SWODY2
SPC AC 161712
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1212 PM CDT MON MAY 16 2011
VALID 171200Z - 181200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
HIGH-AMPLITUDE UPPER-AIR PATTERN FCST THROUGH PERIOD. TWO PRIMARY
MID-UPPER LEVEL CYCLONES ARE ANALYZED OVER ERN CONUS...OVER GA AND
OH. THESE ARE FCST TO UNDERGO FUJIWARA INTERACTION THROUGH DAY-2 AS
THEIR TWO VORTICITY MAXIMA REMAIN DISTINCT WHILE MERGING INTO ONE
DOMINANT GYRE. BY END OF PERIOD...EACH 500-MB VORTICITY MAX WILL
HAVE PERFORMED ABOUT 3/4 ORBIT FROM THEIR PRESENT POSITIONS...AROUND
COMMON CYCLONIC CENTER LOCATED OVER SRN APPALACHIANS.
MEANWHILE...ANOTHER SERIES OF MID-UPPER VORTICITY MAXIMA AND
SHORTWAVES -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER NWRN
CONUS AND ADJACENT PAC WATERS -- WILL EJECT NEWD/NWD OVER NRN
INTERMOUNTAIN REGION AS SUBSTANTIAL SPEED MAX DIGS SEWD ACROSS CA.
BY 18/12Z...RESULTANT STG SHORTWAVE TROUGH SHOULD BE LOCATED OVER NV
AND SRN CA...ANCHORING DEEPENING SYNOPTIC TROUGH OVER WRN CONUS.
AT SFC...WEAK/ELONGATED CYCLONE NOW OVER CAROLINAS PIEDMONT REGION
IS EXPECTED TO DRIFT NWD...WITH SOME FLUCTUATIONS IN STRENGTH IN
RESPONSE TO INTERACTION OF PERTURBATIONS ALOFT. PRECIP-REINFORCED
BAROCLINIC ZONE...AKIN TO OCCLUDED FRONT...SHOULD RESIDE OVER NRN
MD/SRN PA/NRN DELMARVA REGION. FARTHER W...LEE TROUGHING WILL
BECOME MORE PRONOUNCED ALONG HIGH PLAINS FROM MT-TX...WITH EMBEDDED
LOWS POSSIBLE OVER ERN CO AND SHR/BIL REGION. DRYLINE WILL DEVELOP
OVER PORTIONS W-CENTRAL/NW TX AS WEAK MOISTURE RETURN BEGINS...WITH
50S DEW POINTS IN NARROW CORRIDOR E OF PECOS RIVER AND CAPROCK.
...TIDEWATER INLAND TO PIEDMONT...
ORIGINAL COLD FRONTAL ZONE IS EXPECTED TO REMAIN OFFSHORE...KEEPING
OPTIMALLY HIGH-THETAE WARM SECTOR OVER ATLANTIC. HOWEVER...DIURNAL
CONVECTIVE POTENTIAL OVER THIS REGION...S OF OCCLUDED FRONT...WILL
BE SUPPORTED BY COMBINATION OF RESIDUAL BOUNDARY-LAYER
MOISTURE...ENHANCED MIDLEVEL INSTABILITY IN PROXIMITY TO CYCLONE
ALOFT...AND STEEPENING OF LOW-LEVEL LAPSE RATES THROUGH
DIURNAL/DIABATIC HEATING. 500-1000 J/KG MLCAPE MAY DEVELOP IN MOST
SUSTAINED AREAS OF CLEARING...WITH POCKETS OF LOW-MID 60S F SFC DEW
POINTS. FCST LOW-LEVEL HODOGRAPHS ARE SOMEWHAT ELONGATED BUT ALSO
JUST SLIGHTLY CURVED...RESULTING IN SMALL SRH...HOWEVER 35-40 KT
EFFECTIVE SHEAR MAY SUPPORT CONVECTIVE ORGANIZATION. OCCLUDED
FRONTAL ZONE ALSO MAY PROVIDE ENHANCED LOW-LEVEL SUPPORT FOR STORM
ROTATION. ATTM...SVR THREAT APPEARS TO MRGL FOR CATEGORICAL
OUTLOOK...HOWEVER MESOSCALE FOCI MAY RESULT IN MORE CONCENTRATED
AREA WITHIN CURRENT 5% GRID PROBABILITIES.
...PLAINS STATES...
DIURNAL HEATING AND CONVERGENCE INVOF LEE TROUGH...COMBINED WITH
MRGL BOUNDARY-LAYER MOISTURE...MAY SUPPORT TSTMS OVER CENTRAL HIGH
PLAINS LATE AFTERNOON AND EARLY EVENING. PROGGED WEAKNESSES IN
LOW-LEVEL WINDS AND IN DEEP-LAYER SHEAR INDICATED LIMITED POTENTIAL
FOR THIS ACTIVITY TO BECOME WELL-ORGANIZED...THOUGH SOME STG GUSTS
ARE POSSIBLE. A FEW SREF MEMBERS AND OPERATIONAL WRF ALSO INDICATE
BRIEF POTENTIAL FOR LATE-AFTERNOON TSTMS DEVELOPMENT OVER PORTIONS
W-CENTRAL/NW TX...ATOP STRONGLY HEATED AIR MASS NEAR DRYLINE.
LOW-LEVEL SHEAR WILL BE STRONGER OVER THIS REGION THAN FARTHER
NW...BUT TSTM POTENTIAL APPEARS TOO ISOLATED/CONDITIONAL TO ASSIGN
SVR PROBABILITIES ATTM.
AFTER DARK...ELONGATED LLJ OF 45-55 KT IS FCST TO DEVELOP FROM SW TX
TO SWRN ND IN RESPONSE TO LEE-SIDE HEIGHT/PRESSURE FALLS.
HOWEVER...SUSTAINED OFFSHORE FLOW...WHICH STILL IS UNDERWAY OVER
MOST OF GULF COAST ATTM...HAS DONE CONSIDERABLE DAMAGE TO MOISTURE
FIELD OVER MARINE AIR MASS THAT WILL SUPPLY TRAJECTORIES INTO DAY-2
LLJ. WIDELY SCATTERED TO SCATTERED TSTMS MAY DEVELOP LATE IN PERIOD
IN WAA BAND FROM ERN/NRN OK NWWD TO CENTRAL HIGH PLAINS. WHILE
ISOLATED HAIL CANNOT BE RULED OUT...LACK OF MORE ROBUST MOISTURE
PRECLUDES UNCONDITIONAL SVR PROBABILITIES.
..EDWARDS.. 05/16/2011
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