SPC 1300Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0754 AM CDT SUN JUL 26 2015 VALID 261300Z - 271200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL HIGH PLAINS... ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS THE HIGH PLAINS... ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS THE MIDWEST AND MIDDLE MS RIVER/LOWER OH VALLEYS... ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PORTIONS OF THE NORTHEAST STATES... ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PORTIONS OF MT... ...SUMMARY... WIDELY SCATTERED STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED MAINLY THIS AFTERNOON AND EVENING ACROSS PORTIONS OF THE HIGH PLAINS...MIDDLE MISSISSIPPI/LOWER OHIO VALLEYS...AND NORTHEAST STATES. ...SYNOPSIS... AN AMPLIFICATION OF THE WESTERLIES OVER THE NORTHERN HALF OF THE CONUS IS EXPECTED THROUGH TONIGHT. ON THE NORTHERN PERIPHERY OF A SOUTHERN PLAINS UPPER RIDGE...MULTIPLE LOW-AMPLITUDE/CONVECTIVELY RELATED MID-LEVEL DISTURBANCES WILL SPREAD GENERALLY EAST-SOUTHEASTWARD ACROSS THE CENTRAL PLAINS/LOWER MO VALLEY/MIDWEST...ALL WHILE A MORE SUBSTANTIAL UPPER TROUGH AMPLIFIES/DIGS SOUTHEASTWARD OVER THE PACIFIC NORTHWEST/GREAT BASIN THROUGH TONIGHT. ...CENTRAL HIGH PLAINS... ON THE IMMEDIATE NORTHERN PERIPHERY OF THE SOUTHERN HIGH PLAINS-CENTERED UPPER RIDGE...HIGH-BASED THUNDERSTORMS SHOULD INITIALLY DEVELOP ACROSS SOUTHERN/EASTERN CO THIS AFTERNOON...WITH SUBSEQUENT INTENSIFICATION EXPECTED AS THEY MOVE EAST-NORTHEASTWARD ACROSS FAR EASTERN CO AND EVENTUALLY FAR WESTERN KS INTO A HOT/MORE MOIST BOUNDARY LAYER. IT IS PROBABLE THAT STORMS WILL TEND TO CLUSTER BY EARLY EVENING INTO A SLOW EAST/NORTHEASTWARD PROPAGATING MCS...WITH THE AID OF A NOCTURNALLY INCREASING /30+ KT/ SOUTHERLY LOW-LEVEL JET. EPISODIC BOUTS SEVERE WIND/HAIL WILL LIKELY BE THIS AFTERNOON/EVENING...WITH AN INCREASINGLY MORE MARGINAL SEVERE RISK BY THE LATE EVENING/OVERNIGHT HOURS. ...DAKOTAS/NEB... WHILE OVERALL FORCING WILL BE WEAK UNDER THE INFLUENCE OF RISING UPPER HEIGHTS...WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS PARTS OF THE DAKOTAS/WESTERN NEB IN VICINITY OF A LEE TROUGH. WHILE SOMEWHAT STRONGER VERTICAL SHEAR /30-35 KT EFFECTIVE/ WILL RESIDE OVER THE DAKOTAS...AN OVERALL SCENARIO CHARACTERIZED BY MODEST FORCING/VERTICAL SHEAR SUGGESTS THAT CONVECTION WILL NOT BE PARTICULARLY ORGANIZED...ALTHOUGH ISOLATED INSTANCES OF HAIL/WIND WILL NONETHELESS BE POSSIBLE. ...MT... THE LEADING EDGE OF HEIGHT FALLS/FORCING FOR ASCENT RELATED TO THE AMPLIFYING PACIFIC NORTHWEST UPPER TROUGH WILL REACH PORTIONS OF MT LATER TODAY INTO TONIGHT. HIGH-BASED THUNDERSTORMS SHOULD DEVELOP/INCREASE THROUGH MID/LATE AFTERNOON ACROSS CENTRAL MT AND SUBSEQUENTLY SPREAD EAST-NORTHEASTWARD. GIVEN AN ENVIRONMENT CHARACTERIZED BY INCREASINGLY STRONG DEEP-LAYER SOUTHWESTERLY WINDS ATOP DRY/WELL-MIXED BOUNDARY LAYERS...SOME OF THE STRONGER HIGH-BASED STORMS MAY BE CAPABLE OF SEVERE-CALIBER WIND GUSTS AND POSSIBLY SMALL HAIL LATE THIS AFTERNOON/EVENING. IT IS NOT ENTIRELY OUT OF THE QUESTION THAT A FEW OF THESE STORMS WILL DEVELOP INTO/ACROSS FAR EASTERN MT LATE TONIGHT WITHIN A WESTWARD-TRANSITIONING MOIST AXIS. ...MIDWEST/OZARKS AND MIDDLE MS/LOWER OH RIVER VALLEYS... DUAL ELEVATED MCS/S AND WHAT APPEAR TO BE RELATED MCV/S ARE PROGRESSING SOUTHEASTWARD EARLY THIS MORNING ACROSS THE REGION...INCLUDING ONE ACROSS SOUTHEAST MO/SOUTHERN IL AND THE OTHER ACROSS SOUTHERN/EASTERN IA AND NORTHERN MO AS OF 13Z/8AM CDT. ANY SEVERE RISK SHOULD REMAIN MINIMAL EARLY TODAY...BUT SOME REINVIGORATION IS POSSIBLE ACROSS THE REGION PARTICULARLY ON THE WESTERN/SOUTHERN FLANKS OF THE EARLY DAY STORMS WHERE DESTABILIZATION WILL BE MORE CONSEQUENTIAL. SOME HAIL AND ISOLATED DAMAGING WINDS WILL BE POSSIBLE. FARTHER NORTH...WHILE THE EARLY DAY MCS/OUTFLOW CASTS SOME UNCERTAINTY...THERE IS SOME POTENTIAL THAT STORMS MAY REDEVELOP LATE THIS AFTERNOON/EVENING ACROSS PARTS OF IA/SOUTHERN MN IN VICINITY OF A WARM FRONT/RESIDUAL OUTFLOW. WHILE UPPER-LEVEL HEIGHTS WILL BE RISING AND OVERALL FORCING WILL BE WEAK...SEVERE THUNDERSTORMS WILL BE POSSIBLE IF DEEP CONVECTION CAN DEVELOP/REMAIN SUSTAINED WITHIN WHAT SHOULD BE A VERY UNSTABLE ENVIRONMENT. ...NEW ENGLAND/EASTERN NY... AHEAD OF A COLD FRONT...THE AIR MASS SHOULD AT LEAST MODESTLY DESTABILIZE INTO THIS AFTERNOON IN THE WAKE OF THICKER CLOUD COVER AND SCATTERED PRECIPITATION THIS MORNING. WHILE LARGER-SCALE FORCING WILL BE WEAK/NEBULOUS...AT LEAST WIDELY SCATTERED THUNDERSTORMS SHOULD REDEVELOP LATER THIS AFTERNOON...WITH SOME STRONGER STORMS POSSIBLE AS HEATING/DESTABILIZATION OCCURS. RELATIVELY WEAK DEEP-LAYER SHEAR /20-30 KT EFFECTIVE/ AND WEAK MID-LEVEL LAPSE RATES SHOULD TEMPER THE OVERALL SEVERE POTENTIAL...BUT SOME STRONGER WIND GUSTS/MARGINAL HAIL WILL NONETHELESS BE POSSIBLE THIS AFTERNOON/EARLY EVENING. ..GUYER/COOK.. 07/26/2015
from SPC Convective Outlooks http://1.usa.gov/1MQ1cgd
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