DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 242001
SWODY1
SPC AC 241959

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SAT AUG 24 2013

VALID 242000Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN ND AND NRN
MN...

THE ONLY CHANGE TO THE OUTLOOK FOR THIS ISSUANCE IS TO TRIM THE WRN
EDGE OF THE SLIGHT RISK AREA. THE SLIGHT RISK AREA IS NOW LOCATED
ALONG AND EAST OF THE ONGOING CONVECTION IN NERN ND. A FEW STORMS
COULD DEVELOP ACROSS NCNTRL ND BUT WEAK INSTABILITY SHOULD KEEP ANY
SEVERE THREAT MARGINAL JUST EAST OF THE MINOT VICINITY.

..BROYLES.. 08/24/2013

.PREV DISCUSSION... /ISSUED 1130 AM CDT SAT AUG 24 2013/

...SYNOPSIS...
A LARGE-SCALE UPPER RIDGE WILL ENCOMPASS MOST OF THE CONUS
TODAY...WITH UPPER DISTURBANCES ROTATING ALONG IT/S PERIPHERY ACROSS
THE INTERMOUNTAIN WEST AND NRN PLAINS. ONE SUCH UPPER WAVE WAS
LOCATED OVER PARTS OF WY/MT THIS MORNING...AND WILL CONTINUE
PROGRESSING NEWD ACROSS THE NRN PLAINS. AN ASSOCIATED COLD FRONT
WILL SPREAD EWD ACROSS ND AND MN...PROVIDING THE FOCUS FOR
CONVECTION THIS AFTERNOON AND EVENING. MEANWHILE...SEASONABLY RICH
MONSOONAL MOISTURE HAS ADVECTED NWD INTO THE SOUTHWEST AHEAD OF
TROPICAL STORM IVO...AND WILL SUPPORT SCATTERED TO WIDESPREAD
CONVECTION TODAY OVER AZ AND SERN CA.

...NRN PLAINS AND UPPER GREAT LAKES...
A SHORTWAVE UPPER TROUGH IS ADVANCING NNEWD ACROSS ERN WY AND ERN MT
THIS MORNING...WITH ELEVATED CONVECTION NOTED OVER WRN ND. A SFC
COLD FRONT IS FORECAST TO ACCELERATE EWD OUT OF WRN ND THIS
AFTERNOON. ALTHOUGH A WEAK CAPPING INVERSION WAS NOTED AROUND 1.5 KM
AGL IN THE 12Z BIS SOUNDING...STRENGTHENING FRONTAL CONVERGENCE AND
INCREASING FORCING FOR ASCENT ATTENDANT TO THE SHORTWAVE UPPER
TROUGH SHOULD BE SUFFICIENT FOR SFC-BASED CONVECTION BY
MID-AFTERNOON ACROSS CNTRL/ERN ND...PERHAPS EVOLVING OUT OF THE
ELEVATED WRN ND TSTM CLUSTER.

CLOUD COVER ASSOCIATED WITH ANOTHER AREA OF DECAYING ELEVATED
CONVECTION WILL LIKELY PERSIST ACROSS N-CNTRL ND...WITH THE
STRONGEST HEATING LIKELY TO OCCUR S AND E OF THIS AREA...WHERE
MLCAPE VALUES OF 3000-4000 J/KG WILL BE POSSIBLE LATER THIS
AFTERNOON GIVEN STEEP MIDLEVEL LAPSE RATES AND RICH BOUNDARY LAYER
MOISTURE. EVOLUTION INTO AN ORGANIZED LINE SHOULD EVENTUALLY
OCCUR...WITH PRIMARY THREATS OF DMGG WINDS AND LARGE HAIL...WHICH
COULD PERSIST INTO THE LATE EVENING OVER NWRN MN.

ADDITIONAL TSTMS MAY EVOLVE OUT OF SRN CANADA AND MOVE SEWD ACROSS
PORTIONS OF NERN MN AND THE U.P. OF MICHIGAN LATER THIS EVENING.
THIS AREA WILL BE POSITIONED ALONG THE PERIPHERY OF AN EML
PLUME...WHICH MAY SUPPORT ISOLATED INSTANCES OF LARGE HAIL AND A FEW
SVR WIND GUSTS.

...SERN ID...SWRN MT...
A WEAK SHORTWAVE UPPER TROUGH PROGRESSING ACROSS THE WRN GREAT BASIN
WILL CONTRIBUTE TO INCREASING TSTM COVERAGE THIS AFTERNOON ACROSS
PARTS OF ID AND SWRN MT. RELATIVELY RICH MOISTURE /PW AOA 0.8 INCH/
AND STRONG DAYTIME HEATING WILL YIELD MLCAPE VALES RANGING FROM
500-1500 J/KG THIS AFTERNOON. STEEPENING LOW-LEVEL LAPSE RATES AND
MIDLEVEL FLOW OF 20-30 KTS COULD SUPPORT AN ENHANCED RISK FOR
STRONG-SVR WIND GUSTS.

...AZ...SERN CA...
A PLUME OF RICH MONSOONAL MOISTURE HAS RESULTED IN PW VALUES
EXCEEDING 1.5 INCHES ACROSS MUCH OF AZ AND SERN CA. TSTM COVERAGE
SHOULD INCREASE THROUGHOUT THE AFTERNOON AND EVENING AS MLCAPE
VALUES OF 500-1000 J/KG BECOME COMMON. ALTHOUGH DEEP-LAYER SHEAR
WILL BE WEAK...STEEP LOW-LEVEL LAPSE RATES COULD SUPPORT A FEW
STRONG WIND GUSTS. HOWEVER...HEAVY RAIN WILL LIKELY BE THE PRIMARY
THREAT.

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