399
acus01 kwns 230556
swody1
Storm Prediction Center ac 230554
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1154 PM CST Wednesday Feb 22 2012
Valid 231200z - 241200z
..there is a slight risk of severe thunderstorms for parts of the Ohio/Tennessee valleys
and deep south...
...
Intense middle-level jet from the Pacific northwest to the central rockies will
progress eastward on Thursday...aiding in amplification of a short wave
impulse currently over the northern High Plains. This feature should
reach the lower/mid-MO valley by evening and remain
positively-tilted as it ejects across the Midwest towards the lower
Great Lakes through Friday morning. Primary surface cyclone is expected
to be in vicinity of Illinois/ind border by 00z...with a west/E-oriented warm front
shifting northward across the Ohio Valley. This low should track towards Lake
Erie...while an attendant cold front sweeps east/southeastward across the MS/Tennessee
valleys and western Gulf Coast in the evening...before reaching the
central/southern Appalachians and central Gulf Coast by 12z/Fri.
..OH/Tennessee valleys to the central Gulf Coast...
In the wake of the short wave impulse currently over the central/southern
Appalachians...strong low/mid-level westerlies have enveloped the residual
warm sector from the Tennessee Valley to the central Gulf Coast. Although
modest backing to southwesterly low-level flow is expected as the north-central
Continental U.S. Short wave trough amplifies...this type of regime should serve
to limit the vertical extent of Richer Gulf moisture beneath an
expanding eml.
Evening model guidance vary markedly with their handling of the
moisture return towards the lower Ohio Valley. The NAM and
WRF-nmm/Eta-based members of the sref are more aggressive than the
GFS/European model (ecmwf) and WRF-arw/rsm members of the sref...which results in
substantial differences in buoyancy profiles.
Nevertheless...vigorous large-scale ascent coupled with daytime
heating should yield thunderstorm initiation in vicinity of surface cyclone near the
lower Ohio Valley by late afternoon. Here...very strong deep-layer
shear and at least meager instability would promote a risk for
organized thunderstorm clusters and embedded supercells. But given the
uncertainty in the quality of the boundary layer moisture...will
refrain from introducing higher severe probabilities at this time.
With southern extent...confidence lessens on thunderstorm initiation as stronger
large-scale ascent largely remains north of the Ohio Valley. But
convergence along the cold front along with weak middle-level height
falls may result in thunderstorms forming southward across the Tennessee Valley into the
deep south during the evening. Even with only weak
instability...deep-layer shear will be quite favorable for isolated
supercells with all severe threats possible.
Towards the central Gulf Coast...guidance is largely consistent in
maintaining an eml through most of the period. Some potential for
thunderstorm development should exist overnight along the cold front. But
modest instability and veering/weakening low-level winds should
result in a more marginal severe risk relative to farther north.
.Grams/leitman.. 02/23/2012
Mesoscale Discussion
330
acus11 kwns 230526
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 230525
ncz000-vaz000-230700-
Mesoscale discussion 0144
National Weather Service Storm Prediction Center Norman OK
1125 PM CST Wednesday Feb 22 2012
Areas affected...central NC...southern Virginia
Concerning...severe potential...watch unlikely
Valid 230525z - 230700z
An isolated severe threat ongoing with a convective line in west-central
NC will likely continue for a few more hours. However...the threat
should remain isolated and ww issuance does not appear likely at this time.
A nearly continuous line of thunderstorms is ongoing just ahead a
well-defined shortwave trough moving through the southern Appalachian
Mountains regional WSR-88D vwps and forecast soundings over central NC
this evening show very strong deep layer shear with 0-6 km shear
around 70 knots. This along with an eastward storm motion of 40 to 50 knots is
creating a wind damage threat along the leading edge of the line.
Although...a gust of 46 knots was recorded earlier at
Greensboro...observations over the last half hour suggest winds with
the line have recently been below 40 knots suggesting the wind damage
threat is marginal. The orientation of the wind field parallel to
the line and the weak instability could be resulting in the marginal
threat. For this reason...a watch is not expected during the
overnight period.
.Broyles.. 02/23/2012
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...akq...rah...ilm...rnk...
Latitude...Lon 36547788 36217758 35727791 35517810 35167838 34827876
34787923 34967967 35248004 35528009 36687857 36547788
