SPC 2000Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0237 PM CDT TUE MAY 28 2013 VALID 282000Z - 291200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE HIGH PLAINS INTO THE UPPER OH VALLEY... ...KS/OK/TX DRYLINE... RAPID HEATING ACROSS THE HIGH PLAINS HAS CONTRIBUTED TO RECENT CU ENHANCEMENT ALONG THE DRYLINE FROM THE TX/NM BORDER...NEWD INTO THE ERN OK PANHANDLE. THIS BOUNDARY HAS RETREATED SOME OVER THE LAST HOUR DUE TO UPSTREAM SHORT-WAVE INFLUENCE AND PRESSURE FALLS ALONG THE LEE OF THE ROCKIES. IT/S NOT ENTIRELY CLEAR HOW FAR NW THE DRYLINE WILL RETREAT BEFORE SEVERE TSTMS TAKE ROOT AND LIFT NEWD...BUT INDICATIONS SUGGEST AGITATED CU FIELD WILL SOON PRODUCE LIGHTNING. GIVEN THE EXPECTED INCREASE IN CONVECTION ALONG THE DRYLINE HAVE EXTENDED 30 PERCENT SEVERE HAIL PROBS ACROSS SWRN KS. OTHERWISE...1630Z FORECAST REMAINS ON TRACK. ..DARROW.. 05/28/2013 .PREV DISCUSSION... /ISSUED 1125 AM CDT TUE MAY 28 2013/ ...SYNOPSIS... AN UPPER-LEVEL JET STREAK FROM THE NERN PACIFIC INTO WRN GREAT BASIN WILL DEVELOP SEWD INTO THE SRN ROCKIES...CONTRIBUTING TO THE INTENSIFICATION AND INCREASING NEGATIVE TILT OF A LONG-WAVE TROUGH FROM THE PACIFIC NW INTO SRN ROCKIES. WITHIN THIS EVOLVING TROUGH...A VORTICITY RIBBON FROM THE SRN HIGH PLAINS INTO NWRN MEXICO WILL TRANSLATE EWD INTO THE SRN PLAINS IN ADVANCE OF A VIGOROUS VORTICITY MAXIMUM SHIFTING FROM THE GREAT BASIN INTO SRN ROCKIES...ON CYCLONIC SIDE OF UPPER-LEVEL JET STREAK. DOWNSTREAM FROM THESE DEVELOPMENTS...A VORTICITY MAXIMUM OVER THE UPPER MIDWEST WILL CONTINUE ENEWD TODAY INTO THE UPPER GREAT LAKES...IN ADVANCE OF A WEAKER IMPULSE TRACKING FROM THE CNTRL HIGH PLAINS INTO MID-MO VALLEY. IN THE LOW LEVELS...A SURFACE CYCLONE OVER THE MID-MO VALLEY WILL DEVELOP NEWD INTO THE UPPER GREAT LAKES ALONG A WARM FRONT MOVING NWD THROUGH THIS REGION. A FRONTAL SEGMENT WILL TRAIL SWWD THROUGH THE MID OR LOWER-MO VALLEY TO A LEE LOW CURRENTLY E OF DDC WHICH WILL DEVELOP WWD TOWARD THE KS-CO BORDER. A DRYLINE WILL BECOME BETTER DEFINED TODAY FROM THIS LATTER LOW PRESSURE SWD INTO WRN TX. ...UPPER GREAT LAKES/OH VALLEY THIS AFTERNOON AND EVENING... A BROAD SWLY LLJ FROM THE SRN PLAINS THROUGH THE MID-MS AND OH VALLEYS WILL ENHANCE THE NWD FLUX OF AN INCREASINGLY MOIST BOUNDARY LAYER TO THE SOUTH OF THE WARM FRONT WITH DEWPOINTS CLIMBING INTO THE LOW TO MID 60S. VISIBLE SATELLITE SUGGESTS THAT CLOUDS MAY REMAIN RATHER WIDESPREAD...BUT WHERE POCKETS OF STRONGER HEATING CAN OCCUR...THE POTENTIAL FOR MODERATE INSTABILITY WILL EXIST BY AFTERNOON. TSTMS ARE GRADUALLY INTENSIFYING AS OF LATE MORNING OVER WRN LOWER MI AHEAD OF A LEAD VORTICITY MAXIMUM MOVING ACROSS LAKE MI. THIS ACTIVITY SHOULD CONTINUE TO INTENSIFY WITH AN INCREASING THREAT FOR DAMAGING WINDS AND HAIL ACROSS LOWER MI THIS AFTERNOON. FOR ADDITIONAL NEAR-TERM GUIDANCE...SEE MCD 836. ANOTHER ROUND OF TSTMS WILL BE POSSIBLE LATER THIS AFTERNOON INTO EVENING IN ASSOCIATION WITH AN UPSTREAM IMPULSE MOVING THROUGH THE UPPER MIDWEST. HERE TOO...DAMAGING WINDS AND HAIL WILL BE THE PRIMARY HAZARDS. FARTHER S ACROSS THE OH VALLEY...STORMS MAY INCREASE IN COVERAGE AND INTENSITY THIS AFTERNOON AS LIFT IS ENHANCED BY EXISTING OUTFLOW BOUNDARIES. HAIL AND DAMAGING WINDS WILL BE THE PRIMARY HAZARDS WITH THESE STORMS INTO THIS EVENING. ...KS INTO THE LOWER-MO AND MID-MS VALLEY THIS AFTERNOON AND TONIGHT... 12Z REGIONAL SOUNDINGS SHOW THE POTENTIAL FOR STRONG AIR MASS DESTABILIZATION TODAY S OF FRONTAL SEGMENT BOUNDED BY THE LEAD FRONTAL WAVE MOVING INTO THE UPPER GREAT LAKES AND LEE CYCLONE OVER CNTRL KS. HERE...700-500-MB LAPSE RATES OF 9.0-9.5 C/KM COINCIDE WITH LOWEST-100-MB MEAN MIXING RATIOS OF AROUND 14.5 G/KG WHICH WILL YIELD AFTERNOON MLCAPE VALUES APPROACHING 2000-4000 J/KG. CONVERGENCE ALONG THE FRONT AND INFLUENCE OF A WEAK MIDLEVEL IMPULSE MOVING THROUGH THE CNTRL PLAINS SHOULD FOSTER WIDELY SCATTERED TSTMS BY MID TO LATE AFTERNOON. VERTICAL SHEAR WILL BE ENHANCED BY A 40-50 KT MIDLEVEL JET STREAK WHICH WAS SAMPLED BY THE 12Z AMA/DDC/TOP SOUNDINGS...SUPPORTING SUPERCELLS WITH A RISK FOR VERY LARGE HAIL...DAMAGING WINDS AND TORNADOES. STORMS WILL LIKELY GROW UPSCALE INTO ONE OR MULTIPLE MCS/S TONIGHT WITH A CONTINUED THREAT FOR DAMAGING WINDS AND HAIL. ...NRN/CNTRL HIGH PLAINS THIS AFTERNOON AND EVENING... ISOLATED TO WIDELY SCATTERED TSTMS ARE EXPECTED TO DEVELOP THIS AFTERNOON WITHIN POST-FRONTAL UPSLOPE REGIME WHERE DAYTIME HEATING AND STEEP LAPSE RATES CONTRIBUTE TO MODERATE INSTABILITY. THE ELY LOW-LEVEL WIND COMPONENT BENEATH STRENGTHENING SWLY FLOW ALOFT WILL RESULT IN SUFFICIENT VERTICAL SHEAR FOR SUPERCELLS WITH THE PRIMARY HAZARDS BEING LARGE HAIL AND DAMAGING WINDS. ...SRN HIGH PLAINS THIS AFTERNOON AND EVENING... LARGE-SCALE FORCING FOR ASCENT WILL INCREASE TODAY AHEAD OF THE SHORT-WAVE TROUGH MOVING THROUGH THE SRN ROCKIES WHICH SHOULD PROMOTE WIDELY SCATTERED TSTMS ALONG THE DRYLINE BY MID TO LATE AFTERNOON. THE STRONGEST HEATING/AIR MASS DESTABILIZATION IS ANTICIPATED FROM THE TX SOUTH PLAINS NWD THROUGH THE TX/OK PNHDLS AND WRN OK WHERE MLCAPE WILL APPROACH 2000-3000 J/KG. THE 12Z ABQ SOUNDING SAMPLED A WEAKNESS IN THE MID TO UPPER-TROPOSPHERIC FLOW WHICH MAY LIMIT THE STRENGTH OF THE DEEP-LAYER SHEAR ALONG THE DRYLINE LATER TODAY. NONETHELESS...THE DEGREE OF INSTABILITY WILL COMPENSATE WITH A RISK FOR ORGANIZED STORMS...INCLUDING SUPERCELLS CAPABLE OF LARGE HAIL...DAMAGING WINDS...AND PERHAPS A TORNADO OR TWO. ...MD/VA PIEDMONT THIS AFTERNOON AND EVENING... HEATING ALONG/E OF THE BLUE RIDGE WILL COMBINE WITH DEWPOINTS INCREASING INTO THE LOW TO MID 60S TO YIELD A MODERATELY UNSTABLE AIR MASS WITH AFTERNOON MLCAPE OF 1000-1500 J/KG. WIDELY SCATTERED TSTM DEVELOPMENT IS ANTICIPATED THIS AFTERNOON ALONG THE HIGH TERRAIN AND/OR LEE TROUGH AMIDST A KINEMATIC ENVIRONMENT FEATURING MODEST WLY FLOW. AS SUCH...ISOLATED OCCURRENCES OF HAIL AND GUSTY WINDS WILL BE POSSIBLE INTO THIS EVENING.
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_2000.html
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