DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 311939
SWODY1
SPC AC 311937

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0237 PM CDT WED JUL 31 2013

VALID 312000Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF THE CNTRL/SRN HIGH
PLAINS INTO THIS EVENING...

...CNTRL/SRN HIGH PLAINS...
CONTINUED TO SHIFT HIGHER SEVERE HAZARD PROBABILITIES FARTHER SW TO
ACCOUNT FOR PRIMARY CONVECTIVE DEVELOPMENT OCCURRING ACROSS THE SRN
HIGH PLAINS. THIS REGION LIES IN CLOSE PROXIMITY TO THE STOUT
MID/UPPER-LEVEL ANTICYCLONE...RESULTING IN PROGRESSIVELY WEAKER
DEEP-LAYER FLOW WITH SRN EXTENT. BUT A RATHER FAVORABLE
THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY STEEP LAPSE RATES AND
RELATIVELY HIGH PW CONTENT SHOULD PROVE SUFFICIENT FOR A FEW TSTM
CLUSTERS PRODUCING SEVERE HAIL/WIND. COALESCING UPDRAFTS COULD YIELD
A SEMI-ORGANIZED COLD POOL DEVELOPING SWD INTO EARLY/MID-EVENING.

FARTHER N...CONVERGENCE IS QUITE LIMITED ALONG A DECAYING FRONTAL
SURGE OVER THE CNTRL PLAINS. HOWEVER...ISOLATED TSTMS MAY GRADUALLY
DEVELOP EWD FROM THE LEE OF THE FRONT RANGE IN CO/SERN WY WITH
LOCALIZED SEVERE HAIL/WIND POSSIBLE.

...UPPER GREAT LAKES/MS VALLEY...
ADJUSTED LOW SEVERE PROBABILITIES BASED ON CURRENT POSITION OF COLD
FRONT...OTHERWISE NO CHANGE TO PREVIOUS FORECAST REASONING.

...ORE...
NO CHANGE TO PREVIOUS FORECAST.

..GRAMS.. 07/31/2013

.PREV DISCUSSION... /ISSUED 1107 AM CDT WED JUL 31 2013/

...SYNOPSIS...

A STRONG SHORT-WAVE TROUGH AND ASSOCIATED MID AND UPPER-LEVEL WIND
MAXIMA OVER THE UPPER MS VALLEY WILL PROGRESS SEWD ACROSS THE GREAT
LAKES CONTRIBUTING TO THE AMPLIFICATION OF A FULL-LATITUDE TROUGH
EXTENDING FROM HUDSON BAY TO THE SERN CONUS. ELSEWHERE...AN
UPPER-LEVEL ANTICYCLONE WILL REMAIN CENTERED OVER NM WHILE A MID TO
UPPER-LEVEL LOW MOVES ONTO THE PACIFIC NW AND SRN BRITISH COLUMBIA
COASTS.

IN THE LOW LEVELS...AN INITIAL COLD FRONTAL SURGE FROM THE UPPER
MIDWEST THROUGH MID MS VALLEY INTO SRN HIGH PLAINS WILL PROGRESS
EWD/SEWD AHEAD OF A SECONDARY COLD FRONT MOVING THROUGH THE CNTRL
PLAINS AND MID TO LOWER-MO VALLEY.

...CNTRL/SRN HIGH PLAINS THIS AFTERNOON AND EVENING...

12Z REGIONAL SOUNDINGS SHOW THE PRESENCE OF A VERY MOIST BOUNDARY
LAYER /I.E. LOWEST 100-MB MEAN-MIXING RATIOS OF 13-16 G PER KG/
BETWEEN THE ABOVE-MENTIONED COLD FRONTS...AND BENEATH A PLUME OF
STEEP MIDLEVEL LAPSE RATES WHICH WILL CONTRIBUTE TO MODERATE TO
STRONG AFTERNOON INSTABILITY WITH MLCAPE OF 2000-3000+ J/KG. IN THE
ABSENCE OF ANY DISCERNIBLE MIDLEVEL FORCING MECHANISMS...THE
PRESENCE OF THE SYNOPTIC FRONTS AND THE DEVELOPMENT OF A LEE TROUGH
ACROSS WRN KS WILL SERVE AS FOCI FOR STORM DEVELOPMENT. LOW-LEVEL
ELY/SELY WINDS EAST OF THE LEE TROUGH WILL COINCIDE WITH MODEST
/20-30 KT/ NWLY WINDS AT 500 MB...RESULTING IN SUFFICIENT VERTICAL
SHEAR FOR ORGANIZED MULTICELLS AND SOME SUPERCELL STRUCTURES WITH A
RISK FOR LARGE HAIL AND DAMAGING WINDS INTO THIS EVENING.

...UPPER GREAT LAKES THIS AFTERNOON AND EVENING...

HEIGHT FALLS/DCVA ASSOCIATED WITH THE SHORT-WAVE TROUGH MENTIONED IN
THE SYNOPSIS WILL AUGMENT LOW-LEVEL UPLIFT ALONG THE COLD FRONT TO
FOSTER ISOLATED TO WIDELY SCATTERED TSTM DEVELOPMENT THIS AFTERNOON.
MARGINAL AMOUNTS OF VERTICAL SHEAR AND INSTABILITY WILL PRECLUDE AN
ORGANIZED SEVERE WEATHER THREAT...THOUGH ISOLATED OCCURRENCES OF
HAIL AND LOCALLY STRONG WIND GUSTS ARE POSSIBLE.

...OREGON THIS AFTERNOON AND EVENING...

TERRAIN-INDUCED CIRCULATIONS WILL BE BOLSTERED BY DEEPER-LAYER
FORCING FOR ASCENT ASSOCIATED WITH A VORTICITY MAXIMUM ROTATING
AROUND THE PARENT UPPER LOW TO PROMOTE WIDELY SCATTERED TSTMS LATER
TODAY. THE 12Z MFR SOUNDING SHOWED THE PRESENCE OF VERY STEEP LAPSE
RATES IN THE 700-500-MB LAYER WHICH WHEN COUPLED WITH A MODESTLY
MOIST ENVIRONMENT AND 30-40 KT OF DEEP SWLY SHEAR WILL SUPPORT
HIGH-BASED STRONG TO MARGINALLY SEVERE STORMS CAPABLE OF LOCALLY
DAMAGING WIND GUSTS AND SOME HAIL.

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