Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 311959
SWODY1
SPC AC 311957

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT MON AUG 31 2015

VALID 312000Z - 011200Z

...THERE IS A MRGL RISK OF SVR TSTMS FOR CENTRAL AZ...

...SUMMARY...
ISOLATED DAMAGING WINDS MAY OCCUR THIS AFTERNOON AND EVENING ACROSS
PARTS OF ARIZONA.  OTHERWISE...SCATTERED THUNDERSTORMS ARE EXPECTED
ACROSS THE CENTRAL ROCKIES AND HIGH PLAINS...AND ALONG PARTS OF THE
GULF AND ATLANTIC COASTS...AS WELL AS THE OHIO AND MID MISSISSIPPI
VALLEYS.

...CENTRAL AZ THIS AFTERNOON/EVENING...
VISIBLE SATELLITE IMAGERY SHOWS DEVELOPING THUNDERSTORMS ACROSS
CNTRL/ERN AZ. WITH WEAK/GENERALLY SWLY DEEP-LAYER FLOW SITUATED
ACROSS THE REGION...AND SFC DEWPOINTS FALLING ACROSS THE LOWER
DESERTS AS BOUNDARY-LAYER MIXING INCREASES...MOST TSTM ACTIVITY
SHOULD REMAIN RELEGATED TO THE HIGHER TERRAIN AREAS THIS AFTERNOON.
STRONG WIND GUSTS AND SMALL HAIL WILL BE POSSIBLE. ADDITIONAL TSTM
DEVELOPMENT IS POSSIBLE ALONG CONVECTIVE OUTFLOW BOUNDARIES LATER
THIS AFTERNOON AND EVENING ACROSS CNTRL AZ...WITH STRONG WIND GUSTS
THE PREDOMINANT THREAT GIVEN STEEP-LOW LEVEL LAPSE RATES AND LARGE
DCAPE VALUES.

..ROGERS.. 08/31/2015

.PREV DISCUSSION... /ISSUED 1127 AM CDT MON AUG 31 2015/

...SYNOPSIS...
A MIDLEVEL SHORTWAVE TROUGH WILL CONTINUE TO EJECT ENEWD FROM ND/SRN
MANITOBA TO WRN ONTARIO...WELL TO THE E OF A LOW-AMPLITUDE TROUGH
THAT WILL APPROACH THE PAC NW.  A MONSOONAL MOISTURE PLUME AND
ASSOCIATED DIURNAL CONVECTION WILL PERSIST FROM THE CENTRAL ROCKIES
TO THE DESERT SW.  FARTHER E...A DIFFUSE TROUGH WILL PERSIST FROM
THE OH VALLEY TO TX WITH EMBEDDED VORTICITY CENTERS OVER
INDIANA...AR...AND S TX.  A SEPARATE VORTICITY MAX WILL SLOWLY
WEAKEN EJECT NEWD/ENEWD OVER THE MID ATLANTIC COAST TODAY...WITH A
TROPICAL MOISTURE PLUME ACCOMPANYING THIS SYSTEM NEAR THE SC/NC
COASTS ALONG A STALLED FRONT.  SCATTERED THUNDERSTORMS ARE EXPECTED
WITH THE EMBEDDED VORTICITY MAXIMA...BUT THE SEVERE STORM RISK WILL
BE LIMITED BY POOR LAPSE RATES AND/OR WEAK VERTICAL SHEAR.

...CENTRAL AZ THIS AFTERNOON/EVENING...
A LOW-END TRANSITION-TYPE EVENT IS UNDERWAY AS A WEAK SRN STREAM
SHORTWAVE TROUGH TRANSLATES SLOWLY EWD TO THE LOWER CO RIVER
VALLEY...WITH SW FLOW ALOFT OVER CENTRAL AND WRN AZ.  BOUNDARY LAYER
DEWPOINTS IN THE 60S REMAIN ACROSS S CENTRAL AZ...AND THE MODIFIED
12Z PHX SOUNDING SUPPORTS AFTERNOON MLCAPE AOA 1500 J/KG WITH DCAPE
NEAR 1500 J/KG.  SCATTERED THUNDERSTORM DEVELOPMENT IS EXPECTED THIS
AFTERNOON OVER THE RIM WITH OTHER STORM DEVELOPMENT POSSIBLE INTO
THE LOWER DESERTS ON CONVECTIVE OUTFLOW.  THE ENVIRONMENT WILL FAVOR
SUBSTANTIAL PRECIPITATION LOADING AND STRONG DOWNDRAFTS IN A STEEP
LOW-LEVEL LAPSE RATE ENVIRONMENT...WITH THE POTENTIAL FOR ISOLATED
DAMAGING OUTFLOW WINDS.




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