Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS03 KWNS 050719
SWODY3
SPC AC 050718

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0218 AM CDT WED AUG 05 2015

VALID 071200Z - 081200Z

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS THE GREAT PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS OVER PARTS OF THE SOUTH AND
GULF COAST...

...SUMMARY...
A FEW STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE ACROSS THE
GREAT PLAINS ON FRIDAY. OTHER STRONG TO MARGINALLY SEVERE
THUNDERSTORMS WILL BE POSSIBLE ACROSS THE SOUTHEAST. THUNDERSTORMS
ARE ALSO LIKELY TO OCCUR ACROSS THE GREAT BASIN.

...OVERVIEW...
A COMPLEX FLOW REGIME WITH NUMEROUS EMBEDDED SHORTWAVE TROUGHS WILL
PERSIST ON THE PERIPHERY OF A BROAD MIDLEVEL SUBTROPICAL RIDGE
CENTERED OVER THE SRN PLAINS. PRIMARY DISTURBANCES OF INTEREST THIS
PERIOD WILL BE RELATIVELY LOW-AMPLITUDE IN NATURE AND...GIVEN
COMPLEXITY OF THE FLOW...UNCERTAINTY IN SEVERE STORM DEVELOPMENT AND
MODE IS RELATIVELY HIGH.

...GREAT PLAINS...
MIDLEVEL HEIGHTS WILL RISE IN THE WAKE OF A LEADING SHORTWAVE TROUGH
MOVING ACROSS THE NRN PLAINS EARLY IN THE PERIOD ON FRIDAY.
HOWEVER...SURFACE LEE TROUGH AND STEEP LAPSE-RATE PLUME SHOULD
PERSIST ACROSS THE CNTRL HIGH PLAINS GIVEN A BELT OF MODEST MIDLEVEL
WLY FLOW ACROSS THE ROCKIES ON THE NRN FLANK OF SUBTROPICAL RIDGE.
BOTH GFS AND EC MODELS DEPICT LOW AMPLITUDE PERTURBATIONS EJECTING
ACROSS THE HIGH PLAINS LATE IN THE DAY...AHEAD OF A MORE SUBSTANTIAL
UPPER TROUGH CROSSING THE SIERRA. IN COMBINATION WITH DIURNAL
DESTABILIZATION AND A GRADUAL INCREASE IN MASS AND MOISTURE INFLUX
ON THE NOSE OF LLJ...STORMS SHOULD FIRST DEVELOP ACROSS THE FRONT
RANGE AND THEN EXPAND E-NEWD INTO THE EVENING. SHEAR AND INSTABILITY
ARE FORECAST TO BE ADEQUATE FOR STRONG TO SEVERE STORMS WITH HAIL
AND HIGH WINDS. IF TIMING AND LOCATION OF STRONGER FORCING BECOMES
BETTER DEFINED AND CONSISTENT IN UPCOMING MODEL FORECASTS...HIGHER
CONFIDENCE MAY SUPPORT INCREASING SEVERE PROBABILITIES FOR SOME
AREAS.

...SOUTH/GULF COAST...
SHEAR AXIS ON THE ERN FLANK OF THE SUBTROPICAL RIDGE...FROM THE
LOWER MO RIVER VALLEY SEWD TO THE TN VALLEY...WILL BE COINCIDENT
WITH A BROAD ZONE OF 30KT MIDLEVEL NWLY FLOW. ANOTHER ROUND OF
DIURNAL CONVECTION SEEMS LIKELY ACROSS THE DEEP SOUTH AND SOUTHEAST
GIVEN ABUNDANT MOISTURE AND THE PRESENCE OF RESIDUAL BOUNDARIES IN
THE WAKE OF A STRONGER DISTURBANCE PASSING OFF THE ERN SEABOARD.
AFTERNOON STORMS/STORM MERGERS AND STORM/BOUNDARY INTERACTIONS...IN
THE PRESENCE OF MODEST MIDLEVEL FLOW...COULD RESULT IN ISOLATED
DOWNBURST WINDS.

...GREAT BASIN...
A COMPACT AND PROGRESSIVE MIDLEVEL IMPULSE IS FORECAST TO SPREAD
500MB HEIGHT FALLS ON THE ORDER OF 30-60M PER 12H FROM THE SIERRA
E-NEWD ACROSS NRN UT THROUGH FRIDAY AFTERNOON. STRONG THUNDERSTORMS
COULD EVOLVE AS THIS SYSTEM MOVES INTO THE GREAT BASIN.
HOWEVER...FORECAST SOUNDINGS INDICATE DEEP MOISTURE AND LIMITED CAPE
DESPITE INCREASING FLOW/SHEAR AND ASCENT. IF GREATER DESTABILIZATION
IS INDICATED IN LATER FORECASTS...A SEVERE RISK MAY NEED TO BE
INTRODUCED TO PARTS OF THE GREAT BASIN.

..CARBIN.. 08/05/2015



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