MESOSCALE DISCUSSION 1657
   NWS STORM PREDICTION CENTER NORMAN OK
   0216 PM CDT MON SEP 01 2014

   AREAS AFFECTED...PORTIONS OF NORTHERN OKLAHOMA AND SOUTHERN KANSAS

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 011916Z - 012145Z

   PROBABILITY OF WATCH ISSUANCE...60 PERCENT

   SUMMARY...PORTIONS OF NORTHERN OKLAHOMA AND SOUTHERN KANSAS ARE
   BEING MONITORED FOR WATCH ISSUANCE. WHILE WATCH ISSUANCE IS LIKELY
   BY THIS EVENING...IT IS ALSO POSSIBLE THAT ISSUANCE WOULD BE NEEDED
   DURING THE NEXT FEW HOURS. CONVECTIVE TRENDS WILL CONTINUE TO BE
   MONITORED.

   DISCUSSION...OBSERVATIONS FROM THE OKLAHOMA MESONET INDICATE A SFC
   LOW APPROXIMATELY OVER WOODS COUNTY OK. A STATIONARY FRONT EXTENDS
   SW OF THE LOW INTO W-CNTRL OK AND THE ERN TX PANHANDLE...WHILE AN
   OUTFLOW BOUNDARY EXTENDS E/ESE OF THE LOW THROUGH THE TULSA AREA
   INTO NW AR. STRONG INSOLATION BETWEEN A WEAK SFC TROUGH E OF THE
   STATIONARY FRONT HAS ALLOWED SFC TEMPERATURES TO RISE INTO THE
   MIDDLE/UPPER 90S OVER WRN OK. A CORRIDOR OF 7.5-8.0-C/KM SFC-3-KM
   LAPSE RATES CURLS INTO THE SERN SEMICIRCLE OF THE LOW S OF THE
   OUTFLOW BOUNDARY. CORRESPONDINGLY...VIS SATELLITE IMAGERY INDICATES
   BOUNDARY-LAYER CU DEVELOPMENT AT THE ERN/NRN EDGES OF THE STEEPER
   LAPSE RATE PLUME...EXTENDING FROM N-CNTRL OK NWWD INTO BARBER AND
   COMANCHE COUNTIES IN KS.

   MODIFICATIONS TO THE 12Z OUN RAOB AND RAP FORECAST SOUNDINGS SUGGEST
   THAT...WITH SFC TEMP RISES OF ANOTHER 1-2 DEGREES...ISOLATED DEEPER
   CONVECTION COULD BLOSSOM FROM THE ONGOING CU FIELD BY 21-22Z -- AND
   SPREAD E/ESE. AS THE OUTFLOW BOUNDARY CONTINUES TO RETREAT
   NWD...MLCAPE VALUES OF 1500-3000 J/KG WILL LIKELY EXTEND NWD INTO
   FAR SRN KS...AIDED BY STEEP MID-LEVEL LAPSE RATES SURMOUNTING UPPER
   60S/LOWER 70S SFC DEWPOINTS. WHEN COMBINED WITH 30-45 KT OF
   EFFECTIVE BULK SHEAR...ORGANIZED CONVECTIVE STRUCTURES INCLUDING
   SUPERCELLS WITH LARGE HAIL MAY EVOLVE. VNX VWP DATA SUGGEST
   LOW-LEVEL SHEAR IS ONLY MODEST AT PRESENT. HOWEVER...WITH SOME
   DIRECTIONAL VARIABILITY IN THE FLOW BELOW 3 KM AGL ENHANCING SRH --
   ESPECIALLY NEAR THE OUTFLOW BOUNDARY -- A TORNADO COULD OCCUR GIVEN
   THE STEEP LAPSE RATES IN PLACE. AMPLE INHIBITION N OF THE OUTFLOW
   BOUNDARY IN NERN OK AND SERN KS AS EVIDENCED BY
   VIS-SATELLITE-IMPLIED BILLOWS SUGGESTS THAT INITIAL STORMS MAY
   QUICKLY BECOME ELEVATED AS THEY POTENTIALLY DEVELOP INTO A MORE
   STRONGLY CAPPED BOUNDARY LAYER.

   ULTIMATELY...THE SVR-TSTM RISK DURING THE NEXT FEW HOURS IS HIGHLY
   CONDITIONAL...AS DEEP-LAYER FORCING FOR ASCENT IS WEAK AND AT LEAST
   SOME CAPPING ALOFT PERSISTS. CONFIDENCE IN SEVERE-TSTM DEVELOPMENT
   THROUGH 22Z IS MODEST...BUT IS HIGHER INTO THE EVENING WHEN
   LOW-LEVEL MASS FLUXES BECOME BOLSTERED IN ASSOCIATION WITH A
   STRENGTHENING LLJ STREAM AND NOCTURNAL BOUNDARY-LAYER WIND MAXIMUM.

   ..COHEN/HART.. 09/01/2014


   ATTN...WFO...SGF...TSA...ICT...OUN...DDC...

   LAT...LON   36199705 36449821 36799878 37299898 37599828 37669625
               37589525 37249468 36509470 36169520 36199705