USAWX Day 2 issued 0500z for Friday April 30

[Brett Adair]

USA Weather - National Severe Weather Division
Day 2 Severe Weather Outlook **Corrected**
01:19 AM EDT Thursday, April 29, 2004

Severe Weather Outlook for Friday, April 30, 2004
Valid 0500z Friday - 0500z Saturday

National Synopsis
MESO-low will be moving eastward through MS/AL at the beginning of the period with an MCS/LEWP ongoing. Complex will weaken throughout the morning hours and possibly pickup steam later in the day when instability builds once again.

Deep upper level low in the four corners region will begin to make a move NEward throughout the period and make way for some convection likely as height/pressure falls occur across OK/TX. 500mb jet max will eject late in the period enhancing activity across Northern OK/KS/Wrn MO.

Mississippi/Alabama/Georgia
MESO-low centered over Greenwood MS at 0800z will continue to spread convection across this region throughout the early morning hours. Instability values will be rather low due to this being nocturnal, but it will moisten up the boundary layer for action to occur later in the period as destabalization takes place and unstable air builds late in the period. Greatest severe threat coming on Saturday here.

North Texas/Oklahoma/Kansas/Western Missouri
Strong ULL will pull NE through the period and develop strong baroclonic zone by 00z into Srn NE/Eastern KS/Wrn MO as phasing with the northern stream begins. EXTREME instability will build with LI's of -7 to -11C and MLCAPE values of 3500j/kg across much of OK throughout the period. A rather strong cap will be in place, but mid level dry air is expected to erode it rather quickly in the early evening hours. ML Lapse rates of 8.5-9.5°C/km will take over much of the region as well with steepe height falls overtaking the region. A surface low will develop in Srn Kansas and trek NEward into MO through the period. 0-3km SRH values will kick up over 200m*2/s*2 across SE Kansas and give a bit of a tornado threat. Biggest threat will be from large hail and very heavy rainfall due to the 1.5" PWAT values. As vertical wind profiles increase in strength later in the period increase, damamging winds and tornadic potential could rise. This situation will continually be monitored and a categorical upgrade from the Slight risk could be issued in later outlooks if necessary.
ADAIR

[USAwx1]

SR 500mb winds between 8-20 m/s over the region late in the afternoon are also a plus for tornadic activity along the dry line over much of TX/OK/KS.

AND, you can also get weak tornadic development along the leading edge of a bow echo or LEWP where convective interactions may enhance localized shear, which should be MOST important further north as the flow in the mid and upper levels is pretty well aligned.

[Guest]

I for one if i was at SPC would be adding a moderate risk for Tomorrow in the Central/Southern Plains. Lots of the right ingrediants comming together for what looks to be a very active day in this part of the country. Dont be suprised if this happens when they update later tonight.

[Stormsfury]

King, I wouldn't be surprised, either ... but let's err on the side of caution for now especially in light of the recent overaggressiveness of the SPC to hoist PDS watches that never really materialized .. (or the outbreak that materialized well away from the PDS watch).