MESO: Mesoscale Discussion 1305

ACUS11 KWNS 291844
SWOMCD
SPC MCD 291844
COZ000-292115-

MESOSCALE DISCUSSION 1305
NWS STORM PREDICTION CENTER NORMAN OK
0144 PM CDT SAT JUN 29 2013

AREAS AFFECTED...PORTIONS OF CNTRL/ERN CO

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 291844Z - 292115Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THE AREA IS BEING MONITORED FOR AN INCREASING SVR
POTENTIAL...AND THE ISSUANCE OF A WW IS POSSIBLE THIS AFTERNOON.

DISCUSSION...SEVEN- AND NINE-KM CAPPI RADAR DATA INDICATE A GRADUAL
UPTICK IN CONVECTIVE COVERAGE AND INTENSITY OVER THE CO
ROCKIES...WITH THE ACTIVITY BEGINNING TO DEVELOP/SPREAD TOWARD THE
FRONT RANGE AND ADJACENT FOOTHILLS FROM NEAR BOULDER TO COLORADO
SPRINGS. THIS IS IN RESPONSE TO DIURNALLY DEEPENING OROGRAPHIC
CIRCULATIONS...WITH THE STRENGTH/DEPTH OF ASCENT BEING AUGMENTED BY
A LOW-AMPLITUDE IMPULSE PIVOTING AROUND THE ERN FLANK OF A LARGE
WRN-CONUS MID-LEVEL RIDGE. SFC OBSERVATIONS INDICATE LOW-LEVEL FLOW
HAVING BECOME DECIDEDLY MORE UPSLOPE DURING THE PAST HOUR ACROSS THE
HIGH PLAINS IMMEDIATELY ADJACENT TO THE FRONT RANGE...IN RESPONSE TO
SFC PRESSURE FALLS/STRONG HEATING OVER THE WRN-CONUS PLATEAU. IN
TURN...CONVECTION WILL FURTHER INCREASE IN NUMBER/INTENSITY THROUGH
THE AFTERNOON INVOF THE FRONT RANGE. WITH STEEP H7-H5 LAPSE RATES
AROUND 8.2 C/KM PER DNR 12Z RAOB AMIDST MODESTLY HIGH TROPOSPHERIC
MOISTURE CONTENT -- E.G. PW VALUES OF 0.75-1.00 INCH PER GPS DATA --
MLCAPE VALUES OF 500-1200 J/KG WILL LIKELY BECOME COMMON AS
LOW-LEVEL LAPSE RATES EXPERIENCE FURTHER DIURNAL STEEPENING.

THE PRESENCE OF 20-30 KT NNWLY/S IN THE 4-7-KM-AGL LAYER PER FTG/PUX
VWP DATA WILL OFFER SUFFICIENT DEEP SHEAR FOR A FEW ORGANIZED STORM
STRUCTURES/POSSIBLE SUPERCELLS. THIS MAINLY MERIDIONAL FLOW REGIME
WILL ALSO KEEP MOST OF THE CONVECTION CONFINED TO THE FRONT RANGE
AND ADJACENT FOOTHILLS INTO MID AFTERNOON. HOWEVER...SUFFICIENT
CONVERGENCE ALONG A NW/SE-ORIENTED FRONTAL SEGMENT OVER THE CO HIGH
PLAINS...AND AT LEAST SOME VERY MODEST ZONAL COMPONENT WITHIN THE
CONVECTIVE CLOUD LAYER...MAY ALLOW CONVECTION TO IMPACT PARTS OF THE
HIGH PLAINS LATER IN THE DAY. DMGG WINDS AND LARGE HAIL WILL BE
POSSIBLE WITH THE MOST INTENSE STORMS...AND A BRIEF/WEAK TORNADO
CANNOT BE RULED OUT INVOF THE BOUNDARY AND/OR MESOSCALE
CIRCULATION/CONVERGENCE ZONES DEVELOPING OVER THE HIGH PLAINS
IMMEDIATELY ADJACENT TO THE FRONT RANGE.

ATTM...THE STRENGTH OF DEEP-LAYER FORCING FOR ASCENT WILL BE
LIMITED...AND LOW-LEVEL FLOW IS NOT FORECAST TO BE STRONG...WHICH
WILL BOTH MITIGATE THE SVR POTENTIAL/COVERAGE TO SOME EXTENT.
CONVECTIVE TRENDS WILL BE MONITORED THROUGH THE AFTERNOON. IF A MORE
CONSOLIDATED AREA OF GREATER SVR POTENTIAL BECOMES APPARENT...A WW
MIGHT BECOME NEEDED.

..COHEN/MEAD.. 06/29/2013

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

ATTN...WFO...PUB...BOU...

LAT...LON 40610603 40850515 39760431 37650325 37200359 37040468
37460540 39120588 40610603

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