SPC AC 301944
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0244 PM CDT TUE JUN 30 2009
VALID 302000Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE NORTHEAST...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF AR AND OK...
...THERE IS A SLGT RISK OF SVR TSTMS FROM SRN MT/NRN WY INTO THE NRN
HIGH PLAINS...
...NORTHEAST...
SEVERAL BANDS OF STRONG/SEVERE STORMS CONTINUE TO MOVE NNEWD OVER
ERN NY...EXTREME ERN PA...AND NWRN NJ. THESE ARE OCCURRING IN
ASSOCIATION WITH A SHORT WAVE TROUGH ROTATING ACROSS THE LOWER GREAT
LAKES AROUND THE SRN PERIPHERY OF THE QUASI-STATIONARY UPPER LOW.
THE THREAT FOR DAMAGING WIND GUSTS AND LARGE HAIL WILL CONTINUE
DURING THE NEXT SEVERAL HOURS BEFORE GRADUALLY DIMINISHING BY EARLY
EVENING.
...OK/AR...
WIDELY SCATTERED STRONG/SEVERE THUNDERSTORMS HAVE DEVELOPED ALONG
WEAK FRONT/CONVERGENCE ZONE OVER EXTREME SRN MO/NRN AR...ALONG THE
SRN EDGE OF STRONGER NWLY FLOW ALOFT WITHIN A MODERATELY UNSTABLE
ENVIRONMENT WITH MLCAPE OF 1500-2000 J/KG. VISIBLE IMAGERY SHOWS
CU/TCU HAVE DEVELOPED WWD ALONG THE BNDRY INTO WRN OK AND ADDITIONAL
THUNDERSTORMS MAY INITIATE ALONG THE BNDRY. LARGE SURFACE
TEMPERATURE/DEW POINT SPREADS ON THE ORDER OF 25-30F AND ASSOCIATED
INVERTED-V PBL PROFILES INDICATE POTENTIAL FOR STRONG
DOWNBURSTS...AND LARGE HAIL...TO ACCOMPANY ANY STORMS THAT MAY
DEVELOP.
...SRN MT/NRN WY INTO THE NRN HIGH PLAINS...
SATELLITE IMAGERY SHOWS HIGH-BASED CONVECTION MOVING NEWD ACROSS
SERN ID TOWARD SWRN MT...AND OVER PARTS OF NRN WY. CONVECTIVE
ACTIVITY APPEARS TO BE OCCURRING IN ASSOCIATION WITH SEVERAL WEAK
SHORT WAVE TROUGHS MOVING NEWD/EWD ALONG THE NRN PERIPHERY OF THE
SRN PLATEAU UPPER RIDGE. THE ID STORMS MAY INTENSIFY AS THEY MOVE
EWD ACROSS SRN MT WITHIN BAND OF 40 KT WESTERLY MID LEVEL WINDS.
SIMILARLY...CONVECTION OVER NERN WY/SERN MT AREA WILL HAVE POTENTIAL
TO INTENSIFY AS IT MOVES EWD INTO INCREASING LOW LEVEL MOISTURE AND
INSTABILITY OVER THE NRN HIGH PLAINS. STRONGER STORMS WILL BE
CAPABLE OF PRODUCING DAMAGING WINDS AND HAIL.
..WEISS.. 06/30/2009
.PREV DISCUSSION... /ISSUED 1048 AM CDT TUE JUN 30 2009/
...NORTHEAST...
A SHORTWAVE TROUGH CURRENTLY ROTATING INTO WESTERN NY WILL HELP TO
INTENSIFY SCATTERED THUNDERSTORMS BY EARLY AFTERNOON OVER PARTS OF
NY/PA...SPREADING INTO WESTERN NEW ENGLAND. COLD TEMPERATURES ALOFT
AND SUFFICIENT VERTICAL SHEAR WILL PROMOTE A RISK OF WIDELY
SCATTERED SEVERE STORMS CAPABLE OF HAIL AND LOCALLY DAMAGING WINDS.
PLEASE REFER TO SWOMCD NUMBER 1378 AND SEVERE THUNDERSTORM WATCH
NUMBER 533 FOR FURTHER DETAILS.
...NORTHERN PLAINS...
WATER VAPOR IMAGERY SHOWS A BROAD UPPER TROUGH OVER THE NORTHWEST
STATES...WITH A SMALL SHORTWAVE TROUGH MOVING ACROSS MT/WY. THIS
FEATURE WILL SLOWLY MOVE EASTWARD INTO THE NORTHERN HIGH PLAINS THIS
AFTERNOON PROVIDING A FOCUS FOR SCATTERED THUNDERSTORM DEVELOPMENT.
MORNING RAOBS OVER THIS REGION SHOWED A WARM EML/CAPPING LAYER WHICH
WILL ERODE FROM THE WEST THIS AFTERNOON WITH DAYTIME HEATING. THIS
SHOULD RESULT IN A RATHER NARROW AXIS OF WEAK CAP ACROSS EASTERN
MT/WY AND WESTERN ND/SD/NEB. ISOLATED THUNDERSTORMS ARE EXPECTED TO
DEVELOP BY LATE AFTERNOON AND TRACK SOUTHEASTWARD INTO STRENGTHENING
SOUTHERLY LOW LEVEL FLOW. A FEW SUPERCELLS ARE POSSIBLE CAPABLE OF
DAMAGING WINDS AND HAIL.
...SOUTHERN MT...
RATHER STRONG DEEP LAYER VERTICAL SHEAR WILL BE PRESENT THIS
AFTERNOON OVER THE MOUNTAINS OF SOUTHERN MT...WHERE DEWPOINTS IN THE
50S AND STEEP MID LEVEL LAPSE RATES WILL COEXIST. MODELS ARE
CONSISTENT IN SHOWING SCATTERED THUNDERSTORMS DEVELOPING THIS
EVENING WEST OF BIL...SPREADING EASTWARD AFTER DARK. ISOLATED
SUPERCELLS WILL BE POSSIBLE IN THIS AREA WITH RISK HAIL AND DAMAGING
WINDS IN STRONGEST CELLS.
...AR/OK...
SMALL CLUSTER OF THUNDERSTORMS THAT AFFECTED SOUTHERN MO EARLIER
THIS MORNING IS MOVING SOUTHWARD AND SLOWLY WEAKENING OVER AR. THIS
ACTIVITY HAS LEFT AN OUTFLOW BOUNDARY OVER WESTERN AR/EASTERN OK
WHICH MAY BE THE FOCUS FOR A FEW AFTERNOON THUNDERSTORMS.
TEMPERATURES WELL INTO THE 90S AND MLCAPE VALUES OF AROUND 2500 J/KG
WILL PROMOTE STRONG UPDRAFTS/DOWNDRAFTS CAPABLE OF LOCALLY DAMAGING
WINDS. WESTWARD EXTENT OF SEVERE THREAT IS UNCERTAIN...BUT HAVE
INCLUDED MORE OF OK AS NEW MODEL GUIDANCE INDICATES THUNDERSTORMS
MAY BE MORE NUMEROUS IN THIS AREA. ISOLATED STRONG CELLS CAPABLE OF
DAMAGING WINDS MAY EXTEND AS FAR WEST AS THE TX PANHANDLE THIS
EVENING.
...FL...
A VERY MOIST AND UNSTABLE AIRMASS IS IN PLACE ONCE AGAIN THIS
MORNING OVER THE FL PENINSULA WITH PWAT VALUES OVER 2 INCHES.
NUMEROUS THUNDERSTORMS ARE EXPECTED WITH ISOLATED/BRIEF WET
MICROBURSTS POSSIBLE WITH STRONGEST CORES.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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