SWODY1
SPC AC 171947
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT TUE MAY 17 2011
VALID 172000Z - 181200Z
...THERE IS A SLGT RISK OF SVR TSTMS IN THE VA AREA...
...MID ATLANTIC...
AT MID AFTERNOON...STRONG VORTICITY MAX HAD SHIFTED NWWD INTO SRN VA
TO NEAR LYH...WITH STRONGER FORCING LOCATED IN WRN/NRN VA. AS VORT
MAX TURNS MORE WWD TOWARD WV...STRONGER FORCING WILL SPREAD INTO
VA...THOUGH DENSER CLOUDS AND STABLE BOUNDARY LAYER WILL LIMIT WWD
EXTENT OF SEVERE STORMS. WHILE STORMS THUS FAR HAVE BEEN MOSTLY SUB
SEVERE...WITH A FEW DEGREES HEATING...A FEW SEVERE STORMS ARE STILL
POSSIBLE ACROSS NRN AND WRN VA. THE COLD AIR MASS ALOFT SUGGEST HAIL
IS THE MAIN THREAT.
SINCE STRONGER FORCING HAS MOVED NWWD OUT OF NC AND DRIER AIR IS
SLOWLY FILTERING IN AT THE LOWER LEVELS...ONLY LOW SEVERE
PROBABILITIES REMAIN IN NRN NC. ALSO SEVERE PROBABILITIES WERE
LOWERED IN PA AS THE MAIN FORCING SHOULD REMAIN SOUTH OF STATE.
...CENTRAL HIGH PLAINS...
AS UPPER SHORTWAVE TROUGH LIFTS NEWD FROM SWRN CO/NERN NM...STORMS
ARE LIKELY TO DEVELOP NEAR THE CO/KS BORDER BETWEEN 21-00Z...WITH
SHEAR AND INSTABILITY SUPPORTIVE OF ISOLATED SEVERE WEATHER.
HOWEVER...THE BOUNDARY LAYER AIR MASS IMMEDIATELY EAST OF THIS AREA
IS STABLE...SO ANY SEVERE STORMS THAT FORM ARE NOT EXPECTED TO STAY
SEVERE VERY LONG. WILL MAINTAIN LOW SEVERE PROBABILITIES WITH ONLY
MINOR ADJUSTMENTS TO GRAPHICAL LINES.
..IMY.. 05/17/2011
.PREV DISCUSSION... /ISSUED 1125 AM CDT TUE MAY 17 2011/
...MID ATLANTIC...
STRONG VORTICITY MAXIMUM OVER CNTRL/ERN NC AS OF LATE MORNING WILL
PIVOT NWWD TODAY IN RESPONSE TO UPSTREAM IMPULSE TRANSLATING SEWD
THROUGH THE SRN APPALACHIANS. IN THE LOW LEVELS...AN ASSOCIATED
SURFACE LOW OVER CNTRL NC WILL CONCURRENTLY DEVELOP NWWD INTO WRN VA
BY TONIGHT. DCVA IN ADVANCE OF VORTICITY MAXIMUM COUPLED WITH WEAK
LOW-LEVEL WAA WILL SUPPORT A GRADUAL INCREASE IN TSTM COVERAGE THIS
AFTERNOON ACROSS THE REGION.
WHILE THE BOUNDARY LAYER IS NOT OVERLY MOIST...THE PRESENCE OF 500
MB TEMPERATURES AROUND -18 C WILL CONTRIBUTE TO AIR MASS
DESTABILIZATION WITH MLCAPE APPROACHING 1000 J/KG IN AREAS WHERE THE
STRONGEST DIABATIC WARMING OCCURS. WHEN COUPLED WITH 40-45 KT
MIDLEVEL JET STREAK AND RESULTANT 35-40 KT OF DEEP SELY
SHEAR...SETUP WILL FAVOR THE DEVELOPMENT OF ORGANIZED
STORMS...INCLUDING SUPERCELLS...CAPABLE OF LOCALLY DAMAGING WINDS
AND PERHAPS SOME HAIL. AN ISOLATED TORNADO IS POSSIBLE WITH ANY
STORMS THAT CAN FAVORABLY INTERACT WITH THE SYNOPTIC WARM FRONT
AND/OR DIFFERENTIAL HEATING/OUTFLOW BOUNDARIES PRESENT WITHIN WARM
SECTOR.
FOR ADDITIONAL NEAR TERM GUIDANCE ON THIS AREA...SEE MCD 796.
...CNTRL HIGH PLAINS...
VORTICITY MAXIMUM AND ATTENDANT 50-55 KT MIDLEVEL JET STREAK OVER
WRN CO INTO NWRN NM AS OF MID MORNING WILL TRANSLATE NEWD
TODAY...WITH HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT PROGRESSIVELY
OVERSPREADING LEE CYCLONE AND DEVELOPING DRYLINE SITUATED ACROSS ERN
CO INTO THE WRN OK/TX PNHDLS. DESPITE THE FAVORABLY TIMED ARRIVAL
OF THIS IMPULSE...THE PRESENCE OF CONSIDERABLE LEE MOUNTAIN CIRRUS
/AND ITS POTENTIAL NEGATIVE IMPACT ON DAYTIME HEATING/ COMBINED WITH
MARGINAL BOUNDARY LAYER MOISTURE CONTENT WILL TEND TO LIMIT MLCAPE
TO LESS THAN 1000 J/KG THIS AFTERNOON E OF DRYLINE.
THE PRESENCE OF THE STEEP LAPSE RATES AND VERTICALLY VEERING WIND
PROFILES WITH 40-50 KT OF DEEP-LAYER SHEAR WILL BE SUPPORTIVE OF
ISOLATED OCCURRENCES OF DAMAGING WINDS AND/OR SEVERE HAIL WITH ANY
STORMS THAT DEVELOP LATE THIS AFTERNOON INTO EVENING. BUT...THE
POTENTIAL FOR A MORE ORGANIZED SEVERE WEATHER EPISODE WILL LIKELY BE
TEMPERED BY THE MARGINAL BOUNDARY LAYER MOISTURE CONTENT.
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