SPC AC 031958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT THU JUL 03 2008
VALID 032000Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS FOR PORTIONS OF ERN PA NEWD
INTO SRN NEW ENGLAND...
...THERE IS A SLGT RISK OF SVR TSTMS THE INTERIOR PORTIONS OF THE
PACIFIC NW...
...ERN PA NEWD INTO INTO SRN NEW ENGLAND...
A THICK BAND OF CLOUDS AND EMBEDDED SHOWERS WAS LOCATED AHEAD OF A
SEWD MOVING COLD FRONT...THAT AT MID AFTERNOON STRETCHED FROM WRN
NEW ENGLAND SWWD THROUGH NRN NY AND INTO FAR NWRN PA. INSTABILITY IS
WEAK DUE TO POOR LOW-MID LEVEL LAPSE RATES WITHIN THE THICKER CLOUD
BAND..AND STRONGER HEATING EAST OF THE CLOUDS HAD MIXED LOWER
DEWPOINTS TO THE SURFACE. DESPITE WEAK INSTABILITY ...35-40 KT DEEP
LAYER SHEAR MAY RESULT IN A FEW ORGANIZED STRONGER UPDRAFTS THROUGH
00Z...ESPECIALLY NEAR THE ERN EDGE OF THICKER CLOUDS.
...INTERIOR ORE/WA...
WV IMAGERY SHOWED A MID LEVEL SHORTWAVE TROUGH MOVING ENEWD THROUGH
WRN WA/ORE. SCATTERED THUNDERSTORMS HAVE BEEN ONGOING MOST OF THE
MORNING/EARLY AFTERNOON OVER THE CASCADES. AS THIS TROUGH MOVES EWD
INTO AN INCREASINGLY WARMING AND DESTABILIZING AIR MASS...STORM
COVERAGE SHOULD INCREASE IN NUMBER AND INTENSITIES SWD INTO
ORE...AND EWD INTO CENTRAL/ERN WA. ONCE STORMS DEVELOP EAST OF THE
CASCADES...EFFECTIVE SHEAR IN EXCESS OF 40 KT SHOULD FAVOR A FEW
SUPERCELLS OR SMALL BOWS. LARGE HAIL AND DAMAGING WINDS WILL BE THE
PRIMARY SEVERE THREATS BETWEEN 21-03Z.
...CENTRAL HIGH PLAINS...
LOW CLOUDS FROM COOL AND MOIST ELY UPSLOPE FLOW WERE GRADUALLY
DISSIPATING DUE TO SOME HEATING/MIXING. THE AREA WHERE CLOUDS
PERSISTED INTO THE EARLY AFTERNOON HOURS WILL LIKELY REMAIN CAPPED
DUE TO A COOLER AND MORE STABLE BOUNDARY LAYER. HOWEVER...STRONG
INSOLATION OVER THE CLOUD FREE HIGHER TERRAIN HAD RESULTED IN
THUNDERSTORM DEVELOPMENT. MODERATE INSTABILITY AND DIRECTIONAL SHEAR
COULD SUPPORT MULTICELL CLUSTERS OR MARGINAL SUPERCELL
STRUCTURES...WITH THE POSSIBILITY OF ISOLATED HAIL/DAMAGING WINDS
THROUGH ABOUT 02Z/03Z.
...OK NEWD INTO THE LOWER OH VALLEY...
AT MID AFTERNOON...A WEAK COLD FRONT EXTENDED FROM CENTRAL OH SWWD
THROUGH SWRN OK INTO ERN NM. STRONG SURFACE HEATING ALONG AND S OF
THE FRONT...TEMPERATURES IN THE 90S...WILL CONTRIBUTE TO MODERATE
INSTABILITY. HOWEVER...WINDS ALOFT ARE WEAK...SO A FEW CLUSTERS OF
PULSE-TYPE SEVERE STORMS ARE POSSIBLE THIS AFTERNOON...WITH BRIEF
MICROBURSTS THE MAIN THREAT.
...SRN AZ/NM...
CONVECTION HAD ALREADY DEVELOPED OVER THE RIM EWD INTO THE SRN
MOUNTAINS OF NM. MID LEVEL NELY WINDS AT 15 TO 20 KT SHOULD
GRADUALLY PUSH THESE STORMS SSWWD INTO THE DESERT FLOORS...
ESPECIALLY AS COLD POOLS DEVELOP. STRONG WIND GUSTS ARE CERTAINLY
POSSIBLE AS CONVECTION MOVES INTO THE VERY HOT ENVIRONMENT WITH
STEEP LOW LEVEL LAPSE RATES. HOWEVER...RELATIVELY MOIST LAYER
BETWEEN 500-700 MB ON AREA 12Z SOUNDINGS SUGGEST SEVERE THREAT
SHOULD BE TOO ISOLATED FOR A SLIGHT RISK.
..IMY.. 07/03/2008
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