631
acus01 kwns 230046
swody1
Storm Prediction Center ac 230045
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0645 PM CST Wednesday Feb 22 2012
Valid 230100z - 231200z
..there is a slight risk of severe thunderstorms for parts of the Tennessee Valley and
southern Appalachians...
..TN valley...Southern Appalachians...
a marginal/isolated severe risk should exist with ongoing thunderstorm
clusters progressing eastward from the Tennessee Valley. Downstream air mass is
only minimally unstable with surface dew points still holding in the
40s to middle 50s. Although afternoon model forecast have been
insistent on substantial low-level warm/moist advection
tonight...they have been too moist in comparison with metars and 00z
radiosonde observations with the return of the modified Gulf air mass. For
example...00z Jan radiosonde observation sampled MLCAPE around 500 j/kg while 18z NAM
forecast soundings suggested MLCAPE of 1500 to 2000 j/kg should be
present.
Nevertheless...large cyclic hodographs /as sampled by the 00z bmx
radiosonde observation/ are forecast to strengthen this evening...supporting
widespread effective srh at or above 250 m2/s2. Give ample low/deep-layer
shear...activity may intensify somewhat despite the onset of
nocturnal cooling. The relatively greatest severe threat should
exist across parts of northern Alabama/Georgia and eastern Tennessee into perhaps the western
Carolinas through late evening.
..cntrl/northestern Gulf Coast...
Have removed severe probabilities given minimal instability /per 00z
tlh and tbw radiosonde observations/ in vicinity of ongoing isolated thunderstorms. As the large-scale
warm/moist advection regime shifts northeastward and the lack of influence by
the weak short wave impulse over the Tennessee Valley...thunderstorm redevelopment
appears unlikely.
.Grams.. 02/23/2012
Mesoscale Discussion
100
acus11 kwns 222350
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 222349
tnz000-gaz000-alz000-230115-
Mesoscale discussion 0143
National Weather Service Storm Prediction Center Norman OK
0549 PM CST Wednesday Feb 22 2012
Areas affected...NE Alabama...southeast Tennessee...far northwest Alabama
Concerning...severe potential...watch possible
Valid 222349z - 230115z
An isolated severe threat will likely increase some over the next
few hours from middle to eastern Tennessee southward across northern Alabama and far northwest Georgia.
Hail and wind damage will be possible. Ww issuance may be necessary
across the region.
A line of strong thunderstorms is ongoing along an axis of
instability where mesoanalysis shows MUCAPE values from 250 to 750
j/kg. The storms are developing in a strongly sheared environment
with WSR-88D-vwps showing 0-6 km shear values of 70 to 80 knots. This
combined with increasing large-scale ascent as a shortwave trough
approaches from the west and steep middle-level lapse rates of 7.0 to
7.5 c/km should be sufficient for a hail threat with the stronger
cores embedded in the line. Eastward storm motion of 40 knots will help
create a wind damage threat especially as the line becomes nearly
continuous. Supercells with an isolated tornado threat may also
exist on the southern end of the line where instability is maximized and
the low-level jet is forecast to strengthen early this evening.
.Broyles.. 02/22/2012
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...mrx...ffc...ohx...bmx...hun...
Latitude...Lon 35928438 36378455 36558536 35888624 34918734 34258779
33898760 33648692 33748625 34138579 34718521 35348467
35928438
