Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 230556
SWODY1
SPC AC 230555

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT SAT MAY 23 2015

VALID 231200Z - 241200Z

...THERE IS A SLGT RISK OF SVR TSTMS TODAY THROUGH TONIGHT FROM THE
SOUTHERN PLAINS TO THE CENTRAL HIGH PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT RISK AREA
FROM NORTHERN CO...SERN WY AND SWRN NEB TO THE SOUTHERN PLAINS...

...SUMMARY...
ISOLATED TO SCATTERED SEVERE STORMS WITH LARGE
HAIL...TORNADOES...AND DAMAGING WINDS ARE POSSIBLE FROM THE CENTRAL
HIGH PLAINS TO SOUTHWEST TEXAS THIS AFTERNOON AND EVENING.  THE REST
OF THE CENTRAL AND SOUTHERN GREAT PLAINS...SOUTHWARD FROM SOUTHERN
KANSAS...WILL HAVE A POTENTIAL FOR ISOLATED TO SCATTERED SEVERE
STORMS WITH THE POTENTIAL FOR DAMAGING WINDS AND SOME TORNADO
THREAT.

...SYNOPSIS...
A DEEP WRN U.S. LONGWAVE TROUGH WILL BE MAINTAINED THIS FORECAST
PERIOD AS A CLOSED LOW MOVES FROM THE FOUR CORNERS REGION TOWARD ERN
WY AND THE NEXT UPSTREAM SHORTWAVE TROUGH DIGS SOUTH ACROSS CA
TOWARD THE LOWER CO RIVER VALLEY.  THE EQUATORWARD EXTENDING
TROUGH...ATTENDANT TO THE FOUR CORNERS CLOSED LOW...WILL ADVANCE
EAST THROUGH THE SWRN STATES AND NRN MEXICO...RESULTING IN A LARGE
AREA OF HEIGHT FALLS FROM CO/NM INTO THE CENTRAL/SRN PLAINS.
MEANWHILE...DOWNSTREAM HEIGHT RISES ARE EXPECTED FROM THE SOUTHEAST
STATES TO THE GREAT LAKES AS AN UPPER RIDGE BECOMES ANCHORED FROM
THE ERN GULF OF MEXICO TO OFF THE SRN ATLANTIC COAST AND THE
BAHAMAS.  THE EVOLUTION IN THE UPPER FLOW PATTERN WILL RESULT IN
DEEP-LAYER MERIDIONAL FLOW DEVELOPING ACROSS THE GREAT PLAINS BY
TONIGHT.

AT THE SURFACE...A LEE LOW WILL DEEPEN TODAY ACROSS SOUTHEAST
CO...AND THEN TRACK NORTH TOWARD THE NEB PANHANDLE TONIGHT.  A DRY
LINE WILL EXTEND SWD FROM THIS LOW THROUGH FAR WEST TX TO THE ERN
PART OF THE TRANSPECOS REGION IN SOUTHWEST TX THIS AFTERNOON...WHILE
A WARM FRONT ADVANCES NORTH ACROSS OK THIS AFTERNOON AND THROUGH KS
TONIGHT.  THE ERN PORTION OF THE WARM FRONT SHOULD REACH SWRN AR BY
LATER THIS AFTERNOON...AND THEN SHOULD BE DRAPED SEWD ACROSS THE
OZARK PLATEAU TO NRN MS BY 12Z SUNDAY.

...CENTRAL HIGH PLAINS AND SOUTHERN PLAINS...
SEVERAL EMBEDDED IMPULSES WILL TRANSLATE NEWD FROM THE BASE OF THE
WRN U.S. TROUGH AND MEXICO ACROSS THE SRN AND CENTRAL PLAINS
RESULTING IN SEVERAL ROUNDS OF TSTMS WITH EMBEDDED SEVERE STORMS.
CONFIDENCE IS GREATEST FOR A SEVERE STORM POTENTIAL IN VICINITY OF
THE DRY LINE AND NWD INTO ERN CO...WHILE ELSEWHERE ACROSS THE SLIGHT
RISK CONFIDENCE IN OVERALL SEVERE THREAT COVERAGE IS LOWER THIS
FORECAST PERIOD.

SLY LOW-LEVEL WINDS WILL MAINTAIN POLEWARD MOISTURE RETURN ACROSS
THE WARM SECTOR AND INTO THE CENTRAL HIGH PLAINS WHERE LOW-LEVEL
WINDS WILL BE MORE SELY INTO ERN CO TO THE NORTH OF THE DEEPENING
SERN CO SURFACE LOW.  STRONGEST SURFACE HEATING AND STEEPEST LAPSE
RATES TODAY ARE EXPECTED TO BE NEAR AND WEST OF THE DRY LINE AND NWD
ACROSS THE CENTRAL HIGH PLAINS.  IN THESE LOCATIONS...MODERATE
INSTABILITY AND STRONG EFFECTIVE BULK SHEAR OF 40-55 KT SUGGEST
PORTIONS OF THE CENTRAL AND SRN HIGH PLAINS WILL HAVE THE GREATEST
RISK FOR DISCRETE SUPERCELLS WITH ALL SEVERE HAZARDS POSSIBLE.
ALTHOUGH DESTABILIZATION INTO NERN CO MAY BE WEAKER THAN LOCATIONS
FARTHER SWD...CONFIDENCE IN STRONGER FORCING FOR ASCENT AND
SUBSEQUENT STORM DEVELOPMENT EXISTS IN THIS AREA AS THE FOUR CORNERS
LOW TRACKS NEWD.

EAST OF THE HIGH PLAINS...THE LIKELIHOOD FOR LIMITED SURFACE HEATING
EXISTS DUE TO CLOUD COVER.  DESPITE THIS FACTOR AND THE PRESENCE OF
WEAK LAPSE RATES...POCKETS OF MODERATE INSTABILITY WILL BE POSSIBLE.
TSTMS...SOME POSSIBLY STRONG TO SEVERE...WILL BE ONGOING AT 12Z
TODAY ACROSS THE OK/TX PANHANDLES SWD THROUGH WEST TX AND POSSIBLY
INTO FAR WRN OK.  MODELS SUGGEST NEW TSTM DEVELOPMENT WILL BE
POSSIBLE ALONG THE ERN EXTENT OF THIS COMPLEX AS IT SPREADS EWD THIS
MORNING INTO THE AFTERNOON.  ADDITIONAL STORM DEVELOPMENT WILL BE
POSSIBLE ACROSS THE REMAINDER OF THE SRN PLAINS INTO KS AND ACROSS
THE HIGHER TERRAIN OF FAR WEST TX AS FORCING FOR ASCENT SPREAD
ACROSS THIS REGION.  WEAK LAPSE RATES SHOULD LIMIT THE HAIL THREAT
EAST OF THE HIGH PLAINS...WHILE VERTICALLY VEERING WIND PROFILES AND
EFFECTIVE BULK SHEAR OF 30-35 KT FAVORS MIXED MODES WITH A THREAT
FOR DAMAGING WINDS AND ISOLATED TORNADOES.  SEVERE THREAT COULD
LINGER WELL INTO THE OVERNIGHT HOURS AS THE UPPER TROUGH/FORCING
SHIFT EAST.

..PETERS/PICCA.. 05/23/2015



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