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DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1231 AM CDT FRI MAY 18 2012

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CENTRAL AND
SRN PLAINS...

...CENTRAL AND SRN PLAINS...

WEAK HEIGHT FALLS WILL OVERSPREAD THE CNTRL PLAINS DURING THE DAY2
PERIOD AS A SHORT-WAVE TROUGH EJECTS FROM CO/NM INTO NEB/KS/WRN OK
BY 20/00Z.  AS THIS FEATURE SHIFTS EAST SFC PRESSURE WILL RISE IN
THE LEE OF THE NRN/CNTRL ROCKIES FORCING A COLD FRONT TO A POSITION
FROM NRN MN...SWWD ACROSS SERN NEB INTO THE TX PANHANDLE BY PEAK
HEATING.  VERY WARM EML WILL BE IN PLACE ACROSS THE SLGT RISK REGION
EARLY SATURDAY WHICH WILL LIMIT PRE-FRONTAL CONVECTION WITHIN THE
ELONGATED WARM ADVECTION ZONE AHEAD OF THE COLD FRONT.  GIVEN THE
STRENGTH OF THE CAP IT APPEARS SFC TEMPERATURES WILL NEED TO WARM
SIGNIFICANTLY FOR CONVECTIVE DEVELOPMENT...ESPECIALLY SOUTH OF I-70.
EVEN SO...BOTH THE NAM AND GFS SUGGEST INTENSE BOUNDARY LAYER
HEATING WILL OCCUR AHEAD OF THE FRONT ACROSS KS/NWRN OK/TX
PANHANDLE.  THIS WILL WEAKEN THE CAP AND COMBINED WITH FRONTAL
CONVERGENCE SHOULD PROVE ADEQUATE FOR TSTMS TO DEVELOP ALONG/JUST
BEHIND THE ADVANCING WIND SHIFT TOWARD EARLY EVENING.  FORECAST
SOUNDINGS SUGGEST AMPLE DEEP LAYER SHEAR FOR ORGANIZED MULTI-CELL
UPDRAFTS AND PERHAPS EVEN A FEW SUPERCELLS.  LATEST DATA ALSO
SUGGESTS A CONCENTRATION OF POST-FRONTAL CONVECTION MAY BE NOTED DUE
TO THE AFOREMENTIONED STRONG WARM SECTOR CAP.  SOUNDINGS SUPPORT
CONVECTION IMMEDIATELY BEHIND THE FRONT EXTENDING TO THE CANADIAN
BORDER WHERE WEAKER INSTABILITY SHOULD LIMIT SEVERE THREAT SOMEWHAT.
GIVEN THE STEEPEST LAPSE RATES AND STRONGER INSTABILITY MAY BE
RESERVED TO THE CNTRL/SRN PLAINS IT APPEARS THE HIGHER PROBABILITIES
FOR SEVERE HAIL AND DAMAGING WINDS WILL BE NOTED ACROSS THESE AREAS.
WARM ADVECTION DURING THE OVERNIGHT HOURS SHOULD ENHANCE THE
LONGEVITY OF THIS CONVECTION AS IT SHIFTS SLOWLY EAST IN ASSOCIATION
WITH THE FRONTAL ZONE.


...ELSEWHERE...

SLOW-MOVING UPPER TROUGH/LOW WILL BE NOTED ALONG THE MIDDLE
ATLANTIC/SERN U.S. COAST.  WITH SFC RIDGING EXPECTED TO REMAIN
FIRMLY ENTRENCHED ALONG THE APPALACHIANS IT APPEARS THE GREATEST
CONCENTRATION OF CONVECTION WILL OCCUR NEAR THE NC COAST AND ACROSS
THE FL PENINSULA.  VERY ISOLATED TSTMS MAY ALSO DEVELOP DURING THE
HEAT OF THE DAY ACROSS PARTS OF THE TN VALLEY AND CNTRL GULF STATES
BUT WITH LIMITED FORCING AND THE LACK OF MEANINGFUL LOW LEVEL
CONVERGENCE THIS WILL PROVE QUITE SPARSE AND LIKELY WEAK.

..DARROW.. 05/18/2012

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1221 AM CDT FRI MAY 18 2012

VALID 181200Z - 191200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
SHORT WAVE TROUGHS...WITHIN A COUPLE OF DISTINCT BRANCHES OF FLOW
OVER WESTERN NORTH AMERICA...APPEAR LIKELY TO PROGRESS EAST OF THE
CANADIAN ROCKIES...AND ACROSS THE INTERMOUNTAIN WEST AND U.S.
ROCKIES DURING THIS FORECAST PERIOD...BUT WITH LITTLE...IF ANY...
PHASING.  AS THIS OCCURS...MODERATE SOUTHERLY LOW-LEVEL FLOW SHOULD
PERSIST THROUGH MUCH OF THE PLAINS...EAST OF THE LEE SURFACE
TROUGH...WHICH IS EXPECTED TO CONTINUE TO GRADUALLY BE OVERTAKEN BY
A SURFACE FRONT ADVANCING EAST OF THE ROCKIES THROUGH MUCH OF THE
NORTHERN AND CENTRAL HIGH PLAINS BY 12Z SATURDAY.  MODELS DO
INDICATE AT LEAST POCKETS OF BOUNDARY LAYER MOISTENING TODAY ACROSS
PARTS OF THE NORTHERN AND CENTRAL PLAINS INTO THE MISSISSIPPI
VALLEY...AND THE LOWER OHIO VALLEY...ASSOCIATED WITH NORTHWARD
MOISTURE ADVECTION AND EVAPOTRANSPIRATION.  HOWEVER...RETURN FLOW OF
MORE SUBSTANTIVE MOISTURE FROM THE GULF OF MEXICO STILL APPEARS
UNLIKELY TO DEVELOP...AS BROAD UPPER TROUGHING PERSISTS ACROSS MUCH
OF THE GULF STATES AND GULF OF MEXICO INTO THE WESTERN ATLANTIC.  AN
EMBEDDED ELONGATED CIRCULATION WILL PROBABLY CONTINUE TO SLOWLY
SHIFT EAST NORTHEASTWARD OFF SOUTHERN MID ATLANTIC COASTAL AREAS. 
AS THIS OCCURS...WHILE AT LEAST LOW PROBABILITIES FOR THUNDERSTORMS
WILL CONTINUE ACROSS MUCH OF THE SOUTHEAST...CONVECTIVE POTENTIAL IS
EXPECTED TO BE DIMINISHED COMPARED TO PREVIOUS DAYS.

...GREAT BASIN/CENTRAL ROCKIES INTO CNTRL/NRN PLAINS...
DESPITE CONTINUING LOW MOISTURE LEVELS...INSTABILITY ASSOCIATED WITH
STEEP LAPSE RATES...IN CONJUNCTION WITH OROGRAPHIC AND LARGE-SCALE
FORCING FOR UPWARD VERTICAL MOTION...SHOULD BE SUFFICIENT TO SUPPORT
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS.  WHILE THE RISK FOR
LOCALLY STRONG WIND GUSTS... PERHAPS SOME HAIL...MAY NOT BE
COMPLETELY NEGLIGIBLE IN MOST AREAS...CONDITIONS SUPPORTIVE OF
DELINEATION OF LOWER THRESHOLD SEVERE PROBABILITIES APPEAR TO BE
CONFINED TO PORTIONS OF THE CENTRAL/EASTERN DAKOTAS.  THIS IS WHERE
COUPLING OF SOMEWHAT HIGHER BOUNDARY LAYER MOISTURE AND STRONGER
SURFACE HEATING MAY YIELD MIXED LAYER CAPE OF 1000-2000+ J/KG BY
LATE AFTERNOON...TO THE NORTH OF A PLUME OF VERY WARM AND MORE
STRONGLY CAPPING ELEVATED MIXED LAYER AIR ADVECTING NORTHEASTWARD
FROM THE CENTRAL/SOUTHERN HIGH PLAINS.

SOUTHWESTERLY DEEP LAYER MEAN WIND FIELDS ARE EXPECTED TO REMAIN
RATHER WEAK...WITH ONLY WEAK TO MODERATE SHEAR.  BUT MODELS ARE
SUGGESTIVE THAT AN AREA OF STRENGTHENING LARGE-SCALE ASCENT
ASSOCIATED WITH LOWER/MID TROPOSPHERIC WARM ADVECTION BENEATH
DIVERGENT UPPER FLOW COULD SUPPORT CONVECTIVE DEVELOPMENT ACROSS
PARTS OF CENTRAL/EASTERN NORTH DAKOTA BY LATE AFTERNOON.  A
SECONDARY AREA OF STRONGER FORCING FOR UPWARD VERTICAL MOTION MAY
DEVELOP FARTHER TO THE SOUTH...ACROSS SOUTH DAKOTA...LATER THIS
EVENING...WITH THE CONTINUED APPROACH OF THE UPSTREAM IMPULSES.

..KERR/ROGERS.. 05/18/2012