SWODY1
SPC AC 201933
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0233 PM CDT WED OCT 20 2010
VALID 202000Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM SWRN TX INTO SERN NM...
...SERN NM THROUGH SWRN TX...
STATIONARY FRONT EXTENDS FROM THE LOWER MS VALLEY WWD INTO S-CNTRL
AND SWRN TX. ELY-SELY UPSLOPE FLOW HAS BECOME ESTABLISHED NORTH OF
THIS BOUNDARY. MID-UPPER 50S DEWPOINTS HAVE ADVECTED AS FAR NWWD AS
SERN NM BENEATH STEEPER 700-500 MB LAPSE RATES WHERE SURFACE
TEMPERATURES HAVE WARMED INTO THE 70S...BOOSTING MLCAPE TO 1000
J/KG. ZONE OF DIFFLUENT FLOW ALOFT DOWNSTREAM FROM SWRN U.S. UPPER
LOW IS SLOWLY SHIFTING NEWD IN WAKE OF NW-SE ORIENTED DEFORMATION
AXIS. THUNDERSTORMS WILL LIKELY DEVELOP LATER THIS AFTERNOON INTO
THE EVENING WITHIN THIS REGION...INITIALLY OVER THE HIGHER TERRAIN
AND SPREAD NEWD WITH TIME. ESELY LOW LEVEL WINDS INCREASING AND
VEERING TO SWLY 30-35 KT WITH HEIGHT IS RESULTING IN 30-40 KT
EFFECTIVE SHEAR. THIS PROFILE WILL SUPPORT POTENTIAL FOR A FEW
SUPERCELLS. STORMS MAY EVENTUALLY GROW UPSCALE INTO LINES/CLUSTERS
OVERNIGHT. ISOLATED LARGE HAIL AND DAMAGING WIND WILL BE THE PRIMARY
THREATS THROUGH AT LEAST MID EVENING.
...AZ AND NM...
OTHER STORMS HAVE INCREASED OVER THE HIGHER TERRAIN OF NERN AZ INTO
NWRN NM WHERE TEMPERATURES ALOFT ARE COLDER AND STEEP LAPSE RATES
EXIST IN CLOSER PROXIMITY TO UPPER LOW...BUT VERTICAL SHEAR IS
MARGINAL. ISOLATED HAIL COULD ACCOMPANY THE STRONGER CORES GIVEN
STEEP LAPSE RATES AND COLD TEMPERATURES ALOFT. LOW LEVEL
TEMPERATURE-DEWPOINT SPREADS ARE ALSO SUFFICIENT FOR ISOLATED STRONG
DOWNDRAFTS.
..DIAL.. 10/20/2010
.PREV DISCUSSION... /ISSUED 1102 AM CDT WED OCT 20 2010/
...SYNOPSIS...
COLD UPPER LOW REMAINS CUT-OFF FROM PRIMARY WESTERLIES AND WILL MOVE
ONLY SLOWLY E FROM ITS CURRENT LOCATION NEAR SRN CA/BAJA BORDER NEAR
IPL TO SWRN AZ 12Z THU. LOW LEVEL MOISTURE CONTINUES TO RETURN UP
THE RIO GRANDE VALLEY INTO SERN NM AND THIS WILL PERSIST THRU THE
FORECAST PERIOD. WITH STEEP MID LEVEL LAPSE RATES IN PLACE ACROSS
ALL OF NM INTO SWRN TX COUPLED WITH INCREASING UPPER DIVERGENCE
AHEAD OF UPPER LOW...CONDITIONS WILL BECOME INCREASINGLY FAVORABLE
FOR STRONG/SEVERE THUNDERSTORMS LATER THIS AFTERNOON.
...CNTRL/SERN NM INTO SWRN TX...
SELY LOW LEVEL MOIST UPSLOPE FLOW TO BECOME BETTER
ESTABLISHED THIS AFTERNOON AND EVENING IN RESPONSE TO PRESSURE FALLS
DEVELOPING OVER THE SRN/CNTRL ROCKIES. SURFACE DEW POINTS ARE
CURRENTLY IN THE 50S F OVER MUCH OF SWRN TX INTO SERN NM AND
EXPECTED TO INCREASE NWD INTO CENTRAL NM BY EVENING. STEEP LAPSE
RATES COUPLED WITH DIURNAL HEATING WILL DESTABILIZE THE AIR MASS
WITH MLCAPE INCREASING TO 1000-1500 J/KG DURING THE
AFTERNOON.
LARGE SCALE ASCENT WILL GRADUALLY INCREASE IN ASSOCIATION WITH LOW
LEVEL UPSLOPE FLOW AND DIVERGENCE ALOFT IN ADVANCE OF THE UPPER LOW.
WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS
AFTERNOON AS DIABATIC HEATING ELIMINATES ANY REMAINING WEAK CAP.
WIND PROFILES ARE FORECAST TO EXHIBIT VEERING WITH HEIGHT PROVIDING
SUFFICIENT BULK SHEAR TO ENHANCE STORM ORGANIZATION AND INTENSITY.
THIS WILL PROMOTE A FEW SEVERE STORMS...INCLUDING ISOLATED
SUPERCELLS...DURING THE AFTERNOON AND EVENING WITH STRONGER CELLS
CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WIND GUSTS. A BRIEF
TORNADO WOULD ALSO BE POSSIBLE WITH ANY SUPERCELL SERN NM THRU THIS
EVENING WHERE FAVORABLE PARAMETERS SHOULD BE GREATEST. A FEW
STRONGER CELLS WILL LIKELY PERSIST INTO THE OVERNIGHT HOURS MAINLY
OVER PARTS OF SERN NM WHERE THE LOW LEVEL JET INCREASES TO 30 KT OR
MORE. HAVE INCLUDED A LITTLE MORE OF CENTRAL NM IN THE SLIGHT RISK
AS IT NOW APPEARS MOISTURE/INSTABILITY WILL SPREAD FARTHER N.
...FAR SRN NV/SERN CA INTO NM...
DIURNAL HEATING BENEATH COOL MID-LEVEL TEMPERATURES ASSOCIATED WITH
THE UPPER LOW WILL RESULT IN MODEST DESTABILIZATION ACROSS THIS
REGION. LARGE-SCALE ASCENT WILL SUPPORT AN INCREASE IN AFTERNOON
SHOWERS AND THUNDERSTORMS AS THE AIR MASS DESTABILIZES...ACROSS AZ
AND VICINITY INITIALLY AND THEN SPREADING EWD INTO NM LATER IN THE
AFTERNOON/EVENING.
WITH MODERATE MID-LEVEL SLYS/SELYS IN ADVANCE OF THE UPPER
LOW...SHEAR SUFFICIENT FOR SOME UPDRAFT ORGANIZATION MAY ALLOW A FEW
LONGER-LIVED STORMS TO EVOLVE DESPITE MODEST CAPE. WHILE
APPRECIABLE SEVERE WEATHER IS NOT ANTICIPATED...MARGINALLY-SEVERE
HAIL AND/OR GUSTY WINDS MAY OCCUR WITH THE STRONGEST CELLS.
ONLY CHANGE TO EARLIER OUTLOOK WAS TO INCLUDE MORE OF SRN AZ IN THE
SEE TEXT GIVEN THE PROXIMITY OF THE COLD UPPER LOW.
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