SWOMCD
SPC MCD 232329
NDZ000-SDZ000-NEZ000-240100-
MESOSCALE DISCUSSION 2010
NWS STORM PREDICTION CENTER NORMAN OK
0629 PM CDT SUN SEP 23 2007
AREAS AFFECTED...CNTRL DAKOTAS INTO W CNTRL NEB
CONCERNING...SEVERE THUNDERSTORM WATCH 685...
VALID 232329Z - 240100Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 685
CONTINUES.
RECENT NEW CONVECTIVE DEVELOPMENT NORTHWEST THROUGH NORTH OF PIERRE
IS OCCURRING WHERE THE NOSE OF A PRE-FRONTAL LOW-LEVEL THERMAL RIDGE
INTERSECTS THE AXIS OF HIGHER MOISTURE CONTENT AIR RETURNING
NORTHWARD THROUGH THE PLAINS. TEMPERATURES PEAKED IN THE MID/UPPER
90S ACROSS THIS REGION...WEAKENING INHIBITION FOR BOUNDARY LAYER
BASED PARCELS TO NEGLIGIBLE LEVELS. WHILE ONSET OF BOUNDARY LAYER
COOLING IS NOW UNDERWAY...ENOUGH INSTABILITY IS EXPECTED TO LINGER
TO SUPPORT A CONTINUING SEVERE THREAT AT LEAST THROUGH THE 02-04Z
TIME FRAME...AS ACTIVITY DEVELOPS NORTHWARD JUST AHEAD OF SURFACE
FRONT INTO EASTERN NORTH DAKOTA. THIS WILL BE SUPPORTED BY FORCING
ASSOCIATED WITH A WEAKENING MID-LEVEL IMPULSE WHICH IS BEGINNING TO
LIFT THROUGH BROADER ANTICYCLONIC UPPER FLOW FIELD ACROSS THE
WESTERN/CENTRAL DAKOTAS.
SHEAR WITHIN DEEP LAYER SOUTHERLY FLOW REGIME IS STRONG AND
SUPPORTIVE OF UPDRAFT ROTATION...WHICH WILL SUPPORT AT LEAST A
MARGINAL SEVERE HAIL THREAT IN AN ENVIRONMENT WITH MOST UNSTABLE
CAPE IN EXCESS OF 1000 J/KG. OTHERWISE...DOWNWARD MIXING OF
MOMENTUM ASSOCIATED 30-50 KT LOW-LEVEL JET WILL SUPPORT A RISK FOR
DAMAGING WIND GUSTS...BEFORE STORMS BECOME UNDERCUT BY EASTWARD
ADVANCING COLD FRONT LATER THIS EVENING.
.KERR.. 09/23/2007
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...FGF...FSD...ABR...BIS...LBF...UNR...
45670051 46420021 47009996 47459898 47139804 46629791
45019857 44249925 43199956 42040012 41360067 41200164
41990158 43170140 43660099 44290075
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