MESO: Mesoscale Discussion 0641

ACUS11 KWNS 141956
SWOMCD
SPC MCD 141955
IAZ000-NEZ000-SDZ000-KSZ000-142230-

MESOSCALE DISCUSSION 0641
NWS STORM PREDICTION CENTER NORMAN OK
0255 PM CDT TUE MAY 14 2013

AREAS AFFECTED...NWRN KS NEWD ACROSS PORTIONS OF SRN/CNTRL/ERN
NEB...FAR SERN SD...AND NWRN IA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 141955Z - 142230Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...ISOLATED HIGH-BASED THUNDERSTORMS MAY PRODUCE DMGG WIND
GUSTS THROUGH THE AFTERNOON...BUT THE ISSUANCE OF A WW IS NOT
NEEDED.

DISCUSSION...A THERMAL RIDGE CHARACTERIZED BY SEASONALLY ANOMALOUSLY
HOT SFC TEMPERATURES -- FROM THE 90S TO AROUND 105F -- LEADS A COLD
FRONT THAT EXTENDS FROM S-CNTRL MN INTO SWRN NEB. SFC DEWPOINTS HAVE
MIXED OUT INTO THE MIDDLE 30S TO THE LOWER 40S INVOF THIS AXIS...AND
MODIFIED 12Z RAOBS INDICATE NEAR-ZERO CINH FOR A MIXED-LAYER PARCEL
WITH MLCAPE VALUES OF AROUND 250-800 J/KG. DESPITE THE MEAGER
INSTABILITY...FRONTAL ASCENT ALONG WITH CONVERGENCE ACCOMPANYING A
WEAK CYCLONIC WIND-SHIFT AXIS ALIGNING WITH THE THERMAL RIDGE HAVE
SUPPORTED HIGH-BASED CU DEVELOPMENT FROM NWRN KS INTO NWRN IA. THE
MOST CONCENTRATED AREA OF CONVECTIVE DEVELOPMENT HAS THUS FAR BEEN
ACROSS NWRN KS...WHERE MESOSCALE ASCENT IS BEING AUGMENTED OVER THE
PERIPHERY OF A DEEPER DRY SLOT ACROSS CNTRL/SWRN KS.

DEEP CONVECTION ACROSS THE MCD AREA WILL LIKELY BE ISOLATED AND OF A
PULSE MODE OWING TO WEAK FORCING FOR ASCENT AND WEAK DEEP SHEAR.
HOWEVER...WITH MODIFIED 12Z RAOBS INDICATING MIXED-LAYER DEPTHS IN
EXCESS OF 14 KFT IN SOME INSTANCES...DEEP/STRONG SUB-CLOUD
EVAPORATIVE COOLING WITH DCAPE VALUES OF AROUND 1000-2000 J/KG WILL
SUPPORT DRY AND HYBRID WET/DRY MICROBURSTS...POTENTIALLY SUPPORTING
SPORADIC/BRIEF DMGG WIND GUSTS. RELATIVELY STRONGER UPDRAFT MASS
FLUXES WOULD BE CONFINED TO CNTRL NEB AND POINTS NEWD...WHERE
SLIGHTLY HIGHER PW EXISTS -- I.E. 0.70-0.85 INCH PER GPS DATA --
SUPPORTING MODESTLY ENHANCED WATER LOADING AND ENHANCED DOWNDRAFTS.
STORMS SHOULD WEAKEN DURING THE EARLY EVENING AS NOCTURNAL
STABILIZATION TAKES PLACE.

..COHEN/CARBIN.. 05/14/2013

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...DMX...FSD...OAX...GID...LBF...GLD...

LAT...LON 38690162 39200195 40040193 40500114 41199949 41659865
42659705 43459577 43349459 42489478 41659602 40489796
39629967 38690162

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