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acus01 kwns 230602
swody1
Storm Prediction Center ac 230600
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0100 am CDT Wednesday may 23 2012
Valid 231200z - 241200z
..there is a slight risk of severe thunderstorms across the Central Plains/upper
Midwest...
..there is a slight risk of severe thunderstorms across portions of the
Carolinas...
...
Height falls will occur across the southern rockies/Central Plains
as an amplifying longwave trough becomes increasingly prevalent over
the western half of the Continental U.S. During the period. Split upper
flow/weaker westerlies will exist over the eastern Continental U.S. As a
relatively weak/slow-moving upper low continues a northeastward
progression over the southeast coast.
..Central Plains/upper Midwest...
Given the large scale scenario as previously described...Central
High plains surface cyclogenesis is expected today as a cold front
makes a slow but steady southeastward progression from the eastern
Dakotas to Minnesota/eastern Nebraska/western Iowa and western/northern Kansas by
early this evening. Beneath a relatively Stout east-northeastward
advecting elevated mixed layer...steady south-southwesterly moisture
transport will continue to occur along/ahead of the front...but
ample mixing/limited source region moisture will likely limit warm
sector surface dewpoints to the 50s/lower 60s f.
Given the expected strength/extent of the elevated mixed
layer/marginal moisture...surface based deep convective development
will generally be relegated to the immediate southwest-northeast
oriented frontal zone. This seems likely to initially occur by
around middle-afternoon across portions of central/southern Minnesota into far
southeast South Dakota/northeast Nebraska/northwest Iowa. Other/separate development
seems likely to occur this afternoon across northeast Colorado amid
developing low-level upslope trajectories.
With strong vertical shear maximized near/behind the front...very
steep lapse rates and moderate buoyancy...1000-2500 j/kg MLCAPE
/strongest across southeast Nebraska and northern KS/...will support
supercells capable of large hail. A tornado or two will be possible
as well...although marginal moisture content and eventual frontal
undercutting/storm mergers should limit the overall tornado threat.
..southeast states/Carolinas...
A cool middle-level pocket /-14c to -16c/ will overspread the Carolinas
today in associated with a persistent/slow-moving upper low. Coupled
with locally stronger insolation/heating...a very steep lapse
rate/modest shear environment be will be favorable for the
development and sustenance of multicells capable of severe hail and
locally damaging winds...especially this afternoon/early evening.
Given the potential for stronger destabilization...this especially
appears to be the case across the Piedmont/coastal areas of the
Carolinas and perhaps southeast Virginia.
.Guyer/Rogers.. 05/23/2012
Mesoscale Discussion
717
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
