May 13: Mesoscale Discussion #778

Mesoscale Discussion issued for:
-Much of Central and South Illinois
-Extreme East Missouri

CAPE values are currently 500-1000 j/kg along a cold front pushing eastwards.
This front should be able to provide some forcing in the atmosphere, probably enough to kick-start at least scattered storms. They are not expected to be severe, but some may be stronger than others.
Vertical shearing is rather weak at this time.
However, some residual low level lapse rates could be a producer of funnel clouds and possibly a weak tornado.
I, personally, would not issue a watch for this scenario. While I do believe a funnel cloud is possible, I am not confident in the potential for tornadoes, and do not feel confident issuing a watch if it was my choice.

May 13: Tonight's Forecast

DISCUSSION
Scattered thunderstorms continue to develop ahead of a cold front in the Southern US. Severe weather threats of hail and locally damaging winds are confined to the Ohio/Tennessee Valley and down into Mississippi/Alabama.
Weaker shear but strong instability out east in the Appalachians will be productive of a less organized but still potential severe threat. However, with weak high pressures likely pushing east ahead of the cold front, I would not be surprised to see even weaker shearing and somewhat higher instabilities.
In Florida, sea breezes will likely spout scattered thunderstorms, some of which could reach severe limits. A widespread outbreak is not expected.

As the storms ahead of the cold front push east, I am expecting a potential for thunderstorm outflow (cool wind from thunderstorms) combined with scattered pockets of sea breezes to initiate some isolated thunderstorms. I would not expect them to be severe, but local damaging wind gusts and small hail are not off the table.
There are currently some storms in New York, but those are expected to weaken.

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May 12: Tornado Warning- Cline, TX

TORNADO WARNING
TXC463-121245-
/O.NEW.KEWX.TO.W.0003.110512T1206Z-110512T1245Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
706 AM CDT THU MAY 12 2011

THE NATIONAL WEATHER SERVICE IN AUSTIN SAN ANTONIO HAS ISSUED A

* TORNADO WARNING FOR...
  CENTRAL UVALDE COUNTY...

* UNTIL 745 AM CDT.

* AT 704 AM CDT...NWS METEOROLOGISTS HAVE DETECTED A SEVERE
  THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR CLINE...OR ABOUT
  19 MILES EAST OF BRACKETTVILLE...MOVING EAST AT 30 MPH.

* SOME LOCATIONS IN THE WARNING INCLUDE LAGUNA AND UVALDE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF YOU ARE IN A MOBILE HOME OR VEHICLE...GET OUT AND GO TO A STURDY
SHELTER. IF NO SHELTER IS AVAILABLE...LIE FLAT IN THE NEAREST DITCH
OR OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 1000 AM CDT
THURSDAY MORNING FOR SOUTH CENTRAL TEXAS.