Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS02 KWNS 291731
SWODY2
SPC AC 291730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT FRI MAY 29 2015

VALID 301200Z - 311200Z

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE SOUTHERN HIGH PLAINS
TO THE OH VALLEY AND NORTHEAST STATES...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PORTIONS OF MT...

...SUMMARY...
SCATTERED THUNDERSTORMS...SOME STRONG TO POSSIBLY SEVERE WITH GUSTY
WINDS AND HAIL...WILL DEVELOP NEAR AND AHEAD OF A COLD FRONT FROM
PARTS OF THE NORTHEAST STATES AND MIDWEST TO TEXAS ON SATURDAY.
ADDITIONALLY...A FEW STRONG TO POSSIBLY SEVERE STORMS ARE EXPECTED
ACROSS PARTS OF NEW MEXICO...AND IN CENTRAL AND EASTERN MONTANA
SATURDAY AFTERNOON AND EVENING.

...SYNOPSIS...
AS PART OF A STRONGER BELT OF LOW-AMPLITUDE WESTERLIES OVER THE
NORTHERN TIER OF THE U.S. INTO CANADA...AN UPPER TROUGH WILL
PROGRESS EASTWARD FROM ONTARIO THROUGH QUEBEC ON SATURDAY.  MODELS
CONTINUE TO SHOW CONSIDERABLY WEAKER WESTERLIES OVER THE SOUTHERN
TWO-THIRDS OF THE U.S. WITH A WEAK UPPER TROUGH SLOWLY OVERSPREADING
THE MIDWEST/LOWER OH VALLEY AND TOWARD THE LOWER MS RIVER VALLEY.
SHOWERS/TSTMS INCLUDING AT LEAST SOME RISK FOR SEVERE TSTMS WILL
EXIST ALONG/AHEAD OF A SOUTHEASTWARD-MOVING COLD FRONT THAT SHOULD
EXTEND FROM SOUTHERN PORTIONS OF ONTARIO/QUEBEC SOUTHWESTWARD INTO
IL/INDIANA...AND THEN THROUGH AR TO EAST/SOUTH-CENTRAL TX BY
SATURDAY AFTERNOON.

...NORTHEAST STATES TO MIDWEST/OH VALLEY...
THE GREATEST HEIGHT FALLS/STRONGEST FORCING FOR ASCENT WITH THE
ONTARIO/QUEBEC TROUGH SHOULD REMAIN PRIMARILY NORTH OF THE
INTERNATIONAL BORDER ON SATURDAY...WITH WEAK HEIGHT FALLS
OVERSPREADING THE NORTHEAST U.S. SATURDAY NIGHT.  THERE REMAINS
SUFFICIENT UNCERTAINTY WITH THE OVERALL DEGREE OF PEAK
DESTABILIZATION EXPECTED ACROSS THE WARM SECTOR SATURDAY AFTERNOON.
THIS IS DUE IN PART TO THE PRESENCE OF WEAK MIDLEVEL LAPSE RATES AND
THE POTENTIAL FOR ONGOING SHOWERS/TSTMS AND ASSOCIATED CLOUD COVER
NEAR AND SOUTH OF THE COLD FRONT SATURDAY MORNING.
HOWEVER...CORRIDORS OF STRONGER HEATING AND RELATED MODEST BUOYANCY
SHOULD ALLOW FOR THE DEVELOPMENT/INTENSIFICATION OF MOSTLY
MULTICELLS AND LINE SEGMENTS DURING THE AFTERNOON AHEAD OF THE COLD
FRONT.  ISOLATED DAMAGING WINDS SHOULD BE THE PRIMARY HAZARD...WITH
SOME MARGINALLY SEVERE HAIL ALSO POSSIBLE.

...MID-SOUTH TO EAST AND SOUTH TX...
LARGER-SCALE INFLUENCES/VERTICAL SHEAR WILL BE WEAK OVER THIS REGION
ON SATURDAY...BUT SOME STRONG TO SEVERE PULSE-TYPE THUNDERSTORMS
CAPABLE OF HAIL/WIND MAY BE POSSIBLE WITHIN A MOIST/MODERATELY
UNSTABLE ENVIRONMENT NEAR THE SOUTHEASTWARD-MOVING FRONT SATURDAY
AFTERNOON/EARLY EVENING.

...NM AND FAR SOUTHWEST TX...
A FEW STRONG TO SEVERE TSTMS COULD OCCUR ACROSS FAR SOUTHWEST TX
AND/OR CENTRAL/EAST NM COINCIDENT WITH INCREASING POST-FRONTAL
MOISTURE AND WEAK UPSLOPE FLOW.  VERTICAL SHEAR WILL TEND TO BE
30-35 KT SUGGESTING STORM ORGANIZATION WOULD FAVOR A SEVERE THREAT
WITH THE STRONGER STORMS.

...MT...
A LOW-AMPLITUDE SHORTWAVE TROUGH IS EXPECTED TO MOVE EASTWARD NEAR
THE CREST OF THE CENTRAL/SOUTHERN ROCKIES UPPER RIDGE.  TSTMS
SHOULD INITIALLY DEVELOP OVER THE MOUNTAINS/HIGHER TERRAIN OF
WEST-CENTRAL MT SATURDAY AFTERNOON...AND SUBSEQUENTLY DEVELOP
EASTWARD INTO ADDITIONAL PORTIONS OF CENTRAL/EASTERN MT THROUGH THE
LATE AFTERNOON AND EVENING HOURS. ADEQUATE MOISTURE/MARGINAL
BUOYANCY MAY ALLOW FOR SOME STRONGER/POSSIBLY SEVERE THUNDERSTORMS
CAPABLE OF STRONGER WINDS AND/OR ISOLATED HAIL SATURDAY
AFTERNOON/EVENING.

..PETERS.. 05/29/2015



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