Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 301950
SWODY1
SPC AC 301949

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0249 PM CDT SAT APR 30 2016

VALID 302000Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM AR INTO SERN MO AND SRN
IL...

...THERE IS A SLGT RISK OF SVR TSTMS OVER SERN LA...MS...WRN AL...

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE MID MS AND OH VALLEYS
SWD TO THE GULF COAST...

...SUMMARY...
A FEW STRONG TO SEVERE THUNDERSTORMS WITH DAMAGING WINDS AND LARGE
HAIL ARE EXPECTED THROUGH THIS EVENING...PRIMARILY ACROSS THE LOWER
MISSISSIPPI VALLEY...AND FROM PARTS OF ARKANSAS INTO MISSOURI AND
SOUTHWEST ILLINOIS.

THE PREVIOUS FORECAST REMAINS ON TRACK. ONLY A MINOR EXTENSION TO
THE MARGINAL RISK ALONG THE NC/SC BORDER HAS BEEN MADE AS CONDITIONS
CONTINUE TO DESTABILIZE ALONG THE FRONT WITH MARGINALLY SEVERE HAIL
OR WIND POSSIBLE.

..JEWELL.. 04/30/2016

.PREV DISCUSSION... /ISSUED 1128 AM CDT SAT APR 30 2016/

...SYNOPSIS...
THE PRIMARY INITIAL SHORTWAVE TROUGH IS ROTATING NEWD OVER MO THIS
MORNING...AROUND THE ERN PERIPHERY OF THE CLOSED LOW OVER THE KS/NEB
BORDER.  AN ASSOCIATED SURFACE CYCLONE NEAR KANSAS CITY WILL MOVE
SLOWLY EWD AND WEAKEN THROUGH THE PERIOD...WHILE A WARM FRONT
PROGRESSES NWD ACROSS THE LOWER OH VALLEY...AND A COLD FRONT MOVES
SLOWLY EWD ACROSS MO AND SEWD ACROSS TX.

WIDESPREAD CLOUDS/CONVECTION SINCE YESTERDAY HAVE COMPLICATED THE
SITUATION TODAY...LEAVING SUBSTANTIAL UNCERTAINTY FROM THE TN VALLEY
NWD INTO THE LOWER OH VALLEY.  WILL MAINTAIN THE MRGL SEVERE RISK
AND LOW SEVERE PROBABILITIES OVER A BROAD AREA...BUT WILL ATTEMPT TO
FOCUS THE SLGT RISK AREAS WHERE CONFIDENCE IN DESTABILIZATION AND
THE OCCURRENCE OF ADDITIONAL STORMS IS GREATER.

...LOWER MS VALLEY TODAY...
ONGOING CONVECTIVE CLUSTERS IN CENTRAL/S CENTRAL LA ARE EXPECTED TO
PERSIST WHILE SPREADING EWD/NEWD TOWARD SE LA AND CENTRAL/SRN MS.
RICH BOUNDARY LAYER MOISTURE WILL MAINTAIN MODERATE BUOYANCY IN
ADVANCE OF THE CONVECTION...AND DEEP-LAYER VERTICAL SHEAR WILL BE
SUFFICIENT FOR ORGANIZED LINE SEGMENTS/CLUSTERS.  THOUGH LOW-LEVEL
SHEAR IS EXPECTED TO SLOWLY WEAKEN WITH TIME...IT WILL REMAIN
SUFFICIENTLY STRONG TO SUPPORT SOME RISK FOR EMBEDDED CIRCULATIONS
AND PERHAPS A TORNADO OR TWO THIS AFTERNOON.  THE CONVECTION SHOULD
REACH AL LATER THIS AFTERNOON...BUT A SOMEWHAT DRIER BOUNDARY LAYER
AND WEAKER BUOYANCY WITH EWD EXTENT SHOULD RESULT IN SLOW WEAKENING
OF THE STORMS/SEVERE THREAT BY THIS EVENING.

...AR/MO/SRN IL THIS AFTERNOON/EVENING...
WIDESPREAD CLOUDS/RAIN FROM THE LOWER MS VALLEY INTO THE LOWER OH
VALLEY WILL SUBSTANTIALLY LIMIT SURFACE HEATING/DESTABILIZATION FROM
THE MS RIVER EWD...AND N OF THE PRIMARY STORM CLUSTERS ACROSS LA/MS.
HOWEVER...A NARROW CORRIDOR OF SOME CLEARING FROM THE W...AND
LINGERING BOUNDARY LAYER DEWPOINTS AOA 60 F AHEAD OF THE SURFACE
COLD FRONT COULD SUPPORT RENEWED THUNDERSTORM DEVELOPMENT THIS
AFTERNOON.  LARGE-SCALE FORCING FOR ASCENT SHOULD REMAIN WEAK ACROSS
THIS AREA IN THE WAKE OF THE PRIMARY SHORTWAVE TROUGH EXITING TO THE
NE...AND LOW-MIDLEVEL FLOW/SHEAR WILL LIKEWISE WEAKEN.  THUS...THE
PRIMARY CONCERN WITH THIS CONVECTION SHOULD BE ISOLATED LARGE HAIL
FOR A FEW HOURS THIS AFTERNOON/EVENING.

$$



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