Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 271257
SWODY1
SPC AC 271256

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0756 AM CDT FRI MAY 27 2016

VALID 271300Z - 281200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS KS/OK...

...THERE IS A MRGL RISK OF SVR TSTMS ELSEWHERE FROM PORTIONS CENTRAL
HIGH PLAINS TO UPPER MS VALLEY AND UPPER TX COASTAL PLAIN...

...SUMMARY...
SCATTERED THUNDERSTORMS SHOULD DEVELOP THIS AFTERNOON OVER PARTS OF
KANSAS AND OKLAHOMA...OFFERING MAINLY SPORADIC LARGE HAIL AND
DAMAGING GUSTS.  A BROADER...MORE MARGINAL AND NEBULOUS
SEVERE-WEATHER THREAT IS APPARENT FROM PARTS OF THE UPPER
MISSISSIPPI VALLEY TO THE CENTRAL HIGH PLAINS AND SOUTH-CENTRAL AND
SOUTHEAST TEXAS.

...SYNOPSIS...
MOISTURE-CHANNEL IMAGERY THIS MORNING INDICATED WEAK MID/UPPER-LEVEL
CYCLONE OVER ERN CO...WITH SHORTWAVE TROUGH SSWWD ACROSS ERN NM AND
FAR W TX.  AS 500-MB LOW MOVES ONLY SLOWLY EWD TO NWRN KS AND
WEAKENS THROUGH 00Z...BASAL SHORTWAVE TROUGH/VORTICITY LOBE WILL
PIVOT NEWD ACROSS SRN HIGH PLAINS TO NWRN/CENTRAL OK.  BY 12Z...
MID/UPPER-LEVEL PERTURBATION SHOULD WEAKEN FURTHER INTO OPEN-WAVE
TROUGH...WITH VERY DIFFUSE/RESIDUAL LOW PERHAPS STILL LOCATED OVER
ERN NEB OR NRN KS...AND TROUGHING SWD ACROSS OK.  SERIES OF
CONVECTIVELY GENERATED VORTICITY MAXIMA ARE LIKELY TO EJECT NEWD
TODAY FROM OVERNIGHT/MORNING TX CONVECTIVE COMPLEXES DISCUSSED
BELOW.  MEANWHILE...NRN-STREAM SHORTWAVE TROUGH NOW OVER INLAND PAC
NW WILL MOVE SLOWLY EWD TO NRN ROCKIES...CONTRIBUTING TO
DESTABILIZATION ALOFT IN SUPPORT OF GEN TSTM POTENTIAL OVER PORTIONS
NWRN CONUS.

AT SFC...LOW WAS ANALYZED OVER WRN KS WITH COLD FRONT ARCHING ACROSS
NWRN OK...SERN TX PANHANDLE...TX SOUTH PLAINS...TO CENTRAL NM.  COLD
FRONT SHOULD WEAKEN TODAY WHILE REINFORCING BOUNDARY MOVES SEWD OUT
OF ERN CO.  DRYLINE -- LOCATED THIS MORNING FROM SRN CAPROCK REGION
OF W TX TO BIG BEND AREA -- SHOULD MOVE EWD TO POSITION FROM CENTRAL
KS SWD ACROSS W-CENTRAL OK...CENTRAL TX...TO NEAR LRD BY 00Z.
AGGREGATE OUTFLOW BOUNDARY NOW NEAR I-10 IN S TX WILL MOVE NWD
ERRATICALLY AND PERHAPS IN PIECEMEAL FASHION THROUGHOUT TODAY WITH
VARIATIONS IN BOUNDARY-LAYER MIXING...CONVECTIVE REINFORCEMENT...AND
STRENGTH OF IMPINGING WAA TRAJECTORIES.

...CENTRAL/SRN PLAINS INVOF DRYLINE...
NARROW CORRIDOR OF FAVORABLE DIABATIC HEATING ACROSS OK...BROADENING
SOMEWHAT INTO PORTIONS KS...IS EXPECTED NW OF ARKLATEX CLOUD SHIELDS
BY THIS AFTN.  THIS SHOULD PERMIT SFC-BASED BUOYANCY TO DEVELOP
WITHIN RESIDUAL BOUNDARY LAYER MOISTURE -- I.E. DEW POINTS MID/UPPER
50S F IN NRN AREAS TO MID 60S S.  WITH STEEPENING MIDLEVEL LAPSE
RATES INVOF SHORTWAVE TROUGH AND MID/UPPER-LEVEL THERMAL TROUGH...
PRIND MLCAPE 1500-2500 J/KG WILL BE POSSIBLE.  SOMEWHAT WEAK WIND
FIELDS BELOW 600 MB THAT CHANGE DIRECTION ERRATICALLY WITH HEIGHT
WILL LIMIT LOW-LEVEL SHEAR...THOUGH STG/VENTILATING UPPER WINDS
STILL SHOULD AID IN CONVECTIVE ORGANIZATION.  PRIND MULTICELLS AND
AT LEAST A FEW TRANSIENT SUPERCELLS WILL BE POSSIBLE WITH EFFECTIVE
SHEAR MAGNITUDES 40-50 KT...DESPITE SMALL LOW-LEVEL HODOGRAPHS.
THIS WILL SUPPORT POTENTIAL FOR SVR HAIL AND STG/SVR GUSTS...LATTER
BEING MORE PROBABLE WHERE SMALL BOWS OR LOCALIZED COLD-POOL
DEVELOPMENT CAN OCCUR.  SVR POTENTIAL SHOULD WANE AFTER DARK AS
DIABATIC COOLING OCCURS.

...ERN OK TO E TX...
ONGOING MCS OVER LOWER SABINE RIVER REGION AND SWRN LA...OVERTAKING
OUTFLOW BOUNDARY LEFT BY EARLIER CONVECTIVE COMPLEX...MAY PRODUCE
LOCALLY GUSTY WINDS AND ISOLATED HAIL NEAR SVR LIMITS THIS MORNING
BEFORE WEAKENING.  ANOTHER REMNANT MCS...INCLUDING TRAILING SWATH OF
ELEVATED TSTMS...IS MOVING ACROSS CENTRAL/E-CENTRAL TX ATTM...IN
WAKE OF YET ANOTHER EARLIER/LONG-GONE COMPLEX THAT PASSED ACROSS DFW
METROPLEX LAST EVENING.  THIS ACTIVITY IS WEAKENING AS IT ENTERS
VARIABLY STABILIZED BOUNDARY LAYER FROM PREVIOUS METROPLEX
COMPLEX...AS WELL AS SOME TRAJECTORIES EMANATING FROM HOURS-AGO
VERSION OF TRAILING PRECIP CASCADE FROM SE TX MCS.  ISOLATED LARGE
HAIL AND STG GUSTS MAY OCCUR FROM TSTMS ELEVATED ATOP COLLECTIVE
OUTFLOW POOL...AS LLJ WEAKENS TO 30-35 KT RANGE BUT IS MAINTAINED
OVER MODIFIED BOUNDARY-LAYER AIR THROUGH REMAINDER OF MORNING.
BUOYANCY IS EXPECTED TO DIMINISH WITH NWD EXTENT INTO ERN OK AND WRN
AR...WHILE CLOUD DEBRIS FROM ALL THAT CONVECTION IMPEDES DIABATIC
HEATING.  WHILE MRGL/CONDITIONAL SVR THREAT STILL EXISTS ACROSS THIS
AREA...THOSE MULTIPLE MCS PASSAGES ACROSS PROSPECTIVE INFLOW REGION
OVERNIGHT HAVE REDUCED THETAE IN THOSE TRAJECTORIES AND LIKEWISE
REDUCED UNCONDITIONAL SVR RISK.

...CENTRAL/S TX...
CONDITIONAL POTENTIAL EXISTS FOR SVR TSTMS TO DEVELOP THIS AFTN
INVOF NWD-RETREATING/AGGREGATE OUTFLOW BOUNDARY ACROSS PARTS OF
CENTRAL OR S-CENTRAL TX.  MORE FOCUSED THREAT WILL DEPEND ON PACE OF
EROSION OF BOUNDARY THROUGH AFTN...CONVERGENCE/LIFT INVOF THAT
FEATURE AND BENEATH EML-RELATED CAPPING...AND ITS LOCATION.  THOUGH
LOW-LEVEL FLOW SHOULD REMAIN WEAK ON EITHER SIDE OF
BOUNDARY...KEEPING HODOGRAPH SIZES SMALL...VERY UNSTABLE AIR MASS
WILL BE IN PLACE TO ITS S WITH 70S F SFC DEW POINTS IN SUPPORT OF
AROUND 4000 J/KG MLCAPE.  WHERE SUSTAINED/RELATIVELY DISCRETE STORM
CAN FORM...SIGNIFICANT HAIL MAY OCCUR...BUT POTENTIAL CURRENTLY
APPEARS TOO ISOLATED AND DEPENDENT ON MESOSCALE DETAILS TO OUTLINE
SPECIFIC SMALL AREA WITHIN BROADER MRGL RISK.

..EDWARDS/ROGERS.. 05/27/2016

$$


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