MESO: Mesoscale Discussion 1501

ACUS11 KWNS 042051
SWOMCD
SPC MCD 042051
SDZ000-NEZ000-042145-

MESOSCALE DISCUSSION 1501
NWS STORM PREDICTION CENTER NORMAN OK
0351 PM CDT MON JUL 04 2011

AREAS AFFECTED...SWRN...CNTRL AND N-CNTRL SD

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 042051Z - 042145Z

WEAK UPSLOPE FLOW HAS AIDED IN THE INITIATION OF TSTMS OVER THE
BLACK HILLS OF SWRN SD. FURTHER CONVECTIVE DEVELOPMENT ALONG A
SLOW-MOVING COLD FRONT IS POSSIBLE LATER THIS
AFTERNOON/EVENING...AND COULD EVENTUALLY REQUIRE ISSUANCE OF A WW.

SFC ANALYSIS FROM 20Z PLACES A COLD FRONT FROM 25 NW MBG TO 30 S
RAP. A VERY HOT/MOIST BOUNDARY LAYER IS IN PLACE ALONG/AHEAD OF THE
COLD FRONT...WHERE SFC DEW POINTS ARE IN THE LOWER-MID 70S ARE IN
PLACE. UPPER RIDGE AXIS IS CURRENTLY POSITIONED OVERHEAD /PER RECENT
WATER VAPOR IMAGERY/ AND MAY BE CONTRIBUTING TO WEAK CINH WHICH HAS
LIKELY PREVENTED TSTM DEVELOPMENT OVER THE PLAINS THUS FAR. WITH
TIME...UPPER RIDGE SHOULD SLOWLY SHIFT EWD...WITH GRADUAL EROSION OF
CINH LEADING TO A MORE FAVORABLE ENVIRONMENT FOR DISCRETE TSTMS.
GIVEN THE PRESENCE OF RICH BOUNDARY LAYER THETA-E...STEEP MIDLEVEL
LAPSE RATES...AND MLCAPE VALUES EVENTUALLY INCREASING TO 3000-4000
J/KG...A THREAT /CONDITIONAL ON TSTM DEVELOPMENT/ FOR LARGE HAIL AND
DMGG WIND GUSTS SHOULD MATERIALIZE. DESPITE WEAKNESS IN FLOW
THROUGHOUT THE LOWER HALF OF THE TROPOSPHERE...MIDLEVEL WLYS ATOP
S-SELY LOW-LEVEL FLOW SHOULD LEAD TO EFFECTIVE SHEAR VALUES /NEAR 30
KTS/ MARGINALLY SUPPORTIVE OF SUPERCELL STRUCTURES.

FARTHER UPSTREAM...AN UPPER IMPULSE OVER N-CNTRL WY WILL EVENTUALLY
SHIFT INTO THE NRN HIGH PLAINS...AND SHOULD RESULT IN AN EXPECTED
UPSWING IN CONVECTIVE COVERAGE THIS EVENING AS INCREASING FORCED
ASCENT OVERSPREADS THE SFC COLD FRONT.

..ROGERS.. 07/04/2011

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

ATTN...WFO...ABR...UNR...CYS...

LAT...LON 45249897 43809981 43000135 42990288 43230363 43720403
44860224 45690139 45930026 45889910 45819879 45249897

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