DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 092002
SWODY1
SPC AC 092000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT TUE JUL 09 2013

VALID 092000Z - 101200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE CENTRAL
PLAINS EWD INTO THE OHIO VALLEY...

TWO PRIMARY CHANGES HAVE BEEN MADE WITH THIS OUTLOOK.
FIRST...REMOVED SLIGHT RISK ACROSS MUCH OF WI/NERN MN WHERE
STABILIZING INFLUENCE OF MORNING CONVECTION AND WIDESPREAD CLOUD
COVER HAVE MITIGATED AFTERNOON DESTABILIZATION...WITH VALUES
GENERALLY AOB 1000 J/KG OF MLCAPE. AN ISOLATED SVR TSTM CANNOT BE
RULED OUT WHERE MODEST ADDITIONAL DESTABILIZATION IN THE VICINITY OF
SURFACE BOUNDARIES AND 30-40 KTS OF EFFECTIVE BULK SHEAR IS
PRESENT...BUT COVERAGE IS EXPECTED TO BE TOO SPARSE FOR 15 PERCENT
PROBS AND SLIGHT RISK.

THE SECOND SIGNIFICANT CHANGE IS TO EXTEND THE SLIGHT RISK FARTHER
WEST ACROSS PORTIONS OF IOWA WHERE HEATING/DESTABILIZATION HAS
OCCURRED IN ADVANCE OF SURFACE TROUGH/FRONT. SURFACE DEW POINTS IN
THE LOWER TO MID 70S RESIDE BENEATH ERN EDGE OF STEEPER MID-LEVEL
LAPSE RATES...RESULTING IN MLCAPE VALUES BETWEEN 2000 AND 3000 J/KG.
EFFECTIVE SHEARS WOULD BE SUPPORTIVE OF ORGANIZED TSTMS WITH A SVR
WIND AND HAIL THREAT WITH ANY STORM THAT DEVELOPS.

NO OTHER CHANGES WERE MADE TO PREVIOUS OUTLOOK.

..BUNTING.. 07/09/2013

.PREV DISCUSSION... /ISSUED 1129 AM CDT TUE JUL 09 2013/

A LARGE UPPER RIDGE IS PRESENT TODAY OVER THE SOUTHERN AND CENTRAL
UNITED STATES...WHILE A SHORTWAVE TROUGH EMBEDDED IN THE STRONGER
WESTERLIES TRACKS ACROSS THE DAKOTAS/MN. A LARGE MCS ASSOCIATED
WITH THE NORTHERN TROUGH HAS PROGRESSED MUCH FASTER AND FARTHER EAST
THAN FORECAST BY OVERNIGHT MODEL SOLUTIONS. THIS HAS RESULTED IN
SIGNIFICANT FORECAST CHANGES FOR THIS UPDATE...WITH REDUCED SEVERE
PROBABILITIES OVER MUCH OF THE MIDWEST AND MS VALLEY.

...GREAT LAKES INTO MID MS VALLEY...
THE LEADING EDGE OF THE LARGE MCS CURRENTLY EXTENDS FROM WI INTO IL.
THIS ACTIVITY MAY PERSIST EASTWARD ACROSS LAKE MI INTO WESTERN LOWER
MI THIS AFTERNOON WITH A CONTINUED RISK OF LOCALLY SEVERE STORMS.
DAMAGING WINDS APPEAR TO BE THE MAIN THREAT. PERSISTENT CLOUD COVER
OVER EASTERN/NORTHERN LOWER MI AND MUCH OF UPPER MI SHOULD LESSEN
INSTABILITY AND THE RESULTING SEVERE RISK AS STORMS MOVE EASTWARD
THIS EVENING.

...MO/KS...
A TRAILING SURFACE BOUNDARY EXTENDS FROM SOUTHEAST NEB INTO NORTHERN
KS. THIS BOUNDARY SHOULD SETTLE INTO NORTHERN MO BY MID
AFTERNOON...WHEN SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP.
STRONG HEATING IN THIS REGION WILL YIELD STEEP LOW LEVEL LAPSE RATES
AND MODERATE CAPE...OFFSETTING ONLY MARGINAL VERTICAL SHEAR. A FEW
ORGANIZED MULTICELL OR WEAK SUPERCELL STRUCTURES ARE POSSIBLE ALONG
THE BOUNDARY OVER NORTHERN MO AND KS THIS AFTERNOON WITH A RISK OF
DOWNBURSTS OR HAIL IN THE STRONGEST CORES.

...IN/OH/WV/KY...
A MOIST AND QUITE UNSTABLE AIR MASS IS IN PLACE TODAY OVER THE OH
VALLEY...WITH STRONG HEATING OCCURRING OVER MUCH OF THE AREA. 12Z
MODEL SOLUTIONS SHOW SCATTERED THUNDERSTORM DEVELOPMENT THIS
AFTERNOON. PWAT VALUES OF NEAR 2 INCHES COMBINED WITH 25-35 KNOT
WESTERLY MID LEVEL FLOW MAY BE SUFFICIENT FOR ISOLATED SEVERE STORMS
CAPABLE OF DAMAGING WINDS AND HAIL.

...AZ...
LATEST VWP FROM IWA SHOWS 20+ KNOTS OF NORTHEASTERLY MID LEVEL WINDS
OVER SOUTHERN AZ. MEANWHILE...EASTERLY LOW LEVEL WINDS HAVE DRAWN
LOW TO MID 60S DEWPOINTS INTO THE PHX AREA. MOST MODEL SOLUTIONS
SUGGEST THE POTENTIAL FOR SCATTERED THUNDERSTORM DEVELOPMENT OVER
THE HIGHER TERRAIN OF EAST-CENTRAL AND SOUTHEAST AZ LATER TODAY.
STEERING FLOW AND PROPAGATION MIGHT HELP THESE STORMS PERSIST INTO
THE LOWER DESERTS THIS EVENING. ANY STORMS THAT CAN SURVIVE WOULD
HAVE A THREAT OF DAMAGING WINDS.

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