SPC 1300Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0742 AM CDT THU JUL 25 2013 VALID 251300Z - 261200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL AND SRN PLAINS INTO THE UPPER MIDWEST... ...SYNOPSIS... A SIGNIFICANT SHORT-WAVE TROUGH AND ASSOCIATED MID AND UPPER-LEVEL JET STREAKS OVER SASKATCHEWAN AND MANITOBA WILL TRANSLATE SEWD INTO THE NRN PLAINS AND UPPER MS VALLEY WITH AN UPPER-LEVEL LOW EVENTUALLY FORMING OVER CNTRL ONTARIO. THIS SYSTEM WILL BE PRECEDED BY A COUPLE OF LOWER-AMPLITUDE PERTURBATIONS ADVANCING SEWD THROUGH THE NRN AND CNTRL PLAINS. IN THE LOW LEVELS...TWO DISTINCT COLD FRONTAL SURGES WILL ACCOMPANY THESE UPPER-AIR DEVELOPMENTS...THE SRN-MOST OF WHICH WILL BE THE PRIMARY FOCUS FOR STRONG-SEVERE STORM DEVELOPMENT. BY 26/00Z...THIS FRONT WILL STRETCH FROM LOW PRESSURE OVER LAKE SUPERIOR SWWD THROUGH CNTRL WI...NRN IA...TO A LEE CYCLONE OVER WRN KS. A LEE TROUGH WILL EXTEND SWD FROM THE KS LOW INTO WRN TX. ...CNTRL AND SRN PLAINS THIS AFTERNOON INTO TONIGHT... MULTIPLE CLUSTERS OF NOCTURNAL STORMS ARE ONGOING FROM CNTRL SD TO THE ERN TX PNHDL AND WRN OK WHERE A BROAD LOW-LEVEL WAA REGIME IS BEING ENHANCED BY MULTIPLE LOW-AMPLITUDE IMPULSES MOVING SEWD FROM THE ROCKIES. THESE STORMS SHOULD WEAKEN THROUGH THE MORNING...WITH DIURNALLY ENHANCED STORM DEVELOPMENT BEING FOCUSED ALONG RESIDUAL CONVECTIVE OUTFLOW BOUNDARIES...A DEVELOPING LEE TROUGH...AND THE SWD PROGRESSION OF THE SYNOPTIC COLD FRONT INTO THE CNTRL HIGH PLAINS. DECREASING CLOUDS COUPLED WITH THE REPLENISHMENT OF LAPSE RATES FROM THE WEST WILL SUPPORT MODERATE INSTABILITY TODAY WITH MLCAPE OF 1000-2000 J/KG. VERTICAL SHEAR WILL NOT BE OVERLY STRONG BUT SUFFICIENT FOR SUSTAINED/ROTATING STORMS CAPABLE OF DAMAGING WINDS AND HAIL. INCREASED FORCING FOR ASCENT ATTENDANT TO A SHORT-WAVE TROUGH EMERGING FROM THE CNTRL ROCKIES WILL LIKELY CONTRIBUTE TO UPSCALE GROWTH OF STORMS INTO ONE OR MORE SEWD-MOVING MCSS WITH A DAMAGING WIND AND HAIL THREAT CONTINUING INTO EARLY FRIDAY. ...UPPER MIDWEST INTO MID MO VALLEY THIS AFTERNOON AND EVENING... SCATTERED STORM DEVELOPMENT IS ANTICIPATED ALONG THE COLD FRONT THIS AFTERNOON AND DEEP-LAYER ASCENT IS ENHANCED BY THE STRONG SHORT-WAVE TROUGH APPROACHING THE UPPER GREAT LAKES. MODEST MIDLEVEL LAPSE RATES WILL BE OFFSET BY DAYTIME HEATING AND SOME BOUNDARY LAYER MOISTENING WITH MLCAPE VALUES RISING TO 1000-1500 J/KG. WHEN COUPLED WITH STEADILY STRENGTHENING MID AND UPPER-LEVEL FLOW AND RESULTANT VERTICAL SHEAR...THE SETUP APPEARS SUPPORTIVE OF A FEW SEVERE STORMS CAPABLE OF DAMAGING WINDS AND HAIL INTO THIS EVENING. ..MEAD/BOTHWELL.. 07/25/2013
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1300.html
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