DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 111956
SWODY1
SPC AC 111954

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT THU JUL 11 2013

VALID 112000Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN HIGH
PLAINS...

A COUPLE CHANGES HAVE BEEN MADE TO THE OUTLOOK AT 20Z. THE FIRST IS
TO REMOVE THE SLIGHT RISK AREA FROM MOST OF ERN WY AND FOR PART OF
FAR SWRN SD. OBJECTIVE ANALYSIS ACROSS ERN WY SHOW MLCAPE VALUES
BELOW 500 J/KG WITH SFC DEWPOINTS DROPPING INTO THE 40S F SUGGESTING
THE SEVERE THREAT WILL REMAIN MARGINAL THERE. THE SECOND CHANGE IS
TO MOVE THE THUNDER LINE ACROSS NW MN A BIT TO THE EAST TO ACCOUNT
FOR OVERNIGHT CONVECTION.

..BROYLES.. 07/11/2013

.PREV DISCUSSION... /ISSUED 1131 AM CDT THU JUL 11 2013/

...NORTHERN PLAINS...
A BROAD UPPER RIDGE CONTINUES TO DOMINATE THE WEATHER OVER MOST OF
THE SOUTHERN AND CENTRAL UNITED STATES...WITH A RIDGE AXIS EXTENDING
NORTHWARD ALONG THE HIGH PLAINS INTO MT/DAKOTAS. A SHORTWAVE TROUGH
SEEN IN WATER VAPOR LOOPS OVER THE PACIFIC NORTHWEST WILL BEGIN TO
TOP THE RIDGE THIS EVENING...HELPING TO INSTIGATE THUNDERSTORM
DEVELOPMENT. MODELS ARE IN STRONG AGREEMENT THAT CONVECTION WILL
FORM BY LATE AFTERNOON ALONG THE WEST EDGE OF DEEPER LOW LEVEL
MOISTURE OVER EASTERN MT/WY AND SPREAD EASTWARD INTO ND/SD DURING
THE EVENING. SUFFICIENT LOW LEVEL AND DEEP LAYER VERTICAL SHEAR
WILL PROMOTE SUPERCELL STORMS CAPABLE OF LARGE HAIL AND DAMAGING
WINDS. RELATIVELY WARM TEMPERATURES ALOFT AND LARGE SCALE RIDGE
AXIS MAY TEND TO LIMIT THE AREAL COVERAGE OF SEVERE STORMS.

...LOWER MS VALLEY...
MORNING VISIBLE SATELLITE AND RADAR LOOPS SHOW ONGOING CONVECTION
OVER SOUTHERN MS. THESE STORMS WILL PROPAGATE SOUTHWESTWARD INTO LA
THIS AFTERNOON. A VERY MOIST AIR MASS /PWAT VALUES APPROACHING 2
INCHES/ COUPLED WITH FULL SUNSHINE AND 15-25 KNOTS OF DEEP-LAYER
STEERING FLOW MAY BE SUFFICIENT FOR A FEW STRONG/SEVERE STORMS. WET
MICROBURSTS ARE THE MAIN THREAT.

...EAST COAST...
A SURFACE COLD FRONT EXTENDS FROM NEAR NYC SOUTHWESTWARD INTO
VA...WESTERN NC...AND EVENTUALLY INTO NORTHERN AL/MS. BROKEN CLOUD
COVER AHEAD OF THE FRONT IS LIMITING DESTABILIZATION.
HOWEVER...AMPLE LOW LEVEL MOISTURE AND AN ARRAY OF REMNANT OUTFLOW
BOUNDARIES MIGHT RESULT IN A FEW STRONG STORMS TODAY WHERE HEATING
IS MAXIMIZED. LOCALLY DAMAGING WINDS WOULD BE THE MAIN THREAT.

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