DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 010507
SWODY1
SPC AC 010505

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1205 AM CDT SAT SEP 01 2012

VALID 011200Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM NERN AR INTO SERN MO AND
EXTREME SWRN IL...

...SYNOPSIS...

REMNANT OF TD ISAAC LOCATED OVER WRN MO IS EMBEDDED WITHIN SYNOPTIC
UPPER RIDGE. WITH WEAK STEERING FLOW ALOFT...THIS FEATURE WILL MOVE
VERY SLOWLY EWD...REACHING SWRN IL BY 12Z SUNDAY. OTHERWISE...THE
SYNOPTIC PATTERN WILL BE CHARACTERIZED BY A MEAN TROUGH IN THE WRN
AND NERN U.S. WITH HIGH PRESSURE DOMINATING FROM THE CNTRL AND SRN
PLAINS THROUGH THE SERN STATES. THE NRN STREAM SHORTWAVE TROUGH NOW
OVER BRITISH COLUMBIA AND PACIFIC NW WILL CONTINUE EWD INTO ALBERTA
AND NRN MT LATER SATURDAY ACCOMPANIED BY A COLD FRONT. VORTICITY
MAXIMA EMBEDDED WITHIN WEAKER SRN STREAM TROUGH WILL SHEAR EWD AS
THEY MOVE INTO A CONFLUENT FLOW REGIME OVER THE GREAT BASIN AREA.

...PORTIONS OF LOWER THROUGH MID MS VALLEY AND WRN TN VALLEY...

REMNANTS OF ISAAC CONTINUE TO WEAKEN AND IS ENTRAINING DRYER AIR
ALOFT INTO ITS SRN FLANK. THIS SUGGESTS THE BEST POTENTIAL FOR SFC
HEATING AND GREATER INSTABILITY MAY DEVELOP FROM AR...SRN MO INTO
WRN TN SATURDAY. A VORT MAX IS FORECAST TO ROTATE AROUND THE SRN
PERIPHERY OF THE UPPER LOW...AND STORMS WILL LIKELY REDEVELOP WITHIN
EVOLVING LOW LEVEL CONVERGENCE BAND FROM PARTS OF AR INTO SERN MO AS
THE BOUNDARY LAYER DESTABILIZES. MODELS MAINTAIN A 40 KT SWLY LLJ
ALONG SERN FLANK OF THE CIRCULATION WHERE 0-2 KM SHEAR /ALTHOUGH
LESS THAN PREVIOUS DAYS/ MAY BE MARGINALLY SUFFICIENT FOR A THREAT
FOR LOW LEVEL MESOCYCLONES AND A COUPLE OF TORNADOES. ISOLATED
STRONG TO DAMAGING GUSTS MAY ALSO OCCUR WITH THE STRONGER
STORMS...ESPECIALLY WHERE SBCAPE SHOULD BE MAXIMIZED FROM CNTRL
THROUGH NERN AR INTO SERN MO.

...INTERMOUNTAIN REGION/EASTERN GREAT DIVIDE...

CORRIDOR OF MODERATE SOUTHWESTERLY MID LEVEL FLOW /35-40 KT/ WILL
EXTEND FROM SOUTHERN CA/DESERT SOUTHWEST TO THE NORTHERN ROCKIES ON
SATURDAY. STORMS WILL LIKELY DEVELOP OVER THE HIGHER TERRAIN
POSSIBLY AIDED BY EWD SHEARING VORT MAX. SOME OF THESE TSTMS MAY BE
CAPABLE OF STRONG GUSTY WINDS AND/OR MARGINAL HAIL.

...AZ...

TSTMS ARE EXPECTED TO BE A BIT MORE PREVALENT ON SATURDAY AS
MOISTURE GRADUALLY INCREASES INTO PARTS OF AZ/LOWER CO RIVER VALLEY
OVER THE NEXT 24-48 HR. THIS INCREASE IN MOISTURE COUPLED WITH A
MODESTLY ENHANCED BELT OF SOUTH-SOUTHWESTERLY FLOW ALOFT MAY ALLOW
FOR A FEW SUSTAINED/STRONGER TSTMS CAPABLE OF WIND AND/OR MARGINAL
HAIL.

...CNTRL/EASTERN MT...

HEIGHT FALLS ARE EXPECTED TO OCCUR OVER THE REGION ESPECIALLY INTO
SATURDAY AFTERNOON/NIGHT IN ASSOCIATION WITH THE PROGRESSIVE
SHORTWAVE TROUGH. ISOLATED TSTMS MAY DEVELOP OVER THE HIGHER TERRAIN
AHEAD OF THE FRONT AND SHIFT NEWD THROUGH CNTRL AND ERN MT. IN SPITE
OF STEEP LAPSE RATES/INCREASING VERTICAL SHEAR...THE PRIMARY
LIMITATION WILL BE LIMITED MOISTURE/BUOYANCY...ALTHOUGH A DEEPLY
MIXED BOUNDARY LAYER MAY CONTRIBUTE TO GUSTY WINDS WHERE TSTMS
DEVELOP SATURDAY AFTERNOON/EARLY EVENING.

..DIAL/MOSIER.. 09/01/2012

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