Latest Thinking From SPC
Our line of storms continues eastward through Central Mississippi at this hour. It doesn’t have hardly anything to work with in terms of instability.
Perhaps of some greater concern are the storms that have formed ahead of the main line as higher dewpoint air is transported northward on strong low level winds.
There is great spin in the atmosphere across the entire area, but it would take higher dewpoint air to get stronger updrafts that are based near the surface to see any tornado development. That could happen overnight over southern Mississippi into Southwest ALabama, perhaps as far north as Sumter County.
MESOSCALE DISCUSSION 0057
NWS STORM PREDICTION CENTER NORMAN OK
1154 PM CST SAT JAN 23 2010
AREAS AFFECTED…FAR EASTERN LA AND CENTRAL/SOUTHERN MS INTO FAR
WESTERN AL
CONCERNING…SEVERE POTENTIAL…WATCH POSSIBLE
VALID 240554Z – 240730Z
THERE IS SOME CONCERN THAT A SEVERE THREAT /DAMAGING WINDS AND
TORNADO RISK/ COULD DEVELOP IN THE OVERNIGHT ACROSS FAR EASTERN LA
AND MUCH OF CENTRAL/SOUTHERN MS…AND PERHAPS EVENTUALLY FAR W/SW
AL. A WATCH IS NOT ANTICIPATED AT THIS TIME…BUT CONVECTIVE TRENDS
WILL CONTINUE TO BE MONITORED THROUGH THE EARLY MORNING HOURS.
WITHIN A CORRIDOR OF LOW LEVEL CONFLUENCE…A PRE-FRONTAL/PRE-QLCS
BAND OF SCATTERED SHOWERS/TSTMS HAS GRADUALLY INCREASED ACROSS FAR
EASTERN LA/WESTERN MS OVER THE PAST FEW HOURS…WHILE THE PRIMARY
QLCS CONTINUES TO STEADILY PROGRESS EASTWARD ACROSS NORTH
CENTRAL/WEST CENTRAL MS AS OF 0545Z. WITH ONLY A NARROW/MARGINALLY
MOIST WARM SECTOR…MUCH OF THIS PRE-QLCS ACTIVITY IS LIKELY TO
STILL BE ROOTED JUST ABOVE A MARGINALLY MOIST/RELATIVELY STABLE
NEAR-SURFACE LAYER PER OBSERVED STORM MOTIONS AND 00Z OBSERVED
JAN/LCH/LIX RAOBS. HOWEVER…AS LARGE SCALE FORCING FOR ASCENT
MODESTLY INCREASES/HEIGHT FALLS OCCUR OVERNIGHT…ADJUSTED 00Z
OBSERVED JACKSON MS RAOB AND MORE CONTEMPORARY RUC SOUNDINGS IMPLY
THAT STORMS COULD BECOME PROGRESSIVELY ROOTED NEAR THE SURFACE
THROUGH THE EARLY MORNING HOURS PROVIDED A CONTINUED INFLUX OF
SURFACE DEWPOINTS AROUND 62-64 F INTO SOUTH CENTRAL MS. GIVEN THE
HIGH DEGREE OF LOW LEVEL SHEAR /400-700 MS PER S2 OF 0-1 KM SRH PER
JACKSON WSR-88D VWP DATA/ ASSOCIATED WITH AN INTENSIFYING LOW LEVEL
JET…ROTATING STORMS/EVENTUAL SMALL BOWS COULD POSE AN ISOLATED
DAMAGING WIND/TORNADO RISK PROVIDED A SLIGHT INCREASE IN LOW LEVEL
MOISTURE…WITH THE POSSIBILITY THAT STORMS COULD BECOME ROOTED NEAR
THE SURFACE OVERNIGHT.
..GUYER.. 01/24/2010
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