SWODY1
SPC AC 241229
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0729 AM CDT TUE APR 24 2012
VALID 241300Z - 251200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A MIDLEVEL RIDGE WILL REMAIN CENTERED ALONG THE ROCKIES THROUGH THE
D1 PERIOD WITH A GRADUAL EWD PROGRESSION OF DOWNSTREAM TROUGH OVER
THE ERN U.S./NWRN ATLANTIC. SEVERAL WEAKER IMPULSES ARE PRESENT
WITHIN THIS BROADER-SCALE FLOW REGIME...ONE OF WHICH CRESTING RIDGE
AXIS OVER THE NRN ROCKIES WILL TRANSLATE SEWD INTO THE UPPER MS
VALLEY BY 25/12Z. IN THE LOW LEVELS...WARM FRONT ANALYZED FROM A
SURFACE LOW OVER SRN ALBERTA SEWD THROUGH A SECONDARY LOW OVER CNTRL
SD TO ERN NEB WILL INTENSIFY WHILE SHIFTING EWD/SEWD INTO THE
UPPER/MID MS VALLEY.
...ERN PARTS OF WA/ORE INTO NRN HIGH PLAINS...
IN THE WAKE OF LEAD IMPULSE MENTIONED IN SYNOPSIS...THE APPROACH OF
AN UPSTREAM VORTICITY MAXIMUM OVER THE GREAT BASIN WILL AUGMENT
STRONG DAYTIME HEATING ALONG THE HIGH TERRAIN TO FOSTER
ISOLATED-WIDELY SCATTERED TSTM DEVELOPMENT THIS AFTERNOON INTO
TONIGHT. THE PRESENCE OF STEEP LOW TO MIDLEVEL LAPSE RATES...PW
VALUES OF 0.5-0.8 INCH...AND 40-45 KT OF DEEP-LAYER SHEAR WILL
RESULT IN AN ENVIRONMENT FAVORABLE FOR A FEW SUSTAINED/ROTATING
STORMS CAPABLE OF LOCALLY DAMAGING WIND GUSTS AND MARGINALLY SEVERE
HAIL.
...DAKOTAS INTO UPPER MS VALLEY...
CAPPING ASSOCIATED WITH AN EML WILL INTENSIFY TODAY AS MIDLEVEL FLOW
BECOMES INCREASINGLY ZONAL ACROSS CREST OF RIDGE OVER THE NRN HIGH
PLAINS. AT THE SAME TIME...STRONG HEATING OF BOUNDARY LAYER W OF
WARM FRONT AND LEE TROUGH COUPLED WITH THE APPROACH OF MIDLEVEL
IMPULSE MENTIONED ABOVE MAY LOCALLY WEAKEN CAP SUCH THAT ISOLATED
STORM DEVELOPMENT IS POSSIBLE BY LATE AFTERNOON OR EVENING OVER THE
CNTRL DAKOTAS. OTHER STORMS FORMING UPSTREAM OVER THE HIGH PLAINS
OF MT/NRN WY WILL LIKELY MOVE INTO THE REGION THIS EVENING.
FORECAST SOUNDINGS EXHIBIT STEEP LAPSE RATES AND A DEEPLY MIXED
BOUNDARY LAYER WHICH WILL SUPPORT VIGOROUS UP/DOWNDRAFTS WITH A RISK
FOR HAIL AND DAMAGING OUTFLOW WINDS.
SOME POTENTIAL FOR MAINLY SUB-SEVERE HAIL MAY DEVELOP EWD INTO THE
UPPER MS VALLEY OVERNIGHT IN CONJUNCTION WITH ELEVATED TSTMS FORMING
AHEAD OF VORTICITY MAXIMUM APPROACHING FROM THE DAKOTAS.
...MID MO/LOWER OH/TN VALLEYS...
HERE TOO...CAPPING WILL STRENGTHEN DUE TO RISING MIDLEVEL HEIGHTS
AND THE ADVECTION OF NRN ROCKIES EML WITHIN PREVAILING NWLY FLOW
REGIME. SWLY LOW-LEVEL FLOW ON BACKSIDE OF SURFACE ANTICYCLONE
CENTERED OVER THE N-CNTRL GOM WILL ALLOW FOR BOUNDARY LAYER MOISTURE
TO INCREASE WITH DEWPOINTS RISING THROUGH THE 50S TO THE W OF WARM
FRONT. THIS MOISTURE WILL COMBINE WITH STRONG DAYTIME HEATING AND
THE EML TO YIELD AFTERNOON MLCAPE VALUES POSSIBLY APPROACHING
1000-1500 J/KG ACROSS PARTS OF MO AND ERN KS. HOWEVER...THE
STRENGTHENING CAP IS EXPECTED TO INHIBIT SURFACE-BASED TSTM
DEVELOPMENT WITHIN WARM SECTOR THROUGH THE PERIOD.
THE POTENTIAL FOR ELEVATED TSTMS CAPABLE OF MARGINALLY SEVERE HAIL
WILL INCREASE THIS EVENING AND TONIGHT AS WAA/ISENTROPIC ASCENT IS
ENHANCED ALONG/E OF WARM FRONT BY STRENGTHENING WLY LLJ.
..MEAD/LEITMAN.. 04/24/2012
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