SPC 1730Z Day 2 Outlook
DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1230 PM CDT SAT APR 28 2012 VALID 291200Z - 301200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS TROUGH SRN MO TO THE LOWER OH VALLEY... ...SYNOPSIS... LESS AMPLIFICATION OF THE BLOCKING PATTERN OVER THE NRN U.S. INTO CANADA IS EXPECTED ON SUN AS THE BLOCK BEGINS TO BREAK DOWN DURING D2. A CLOSED LOW LOCATED OVER WRN ND AT 12Z SUN WILL CONTINUE TO MOVE NWD INTO CENTRAL CANADA AND WEAKEN INTO AN OPEN WAVE...WITH AN ATTENDANT BROAD LONGWAVE TROUGH EVOLVING ACROSS THE WRN TWO-THIRDS OF THE CONUS. THIS PATTERN CHANGE WILL OCCUR AS THE DEEP CLOSED LOW OVER ERN CANADA WEAKENS AND MOVES TOWARD GREENLAND...AND A STRONG SHORTWAVE TROUGH DIGS SEWD ACROSS THE NERN STATES AND OFFSHORE... WHILE THE NRN ONTARIO/GREAT LAKES/TN VALLEY RIDGE AXIS SHIFTS EWD. MEANWHILE...A SHORTWAVE TROUGH/ATTENDANT MID-UPPER LEVEL JETS...NOW MOVING SEWD THROUGH NRN CA/WRN NV...WILL TRACK ENEWD FROM AZ/NM INTO THE SRN/CENTRAL HIGH PLAINS SUN AFTERNOON...REACHING THE MID/UPPER MS VALLEY BY 12Z MON. AT THE SURFACE...A FRONT IS EXPECTED TO INITIALLY EXTEND WNWWD FROM NC THROUGH KY TO CENTRAL MO...AND THEN SWWD THROUGH OK TO W CENTRAL TX/SERN NM. LITTLE MOVEMENT OF THIS BOUNDARY IS EXPECTED THROUGH THE FIRST HALF OF D2...WITH INDICATION THAT THE MO/LOWER OH VALLEY PORTION WILL ADVANCE NNEWD SUN NIGHT WITH THE APPROACH OF THE CA/NV TROUGH. ...OK/SRN KS THROUGH SRN MO TO LOWER OH VALLEY... A MOIST AIR MASS WILL BE MAINTAINED ALONG THE EXTENT OF THE QUASI-STATIONARY SURFACE FRONT FROM OK INTO SRN MO AND THE LOWER OH VALLEY THIS FORECAST PERIOD. EXTENSIVE CLOUDS AND ONGOING SHOWERS/TSTMS ARE EXPECTED ACROSS MUCH OF THIS REGION AT 12Z SUN... WHICH COULD LIMIT THE OVERALL DESTABILIZATION. HOWEVER...THESE AREAS WILL RESIDE ALONG THE NRN EXTENT OF AN EML WHERE THE CAP SHOULD BE WEAKER...AND ANY SURFACE HEATING WILL AID IN REDUCING INHIBITION FOR DEEP MOIST CONVECTIVE DEVELOPMENT. THIS FACTOR COMBINED WITH EFFECTIVE BULK SHEAR OF 35-50 KT EXPECTED INVOF THIS BOUNDARY THROUGH THE DAY INTO THE EVENING SUGGESTS THE POTENTIAL FOR STORM ORGANIZATION AND ATTENDANT SEVERE WEATHER THREAT WITH THE STRONGER CELLS. THUS...THE SLIGHT RISK HAS BEEN EXTENDED ENEWD ACROSS OK/SRN KS INTO SRN MO AND THE LOWER OH VALLEY. ...SRN/CENTRAL HIGH PLAINS... MODELS MAINTAIN THE POTENTIAL FOR THE WARM SECTOR OVER WRN TX BENEATH STEEP MIDLEVEL LAPSE RATES TO BECOME MODERATELY UNSTABLE /MLCAPE OF 1500-2000 J PER KG/ AS THE BOUNDARY LAYER WARMS DURING THE AFTERNOON. IT STILL APPEARS THIS AREA WILL REMAIN CAPPED MUCH OF THE DAY. HOWEVER...STORMS MAY DEVELOP OVER THE HIGHER TERRAIN IN A MORE DEEPLY MIXED BOUNDARY LAYER OF ERN NM AS WELL AS NEAR THE FRONT/DRYLINE INTERSECTION WHERE CONVERGENCE SHOULD BE MAXIMIZED. SOME OF THIS ACTIVITY WILL INITIALLY BE WEST OF THE MOIST AXIS AND HIGH BASED...BUT STORMS SHOULD INTENSIFY AS THEY DEVELOP EWD INTO THE BETTER INSTABILITY ACROSS WRN TX. EFFECTIVE VERTICAL SHEAR OF 40-50 KT WILL BE SUFFICIENT FOR SUPERCELLS. FARTHER NORTH OTHER STORMS MAY DEVELOP OVER THE HIGHER TERRAIN FROM NERN NM INTO SCNTRL-SERN CO WHERE INSTABILITY WILL BE LESS /MLCAPE 1000-1500 J PER KG/...THOUGH STILL SUFFICIENT FOR STRONGER TSTM DEVELOPMENT AND STORM ORGANIZATION GIVEN SIMILAR SHEAR VALUES. WEAKER INSTABILITY EXTENDING NNEWD ACROSS THE REST OF ERN CO/WRN KS INTO SWRN NEB SHOULD LIMIT THE SEVERE WEATHER THREAT...BUT LOW PROBABILITIES APPEAR WARRANTED GIVEN EFFECTIVE BULK SHEAR AROUND 40 KT. ..PETERS.. 04/28/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day2otlk_1730.html
Be First to Comment