000
acus01 kwns 250540
swody1
Storm Prediction Center ac 250539
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1239 am CDT Sat may 25 2013
Valid 251200z - 261200z
..there is a slight risk of severe thunderstorms central through northern High
Plains...
...
Synoptic pattern will undergo little change Saturday with an upper
ridge over the central U.S. Flanked by troughs over the western and eastern
states. At the surface a Lee trough/dryline will persist over the High
Plains while a warm front lifts slowly northward through the central/northern
plains.
..cntrl and northern plains area...
Southeasterly winds east of Lee trough will advect upper 50s dewpoints into
the northern High Plains with low-middle 60s farther south over the Central
Plains. Meanwhile...west-southwesterly winds aloft will advect steep middle-level
lapse rates above the moistening boundary layer contributing to an
axis of 1500-2500 j/kg MLCAPE. The atmosphere will remain capped to
surface based storms until middle afternoon when diabatic warming will
augment orographic forcing where a moist southeasterly upslope regime will
exist from northestern Colorado...eastern Wyoming into eastern Montana. Storms are expected to
develop over the higher terrain and subsequently spread eastward into the
axis of moderate instability across the High Plains. This region
will reside on southern fringe of stronger flow aloft with 35-40 knots winds
at 500 mb above southeasterly near surface winds resulting in favorable vertical
shear for supercells. Very large hail will be the initial primary
threat...through isolated tornadoes may also be possible. A few
storms may eventually congeal into lines/clusters with an increasing
damaging wind threat during the evening...sustained by a
strengthening southerly low level jet. Severe threat is expected to gradually wane
toward late evening.
..srn High Plains...
Isolated to widely scattered storms are expected to once again
develop over the higher terrain and spread eastward into the southern High
Plains. These storms will exist in a weak shear environment...but
steep lapse rates...moderate instability and 25+ f low level
temperature-dewpoint spreads will support a threat for isolated
large hail and downburst winds.
.Dial/Dean.. 05/25/2013
Mesoscale Discussion
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acus11 kwns 250450
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 250450
nez000-250545-
Mesoscale discussion 0794
National Weather Service Storm Prediction Center Norman OK
1150 PM CDT Friday may 24 2013
Areas affected...S central and central Nebraska
Concerning...severe potential...watch possible
Valid 250450z - 250545z
Probability of watch issuance...40 percent
Summary...storms will continue to congeal into an mesoscale convective system across S
central/central Nebraska the next few hours...with isolated large hail
the main threat. A new Severe Thunderstorm Watch will be possible.
Discussion...convection continues to develop across S central into
central Nebraska in a zone of increasing low-level warm air advection...on the nose of a
50 knots low level jet. The storms currently reside in the lingering instability
axis across S central Nebraska...with instability expected to diminish
gradually overnight and with eastward extent. As such...there will be a
risk of primarily large hail in the next couple of hours when the
storms are at their peak and still maintain some supercell
structure. The convection will also tend to become a little more
elevated with time as the surface layer cools...which will become
more hostile for damaging gusts at the surface. The situation will
be discussed with the weather forecast office Hastings to determine the need for a new
Severe Thunderstorm Watch.
.Thompson/guyer.. 05/25/2013
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...oax...Gid...lbf...gld...
Latitude...Lon 41479731 40959723 40579765 40269860 40050025 40340096
40880108 41460057 41999939 42109810 41859756 41479731
