ACUS01 KWNS 152000
SWODY1
SPC AC 151958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT THU JUL 15 2010
VALID 152000Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE GREAT LAKES TO THE
CNTRL/SRN PLAINS AND CO FRONT RANGE...
...GREAT LAKES/MIDWEST...
TSTMS SHOULD CONTINUE TO INCREASE THROUGH LATE AFTERNOON ALONG
ADVANCING COLD FRONT AND PRE-FRONTAL WIND SHIFT. WITH A PRE-COLD
FRONTAL AXIS OF LOWER TO MIDDLE 70S F SURFACE DEWPOINTS ACROSS
MO/IL/INDIANA INTO LOWER MI AT MID AFTERNOON...LATEST OBJECTIVE
ANALYSIS SUGGESTS MLCAPE VALUES APPROACHING 2000-3500 J/KG. A
SPECIAL 18Z LINCOLN IL OBSERVED RAOB WAS INDICATIVE OF 4000 J/KG
MLCAPE IN CONJUNCTION WITH AROUND 25-30 KT OF DEEP LAYER SHEAR.
DAMAGING WINDS WILL BE THE PRIMARY CONCERN. FOR ADDITIONAL NEAR-TERM
INFORMATION...CONSULT MESOSCALE DISCUSSION 1316 AND EXISTING
WATCHES/SUBSEQUENT MESOSCALE DISCUSSIONS.
...CO FRONT RANGE/ADJACENT PLAINS...
SEE MESOSCALE DISCUSSION 1315 AND PRIOR OUTLOOK DISCUSSION BELOW.
..GUYER.. 07/15/2010
.PREV DISCUSSION... /ISSUED 1127 AM CDT THU JUL 15 2010/
...GREAT LAKES INTO CNTRL/SRN PLAINS...
A DEEP-LAYER LOW WILL SLOWLY TRAVERSE NRN ONTARIO THIS PERIOD WITH
AN ASSOCIATED SHORT WAVE TROUGH TRANSLATING THROUGH BASAL PORTION
FROM THE UPPER MS VALLEY ACROSS THE GREAT LAKES. THIS SHORT WAVE
TROUGH WILL BE ACCOMPANIED BY A BELT OF 30-40 KT MIDLEVEL FLOW WHICH
WILL OVERSPREAD NRN PORTION OF ATTENDANT SYNOPTIC FRONT PROGRESSING
THROUGH THE GREAT LAKES AND OH VALLEY. WHILE 12Z OBSERVED SOUNDINGS
INDICATE THAT MIDLEVEL LAPSE RATES ARE QUITE WEAK ACROSS PRE-FRONTAL
WARM SECTOR...DAYTIME HEATING COMBINED WITH A MOIST BOUNDARY LAYER
WILL RESULT IN A MODERATELY UNSTABLE AIR MASS BY AFTERNOON WITH
MLCAPE RANGING FROM 1000-2000 J/KG OVER LOWER MI TO 2000-3000 J/KG
ACROSS THE OH VALLEY.
SUSTAINED LOW-LEVEL CONVERGENCE COUPLED WITH INCREASED HEIGHT
FALLS/FORCING ASSOCIATED WITH ABOVE-MENTIONED SHORT WAVE TROUGH ARE
EXPECTED TO FOSTER SCATTERED TSTMS THIS AFTERNOON ALONG THE FRONT
WITH STORMS GROWING UPSCALE INTO LINE SEGMENTS CAPABLE OF MAINLY
DAMAGING DOWNBURST WINDS.
VERTICAL SHEAR WILL CONTINUE TO DECREASE WITH SWWD EXTENT ALONG THE
FRONTAL ZONE ACROSS THE OZARKS INTO PLAINS. HOWEVER...THE HOT AND
HUMID BOUNDARY LAYER WILL RESULT IN AFTERNOON MLCAPE OF 2000-3500
J/KG. EXPECT TSTMS TO INCREASE IN COVERAGE AND INTENSITY LATER
TODAY...FOCUSED ALONG SYNOPTIC FRONT AND PRE-EXISTING OUTFLOW
BOUNDARIES REMNANT FROM WEDNESDAY NIGHT TSTM ACTIVITY. ENVIRONMENT
WILL BE SUPPORTIVE OF VIGOROUS PULSE STORMS WITH THE POTENTIAL FOR
LOCALLY DAMAGING WIND GUSTS.
...CO FRONT RANGE...
MID AND HIGH-LEVEL WIND FIELD WILL GRADUALLY VEER TO NWLY OWING TO
THE WWD RETROGRESSION OF MIDLEVEL RIDGE AXIS. AT THE SAME
TIME...SURFACE-850 MB FLOW WILL BECOME INCREASINGLY
SLY/SELY...RESULTING IN VERTICALLY-VEERING WIND PROFILES WITH 30-35
KT OF DEEP-LAYER SHEAR. THE 12Z DNR SOUNDING SHOWED THE PRESENCE OF
A MOIST LOW-LEVEL AIR MASS BENEATH MODESTLY STEEP MIDLEVEL LAPSE
RATES...WHICH WHEN COUPLED WITH DAYTIME HEATING SHOULD RESULT IN A
MODERATELY UNSTABLE AIR MASS WITH MLCAPE APPROACHING
1000-1500 J/KG.
DESPITE THE ABSENCE OF ANY APPRECIABLE LARGE-SCALE FORCING
MECHANISMS...DIURNALLY ENHANCED TSTMS ARE LIKELY TO FORM AND MOVE
OFF THE FOOTHILLS INTO A PROGRESSIVELY MORE UNSTABLE ENVIRONMENT.
THE STRONGER STORMS WILL LIKELY EXHIBIT MIDLEVEL ROTATION WITH THE
RISK FOR MAINLY HAIL AND GUSTY WINDS.
...NRN MN...
VISIBLE SATELLITE IMAGERY SHOWS AN INCREASE IN CONVECTIVE CLOUDS
OVER SRN MANITOBA THIS MORNING IN CONJUNCTION WITH A VORTICITY
MAXIMUM PROGRESSING SEWD THROUGH THE REGION. STRONG DAYTIME HEATING
AND MODEST BOUNDARY LAYER MOISTURE WILL YIELD POCKETS OF WEAK
CONVECTIVE INSTABILITY TODAY AHEAD OF THIS CONVECTIVE ACTIVITY WITH
MLCAPE INCREASING TO A FEW HUNDRED J/KG. KINEMATIC ENVIRONMENT WILL
FEATURE DEEP NWLY SHEAR OF 40-50 KT WHICH MAY BE SUPPORTIVE OF SOME
STORM ORGANIZATION INTO BANDS OR CLUSTERS WITH THE THREAT FOR
LOCALLY STRONG WIND GUSTS THROUGH THIS EVENING.
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