DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0735 AM CDT TUE MAY 07 2013

VALID 071300Z - 081200Z

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

...SYNOPSIS...
STRENGTHENING OF A SUBTROPICAL JET STREAK IS ALREADY EVIDENT IN
SATELLITE LOOPS OVER THE LOWER LATITUDE EASTERN PACIFIC. AND IT
APPEARS THAT A CONTINUED PHASING OF THIS FEATURE WITH AN IMPULSE IN
THE SOUTHERN BRANCH OF A SPLIT MID-LATITUDE PACIFIC JET WILL
CONTRIBUTE TO FURTHER INTENSIFICATION OF MID/UPPER FLOW EAST
NORTHEASTWARD ACROSS BAJA INTO THE NORTHERN MEXICAN PLATEAU LATER
TODAY AND TONIGHT. THIS IS EXPECTED TO CONTRIBUTE TO THE EASTWARD
ACCELERATION OF A CLOSED LOW ACROSS THE SOUTHERN SIERRA NEVADA INTO
THE FOUR CORNERS REGION BY 12Z WEDNESDAY. AS THIS OCCURS...A CLOSED
LOW NEAR THE SOUTHERN APPALACHIANS SHOULD BECOME MORE PROGRESSIVE AS
WELL...GRADUALLY ACCELERATING NORTHEASTWARD INTO THE MID ATLANTIC
COAST STATES.

IN THE WAKE OF THE SOUTHEASTERN CLOSED LOW...MOISTURE RETURN FROM
THE GULF OF MEXICO APPEARS LIKELY TO REMAIN RATHER MODEST...AND
GENERALLY CONFINED TO THE RIO GRANDE VALLEY...PERHAPS NORTHWARD INTO
PARTS OF THE TEXAS SOUTH PLAINS BY LATE TONIGHT. BUT...LOW-LEVEL
WARMING...AND SOME MOISTENING ASSOCIATED WITH
EVAPOTRANSPIRATION...BENEATH STEEPENING MID-LEVEL LAPSE RATES...WILL
CONTRIBUTE TO DESTABILIZATION AND INCREASING POTENTIAL FOR
THUNDERSTORM ACTIVITY ACROSS THE PLAINS TODAY. MEANWHILE...DESPITE
SOME STABILIZATION OF MID-LEVEL LAPSE RATES ACROSS MUCH OF THE
INTERMOUNTAIN WEST COMPARED TO PRIOR DAYS...A GRADUAL MOISTENING OF
LOWER/MID-LEVELS IS EXPECTED TO COMPENSATE...CONTRIBUTING TO ENOUGH
INSTABILITY WITH SURFACE HEATING FOR SCATTERED THUNDERSTORMS...AIDED
BY OROGRAPHIC AND SYNOPTIC FORCING FOR UPWARD VERTICAL MOTION.
SCATTERED THUNDERSTORM ACTIVITY WILL ALSO PERSIST IN ASSOCIATION
WITH THE EASTERN UPPER LOW. ALTHOUGH MOST STORMS PROBABLY WILL
REMAIN RELATIVELY WEAK IN NATURE...THE RISK FOR SEVERE STORMS MAY
NOT BE NEGLIGIBLE...PARTICULARLY ACROSS PARTS OF THE SOUTH CENTRAL
HIGH PLAINS.

...S CNTRL HIGH PLAINS...
ONGOING WEAK THUNDERSTORM ACTIVITY IS EXPECTED TO SPREAD NORTHEAST
OF THE REGION DURING THE DAY...IN ASSOCIATION WITH A WEAK SHORT WAVE
IMPULSE EMERGING FROM THE INTERMOUNTAIN WEST. THIS FEATURE IS
EXPECTED TO EVENTUALLY TURN EASTWARD TOWARD THE MID MISSOURI
VALLEY...AROUND THE SOUTHERN PERIPHERY OF A QUASI-STATIONARY WEAK
MID-LEVEL CYCLONIC CIRCULATION OVER THE DAKOTAS...WHILE SHORT WAVE
RIDGING BUILDS FROM THE SOUTHERN INTO CENTRAL ROCKIES...AHEAD OF THE
UPSTREAM CLOSED LOW.

IN THE WAKE OF THIS INITIAL CONVECTION...STRONG SURFACE HEATING IS
EXPECTED TO CONTRIBUTE TO AN AXIS OF WEAK TO MODERATE
DESTABILIZATION FROM THE TEXAS SOUTH PLAINS THROUGH THE TEXAS/
OKLAHOMA PANHANDLE REGION INTO WESTERN KANSAS. WHILE SURFACE DEW
POINTS MAY NOT BE MUCH HIGHER THAN THE UPPER 40S TO NEAR 50F AT PEAK
LATE AFTERNOON HEATING/MIXING...THIS STILL MAY BE SUFFICIENT FOR
CAPE OF 500-1000+ J/KG...AND SCATTERED STORM DEVELOPMENT.

MODELS SUGGEST A BELT OF 30-40 KT WESTERLY MID-LEVEL FLOW WILL
OVERSPREAD THE INSTABILITY AXIS ACROSS THE PANHANDLE REGION INTO
WESTERN KANSAS...WHERE A MODEST SOUTHERLY 850 MB JET WILL CONTRIBUTE
TO SUFFICIENT VERTICAL SHEAR FOR SUPERCELL STRUCTURES. WITH
THERMODYNAMIC PROFILES CHARACTERIZED BY A DEEPLY MIXED BOUNDARY
LAYER WITH SIZABLE TEMPERATURE/DEW POINT SPREADS...LARGE HAIL AND
DAMAGING WIND GUSTS APPEAR THE PRIMARY SEVERE THREATS WITH
STORMS...WHICH SHOULD PERSIST INTO EARLY EVENING.

ADDITIONAL STORM DEVELOPMENT IS POSSIBLE LATER THIS EVENING INTO THE
OVERNIGHT HOURS...ACROSS THE CENTRAL PLAINS TOWARD THE MIDDLE
MISSOURI VALLEY...SUPPORTED BY FORCING ASSOCIATED WITH ENHANCED WARM
ADVECTION ON THE NOSE OF A STRENGTHENING LOW-LEVEL JET. WEAK
INSTABILITY PROBABLY WILL LIMIT SEVERE POTENTIAL WITH THIS
ACTIVITY...BUT EVAPORATIVE COOLING ASSOCIATED WITH SIZABLE SUB-CLOUD
TEMPERATURE-DEW POINT SPREADS COULD CONTRIBUTE TO DOWNWARD MIXING OF
HIGHER MOMENTUM AIR TO THE SURFACE...AND A FEW STRONG SURFACE GUSTS.

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0404 AM CDT SUN APR 28 2013

VALID 011200Z - 061200Z

...DISCUSSION...
GOOD AGREEMENT EXISTS AMONG LATEST MODEL GUIDANCE SHOWING A SHARP
COLD FRONT SPREADING RAPIDLY ACROSS THE SRN HIGH PLAINS AND OFF THE
TX GULF COAST FROM D4/WED THROUGH D5/THU. AS THE FRONT CONTINUES
EAST TOWARD THE LOWER MS VALLEY...UPPER SYSTEM BEGINS TO FORM A DEEP
CUTOFF LOW OVER THE CNTRL/SRN PLAINS OR OZARK PLATEAU WITH UNUSUALLY
COOL AIR SPREADING ACROSS THESE AREAS THROUGH D6/FRI.

CURRENT INDICATIONS ARE THAT THE COLD FRONT AND DRYLINE SHOULD
PROVIDE SUFFICIENT FOCUS FOR VIGOROUS CONVECTIVE DEVELOPMENT DURING
D4/WED AFTERNOON FROM SWRN OK INTO NWRN TX. PATTERN SHOULD ALSO
SUPPORT MODEST INSTABILITY AND SHEAR ACROSS THESE AREAS THAT WILL
PROVE ADEQUATE FOR SEVERE/ORGANIZED STORMS GIVEN ANTICIPATED
MAGNITUDE OF DYNAMIC FORCING ALONG THE FRONT SPREADING INTO THE
REGION. SITUATION SHOWS SOME SIMILARITIES TO RECENT 17 APRIL SRN
PLAINS EVENT PERHAPS DISPLACED FARTHER SOUTH AND WITH POSSIBLY
WEAKER SHEAR. NONETHELESS...THE POTENTIAL FOR GREATER MOISTURE
ACROSS TX SHOULD FUEL INCREASING CONVECTIVE COVERAGE ALONG AND
BEHIND THE BOUNDARY AS IT SURGES INTO THESE AREAS THROUGH WED NIGHT
AND INTO THU MORNING.

SEVERE POTENTIAL MAY CONTINUE INTO D5/THU ALONG THE ADVANCING FRONT
INTO THE LOWER MS VALLEY BUT STRONGER FORCING APPEARS TO BECOME
INCREASINGLY DISPLACED FROM GREATER POTENTIAL INSTABILITY WITH TIME
AS THE DEEP-LAYER CYCLONE BEGINS TO CUTOFF OVER ERN PORTIONS OF THE
GREAT PLAINS. INCREASING SPREAD IN GUIDANCE IN THE HANDLING OF THE
SLOWLY ADVANCING FRONT ACROSS THE MS/TN VALLEYS THROUGH D6/FRI AND
D7/SAT PRECLUDE ADDING ADDITIONAL OUTLOOK AREAS AT THIS FORECAST
RANGE.

MESOSCALE DISCUSSION 0331
NWS STORM PREDICTION CENTER NORMAN OK
0322 PM CDT FRI MAR 29 2013

AREAS AFFECTED...PORTIONS OF THE TX PANHANDLE/SOUTH PLAINS...NWRN TX
AND SWRN OK

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 292022Z - 292245Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...WIDELY SCTD SVR TSTMS WITH LARGE HAIL AND DAMAGING WINDS
MAY DEVELOP AFTER 2030Z. A WW MAY BE NEEDED PRIOR TO 22Z.

DISCUSSION...FORCING FOR ASCENT ASSOCIATED WITH AN UPPER LEVEL
IMPULSE MOVING INTO W TX WILL OVERSPREAD A MODERATELY UNSTABLE AIR
MASS EAST OF A SHARPENING SFC DRYLINE THROUGH LATE AFTN. BY
22Z...THE DRYLINE SHOULD EXTEND SWD FROM A WEAK SFC LOW OVER THE SRN
TX PANHANDLE S/SWWD INTO THE TRANS-PECOS REGION. LATEST VISIBLE
IMAGERY SUGGESTS SOME INCREASE IN CU FIELD NEAR THE CAPROCK TO THE
SW OF CDS. CONTINUED DAYTIME HEATING AND FORCING FOR ASCENT SHOULD
REDUCE CIN SUFFICIENTLY FOR WIDELY SCTD TSTM DEVELOPMENT AFT 2030Z.
WITH STEEP MID-LEVEL LAPSE RATES /8-8.5 DEG C/KM/ AND DEEP-LAYER
SHEAR OF 35-40 KT...ENVIRONMENT WILL BE FAVORABLE FOR LARGE HAIL AND
DAMAGING WINDS. ONE OR MORE ESEWD-MOVING CLUSTERS OF STORMS MAY
EVENTUALLY DEVELOP OVER TIME INTO EARLY EVENING WITH PRIMARILY A
THREAT FOR DAMAGING WINDS.