SWODY1
SPC AC 200507
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1207 AM CDT TUE APR 20 2010
VALID 201200Z - 211200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
THE PRIMARY FEATURE OF INTEREST THIS PERIOD IS AN INTENSE MID AND
UPPER-LEVEL TROUGH WHICH WILL EVOLVE INTO A CLOSED SYSTEM WHILE
DEVELOPING SEWD FROM THE WEST COAST INTO THE GREAT BASIN. AN
ASSOCIATED SURFACE LOW IS FORECAST TO DEEPEN OVER NRN NV TODAY
BEFORE DEVELOPING NWD INTO SWRN ID TONIGHT. A TRAILING PACIFIC
FRONT WILL SHIFT EWD FROM THE VICINITY OF THE WA/ORE/NRN CA COASTS
INTO THE GREAT BASIN AND LOWER CO VALLEY DURING THE FORECAST
PERIOD.
FARTHER E...A VORTICITY MAXIMUM CURRENTLY OVER SERN MT WILL
GRADUALLY WEAKEN WHILE TRANSLATING SEWD INTO AN INCREASINGLY
CONFLUENT MIDLEVEL FLOW REGIME OVER THE CNTRL PLAINS. AN ASSOCIATED
COLD FRONTAL SEGMENT WILL SAG SWD THROUGH THE CNTRL HIGH PLAINS IN
CONCERT WITH THE PASSING UPPER SYSTEM.
...CNTRL/SRN HIGH PLAINS...
00Z MESOSCALE MODEL GUIDANCE IS IN RELATIVELY GOOD AGREEMENT IN
SUGGESTING THAT THE GLANCING INFLUENCE OF ABOVE-MENTIONED VORTICITY
MAXIMUM WILL SERVE TO FOCUS SCATTERED TSTMS ALONG AND AHEAD OF THE
COLD FRONT MOVING SWD THROUGH ERN CO...SWRN NEB AND WRN KS. THE
AMBIENT AIR MASS WILL FEATURE RELATIVELY STEEP LAPSE RATES AND
BOUNDARY LAYER DEWPOINTS IN THE 40S TO AROUND 50 F...CONTRIBUTING TO
AFTERNOON MLCAPE OF AROUND 1000 J/KG. SIMILAR TO PREVIOUS
DAYS...THE WIND FIELD WILL NOT BE PARTICULARLY STRONG...BUT WILL
STILL EXHIBIT SELY SURFACE WINDS VEERING TO NWLY IN THE MID- AND
HIGH-LEVELS WITH 30-40 KT OF DEEP-LAYER SHEAR.
INITIAL STORM MODE MAY EXHIBIT PERIODIC SUPERCELLULAR
CHARACTERISTICS BEFORE ACTIVITY GROWS UPSCALE INTO A
FORWARD-PROPAGATING MCS. HAIL AND STRONG WIND GUSTS WILL BE
POSSIBLE WITH THE STRONGEST STORMS THROUGH THIS EVENING.
HOWEVER...IT APPEARS THAT THE SOMEWHAT COOL BOUNDARY LAYER
TEMPERATURES AND MARGINAL LOW-LEVEL MOISTURE/INSTABILITY MAY TEMPER
THE POTENTIAL FOR A MORE ORGANIZED SEVERE EVENT. SHOULD LATER DATA
INDICATE STRONGER INSTABILITY THAN IS CURRENTLY FORECAST...AN
UPGRADE TO SLIGHT RISK MAY BE NECESSARY.
FARTHER S...ADDITIONAL STORMS WILL BE POSSIBLE ALONG THE LEE TROUGH
NEAR THE TX/NM BORDER...OR ALONG THE RATON MESA. COMPARABLY WARMER
MIDLEVEL TEMPERATURES WILL YIELD A SLIGHTLY MORE STABLE AIR MASS
THAN POINTS TO THE N...THOUGH THE STRONGER STORMS WILL STILL BE
CAPABLE OF SOME HAIL AND LOCALLY GUSTY WINDS.
...NRN NV/SERN ORE/SWRN ID...
DESPITE THE PRESENCE OF A RELATIVELY DRY AIR MASS /I.E. PW VALUES
LESS THAN .75-.50 INCH/...STEEPENING MIDLEVEL LAPSE RATES/DYNAMIC
COOLING ASSOCIATED WITH THE UPPER TROUGH WILL CONTRIBUTE TO POCKETS
OF WEAK INSTABILITY AHEAD OF THE PACIFIC FRONT THIS AFTERNOON. THE
STRONG DYNAMIC FORCING FOR ASCENT COUPLED WITH MESOSCALE LIFT ALONG
THE COLD FRONT MAY FOSTER SCATTERED...LOW-TOPPED TSTMS THIS
AFTERNOON INTO EVENING WHICH WILL MOVE RAPIDLY NNEWD WITHIN
STRENGTHENING DEEP-LAYER WIND FIELD. HAIL AND STRONG WIND GUSTS MAY
ACCOMPANY THESE STORMS THROUGH THE EVENING GIVEN THE STEEP LAPSE
RATES AND COOL THERMODYNAMIC PROFILES.
..MEAD/SMITH.. 04/20/2010
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