DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1018 AM CST SAT NOV 16 2013

VALID 161630Z - 171200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM LATE THIS AFTERNOON INTO
EARLY SUNDAY ACROSS PARTS OF THE LOWER MO VALLEY INTO UPPER
MIDWEST...

...SYNOPSIS...

A SHORT-WAVE TROUGH OVER THE PACIFIC NW AND NRN INTER-MOUNTAIN
REGION WILL UNDERGO CONSIDERABLE AMPLIFICATION WHILE SHIFTING INTO
THE CNTRL CONUS IN RESPONSE TO THE EQUATORWARD PROGRESSION OF MID
AND UPPER-LEVEL WIND MAXIMA INTO THE BASE OF THE PARENT SYSTEM.
MEANWHILE...A PRECEDING VORTICITY MAXIMUM WILL EJECT FROM THE CNTRL
PLAINS NEWD THROUGH THE UPPER GREAT LAKES.

IN THE LOW LEVELS...A SURFACE CYCLONE ATTENDANT TO THE LEAD
MID/UPPER-LEVEL SYSTEM WILL DEVELOP FROM N-CNTRL NEB TOWARD THE MN
ARROWHEAD AHEAD OF A RAPIDLY DEEPENING LOW PRESSURE CENTER WHICH
WILL TRACK FROM NERN CO TO CNTRL IA BY 17/12Z. AN ASSOCIATED WARM
FRONT WILL MOVE NWD INTO THE UPPER GREAT LAKES AHEAD OF A
STRENGTHENING COLD FRONT WHICH WILL ADVANCE EWD INTO THE UPPER MS
AND MID/LOWER MO VALLEYS...CNTRL/ERN KS SWD THROUGH THE RED RIVER
VALLEY OF TX/OK.

...LOWER MO VALLEY INTO UPPER MIDWEST LATER TODAY INTO SUNDAY
MORNING...

A 50 KT SWLY LLJ WILL MAINTAIN THE POLEWARD FLUX OF AN INCREASINGLY
MOIST BOUNDARY LAYER THROUGH THE NWD-EXPANDING WARM SECTOR WITH
SURFACE DEWPOINTS RISING THROUGH THE 50S TO PERHAPS AROUND 60 F.
THIS PROCESS WILL OCCUR BENEATH A PLUME OF STEEP MIDLEVEL LAPSE
RATES /REF. 12Z TOP SOUNDING/ WITH MLCAPE VALUES STEADILY INCREASING
TO 500-1000 J/KG TO THE SOUTH OF THE WARM FRONT AFTER 17/00Z.

AN INITIAL RISK FOR ISOLATED SEVERE STORMS MAY MATERIALIZE IN THE
16/21Z-17/03Z TIME FRAME ACROSS SRN IA/NRN MO WHERE SUSTAINED
LOW-LEVEL CONVERGENCE ALONG THE COLD FRONT MAY BE SUFFICIENT TO
INITIATE A STORM OR TWO. SHOULD THIS SCENARIO
UNFOLD...MODEL-DERIVED FORECAST SOUNDINGS SHOW THE PRESENCE OF
FAIRLY SIZABLE CLOCKWISE-CURVED HODOGRAPHS WHICH WILL SUPPORT
SUPERCELL EVOLUTION AND A RISK FOR A TORNADO OR TWO IN ADDITION TO
SOME MARGINALLY SEVERE HAIL AND LOCALLY DAMAGING WINDS.

A SECONDARY THREAT FOR SEVERE STORMS IS EXPECTED TO EVOLVE IN THE
17/09-12Z TIME FRAME AHEAD OF THE RAPIDLY DEEPENING SURFACE LOW OVER
PARTS OF IA INTO NWRN IL AS LARGE-SCALE FORCING FOR ASCENT
STRENGTHENS WITH THE APPROACH OF THE PRIMARY UPPER-LEVEL SYSTEM.
POOR LOW-LEVEL LAPSE RATES OWING TO NOCTURNAL COOLING IN THE
BOUNDARY LAYER CASTS SOME UNCERTAINTY AS TO WHETHER STORMS WILL BE
SURFACE BASED. A MARGINALLY SEVERE HAIL THREAT WILL EXIST EVEN FOR
SLIGHTLY ELEVATED STORMS WITH A GROWING RISK FOR TORNADOES AND
DAMAGING WINDS FROM 17/12Z AND BEYOND AS STORMS BECOME PROGRESSIVELY
ROOTED IN THE BOUNDARY LAYER.

...MID SOUTH INTO OH VALLEY LATE TONIGHT INTO SUNDAY MORNING...

LATEST MODEL GUIDANCE REMAINS CONSISTENT WITH EARLIER RUNS IN
SUGGESTING THE FORMATION OF A SW-NE-ORIENTED CONVECTIVE BAND
SITUATED ALONG THE WRN PERIPHERY OF THE RETREATING EAST COAST
SURFACE ANTICYCLONE...AND ALONG THE AXIS OF THE NOCTURNAL LLJ. THIS
REGIME WILL EVOLVE ALONG THE ERN EDGE OF THE NWD-EXPANDING WARM
SECTOR WITH STORMS LIKELY BEING SLIGHTLY ELEVATED. AS
SUCH...SUB-SLIGHT-RISK PROBABILITIES WILL BE MAINTAINED...THOUGH
MODEL AND OBSERVATIONAL DATA TRENDS WILL BE MONITORED FOR A POSSIBLE
UPGRADE IN SUBSEQUENT DAY 1 OUTLOOKS.

..MEAD/DEAN.. 11/16/2013