DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 291230
SWODY1
SPC AC 291228

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0728 AM CDT FRI MAR 29 2013

VALID 291300Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
PARTS OF THE SOUTHERN HIGH PLAINS...

...SYNOPSIS...
UPPER FLOW WILL REMAIN SPLIT ACROSS THE CENTRAL AND EASTERN PACIFIC
INTO THE U.S. THROUGH THIS FORECAST PERIOD AND BEYOND...AS BLOCKING
BECOMES INCREASINGLY PROMINENT WEST OF THE PACIFIC COAST.
DOWNSTREAM OF THE CLOSED LOW PORTION OF THE BLOCK...WITHIN THE
SOUTHERN STREAM...BROAD RIDGING...CURRENTLY EXTENDING FROM THE
PACIFIC COAST STATES INTO THE PLAINS...DOES APPEAR LIKELY TO BECOME
INCREASINGLY SUPPRESSED. MODELS SUGGEST THAT THIS WILL OCCUR IN
RESPONSE TO THE EASTWARD PROGRESSION OF A SOUTHERN STREAM SHORT WAVE
IMPULSE THROUGH THE RIDGE...ACROSS THE SOUTHERN ROCKIES INTO THE
SOUTHERN HIGH PLAINS...AND THE FIRST COUPLE IN A SERIES OF SHORT
WAVE IMPULSES DIGGING WITHIN AN INCREASINGLY PROMINENT NORTHERN
STREAM...ACROSS WESTERN/CENTRAL CANADA INTO THE NORTH-CENTRAL UNITED
STATES.

UPPER DEVELOPMENTS...IN CONJUNCTION WITH A CONTINUING WEAK TO MODEST
RETURN FLOW OF MOISTURE FROM THE WESTERN GULF OF MEXICO INTO THE
SOUTHERN AND CENTRAL PLAINS...WHERE MID-LEVEL LAPSE RATES HAVE
BECOME QUITE STEEP...ARE EXPECTED TO SUPPORT AN INCREASING RISK FOR
THUNDERSTORMS LATER TODAY INTO TONIGHT. SOME OF THIS ACTIVITY COULD
BECOME SEVERE...MAINLY ACROSS PARTS OF THE SOUTHERN HIGH PLAINS.

...CENTRAL/SOUTHERN PLAINS...
WEAK CONVECTIVE DEVELOPMENT IS ONGOING ACROSS PARTS OF SOUTHEAST
KANSAS AND EASTERN OKLAHOMA INTO THE OZARK PLATEAU. THIS IS
ASSOCIATED WITH MOISTURE RETURN WITHIN A LOWER/MID TROPOSPHERIC WARM
ADVECTION REGIME...ABOVE A RESIDUAL COOL AND STABLE BOUNDARY
LAYER...ON THE NORTHEASTERN PERIPHERY OF MORE STRONGLY CAPPING
ELEVATED MIXED LAYER AIR WHICH HAS ADVECTED EAST OF THE SOUTHERN
ROCKIES. THIS ACTIVITY MAY PERSIST UNTIL WESTERLY 850 MB FLOW
ACROSS THE SOUTHERN PLAINS BEGINS TO BACK TO A MORE SOUTHERLY
COMPONENT TOWARD MID DAY...AHEAD OF THE APPROACHING SHORT WAVE
IMPULSE.

IN THE MEANTIME...STRONG SURFACE HEATING ACROSS THE SOUTHERN HIGH
PLAINS WILL CONTRIBUTE TO STEEPENING LOW-LEVEL LAPSE RATES...A
SHARPENING DRY LINE ACROSS THE TEXAS PANHANDLE AND SOUTH
PLAINS...AND A STRENGTHENING BAROCLINIC ZONE ACROSS THE TEXAS
PANHANDLE INTO THE RED RIVER VALLEY BY LATE THIS AFTERNOON. THESE
FEATURES...PARTICULARLY NEAR THEIR INTERSECTION ACROSS THE TEXAS
PANHANDLE/NORTHWEST TEXAS...SEEM LIKELY TO PROVIDE THE FOCUS FOR
STRONGEST CONVECTIVE DEVELOPMENT...IN THE PRESENCE OF MIXED LAYER
CAPE ON THE ORDER OF 1000-1500 J/KG.

GIVEN THE FAVORABLE THERMODYNAMIC ENVIRONMENT...VEERING OF WINDS
WITH HEIGHT BENEATH MODEST WESTERLY MID/UPPER FLOW SHOULD PROVIDE
SUFFICIENT SHEAR FOR SEVERE STORMS...INCLUDING SUPERCELLS...CAPABLE
OF PRODUCING LARGE HAIL AND LOCALLY DAMAGING WIND GUSTS. IT APPEARS
POSSIBLE THAT FORCING ASSOCIATED WITH THE MID-LEVEL IMPULSE COULD
CONTRIBUTE TO A CONSOLIDATING STORM CLUSTER ALONG THE FRONTAL ZONE
ACROSS PARTS OF SOUTHWESTERN OKLAHOMA AND NORTHWEST TEXAS DURING THE
EVENING HOURS...WITH PERHAPS A WINDOW OF OPPORTUNITY FOR MORE
WIDESPREAD STRONG/SEVERE GUSTS...BEFORE POTENTIAL DIMINISHES WITH
BOUNDARY LAYER COOLING.

..KERR/LEITMAN.. 03/29/2013

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