SPC MD 1800

MD 1800 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR EASTERN CO/WESTERN NEB/SOUTHERN SD/FAR NORTHWEST KS


MESOSCALE DISCUSSION 1800
NWS STORM PREDICTION CENTER NORMAN OK
0348 PM CDT WED AUG 22 2012

AREAS AFFECTED...EASTERN CO/WESTERN NEB/SOUTHERN SD/FAR NORTHWEST KS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 222048Z - 222245Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED DOWNBURST/SEVERE HAIL POTENTIAL WILL EXIST ACROSS
THE HIGH PLAINS INCLUDING PORTIONS OF EASTERN CO/FAR NORTHWEST KS AS
WELL AS WESTERN NEB INTO SOUTHERN SD. A WATCH IS NOT CURRENTLY
ANTICIPATED AS MARGINAL BUOYANCY/VERTICAL SHEAR SHOULD LIMIT THE
OVERALL EXTENT/DURATION OF THE SEVERE RISK.

DISCUSSION...MUCH OF THE REGION IS UNDER THE SOUTH-PERIPHERAL
INFLUENCE OF A SHORTWAVE TROUGH SPREADING EAST-NORTHEASTWARD OVER
THE NORTHERN HIGH PLAINS AND CANADIAN ROCKIES PER WATER VAPOR
IMAGERY. STEADY LEE TROUGH DEVELOPMENT/SHARPENING HAS BEEN OCCURRING
TODAY ACROSS THE CENTRAL HIGH PLAINS IN TANDEM WITH A 1006 MB
SURFACE LOW CENTERED ACROSS SOUTHWEST SD/NORTHWEST NEB AT MID
AFTERNOON. ISOLATED TSTMS HAVE INCREASED SINCE 1930-2000Z IN
VICINITY OF THIS LEE TROUGH ESPECIALLY ACROSS PARTS OF EASTERN
CO...ALTHOUGH ADDITIONAL ISOLATED/WIDELY SCATTERED DEVELOPMENT MAY
OCCUR ACROSS WESTERN NEB TO NEAR THE SURFACE LOW IN SOUTHERN SD
THROUGH EARLY/MID EVENING.

BUOYANCY AND DEEP TROPOSPHERIC WIND SPEEDS ARE BOTH RELATIVELY
WEAK...HOWEVER FACTORS SUCH AS STEEP LAPSE RATES AND WINDS VEERING
WITH HEIGHT MAY RESULT IN SOME SEMI-SUSTAINED HIGH-BASED
STRUCTURES/BRIEF SUPERCELLS. GIVEN A WELL-MIXED BOUNDARY LAYER
/35-50 F SFC TEMPERATURE-DEWPOINT SPREADS/ AND AN AMPLE DCAPE
ENVIRONMENT...ISOLATED DAMAGING WINDS AND PERHAPS SEVERE HAIL WILL
BE POSSIBLE. A COOLING POST-SUNSET BOUNDARY LAYER SHOULD EVENTUALLY
ACCOUNT FOR A WEAKENING TREND ACROSS THE CENTRAL HIGH
PLAINS...ALTHOUGH TSTMS MAY PERSIST A BIT LONGER THIS EVENING ACROSS
NORTHERN NEB AND SOUTHERN SD WITH AID OF A STRENGTHENING LOW LEVEL
JET/WARM ADVECTION REGIME.

..GUYER/MEAD.. 08/22/2012

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

ATTN...WFO...FSD...ABR...LBF...UNR...GLD...PUB...BOU...CYS...

LAT...LON   44110134 44229957 43719885 42759885 42000101 39510173
            38240334 38920433 41970350 44110134

via SPC Forecast Products http://www.spc.noaa.gov/products/md/md1800.html