DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 020600
SWODY1
SPC AC 020558

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT TUE APR 02 2013

VALID 021200Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF WRN...SWRN
AND CENTRAL TX...

...SYNOPSIS...
A SPLIT FLOW REGIME WILL PERSIST ACROSS THE WRN HALF OF THE CONUS AS
A MEAN RIDGE IS MAINTAINED ALONG THE U.S. WEST COAST. A PROMINENT
UPPER LOW...CURRENTLY MOVING INTO SRN QUEBEC PER WATER VAPOR
IMAGERY...WILL PROGRESS NEWD THIS FORECAST PERIOD WITH UPSTREAM
HEIGHT RISES EXPECTED ACROSS THE MID-UPPER MS VALLEY REGION.
MEANWHILE...THE CLOSED LOW CENTERED OVER THE GREAT BASIN MON EVENING
SHOULD UNDERGO SOME WEAKENING AS IT EVOLVES INTO A POSITIVELY-TILTED
OPEN WAVE TRACKING TOWARD NM AND THE SRN HIGH PLAINS.

A COLD FRONT STRETCHING FROM THE TN VALLEY WWD INTO N TX SHOULD HAVE
GREATER SWD MOVEMENT WITH ITS TX PORTION. MODELS CONTINUE TO DIFFER
/00Z NAM REMAINS FASTER THAN THE 00Z GFS/12Z ECMWF/ WITH THIS SWD
FRONTAL MOVEMENT ACROSS WEST CENTRAL INTO SW TX FROM THIS MORNING
INTO THE AFTERNOON. GIVEN THE PRESENT LOCATION OF THE COLD FRONT
INTO THE NRN PORTION OF THE WFO MIDLAND CWA...THE NAM MAY HAVE A
BETTER FORECAST FOR DAY 1...INDICATING THE FRONT WILL HAVE MOVED S
OF KMAF BY MID-LATE AFTERNOON. DESPITE THE MODEL DIFFERENCE IN
FRONTAL PLACEMENT...THE NWD EXTENT OF THE SLIGHT RISK WILL BE
MAINTAINED BETWEEN KMAF TO KLBB FOR THE POTENTIAL OF ELEVATED SEVERE
STORMS LATER IN THE FORECAST PERIOD. MEANWHILE...A DRY LINE SHOULD
INTERSECT THE COLD FRONT ABOUT 40 SW KMAF BY MID AFTERNOON AND
EXTEND SWD INTO THE TX BIG BEND REGION.

...WRN AND SWRN THROUGH CENTRAL TX...
LOW LEVEL MOISTURE RETURN ACROSS THE WRN EXTENT OF THE WARM SECTOR
SHOULD RESULT IN SURFACE DEW POINTS IN THE UPPER 50S TO AROUND 60 F
REACHING THE WRN PART OF THE EDWARDS PLATEAU NW OF KDRT. STEEP
MIDLEVEL LAPSE RATES /8-8.5 C PER KM/ ACROSS MUCH OF THE SLIGHT RISK
AREA COMBINED WITH THE MOISTURE RETURN AND SURFACE HEATING WILL
RESULT IN A MODERATELY UNSTABLE ENVIRONMENT /MLCAPE 1500-2000 J PER
KG/.

ASCENT ATTENDANT TO GRADUAL HEIGHT FALLS WITH THE APPROACH OF THE
GREAT BASIN TROUGH AND CONVERGENCE INVOF THE COLD FRONT AND DRY LINE
SHOULD ENCOURAGE TSTM DEVELOPMENT THIS AFTERNOON...GIVEN MODERATE
INSTABILITY AND STEEP LAPSE RATES. STRENGTHENING WLY MIDLEVEL WINDS
ATOP BACKING/SELY LOW LEVEL FLOW WILL RESULT IN A VERTICALLY VEERING
WIND PROFILE AND EFFECTIVE BULK SHEAR OF 40-50 KT. THUS...SUPERCELLS
WILL BE LIKELY WITH HAIL AND DAMAGING WINDS THE PRIMARY THREATS.
HOWEVER...FORECAST SOUNDINGS/HODOGRAPHS SUGGEST THE TORNADO THREAT
CANNOT BE RULED...GIVEN LOW LEVEL DIRECTIONAL SHEAR WHICH SHOULD
INCREASE BY EARLY EVENING...AS SURFACE WINDS UNDERGO FURTHER BACKING
WITH THE APPROACH OF THE COLD FRONT. THERE IS SOME INDICATION THAT
INITIAL ACTIVITY COULD GROW UPSCALE INTO A FORWARD PROPAGATING MCS
ACROSS THE EDWARDS PLATEAU WITH THE SEVERE WEATHER THREAT PERSISTING
THROUGH THE EVENING.

FARTHER NW TO THE N OF THE COLD FRONT...ELEVATED TSTMS WILL BE
POSSIBLE LATER IN THE EVENING AND OVERNIGHT/EARLY WED MORNING AS
FURTHER HEIGHT FALLS AND INCREASING LOW LEVEL WAA SUPPORT
CONVECTION/EMBEDDED TSTMS OVER WEST CENTRAL TX AND POSSIBLY SERN NM.
STEEPENING MIDLEVEL LAPSE RATES AND MODERATE ELEVATED INSTABILITY
WILL SUPPORT MAINLY A HAIL THREAT...SOME REACHING SEVERE VALUES.

...PART OF SOUTH CENTRAL TO SERN AND E TX...
LOW SEVERE HAIL/DAMAGING WIND PROBABILITIES EXTEND E/NEWD ACROSS
SOUTH CENTRAL TO SERN AND PART OF E TX WHERE MODELS SUGGEST LOW
LEVEL MOISTENING AND DIABATIC HEATING WILL DECREASE WEAKER SURFACE
BASED INHIBITION. STORMS MAY DEVELOP IN THIS PART OF THE WARM
SECTOR AS DEEP LAYER ASCENT IS AUGMENTED BY A WEAK SRN STREAM
IMPULSE OR TWO TRACKING ENEWD ACROSS THIS REGION. WEAK INSTABILITY
SHOULD LIMIT THE SEVERE WEATHER THREAT.

..PETERS/COHEN.. 04/02/2013

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