SWODY3
SPC AC 200727
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0227 AM CDT TUE APR 20 2010
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM SWRN KS SWD INTO PARTS OF
WRN AND CENTRAL TX...
...SYNOPSIS...
LARGE WRN UPPER LOW/TROUGH IS FORECAST TO EXPAND WITH TIME WHILE
SHIFTING SLOWLY EWD ACROSS THE INTERMOUNTAIN WEST. MEANWHILE
FARTHER E...THE PERSISTENT TROUGH OVER ERN NOAM SHOULD TAKE ON A
MORE NEGATIVE TILT WITH TIME WHILE ALSO PROGRESSING EWD.
AT THE SURFACE...A COLD FRONT WILL CONTINUE CROSSING THE ROCKIES
AHEAD OF THE WRN UPPER SYSTEM...SHIFTING INTO THE HIGH PLAINS DURING
THE AFTERNOON/EVENING AND EVENTUALLY OVERTAKING A SRN PLAINS DRYLINE
OVERNIGHT. THE ADVANCE OF THIS STORM SYSTEM INTO THE PLAINS WILL
SUPPORT A SUBSTANTIAL INCREASE IN SEVERE WEATHER ACTIVITY THIS
PERIOD.
...SWRN KS SWD INTO PARTS OF WRN AND CENTRAL TX...
AS THE UPPER RIDGE AXIS FINALLY BEGINS SHIFTING E OF THIS REGION
AHEAD OF THE ADVANCING UPPER SYSTEM...EXPECT MORE ACTIVE AFTERNOON
STORM DEVELOPMENT -- NEAR A SURFACE LOW INVOF SERN CO AND SWD ALONG
THE TRAILING TROUGH/DRYLINE WHICH SHOULD BE MOVING ACROSS THE TX/OK
PANHANDLES AND TX SOUTH PLAINS/TRANSPECOS REGIONS DURING THE
AFTERNOON. AIRMASS AHEAD OF THE TROUGH/DRYLINE WILL BE
DESTABILIZING THROUGH THE AFTERNOON...AS CONTINUED NWD ADVECTION OF
LOW TO MID 60S DEWPOINTS ACROSS THE SRN PLAINS COMBINES WITH DIURNAL
HEATING TO YIELD AN AXIS OF 1000 TO 2000 J/KG MIXED-LAYER CAPE.
THIS HEATING/DESTABILIZATION COMBINED WITH THE APPROACH OF THE WRN
UPPER TROUGH/EWD RETREAT OF THE RIDGE WILL RESULT IN A WEAKENING CAP
-- AND EVENTUALLY STORM DEVELOPMENT BY MID TO LATE AFTERNOON.
AS STRONGER MID-LEVEL SWLYS SPREAD SLOWLY EWD ACROSS THE HIGH PLAINS
ATOP LOW-LEVEL SELYS...SHEAR PROFILES WILL BECOME QUITE SUPPORTIVE
OF UPDRAFT ROTATION ALONG THE TROUGH/DRYLINE. THEREFORE...IT
APPEARS THAT AT LEAST A FEW SIGNIFICANT SEVERE/SUPERCELL STORMS WILL
EVOLVE DURING THE LATE AFTERNOON AND INTO THE EARLY EVENING HOURS.
VERY LARGE HAIL APPEARS TO BE THE MAIN SEVERE THREAT...THOUGH
LOCALLY-DAMAGING WINDS AND A COUPLE OF TORNADOES WILL ALSO BE
POSSIBLE.
OVERNIGHT...STORMS MAY BECOME MORE LINEARLY-ORGANIZED AS A COLD
FRONT OVERTAKES THE DRYLINE. SEVERE THREAT SHOULD CONTINUE INTO THE
OVERNIGHT AHEAD OF THE FRONT/DRYLINE. SOME THREAT MAY ALSO EXPAND
NWD -- MAINLY IN THE FORM OF HAIL AS ELEVATED CONVECTION INCREASES
IN CONJUNCTION WITH A STRENGTHENING NOCTURNAL LOW-LEVEL JET.
..GOSS.. 04/20/2010
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