Sunday, October 27, 2013

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 270732
SWODY3
SPC AC 270730

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT SUN OCT 27 2013

VALID 291200Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SOUTHERN HIGH
PLAINS...

...SYNOPSIS...
AN AMPLIFIED LARGE-SCALE PATTERN WILL CONTINUE OVER THE CONUS ON
TUESDAY...ACCENTUATED BY AN INCREASINGLY EASTWARD-PROGRESSIVE UPPER
TROUGH OVER THE ROCKIES/SOUTHWEST STATES. THE INFLUENCES OF THIS
TROUGH COINCIDENT WITH A VERY MOIST AIRMASS /FOR THE SEASON/ ACROSS
THE SOUTH-CENTRAL CONUS WILL LEAD TO TSTM POTENTIAL ACROSS THE
CENTRAL/SOUTHERN PLAINS TO THE LOWER/MIDDLE MO RIVER VALLEY AND
MIDDLE MS VALLEY...INCLUDING A RISK FOR AT LEAST SOME SEVERE TSTMS.

...SOUTHERN/CENTRAL PLAINS TO LOWER/MIDDLE MO VALLEY...
INFLUENCED BY LEE SIDE TROUGHING AND A SOUTHEAST STATES
ANTICYCLONE...PERSISTENT SOUTHERLY LOW-LEVEL TRAJECTORIES AND AN
INCREASINGLY MOIST SOURCE REGION AIRMASS WILL MAINTAIN A RELATIVELY
HIGH MOISTURE CONTENT BOUNDARY LAYER ACROSS MUCH OF THE
SOUTHERN/CENTRAL PLAINS...WITH A GRADUAL EASTWARD-EXPANSION ACROSS
THE MIDDLE MS VALLEY/OZARKS. THIS MOISTURE WILL LIKELY CONTRIBUTE TO
A MODERATELY UNSTABLE AIRMASS TO THE EAST OF A SOUTHERN HIGH PLAINS
SURFACE LOW AND LEE TROUGH/DRYLINE...AND TO THE SOUTH/SOUTHEAST OF
WHAT WILL LIKELY BE A CONVECTIVELY REINFORCED FRONTAL BOUNDARY
ACROSS PARTS OF KS AND THE ADJACENT LOWER MO VALLEY/MIDDLE MS
VALLEY.

THAT SAID...UNCERTAINTIES EXIST REGARDING THE TIMING/MAGNITUDE OF
THE SEVERE POTENTIAL OVER THE REGION...ESPECIALLY GIVEN GUIDANCE
VARIABILITY AND THE GENERAL POSITIVE TILT OF THE UPSTREAM ROCKIES
UPPER TROUGH. OF NOTE...THE 00Z DETERMINISTIC GFS FEATURES A
FASTER/MORE EASTWARD SOLUTION OF THE WESTERN STATES TROUGH AS
COMPARED TO THE MORE SIMILAR 00Z ECMWF/NAM GUIDANCE. THESE
DIFFERENCES INFLUENCE THE SPATIAL/TEMPORAL VARIABILITY OF THE
PRIMARY SEVERE POTENTIAL. THIS WOULD GENERALLY BE A LATER/MORE
NOCTURNAL RISK PER THE 00Z NAM/ECWMF VERSUS A GREATER LIKELIHOOD OF
POSSIBLE DEEP CONVECTIVE DEVELOPMENT NEAR PEAK-HEATING WITH THE 00Z
GFS.

REGARDLESS...A VERY MOIST/UNSTABLE AIRMASS WILL RESIDE TO THE EAST
OF THE HIGH PLAINS SURFACE LOW AND LEE TROUGH/DRY LINE...WITH STRONG
VERTICAL SHEAR /40-55 KT/ OVERSPREADING THE WARM SECTOR. WHILE
GUIDANCE VARIABILITY REMAINS CONSIDERABLE...AND MASS CONVERGENCE MAY
REMAIN MODEST INTO EARLY EVENING...CURRENT THINKING IS THAT AT LEAST
A CONDITIONAL/ISOLATED-TYPE SEVERE RISK WILL EXIST. THIS WOULD MAIN
BE ACROSS THE SOUTHERN HIGH PLAINS TUESDAY AFTERNOON/EARLY
EVENING...OR MORE CERTAINLY BY LATE EVENING/OVERNIGHT ACROSS THE
SOUTHERN HIGH PLAINS/LOWER MO VALLEY AS STRONGER FORCING FOR ASCENT
INFLUENCES THE REGION.

..GUYER.. 10/27/2013

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