Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS02 KWNS 251721
SWODY2
SPC AC 251720

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1220 PM CDT MON MAY 25 2015

VALID 261200Z - 271200Z

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

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL GULF
COAST STATES...TN VALLEY AND OH VALLEY...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF SRN
PLAINS...CNTRL PLAINS...ARKLATEX...LOWER TO MID MS VALLEY...CNTRL
GULF COAST STATES...TN VALLEY...OH VALLEY...SRN AND CNTRL
APPALACHIANS AND LOWER GREAT LAKES...

...SUMMARY...
SEVERE THUNDERSTORMS WITH WIND DAMAGE AND HAIL ARE EXPECTED TO OCCUR
ACROSS PARTS OF THE SOUTHERN PLAINS ON TUESDAY. OTHER SEVERE
THUNDERSTORMS WITH WIND DAMAGE AND HAIL WILL BE POSSIBLE FROM THE
CENTRAL GULF COAST STATES INTO PARTS OF THE TENNESSEE AND OHIO
VALLEYS ON TUESDAY. MARGINALLY SEVERE THUNDERSTORMS WITH STRONG WIND
GUSTS WILL ALSO BE POSSIBLE FROM THE ARKLATEX AND LOWER MISSISSIPPI
VALLEY NORTHWARD INTO THE MID MISSISSIPPI VALLEY AND LOWER GREAT
LAKES.

...SRN PLAINS...
A SHORTWAVE TROUGH IS FORECAST TO MOVE EWD ACROSS THE SRN PLAINS ON
TUESDAY. AT LOW-LEVELS...A MOIST AIRMASS WILL BE IN PLACE ACROSS
MUCH OF TX EXTENDING NWD INTO OK WITH SFC DEWPOINTS IN THE UPPER 60S
AND LOWER 70S F. A DRYLINE SHOULD SHARPEN FROM WRN OK SSWWD ACROSS
WEST TX WITH MODERATE TO STRONG INSTABILITY IN PLACE TO THE EAST OF
THE DRYLINE BY AFTERNOON. DUE TO LIMITED CAPPING...SOME THUNDERSTORM
ACTIVITY COULD DEVELOP DURING THE DAY ALONG THE INSTABILITY AXIS AND
AHEAD OF THE SHORTWAVE TROUGH. CONVECTIVE COVERAGE SHOULD MARKEDLY
INCREASE DURING THE LATE AFTERNOON WITH MODEL FORECASTS SUGGESTING
THUNDERSTORMS WILL INITIATE FROM WCNTRL OK SSWWD ACROSS NCNTRL TX
INTO PARTS OF THE WRN TX HILL COUNTRY WITH SEVERAL CLUSTERS OF
THUNDERSTORMS ORGANIZING AND MOVING EWD ACROSS THE SRN PLAINS DURING
THE LATE AFTERNOON AND EARLY EVENING.

FORECAST SOUNDINGS AT 00Z/WED ALONG THE INSTABILITY AXIS FROM
OKLAHOMA CITY SWWD TO WICHITA FALLS SHOW IMPRESSIVE THERMODYNAMICS
WITH MLCAPE OF 4000 TO 5000 J/KG AND 850 TO 500 MB LAPSE RATES
APPROACHING 8.0 C/KM. THE WIND PROFILE SHOWS DIRECTIONAL SHEAR IN
THE LOW TO MID-LEVELS WITH STRONG SPEED SHEAR ABOVE 500 MB. THIS
ENVIRONMENT SHOULD BE FAVORABLE FOR ORGANIZED SEVERE STORMS AND
POSSIBLY SUPERCELLS WITH LARGE HAIL IF CONVECTION CAN REMAIN
DISCRETE. HOWEVER...A BOW STRUCTURED LINEAR MCS COULD ALSO DEVELOP
WHICH WOULD FAVOR DAMAGING WIND GUSTS AS THE MAIN THREAT. ALTHOUGH
LOW-LEVEL SHEAR IS FORECAST TO REMAIN RELATIVELY WEAK ACROSS THE SRN
PLAINS ON TUESDAY...A COUPLE TORNADOES COULD STILL OCCUR WITH
SUPERCELLS OR WITH THE BETTER ORGANIZED LINE SEGMENTS.

...CNTRL GULF COAST STATES/TN AND OH VALLEYS...
SOUTHWEST FLOW AT MID-LEVELS IS FORECAST ON TUESDAY ACROSS THE OH
AND TN VALLEYS AS A SHORTWAVE TROUGH MOVES NEWD ACROSS THE MID MS
VALLEY. AN MCS COULD BE ONGOING AT THE START OF THE PERIOD ACROSS
PARTS OF THE LOWER TO MID MS VALLEY. TO THE EAST OF THE MORNING
CONVECTION...A MOIST AIRMASS SHOULD ENABLE MODERATE INSTABILITY TO
DEVELOP BY AFTERNOON. MODEL CONSENSUS PLACES THE INSTABILITY AXIS
FROM WRN AL NNEWD INTO ECNTRL TN AND CNTRL KY WHERE SCATTERED STRONG
TO SEVERE THUNDERSTORMS APPEAR LIKELY TO INITIATE DURING THE EARLY
TO MID AFTERNOON.

FORECAST SOUNDINGS AT 21Z FROM BIRMINGHAM AL NNEWD ACROSS ECNTRL TN
INTO CNTRL KY SHOW MLCAPE FROM 1500 TO 2500 J/KG WITH UNIDIRECTIONAL
WIND PROFILES AND SUBSTANTIAL SPEED SHEAR IN THE MID-LEVELS. THIS
ENVIRONMENT COULD BE FAVORABLE FOR ORGANIZED MULTICELL LINE SEGMENTS
WITH WIND DAMAGE POTENTIAL DURING THE AFTERNOON. ALTHOUGH DEEP-LAYER
SHEAR APPEARS MARGINAL FOR SUPERCELLS...AN ISOLATED TORNADO THREAT
CAN NOT BE RULED OUT WITH LINE SEGMENTS THAT CAN DEVELOP BOWING
STRUCTURES.

..BROYLES.. 05/25/2015



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