW-oriented weak surface
front. Steep lapse rates and modest deep shear will support a threat
for multicell storms capable of severe hail and wind...especially
across the Piedmont/coastal areas of the Carolinas and far southeastern Virginia.
..srn MS and eastern la this afternoon...
Strong heating amidst a northeastward-advancing warm front will support
isolated to widely scattered thunderstorms. Boundary-layer dewpoints in the
lower 60s near and SW of the front will support moderate to strong
destabilization...with steep low-level lapse rates likely yielding
dcape values in excess of 1000 j/kg. Very weak flow throughout the
troposphere will support a pulse convective Mode...and a low threat
for damaging wind gusts and perhaps marginally severe hail cannot be ruled
out with the strongest storms.
.Cohen/corfidi.. 05/23/2012
Mesoscale Discussion
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acus11 kwns 230141
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 230141
mnz000-sdz000-ndz000-230245-
Mesoscale discussion 0876
National Weather Service Storm Prediction Center Norman OK
0841 PM CDT Tuesday may 22 2012
Areas affected...parts of eastern North Dakota...northwestern and west central
Minnesota
Concerning...severe potential...watch possible
Valid 230141z - 230245z
Probability of watch issuance...40 percent
Summary...the severe weather threat for remaining valid portions of
Tornado Watch 290 and Severe Thunderstorm Watch 291 continues. It
is not certain that a new ww will be needed...but trends are being
monitored for the possibility of a new ww east of 290/291.
Discussion...recent increase in storm development...southwest of
Jamestown ND into the Aberdeen South Dakota area...appears to be where
Lower/Middle tropospheric warm advection is becoming enhanced...near
the northern edge of more strongly capping elevated mixed layer
air...as the exit region of a strong middle/upper jet streak continues
to nose east northeast of the northern rockies this evening. This
forcing will gradually spread east northeastward into parts of
northwest and west central Minnesota through 03-05z. As it
does...it appears that it may begin to outrun a waning pre-frontal
low-level instability axis. Potential for significant upscale
convective growth is becoming more uncertain...but it does appear
possible that at least scattered vigorous convective development may
begin to spread to the east of current watches within the next hour
or two...accompanied by at least some risk for hail/locally strong
wind gusts.
.Kerr/Thompson.. 05/23/2012
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...fgf...abr...bis...
Latitude...Lon 48199839 48519719 48439623 46889558 45689633 45459694
45509772 46309880 47269881 47639888 48199839
