SWOMCD
SPC MCD 241948
SDZ000-NEZ000-COZ000-WYZ000-242145-
MESOSCALE DISCUSSION 2148
NWS STORM PREDICTION CENTER NORMAN OK
0248 PM CDT SUN AUG 24 2008
AREAS AFFECTED...NCENTRAL/NERN CO...ERN WY...WRN NEB PANHANDLE...WRN
SD
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 241948Z - 242145Z
TSTMS ARE EXPECTED TO INCREASE IN AREAL COVERAGE FROM NCENTRAL CO
INTO NERN WY/BLACK HILLS OF SD THROUGH 22Z. A FEW OF THE TSTMS MAY
POSE A THREAT FOR SVR HAIL/DMGG WINDS. NRN PORTIONS OF THE AREA IS
BEING MONITORED FOR A POSSIBLE WW.
TSTMS HAVE ALREADY BEGUN TO DEVELOP IN THE HIGHER TERRAIN OF
NCENTRAL CO/SCENTRAL WY...WHERE MODEST MOISTURE CONVERGENCE ALONG
THE LEE TROUGH IS COMBINED WITH INCREASING DIURNAL UPSLOPE FLOW.
FORECAST SOUNDINGS AND THE PLATTEVILLE PROFILER INDICATE THAT
RELATIVELY WEAK MID LEVEL WINDS /AOB 10 KTS/ WILL LIMIT ANY
POTENTIAL FOR ROTATING UPDRAFTS IN NERN CO SERN WY FOOTHILLS...FRONT
RANGE AND HIGH PLAINS. HOWEVER...THE COMBINATION OF STEEP LOW-MID
LEVEL LAPSE RATES AND SOME DIRECTIONAL SHEAR SHOULD SUPPORT AT LEAST
THE POTENTIAL FOR MARGINAL SVR WIND/HAIL. IN ADDITION...SLOW STORM
MOTIONS AND RELATIVELY HIGH PWAT VALUES WILL SUPPORT THE THREAT FOR
LOCALLY HEAVY RAINFALL RATES.
FURTHER NORTH...SLIGHTLY STRONGER MID LEVEL FLOW OVER NERN WY/WRN SD
EXISTED IN ASSOCIATION WITH A SUBTLE VORT MAX ROTATING EWD AROUND
THE UPPER RIDGE. SFC CONVERGENCE INVOF OF A SFC LOW EAST OF THE BIG
HORN MTNS AND UPSLOPE FLOW /ESPECIALLY OVER THE BLACK HILLS/
COMBINED WITH WEAKENING CINH /LESS THAN 100 J/KG AT 19Z OVER THE
BLACK HILLS/ SHOULD AID IN TSTM DEVELOPMENT IN THIS REGION BETWEEN
21-22Z. STRONG VERTICAL SHEAR /AROUND 35 KTS/ OWING TO 20 KT MID
LEVEL WINDS WILL SUPPORT THE POTENTIAL FOR GREATER TSTM
ORGANIZATION. ADDITIONALLY...MODERATE INSTABILITY /MLCAPE AROUND
2000 J/KG/ WILL AID IN STRONG UPDRAFTS CAPABLE OF PRODUCING
HAIL/DMGG WINDS. MAIN UNCERTAINTY ATTM FOR WW ISSUANCE IN THIS
REGION IS HOW FAR EAST OF HIGHER TERRAIN WILL CONVECTIVE DEVELOPMENT
OCCUR /GIVEN INCREASING CINH AS NOTED BY THE 19Z RAP SOUNDING/ AND
THUS AREAL COVERAGE OF SVR THREAT.
..CROSBIE.. 08/24/2008
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...UNR...BOU...CYS...RIW...
44940302 44860383 44860580 43960629 43030619 41470578
40180588 39700559 39640405 40260315 41290308 42870287
44410253
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