Tornado Watch Possible Soon
The Storm Prediction Center is considering a Tornado Watch for much of Middle and West Tennessee and a small part of North Alabama. (They say an 80% chance that they’ll issue it):
SUMMARY…BOUNDARY-LAYER DESTABILIZATION IS FCST TO CONTINUE FOR A
FEW MORE HOURS ALONG/AHEAD OF CONFLUENCE ZONE OUTLINED BELOW…IN
SERN QUADRANT OF REMAINS OF ISAAC. AMIDST AT LEAST MRGL LOW-LEVEL
SHEAR. THIS WILL RESULT IN FAVORABLE ENVIRONMENT FOR SMALL
BOWS…EMBEDDED MESOCYCLONES IN QUASI-LINEAR SEGMENTS…AND A FEW
SMALL/DISCRETE SUPERCELLS. A FEW TORNADOES AND DAMAGING GUSTS ARE
DISCUSSION…SFC MESOANALYSIS SHOWS CONFLUENCE LINE FROM NEAR
SRC-NQA-BWG-25 S FTK. NRN PORTION OF THIS FEATURE IS TRANSLATING
EWD ABOUT 10 KT…WHILE SRN PORTION OVER TN REMAINS QUASISTATIONARY.
AIR MASS NW OF THIS LINE WAS DRIER FROM SFC-500 MB…BASED ON RAOB
AND SFC ANALYSES…AND CONTAINED MORE VEERED DEEP-LAYER FLOW.
MEANWHILE SFC DEW POINTS LOW-MID 70S F AND PW 2-2.25 INCHES WERE
COMMON TO ITS SE. LOW-LEVEL SRH AND BUOYANCY EACH DIMINISH WITH NWD
EXTENT ACROSS KY. ALTHOUGH VIS IMAGERY INDICATES THIS AREA STILL IS
COVERED BY BKN-OVC CLOUD COVER…SUFFICIENT BREAKS AND ADVECTION OF
DIABATICALLY HEATED BOUNDARY-LAYER AIR FROM SW SHOULD BE SUFFICIENT
TO MINIMIZE MLCINH THROUGH REMAINDER AFTN. MODIFIED RAOBS AND FCST
SOUNDINGS SUGGEST PLUME OF MLCAPE 500-1500 J/KG ALONG AND E OF
CONFLUENCE LINE FROM NRN MS TO SERN KY. THOSE SOURCES…ALONG WITH
VWP INDICATE EFFECTIVE SRH 150-250 J/KG FROM MID TN/AL BORDER NE MSL
TO CENTRAL KY ABOUT HALFWAY BETWEEN GLW-LEX. MORE VEERED/WLY
COMPONENT OF SFC WINDS LEAD TO SMALLER HODOGRAPHS SWWD ACROSS NRN MS
AND SWRN TN…BUT WITH SOME INCREASE IN LOW-LEVEL SHEAR POSSIBLE
THIS EVENING. VIS IMAGERY ALSO SHOWS DEEPER CONVECTIVE ELEMENTS
DEVELOPING OVER SERN TN…NRN MS AND NWRN AL THAT COULD MOVE INTO
MORE FAVORABLE ENVIRONMENTS WITH TIME.
Right now, the radar is pretty quiet around the Tennessee Valley. We expect storms to develop over Middle and West Tennessee between now and 4 PM; those storms will gradually shift southeast through 10 PM across North Alabama.
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We will be keeping watch over the situation around here, but we will only break into programming if it is absolutely necessary.