Post by SKYSUMMIT on Feb 25, 2008 9:09:33 GMT -6
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0643 AM CST MON FEB 25 2008
VALID 251300Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS MAINLY TONIGHT FROM THE
ARKLATEX EWD ACROSS MS/SRN AL...
...LOWER MS VALLEY AREA THIS EVENING INTO TONIGHT...
A SRN STREAM MID LEVEL TROUGH NOW EMERGING OVER THE SRN HIGH PLAINS
AND AN ASSOCIATED SURFACE CYCLONE IN NRN KS WILL PROGRESS EWD TO THE
LOWER MS AND LOWER OH VALLEYS AND AMPLIFY TONIGHT IN RESPONSE TO
PHASING OF THE SRN AND NRN STREAMS. THIS SYSTEM WILL BE ACCOMPANIED
BY A PLUME OF STEEP MID LEVEL LAPSE RATES ALREADY OVER THE SRN
PLAINS. BENEATH THE STEEP LAPSE RATES...INDUCED SLY FLOW IN THE
WARM SECTOR WILL DRAW BOUNDARY LAYER DEWPOINTS IN THE 60S NWD ACROSS
THE NW GULF COAST TOWARD THE ARKLATEX. THIS DIFFERENTIAL
ADVECTION...ALONG WITH DAYTIME HEATING INVOF A DEVELOPING DRYLINE
ACROSS TX...WILL RESULT IN MLCAPE VALUES OF 1000-1500 J/KG IN A
NARROW CORRIDOR FROM THE MIDDLE TX COAST TO THE ARKLATEX BY THIS
EVENING.
AN INITIALLY SHALLOW MOIST BOUNDARY LAYER...RELATIVELY LATE ARRIVAL
OF THE RICHER LOW-LEVEL MOISTURE...AND STRONG CONVECTIVE INHIBITION
ASSOCIATED WITH THE ELEVATED MIXED LAYER WILL LIKELY DELAY
CONVECTIVE INITIATION UNTIL 00-03Z INVOF THE DRYLINE/COLD FRONT
INTERSECTION. THEREAFTER...CONVECTION SHOULD SPREAD QUICKLY EWD
OVERNIGHT ACROSS SE AR/NRN LA/MS/TN/AL. DESPITE THE LOSS OF DAYTIME
HEATING...LOW-LEVEL MOISTENING SHOULD BE SUFFICIENT TO MAINTAIN DEEP
CONVECTION THROUGH THE NIGHT AS BOUNDARY LAYER DEWPOINTS IN THE 60S
SPREAD NWD FARTHER E INTO MS AND SRN AL.
LOW-LEVEL SWLY FLOW NEAR 50 KT AND MID LEVEL WSWLY FLOW OF 70-90 KT
WILL CONTRIBUTE TO STRONG VERTICAL SHEAR IN THE WARM SECTOR. THE
INITIAL CONVECTION MONDAY EVENING MAY CONSIST OF SUPERCELLS WITH AN
ATTENDANT THREAT FOR A COUPLE OF TORNADOES...DAMAGING WINDS...AND
LARGE HAIL. THE SEVERE THREAT SHOULD TRANSITION PRIMARILY TO
DAMAGING WINDS OVERNIGHT WITH MORE LINEAR CONVECTIVE STRUCTURES IN
AN ENVIRONMENT WITH ONLY LIMITED INSTABILITY.
..THOMPSON.. 02/25/2008
