Severe Storm Outlook Narrative (AC)
Issued by NWS

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402
ACUS02 KWNS 031732
SWODY2
SPC AC 031730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT TUE MAY 03 2016

VALID 041200Z - 051200Z

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS THE CENTRAL AND SOUTHERN
FL PENINSULA...

...SUMMARY...
SCATTERED THUNDERSTORMS ARE EXPECTED OVER THE FLORIDA PENINSULA
WEDNESDAY...AND A FEW MAY BE STRONG TO SEVERE ACROSS MAINLY THE
SOUTHERN HALF OF THE PENINSULA.  ISOLATED STRONG STORMS WITH SMALL
HAIL WILL DEVELOP ACROSS THE OHIO AND TENNESSEE VALLEYS...WITH
ISOLATED STRONG STORMS PRODUCING SMALL HAIL AND STRONG WIND GUSTS
POSSIBLE FROM NORTHERN CALIFORNIA TO EASTERN WASHINGTON.

...SYNOPSIS...
A HIGHLY AMPLIFIED MID-UPPER LEVEL FLOW PATTERN WILL PREVAIL THROUGH
MIDWEEK AS AN OMEGA BLOCK DEVELOPS ACROSS THE CONTIGUOUS U.S. THIS
FORECAST PERIOD.  A SHORTWAVE TROUGH MOVING TO THE SOUTH/SOUTHEAST
ACROSS THE SOUTHERN PLAINS TODAY WILL PROGRESS THROUGH THE BASE OF
THE DEEPENING EASTERN U.S. TROUGH ON WEDNESDAY...ADVANCING ACROSS
THE GULF OF MEXICO THROUGH 05/00Z. THIS SHORTWAVE TROUGH WILL THEN
SPREAD ACROSS THE FL PENINSULA WEDNESDAY NIGHT.  MEANWHILE...AN
UPSTREAM SHORTWAVE TROUGH TRACKING ACROSS THE UPPER GREAT LAKES
TODAY WILL UNDERGO FURTHER AMPLIFICATION WEDNESDAY AS IT SPREADS
ACROSS THE OH/TN VALLEYS.  A DEEP LONGWAVE TROUGH LOCATED OFF THE
U.S./CANADIAN WEST COAST WILL SHIFT SLOWLY TO THE EAST.

...FL PENINSULA...
SCATTERED THUNDERSTORMS WILL LIKELY BE ONGOING AT 12Z WEDNESDAY
ALONG THE SYNOPTIC FRONT EXTENDING ACROSS SOUTHERN GA/NORTHERN
FL...AND IMMEDIATELY AHEAD OF AFOREMENTIONED SOUTHERN PLAINS
SHORTWAVE TROUGH OVER THE CNTRL/ERN GULF.  THIS CONVECTION AND
CLOUDINESS ACROSS THE NORTHERN PENINSULA IS EXPECTED TO INHIBIT
SUFFICIENT INSTABILITY FROM OCCURRING TO SUPPORT A MARGINAL SEVERE
RISK ON WEDNESDAY.  THEREFORE...THIS PORTION OF FL HAS BEEN REMOVED
FROM THE CAT1 SEVERE RISK FOR DAY 2.

MEANWHILE...DEEP WESTERLY FLOW INCREASING THROUGH WEDNESDAY WILL
MAINTAIN A RATHER MOIST ENVIRONMENT ACROSS THE WARM SECTOR WITH
PRECIPITABLE WATER VALUES EXCEEDING 1.5-1.75 INCHES.  EARLY DAY
DIABATIC HEATING WITHIN AN AIR MASS...THAT SHOULD HAVE VERY LITTLE
INHIBITION...AND FORCING FOR ASCENT ATTENDANT TO A WEAK MIDLEVEL
IMPULSE MOVING ACROSS THE FL PENINSULA THROUGH 18Z WILL SUPPORT
THUNDERSTORM DEVELOPMENT.  WEAK LAPSE RATES WILL LIMIT
DESTABILIZATION THROUGH DAY 2 AND OVERALL COVERAGE OF STRONG TO
SEVERE STORMS.  HOWEVER...35-40 KT OF EFFECTIVE BULK SHEAR AND THE
RICH MOISTURE SUGGEST STRONG CONVECTION MAY DEVELOP.  IN ADDITION TO
STORMS DEVELOPING ALONG THE SOUTHWARD MOVING COLD FRONT...STORMS
WILL ALSO DEVELOP IN VICINITY OF SEA BREEZE BOUNDARIES AND SHOULD
MOVE INLAND FROM THE GULF OF MEXICO.  AT THIS TIME...ORGANIZED
MULTI-CELL UPDRAFTS REMAIN THE EXPECTED MOST COMMON STORM MODE...
WITH GUSTY WINDS AND PERHAPS MARGINALLY SEVERE HAIL BEING THE
PRIMARY SEVERE THREATS.

...OH/TN VALLEYS TO APPALACHIANS...
FOCUSED ZONE OF ASCENT ATTENDANT AMPLIFYING TROUGH INTO THIS REGION
ON WEDNESDAY AND WITHIN EXIT REGION OF ACCOMPANYING DIGGING
MIDLEVEL JET WILL AID CONVECTIVE DEVELOPMENT BY MID DAY FROM THE
LOWER GREAT LAKES INTO THE TN VALLEY.  MODELS CONTINUE TO INDICATE
COLD 500-MB TEMPERATURES /-20 TO -24 C/ SPREADING INTO THE OH/TN
VALLEYS ATOP SURFACE HEATING...STEEPENING LAPSE RATES. CONVECTION IS
EXPECTED TO EVOLVE FAIRLY EARLY ALONG SURFACE WIND SHIFT. ALTHOUGH
LOW-LEVEL MOISTURE WILL BE LIMITED...ROBUST LOW-TOPPED UPDRAFTS
COULD GENERATE SMALL HAIL GIVEN THE COLD THERMAL PROFILES.

...NORTHERN CA TO EASTERN WA...
WEAK FORCING FOR ASCENT AND STEEP LAPSE RATES SUGGEST A FEW STRONG
STORMS MAY DEVELOP OVER NORTHERN CA THROUGH CENTRAL/EASTERN ORE TO
EASTERN WA WEDNESDAY AFTERNOON AND EVENING AHEAD OF THE APPROACHING
WEST COAST TROUGH.  SMALL HAIL AND/OR LOCALLY STRONG WIND GUSTS MAY
OCCUR.

..PETERS.. 05/03/2016

$$



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