Saturday, September 19, 2009
The threat continues for Sunday, but still a minimal risk. No slight risk has been issued, and the largest threat is that of downburst winds. Further development of this may occur, but at the moment it remains minimum.
From the Storm Prediction Center:
…OH AND TN VALLEYS…
A BROAD UPPER-LEVEL TROUGH WILL BE IN PLACE ACROSS MUCH OF THE CNTRL
AND ERN STATES. A SLIGHTLY MORE AMPLIFIED AND NEGATIVLEY TILTED
SECTION OF THE TROUGH IS FORECAST FROM THE MID-MS VALLEY SEWD ACROSS
THE GULF COAST STATES. SCATTERED THUNDERSTORMS SHOULD BE ONGOING
SUNDAY MORNING ALONG AND AHEAD OF THE AXIS OF THE UPPER-LEVEL TROUGH
WITH STORM COVERAGE INCREASING DURING THE AFTERNOON DUE TO
DESTABILIZATION. ALTHOUGH…VERTICAL SHEAR PROFILES ACROSS THE
REGION APPEAR ON THE LOW-SIDE FOR SEVERE STORMS…BOUNDARY LAYER
FLOW ASSOCAIATED WITH A LOW-LEVEL JET FROM NE MS NWD INTO IND AND OH
MAY BE ENOUGH FOR A FEW STRONG WIND GUSTS WITH THE MORE PERSISTENT
LINE-SEGMENTS.
NAM CAPE forecasts show instability to be greatest after 12:00 PM, so storms could be anywhere from early to mid afternoon, and even through the evening. With weak capping and moderate LIs, thunderstorms will be probable. Also, I took a look at the NAM helicity, and the numbers are near or above 150! Now, if I am reading this right (http://www.theweatherprediction.com/severe/indices/) this could be a good sign. Also, current NAM EHI forecasts show a pocket of a value of 1, which could also be handy. I should also mention that dewpoints are going to be crazy, in the 70 F region.
Something that I need to keep telling myself, and you as reader should know too, is that forecast models ARE NOT LAW! Though things may look somewhat favorable for now, when the day comes it could be drastically different. So, even though the data looks good so far, things wont really be known until we have tomorrows sounding. Even at THAT, the sounding is only accurate for that hour ALONE. Remember that this is all speculative.
Further updates will come by tomorrow morning or afternoon, and if a slight risk is issued tonight I will make an update then.
Check back for more info!
