3/13/05 FCST: LA/MS/AL/WRN GA

[Brett Adair]

Looks like instability will build in the wake of a rather weak frontal boundary that will come into the region tomorrow. SRH values over 600 engulf NRN MS/AL by 20z. FCST SNDGS suggest that little CINH will allow initiation with a little forcing/uplift from the boundary and associated low pressure that should pass through the region. SPC Day 1 should have a SLGT...we will see. If moisture return is enough, torandic supercells can not be counted out via the WRF/meso-ETA.

 

[Scott Olson]

Looks like it would be mostly elevated convection at least until evening. I do think that the northern Lousiana region could see some action with some supercells possible and severe hail.

 

[Mike Johnston]

I agree that northern LA may be the place to watch, falling in between moisture convergence just to the east, and thermal ridge just to the west. 6 Hr RUC model shows CAPE and Helicity may have EHI in the 2.0 to 2.5 range by late afternoon. Shreveport actual dewpoint up to 60 at 11 am.

 

[Alex Lamers]

...Next Several Hours (Through 3 PM CST)...
Looks like capping inversion will continue to erode from east to west across the area of concern per latest modified RUC analysis products. As a result we should see the cu fields continue to develop at a more advanced rate in a corridor from Central Mississippi or about 30 miles west of Tuscaloosa, AL into Northern Louisiana or about 25 miles south-southeast of Shreveport. Per RUC forecast of convective precipitation...it appears possible that several more hours of heating and persistent convergence could initiate a few rw/t across the area beginning primarily in West-Central Mississippi.

...Beyond (After 3 PM CST)...
As a weak vorticity maximum located over Western Texas continues to propogate eastward embedded in a subtropical jet stream drifting north look for vertical motions to begin to increase over a broader area. The timed arrival in the Louisiana and Mississippi region would be between 4 PM and 8 PM. During this timeframe it appears that any isolated activity would increase in coverage. With relatively high levels of vertical wind shear expected and a decent directional component to that shear...I would anticipate a large hail threat from any severe tstm. LCLs continue to rise over the past several hours and SPC mesoanalysis shows some low-level dry air being advected in from Northern Texas...which could be a product of large volumes of middle to upper tropospheric dry air traversing the area. As a result the tornado threat would appear to be relatively nominal but the backing of surface flow to a more southerly direction continues to enhance SRH/EHI values. Therefore...I suppose an isolated tornado touchdown would not be out of the question and the most likely location would be in close proximity to the low and front over NE LA into WC MS. Damaging winds should also be a threat with the svr tstms.

...Alex Lamers...

 

[Scott Olson]

Thing are actually looking pretty good so far. The Shreveport WFO seems to be really discounting this whole thing but I think real-time observations are showing a little more moisture than they probably expected. If I was actually in Northern LA I would probably either wait for the convection that will form later in the afternoon or early evening with good cape and tons of helicity or go straight east in MS where it looks like the models are indicating the storms to start.