SWODY2
SPC AC 291739
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1239 PM CDT SUN MAY 29 2011
VALID 301200Z - 311200Z
...THERE IS A MDT RISK OF SVR TSTMS EXTENDS FROM FAR SERN ND...ERN
SD...FAR NERN NEB INTO MUCH OF WEST CENTRAL/SWRN MN AND FAR NWRN
IA...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
AREA EXTENDING FROM THE ERN DAKOTAS/MN SWD TO THE SRN PLAINS...
...SYNOPSIS...
UPPER TROUGH/CLOSED LOW MOVING ACROSS THE GREAT BASIN TODAY WILL
TAKE ON A NEGATIVE TILT AND DEEPEN ON MONDAY AS IT TRACKS TOWARD AND
INTO THE NRN PLAINS. STRONG JET STREAK AND ATTENDANT MIDLEVEL
SHORTWAVE TROUGH ROUNDING THE BASE OF THE WRN TROUGH BY 12Z MONDAY
WILL EJECT NEWD ACROSS THE CENTRAL PLAINS TO THE UPPER MS VALLEY BY
12Z TUESDAY. PRIMARY SURFACE LOW INITIALLY LOCATED OVER THE NRN
HIGH PLAINS MONDAY MORNING WILL MOVE NEWD THROUGH WRN ND TO SOUTH
CENTRAL CANADA...AND APPEARS TO EVOLVE INTO MORE OF AN OCCLUSION BY
LATE DAY 2/EARLY DAY 3. MEANWHILE...A DRY LINE WILL BECOME DEFINED
FROM THE SRN PLAINS THROUGH CENTRAL KS/NEB TO ERN SD AS A WARM FRONT
MOVES NWD THROUGH THE DAKOTAS AND UPPER MS VALLEY. A COLD FRONT
WILL ADVANCE EWD THROUGH THE NRN AND CNTRL PLAINS... OVERTAKING THE
DRY LINE AND PROGRESSING INTO THE UPPER MS VALLEY LATER MONDAY
NIGHT.
...ERN DAKOTAS/UPPER MS VALLEY TO THE CENTRAL PLAINS...
NEGATIVE-TILT OF UPPER TROUGH INTO THE NRN PLAINS...STRENGTHENING
WIND FIELDS/SHEAR AND MODERATE INSTABILITY SUPPORT AN UPGRADE TO A
MODERATE RISK FOR VERY LARGE HAIL...A STRONG TORNADO OR TWO AND
DAMAGING WINDS ACROSS PARTS OF THE ERN DAKOTAS/MID MO VALLEY TO
UPPER MS VALLEY. SLY LOW LEVEL WINDS THROUGH THE DAY WILL MAINTAIN
NWD MOISTURE RETURN WITH SURFACE DEWPOINTS IN THE MID-UPPER 60S
REACHING THE NRN EXTENT OF THE WARM SECTOR OVER THE ERN
DAKOTAS/UPPER MS VALLEY MONDAY MORNING/AFTERNOON. PLUME OF STEEP
MIDLEVEL LAPSE RATES EXTENDING NNEWD ALONG AND E OF THE DRY LINE
COMBINED WITH SURFACE HEATING WILL CONTRIBUTE TO A MODERATELY
UNSTABLE AIR MASS /MLCAPE 2000-2500 J PER KG/. GIVEN THE EXPECTED
INCREASE IN DEEP LAYER ASCENT AS THE NEGATIVELY TILTED TROUGH MOVES
ACROSS THE CENTRAL/NRN PLAINS...THE STRONG CAP ALONG THE DRY LINE
SHOULD BEGIN TO WEAKEN BY MID AFTERNOON SUPPORTING CONVECTIVE
INITIATION. DEGREE OF INSTABILITY AND EFFECTIVE BULK SHEAR /45-55
KT/ WITH VECTORS GENERALLY PARALLEL TO THE DRY LINE/COLD FRONT WILL
SUPPORT STORM ORGANIZATION. ALTHOUGH A LINEAR MODE SHOULD BE
PREDOMINATE..SOME CROSSING OF THE SHEAR VECTORS TO THE INITIATING
BOUNDARIES SUGGESTS EMBEDDED SUPERCELLS WILL ALSO BE POSSIBLE.
GIVEN THESE FACTORS...ALL FACETS OF SEVERE WEATHER ARE EXPECTED
DURING THE LATE AFTERNOON AND EARLY EVENING. STRENGTHENING WIND
FIELDS AND GREATER LINEAR FORCING AS THE SYSTEM BECOMES MORE
NEGATIVELY-TILTED SUGGESTS AN MCS WITH AN ENHANCED DAMAGING WIND
THREAT WILL BE POSSIBLE AS STORMS MOVE INTO WRN MN AND NWRN IA.
...WRN OK AND WRN TX...
THE ATMOSPHERE WILL BECOME MODERATELY UNSTABLE IN MOIST WARM SECTOR
ACROSS WRN OK AND WRN TX. A STRONG EML WILL CAP THE BOUNDARY
LAYER...BUT A FEW STORMS SHOULD DEVELOP SWD THROUGH WRN OK AND WRN
TX WITHIN ZONE OF MIXING AND CONVERGENCE ALONG THE DRYLINE AND
BENEATH DIFFLUENT FLOW REGIME BY LATE AFTERNOON. THIS AREA WILL
EXIST ALONG THE SRN EXTENT OF STRONGER 700-500 MB FLOW WITH
EFFECTIVE SHEAR VECTORS /AROUND 40 KT/ CROSSING THE DRY LINE. THIS
WILL SUPPORT SUPERCELLS. THE PRIMARY THREATS SHOULD BE LARGE
HAIL...SOME VERY LARGE...AND DAMAGING WINDS. LATEST MODELS DO
SUGGEST THAT A TORNADO THREAT CANNOT BE RULED OUT AS WELL. GIVEN
GREATER AGREEMENT AMONGST THE MODELS FOR A SIMILAR THREAT WITH SWD
EXTENT INTO WRN TX...THIS OUTLOOK HAS EXTENDED THE SLIGHT RISK
FARTHER S.
..PETERS.. 05/29/2011
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