Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS03 KWNS 210831
SWODY3
SPC AC 210830

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CST SUN DEC 21 2014

VALID 231200Z - 241200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY INTO
THE GULF COASTAL REGION...

...THERE IS A MRGL RISK OF SVR TSTMS OVER THE LOWER MS VALLEY INTO A
PORTION OF THE SERN STATES AND NRN FL...

...SUMMARY...
POTENTIAL WILL EXIST FOR A FEW STRONG TO SEVERE THUNDERSTORMS FROM
SOUTHERN PORTIONS OF THE LOWER MISSISSIPPI VALLEY THROUGH THE GULF
COASTAL REGION TUESDAY INTO TUESDAY NIGHT. THE PRIMARY THREATS WILL
BE ISOLATED DAMAGING WIND GUSTS AND A COUPLE OF TORNADOES. SOME HAIL
WILL ALSO BE POSSIBLE...MAINLY OVER THE LOWER MISSISSIPPI VALLEY
REGION.

...SYNOPSIS...

HIGH-AMPLITUDE UPPER TROUGH WILL ADVANCE SLOWLY THROUGH THE PLAINS
WITH AN EMBEDDED SRN STREAM SHORTWAVE TROUGH REACHING THE LOWER MS
VALLEY REGION TUESDAY NIGHT. PRIMARY SFC CYCLONE ATTENDANT TO THE
NRN-STREAM SHORTWAVE TROUGH WILL WEAKEN AS IT MOVES TOWARD THE WRN
GREAT LAKES. THE TRAILING COLD FRONT WILL CONTINUE THROUGH THE MS
VALLEY AND LIKELY EXTEND FROM THE GREAT LAKES SWD INTO AL BY THE END
OF THIS PERIOD. WEAK CYCLOGENESIS WILL ALSO BE POSSIBLE IN
ASSOCIATION WITH THE SRN-STREAM IMPULSE...AND THIS FEATURE SHOULD
LIFT NEWD ALONG THE FRONT THROUGH MS INTO THE TN VALLEY OVERNIGHT. A
WARM FRONT SHOULD STALL OVER THE GULF COAST REGION.

...LOWER MS VALLEY THROUGH THE GULF COASTAL REGION AND NRN FL...

PRIMARY COMPLICATING FACTOR THIS FORECAST IS POTENTIAL FOR NUMEROUS
SHOWERS AND THUNDERSTORMS TO DEVELOP EARLY IN PERIOD OVER A PORTION
OF THE SERN STATES WITHIN ZONE OF ISENTROPIC ASCENT ALONG AND NORTH
OF COASTAL FRONT. THIS SHOULD LIMIT BOUNDARY-LAYER DESTABILIZATION
POTENTIAL WITH NWD EXTENT AWAY FROM THE GULF COAST. GREATEST CAPE
EARLY TUESDAY IS LIKELY OVER LA AND SRN MS WHERE REMNANT EML WILL
HAVE ADVECTED ABOVE WRN FRINGE OF THE MOIST AXIS. MUCAPE IN THIS
REGION MAY APPROACH 1500 J/KG. STORMS WILL LIKELY INCREASE DURING
THE DAY ALONG AND NORTH OF THE WARM FRONT FROM THE GULF COAST AREA
NWD INTO THE SERN STATES PROMOTED BY A BROAD SLY LLJ. GIVEN
EFFECTIVE SHEAR FROM 40-50 KT...POTENTIAL WILL EXIST FOR A FEW
SUPERCELLS...AND STORMS MAY BECOME ROOTED NEAR THE SFC OVER SRN
PORTIONS OF THE LOWER MS VALLEY AND GULF COAST REGION. OTHER STORMS
MAY DEVELOP AS SEWD ADVANCING FRONT INTERCEPTS THE MOIST AXIS.
ACTIVITY WILL DEVELOP EWD DURING THE DAY AND OVERNIGHT THROUGH THE
SERN STATES AND GULF OF MEXICO AND EVENTUALLY INTO NRN FL. WILL
MAINTAIN A LOWER-END SLIGHT RISK THIS UPDATE GIVEN THE CONDITIONAL
NATURE OF THE THREAT.

..DIAL.. 12/21/2014




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