SWODY1
SPC AC 291958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT WED JUN 29 2011
VALID 292000Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE NRN INTERMOUNTAIN
REGION AND NRN ROCKIES...
...NRN INTERMOUNTAIN REGION/NRN ROCKIES...
STORMS HAVE BEEN GRADUALLY DEVELOPING FROM CENTRAL ID INTO SWRN
MT...DOWNSTREAM FROM THE CENTRAL CA UPPER LOW WITHIN LEFT EXIT
REGION OF UPPER LEVEL JET STREAK OVER NV INTO SRN ID. STORMS ARE
EXPECTED TO GRADUALLY INCREASE IN INTENSITY THIS AFTERNOON AND
EVENING AS THEY MOVE NEWD WITHIN ENVIRONMENT OF SUFFICIENT
INSTABILITY/STEEP LAPSE RATES...DRY SUBCLOUD LAYER AND STRONG DEEP
LAYER SHEAR. STRONGER CELLS WILL BE CAPABLE OF PRODUCING DAMAGING
WINDS AND HAIL. SEE MESOSCALE DISCUSSION 1441 FOR MORE DETAILED
INFORMATION.
...CENTRAL/NRN NV INTO SWRN ID...
A FEW STRONG STORMS HAVE DEVELOPED IMMEDIATELY EAST/NORTHEAST OF THE
UPPER LOW OVER CENTRAL CA...AND THIS ACTIVITY WILL CONTINUE THROUGH
THE EVENING HOURS AS PRONOUNCED DYNAMIC FORCING FOR ASCENT
OVERSPREADS THE REGION. THERE WILL BE A RISK FOR MARGINALLY SEVERE
HAIL AND STRONG WINDS WITH MORE INTENSE CELLS...BUT OVERALL LIMITED
COVERAGE WILL PRECLUDE HIGHER SEVERE PROBABILITIES.
...CENTRAL/ERN UT INTO WRN WY...
NNE-SSW BANDS OF CONVECTION HAVE BEEN FORMING OVER UT INTO SWRN
WY...WHERE THE ENVIRONMENT IS CHARACTERIZED BY A DEEP BOUNDARY LAYER
WITH CONSIDERABLE DRY AIR IN THE SUB-CLOUD LAYER. THIS WILL ENHANCE
POTENTIAL DOWNDRAFT STRENGTH...AND STEEP LAPSE RATES WILL PROMOTE
DOWNWARD TRANSFER OF MOMENTUM WITH A RISK OF ISOLATED STRONG
MICROBURST WINDS.
..WEISS.. 06/29/2011
.PREV DISCUSSION... /ISSUED 1126 AM CDT WED JUN 29 2011/
...MT/ID THIS AFTERNOON INTO TONIGHT...
VORTICITY MAXIMUM CURRENTLY PIVOTING AROUND ERN PERIPHERY OF UPPER
LOW WILL EJECT NEWD ACROSS REGION TODAY INTO INCREASINGLY CONFLUENT
FLOW REGIME OVER THE NRN INTERMOUNTAIN REGION. FORCING FOR ASCENT
ASSOCIATED WITH THIS FEATURE COUPLED WITH FRONTAL CONVERGENCE AND
OROGRAPHIC INFLUENCES ARE EXPECTED TO FOSTER AN INCREASE IN TSTMS
THIS AFTERNOON INTO TONIGHT. 12Z BOI SOUNDING AND GPS PW DATA
INDICATE A PLUME OF HIGHER MOISTURE CONTENT ALONG AND AHEAD OF
PACIFIC FRONT. WHEN COUPLED WITH A STEEP LAPSE RATE
ENVIRONMENT...EXPECT AFTERNOON MLCAPE TO APPROACH 1000-1500 J/KG.
THIS INSTABILITY AXIS WILL COINCIDE WITH A BELT OF 45-55 KT SWLY
WINDS AT 500 MB...RESULTING IN SUFFICIENT DEEP-LAYER SHEAR FOR
ORGANIZED STORM MODES INCLUDING SUPERCELLS AND BOWING STRUCTURES.
LARGE HAIL AND DAMAGING WIND GUSTS WILL BE THE PRIMARY HAZARDS OWING
TO THE STEEP LAPSE RATES AND POTENTIAL FOR STRONG EVAPORATIVE
COOLING IN THE SUB-CLOUD LAYER.
...ERN UT/WRN CO/WRN WY THIS AFTERNOON/EVENING...
ENVIRONMENT IS EXPECTED TO REMAIN DRIER THAN POINTS TO THE NORTH AND
WEST TODAY...THOUGH THE PRESENCE OF STEEP LAPSE RATES WILL BE
SUPPORTIVE OF MLCAPE OF 250-500 J/KG AHEAD OF THE FRONT THIS
AFTERNOON AND EVENING. THE LEADING EDGE OF WEAK HEIGHT FALLS
ATTENDANT TO THE MID AND UPPER-LEVEL TROUGH COMBINED WITH
PRE-FRONTAL CONFLUENT FLOW IN THE LOW LEVELS WILL CONTRIBUTE TO
WIDELY SCATTERED TSTMS THIS AFTERNOON INTO TONIGHT. LOCALLY
DAMAGING WIND GUSTS WILL ACCOMPANY THESE STORMS DUE TO THE
DEVELOPMENT OF A DEEPLY MIXED BOUNDARY LAYER WITH LARGE T-TD
SPREADS.
...MN/WI LATE TONIGHT...
EWD PROGRESSION OF HEIGHT FALLS INTO THE HIGH PLAINS DURING THE
LATTER HALF OF D1 WILL SERVE TO ENHANCE NOCTURNAL LLJ
STRENGTH/BREADTH FROM THE SRN HIGH PLAINS INTO THE UPPER MS VALLEY.
THIS PROCESS WILL OCCUR BENEATH EWD-EXPANDING EML...RESULTING IN THE
DEVELOPMENT OF MODERATE-STRONG ELEVATED INSTABILITY.
HOWEVER...GIVEN THE ANTICIPATED STRENGTHENING OF THE
CAP...UNCERTAINTY EXISTS WITH REGARD TO EXACTLY WHERE ANY MORE
ROBUST HAIL POTENTIAL WILL DEVELOP LATE TONIGHT INTO THU MORNING.
...SERN ATLANTIC AND GULF COASTS THIS AFTERNOON/EVENING...
12Z REGIONAL SOUNDINGS INDICATE THE PRESENCE OF A VERY MOIST AIR
MASS WITH PW VALUES OF AROUND 2 INCHES. HOWEVER...CONSIDERABLE TSTM
DEVELOPMENT ON TUE HAS RESULTED A NOTABLE WEAKENING TO THE MIDLEVEL
LAPSE RATES. DEVELOPING SEA BREEZE CIRCULATIONS COMBINED WITH THE
PRESENCE OF THE SYNOPTIC FRONT AND PRE-FRONTAL TROUGH ARE EXPECTED
TO FOCUS SCATTERED-WIDESPREAD TSTMS ONCE AGAIN TODAY.
HOWEVER...GIVEN THE POOR MIDLEVEL LAPSE RATES AND THE CONTINUED WEAK
VERTICAL SHEAR...TSTMS ARE EXPECTED TO REMAIN RATHER DISORGANIZED
WITH LOCALLY DAMAGING WIND GUSTS POSSIBLE.
...ARKLATEX/RED RIVER VALLEY THIS AFTERNOON/EVENING...
RESIDUAL OUTFLOW BOUNDARIES REMNANT FROM DECAYED NOCTURNAL TSTM
ACTIVITY MAY ONCE AGAIN SERVE AS THE FOCI FOR ISOLATED TSTM
DEVELOPMENT THIS AFTERNOON AND EVENING. 12Z FWD SOUNDING SUGGESTS
THAT AS TEMPERATURES WARM INTO THE MID/UPPER 90S THE CAP WILL BECOME
INCREASINGLY WEAK WITH MLCAPE APPROACHING 3000 J/KG. WHILE VERTICAL
SHEAR WILL REMAIN RATHER WEAK...THE THERMODYNAMIC ENVIRONMENT WILL
BE SUPPORTIVE OF SOME HAIL AND LOCALLY DAMAGING WIND GUSTS SHOULD
STORMS DEVELOP.
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