RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 PM CDT SAT MAY 25 2013
VALID 252000Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NORTHERN
AND CENTRAL HIGH PLAINS...
SEVERE PROBABILITIES HAVE BEEN ADJUSTED UPWARD ACROSS THE SRN HIGH
PLAINS INTO PORTIONS OF WRN KS FOR THIS AFTERNOON/EVENING. DESPITE
RELATIVELY WEAK DEEP LAYER SHEAR...VERY STEEP LAPSE RATES WILL
CONTRIBUTE TO SOMEWHAT GREATER RISK OF HAIL/WIND WITH ANY STORMS
THAT MANAGE TO ORGANIZE FROM SERN NM ACROSS THE WRN TX PANHANDLE
INTO WRN KS. LATEST VIS/RADAR IMAGERY SUGGEST DEEPENING CONVECTION
ACROSS LINCOLN COUNTY NM AND CONSIDERABLE CU IS NOW OBSERVED NWD
ALONG THE LEE SLOPES OF THE NM ROCKIES. FOR THIS REASON HAVE
INCREASED SEVERE PROBS TO 15 PERCENT FOR HAIL/WIND.
ELSEWHERE...1630Z OUTLOOK HAS BEEN CHANGED LITTLE. STRONG HEATING
ACROSS THE HIGH PLAINS WILL PROVE INSTRUMENTAL IN SEVERE
THUNDERSTORM DEVELOPMENT FROM ERN MT INTO THE NEB PANHANDLE. LATEST
VIS IMAGERY SUGGESTS THIS PROCESS IS IN ITS INFANCY AND TSTMS SHOULD
EVOLVE ALONG WRN FRINGE OF MOISTURE/INSTABILITY OVER THE NEXT FEW
HOURS.
..DARROW.. 05/25/2013
.PREV DISCUSSION... /ISSUED 1127 AM CDT SAT MAY 25 2013/
...SYNOPSIS...
LITTLE CHANGE TO THE SYNOPTIC PATTERN IS FORECAST DURING THE D1
PERIOD WITH UPPER LOWS CENTERED OVER THE PACIFIC NW INTO SWRN CANADA
AND NEW ENGLAND...AND RIDGING FROM MB/ON SWD INTO THE MID/LOWER-MS
VALLEY. WITHIN THE PREVAILING SWLY MIDLEVEL FLOW REGIME FROM THE
GREAT BASIN INTO NRN/CNTRL HIGH PLAINS...MORNING WATER VAPOR IMAGERY
SHOWS A WEAK IMPULSE OVER WY WHICH SHOULD CONTINUE NEWD INTO THE
DAKOTAS TODAY. ELSEWHERE...A SHEARED VORTICITY MAXIMUM OVER TX WILL
SLOWLY PROGRESS EWD.
IN THE LOW LEVELS...AN ELONGATED LEE CYCLONE WILL BE MAINTAINED FROM
ERN WY INTO SWRN NEB/NERN CO. A TROUGH/DRYLINE WILL EXTEND SWD FROM
THE LOW PRESSURE TO ALONG THE TX-NM BORDER WITH AN INVERTED TROUGH
SITUATED OVER CNTRL OR ERN MT. A WARM FRONT WILL STRETCH SEWD FROM
AN INTERSECTION WITH THE LEE TROUGH ACROSS SERN MT INTO THE MID-MO
VALLEY WHILE AN OUTFLOW BOUNDARY GRADUALLY MODIFIES ACROSS NRN KS.
...NRN/CNTRL HIGH PLAINS THIS AFTERNOON INTO TONIGHT...
A GRADUAL DEEPENING OF THE LEE CYCLONE WILL RESULT IN THE BACKING
AND STRENGTHENING OF THE LOW-LEVEL WIND FIELD WHICH...IN TURN...WILL
ENHANCE THE NWWD FLUX OF AN INCREASINGLY MOIST PBL FROM THE CNTRL
PLAINS INTO SD. THIS PROCESS WILL OCCUR BENEATH AN EML...
CHARACTERIZED BY 700-500-MB LAPSE RATES OF 7.5-8.5 C/KM...PER 12Z
RAOBS. WHEN COUPLED WITH DAYTIME HEATING...THE AIR MASS FROM SERN
MT INTO THE CNTRL PLAINS IS EXPECTED TO BECOME MODERATELY TO
STRONGLY UNSTABLE WITH MLCAPE VALUES APPROACHING 1500-3000 J/KG.
ELEVATED TSTMS HAVE ALREADY DEVELOPED THIS MORNING OVER ERN MT INTO
WRN ND AND NERN WY WHERE DCVA ASSOCIATED WITH ABOVE-MENTIONED
VORTICITY MAXIMUM AND LOW-LEVEL WAA ARE INTERACTING WITH A STEEP
LAPSE RATE ENVIRONMENT /SEE 12Z RAP SOUNDING/. THE MORE RECENT
STORM DEVELOPMENT NEAR AND N OF THE BLACK HILLS WILL LIKELY PERSIST
TODAY WITH STORMS EVENTUALLY BECOMING ROOTED WITHIN THE
DESTABILIZING PBL...ALONG AND S OF SURFACE WARM FRONT. OTHER
SURFACE-BASED STORMS SHOULD DEVELOP THIS AFTERNOON ALONG THE LEE
TROUGH AND/OR FAVORED TERRAIN AS DAYTIME HEATING AND THE INFLUENCE
OF THE MIGRATORY SHORT-WAVE TROUGH OVERCOME REMAINING CONVECTIVE
INHIBITION.
SUPERCELLS APPEAR LIKELY AS THE INITIAL STORM MODE GIVEN A
VERTICALLY VEERING WIND PROFILE WITH 40-50 KT OF WLY DEEP-LAYER
SHEAR. LARGE HAIL WILL BE THE PREDOMINANT HAZARD...THOUGH A FEW
TORNADOES WILL BE POSSIBLE THIS AFTERNOON INTO EVENING FROM SERN MT
INTO WRN PARTS OF SD/NEB WHERE A CORRIDOR OF ENHANCED LOW-LEVEL
SHEAR IS FORECAST. UPSCALE GROWTH OF STORMS INTO CLUSTERS OR AN MCS
IS ANTICIPATED LATER THIS EVENING INTO TONIGHT WITH A CONTINUED
THREAT FOR HAIL AND DAMAGING WINDS.
...SRN HIGH PLAINS THIS AFTERNOON AND EVENING...
THE JUXTAPOSITION OF A MOIST PBL AND EML WILL PROMOTE MODERATE
INSTABILITY THIS AFTERNOON ALONG THE LENGTH OF THE LEE
TROUGH/DRYLINE WITH AFTERNOON MLCAPE VALUES OF 1000-2500 J/KG
FORECAST. THOUGH LARGE-SCALE FORCING FOR ASCENT WILL REMAIN
NEGLIGIBLE THROUGH THE PEAK OF THE DIURNAL HEATING CYCLE...LOW-LEVEL
CONVERGENCE ALONG WITH OROGRAPHIC INFLUENCES WILL PROMOTE ISOLATED
STORM DEVELOPMENT AMIDST A KINEMATIC ENVIRONMENT FEATURING VEERING
WINDS WITH HEIGHT. MARGINAL VERTICAL SHEAR /BULK SHEAR VALUES AOB
30-35 KT/ MAY LIMIT THE DEGREE OF STORM ORGANIZATION...THOUGH
ISOLATED OCCURRENCES OF HAIL AND DAMAGING WINDS WILL BE POSSIBLE
THROUGH THIS EVENING.
...CNTRL/SRN TX THIS AFTERNOON INTO TONIGHT...
THE INFLUX OF A VERY MOIST AIR MASS /I.E. PW VALUES APPROACHING TWO
INCHES/ SHOULD MAINTAIN SCATTERED TSTMS INVOF MIDLEVEL VORTICITY
MAXIMUM SLOWLY MOVING ACROSS CNTRL TX. DEEP-LAYER VERTICAL SHEAR IS
WEAK...THOUGH THE MOIST/LOW LCL ENVIRONMENT COUPLED WITH MODEST
LOW-LEVEL SHEAR MAY BE SUFFICIENT TO SUPPORT STORM ROTATION WITH A
RISK FOR A BRIEF TORNADO. OTHERWISE...EXCESSIVE RAINFALL WILL
REMAIN THE PRIMARY HAZARD.
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