[LeArc] CONVECTIVE OUTLOOK

[Duane Whittingham]

STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK 
DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS.
   
VALID 081630Z - 091200Z
   

...SRN IA/WRN MO TO ERN KS/OK/N TX...
LOW-LEVEL MOISTURE IS SPREADING NWD FROM TX/OK...WITH BOUNDARY
LAYER DEW POINTS EXPECTED TO RISE TO THE MID-UPPER 50S ACROSS WRN
AND NRN MO/SE KS...NEAR 60 F ACROSS CENTRAL OK...AND THE LOWER 60S
N CENTRAL/NW TX TO THE E OF THE DRYLINE BY LATE AFTERNOON.  AN
ELEVATED MIXED LAYER /LAPSE RATES IN EXCESS OF 8 C/KM FROM 850-500
MB/ HAS ALREADY OVERSPREAD MUCH OF KS/OK/TX...AND THESE STEEP LAPSE
RATES WILL COMBINE WITH THE INCREASING MOISTURE AND RELATIVELY COOL
MID LEVEL TEMPERATURES TO SUPPORT SBCAPE VALUES OF 1250-2000 J/KG
BY LATE AFTERNOON/EVENING FROM N TX TO ERN KS AND NW MO.  
   
A LARGE PLUME OF THICK CIRRUS COVERS THE WARM SECTOR THIS
MORNING...AND EXTRAPOLATION OF SATELLITE IMAGERY SUGGESTS THE W
EDGE OF THE CLEARING LINE WILL NOT REACH THE DRYLINE UNTIL ABOUT
22-00Z.  THESE CLOUDS WILL TEND TO INHIBIT SURFACE HEATING
SOME...BUT TEMPERATURES SHOULD STILL REACH THE MID 70S THIS
AFTERNOON.  IT APPEARS THAT CONVECTIVE INITIATION WILL BY DELAYED
UNTIL NEAR 00Z WHEN A LEAD SHORTWAVE TROUGH OVER CENTRAL NM/CO AREA
REACHES THE DRYLINE/TRIPLE POINT LOW.
   
THE MOST LIKELY AREA FOR INITIAL THUNDERSTORM DEVELOPMENT WILL
BE ALONG THE BAROCLINIC ZONE ACROSS ERN KS AND NW/NRN MO
WHERE ASCENT WILL BE STRONGEST LATE TODAY.  SUPERCELLS WILL BE
POSSIBLE IN THE FIRST COUPLE OF HOURS AFTER INITIATION FROM ERN KS
NEWD ALONG THE FRONT TO NRN MO...BUT THESE STORMS WILL LIKELY
EVOLVE INTO A LINE THIS EVENING/OVERNIGHT AS THE LOW DEVELOPS
RAPIDLY NEWD AND THE COLD FRONT SURGES SEWD.  WHILE AN ISOLATED
TORNADO WILL BE POSSIBLE THIS EVENING...SCATTERED TO NUMEROUS LARGE
HAIL AND DAMAGING WINDS WILL BE THE MAIN THREATS.  FARTHER
S...THUNDERSTORMS WILL BE MORE ISOLATED IN COVERAGE ALONG THE
DRYLINE ACROSS OK...AND POSSIBLY EXTREME N CENTRAL TX.  VERTICAL
SHEAR STRENGTH/ORIENTATION WILL FAVOR SUPERCELLS THIS AREA.  THE
MAIN SEVERE THREAT WITH ANY DRYLINE SUPERCELLS WILL BE LARGE
HAIL...THOUGH AN ISOLATED TORNADO OR TWO COULD OCCUR THIS EVENING
ACROSS CENTRAL/ERN OK IF A SUPERCELL CAN MOVE E OF THE DRYLINE INTO
THE REGION OF RICHER LOW-LEVEL MOISTURE AND STRONG LOW-LEVEL SHEAR.
   
   
...ARKLATEX AREA THIS AFTERNOON/TONIGHT...
RECENT ETA RUNS HAVE DEVELOPED A CLUSTER OF THUNDERSTORMS THIS
AFTERNOON INVOF THE ARKLATEX...WHICH THEN SPREADS N/NEWD INTO AR. 
COMPARISON OF ETA FORECAST SOUNDINGS WITH 12Z OBSERVATIONS AND
CORRESPONDING ETA KF SOUNDINGS SUGGESTS THAT THIS CONVECTION MAY
LARGELY BE A REFLECTION OF THE BMJ CONVECTIVE PARAMETERIZATION IN
THE OPERATIONAL ETA.  THE STORMS APPEAR TO INITIATE IN RESPONSE TO
MID LEVEL MOISTENING...AND THE BMJ SHALLOW CONVECTION SCHEME ALSO
TENDS TO REMOVE THE CAP FROM BELOW.  ACTUALLY...DO NOT ANTICIPATE
SURFACE-BASED THUNDERSTORMS THIS AREA THIS AFTERNOON.  WHILE THERE
IS A SLIGHT CHANCE OF ELEVATED CONVECTION ACROSS AR BEFORE DARK...
THE SEVERE THREAT THIS AREA WILL LIKELY BE DELAYED UNTIL TONIGHT AS
THE COLD FRONT MOVES SEWD.   
    
..THOMPSON.. 03/08/02
 
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Duane Whittingham (N9SSN) - Producer
Tom and Darryl Radio Shows
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