MESOSCALE DISCUSSION 1581 NWS STORM PREDICTION CENTER NORMAN OK 1253 PM CDT THU AUG 01 2013 AREAS AFFECTED...NEB...SWRN SD CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY VALID 011753Z - 012000Z PROBABILITY OF WATCH ISSUANCE...95 PERCENT SUMMARY...ISOLATED TO SCATTERED SUPERCELLS WILL FORM BY MID-AFTERNOON WITH INITIAL PRIMARY RISKS OF VERY LARGE HAIL AND A FEW TORNADOES. A WW WILL BE ISSUED WITHIN THE HOUR...WITH MODERATE UNCERTAINTY OVER THE SPATIAL EXTENT OF AN INITIAL WW. DISCUSSION...17Z SURFACE ANALYSIS PLACED A 1012 MB CYCLONE NEAR BFF...WITH A QUASI-STATIONARY FRONT EXTENDING NEWD AND THEN E ACROSS SRN SD. SURFACE-BASED CB/S HAVE FORMED ALONG THIS FRONT IN SHANNON/BENNETT COUNTIES SD. ADDITIONAL CU DEVELOPMENT HAS BEEN NOTED ALONG RESIDUAL OUTFLOW IN CNTRL NEB /CENTERED OVER VALLEY COUNTY/. ALTHOUGH LARGE-SCALE FOR ASCENT IS NEBULOUS...CONTINUED SURFACE HEATING WILL YIELD INCREASING DESTABILIZATION AND MINIMAL CAPPING WITH SUSTAINED SURFACE-BASED TSTMS EXPECTED DURING THE AFTERNOON /SUPPORTED BY RECENT HRRR RUNS/. STRONG DEEP-LAYER SHEAR AND STEEP MID-LEVEL LAPSE RATES WILL BE QUITE FAVORABLE FOR SUPERCELLS PRODUCING LARGE HAIL /SOME SIGNIFICANT/. VEERING OF THE LOW-LEVEL WIND PROFILE ALONG WITH THE PRESENCE OF THE BOUNDARIES WILL SUPPORT A RISK FOR A COUPLE OF TORNADOES AS WELL. ..GRAMS/MEAD.. 08/01/2013 ATTN...WFO...FSD...OAX...TOP...GID...LBF...UNR...GLD...BOU... CYS...
Thursday, August 1, 2013
New Tornado Watch Coming for Parts of Nebraska, South Dakota
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