Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Tucson, AZ...Salt Lake City, UT...West Valley City, UT...Provo, UT...West Jordan, UT...
SPC AC 271958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT SAT SEP 27 2014
VALID 272000Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF AZ INTO SRN
UT...
...SUMMARY...
WIDELY SCATTERED SEVERE THUNDERSTORMS WILL CONTINUE TO BE POSSIBLE
THIS AFTERNOON AND EVENING ACROSS MUCH OF ARIZONA AND SOUTHERN UTAH.
DAMAGING WIND GUSTS AND LARGE HAIL WILL BE THE PRIMARY HAZARDS WITH
THESE STORMS.
THE PRIMARY ADJUSTMENT IN THIS UPDATE IS TO TRIM THE WRN EDGE OF THE
SLIGHT RISK AND GEN-TSTM LINES TO REFLECT LOW-LEVEL
DRYING/STABILIZATION THAT IS SLOWLY ADVANCING FROM WEST TO EAST
ACROSS SWRN UT/WRN AZ. OTHERWISE...THE PREVIOUS FORECAST REASONING
REMAINS VALID. THUS FAR...ORGANIZED STORM STRUCTURES HAVE ONLY BEEN
TRANSIENT WITHIN THE BROADER PLUME OF CONVECTION...BUT SOME UPTICK
IN INTENSITY IS POSSIBLE AS ONGOING STORMS MOVE INTO AREAS WHERE
MODERATE DESTABILIZATION IS OCCURRING. OCCASIONAL EMBEDDED
SUPERCELLS AND BOWING STRUCTURES CAPABLE OF PRIMARILY DAMAGING WIND
AND ISOLATED LARGE HAIL WILL CONTINUE TO BE POSSIBLE INTO THE
EVENING ACROSS MUCH OF AZ INTO SRN UT. ALSO...WHILE THE 5 PERCENT
TORNADO AREA HAS BEEN DROPPED...A BRIEF TORNADO CANNOT BE RULED OUT
WITH ANY LONGER-LIVED SUPERCELL THAT CAN DEVELOP.
..DEAN/MEAD.. 09/27/2014
.PREV DISCUSSION... /ISSUED 1112 AM CDT SAT SEP 27 2014/
...SYNOPSIS...
A MID TO UPPER-LEVEL CYCLONE SITUATED OVER CNTRL CA WILL EDGE ONLY
SLIGHTLY EWD INTO NV OWING TO A PERSISTENT DOWNSTREAM BLOCKING
PATTERN EAST OF THE ROCKIES. SEVERAL VORTICITY MAXIMA WILL PIVOT
AROUND THE LOW WHILE A BELT OF 50-60 KT FLOW AT 500 MB SPREADS EWD
TOWARD THE FOUR CORNERS REGION.
AT THE SURFACE...AN AREA OF LOW PRESSURE OVER E-CNTRL NV AS OF MID
MORNING WILL GRADUALLY FILL OVER THE SAME GENERAL AREA WHILE AN
ASSOCIATED PACIFIC FRONT SLOWLY SHIFTS EWD THROUGH WRN AZ.
MEANWHILE...A COLD FRONT FROM THE NV SURFACE LOW NEWD THROUGH THE
CNTRL ROCKIES INTO UPPER MS VALLEY WILL CONTINUE SWD THROUGH THE NRN
PLAINS.
...AZ/UT TODAY INTO THIS EVENING...
A N-S-ORIENTED BAND OF TSTMS IS ONGOING IMMEDIATELY AHEAD OF THE
PACIFIC FRONT WHERE DCVA/HEIGHT FALLS HAVE OVERSPREAD A MOIST AND AT
LEAST MARGINALLY UNSTABLE AIR MASS WITH PW VALUES OF 1.0-1.5 INCHES.
BREAKS IN THE CLOUDS COUPLED WITH THE CONTINUED POLEWARD FLUX OF A
MOIST BOUNDARY LAYER SHOULD SUPPORT DESTABILIZATION OF THE
DOWNSTREAM ENVIRONMENT ACROSS CNTRL/ERN AZ AND PERHAPS SERN UT WHERE
MLCAPE MAY APPROACH 500-1500 J/KG.
IN THE WAKE OF THE INITIAL VORTICITY MAXIMUM CURRENTLY PIVOTING NEWD
THROUGH THE LOWER CO VALLEY...AN UPSTREAM IMPULSE IS EXPECTED TO
ROTATE ACROSS THE REGION LATER TODAY. THIS FORCING MECHANISM IN
CONCERT WITH LOW-LEVEL UPSLOPE FLOW SHOULD SUSTAIN THE CURRENT
CONVECTIVE BAND EWD ACROSS THE SLIGHT RISK AREA. GIVEN THE FAVORABLE
OVERLAP OF THE MOIST AND AT LEAST MODESTLY UNSTABLE WARM SECTOR WITH
AN EWD-MIGRATING MID-LEVEL JET AND RESULTING 35-50 KT OF DEEP-LAYER
SHEAR...THE SETUP WILL REMAIN SUPPORTIVE OF EMBEDDED SUPERCELLS AND
BOWING STRUCTURES CAPABLE OF DAMAGING WINDS...SEVERE HAIL AND
PERHAPS A TORNADO.
WHILE THE THREAT FOR ISOLATED DAMAGING WINDS AND HAIL MAY PERSIST
INTO THE OVERNIGHT HOURS...ORGANIZED SEVERE WEATHER POTENTIAL IS
EXPECTED TO DIMINISH BY MID TO LATE EVENING AS THE BOUNDARY LAYER
BEGINS TO COOL AND STABILIZE.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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