SWODY1
SPC AC 041905
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0205 PM CDT THU JUN 04 2009
VALID 042000Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SOUTHERN VA/NORTHERN
NC...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL/SOUTHERN
HIGH PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE PACIFIC
NORTHWEST/NORTHERN INTERMOUNTAIN WEST...
...SOUTHERN VA AND NC...
HAVE INTRODUCED CATEGORICAL SLIGHT RISK FOR PORTIONS OF SOUTHERN VA
INTO NC. STRONG/SEVERE TSTM POTENTIAL SHOULD REMAIN SOMEWHAT FOCUSED
IN VICINITY OF WEST-EAST FRONTAL ZONE ACROSS SOUTHERN VA/NORTHERN
NC. WITHIN THIS CORRIDOR...MODEST MID TROPOSPHERIC FLOW PER REGIONAL
WSR-88D VWP DATA...ENHANCED VORTICITY ALONG LOW LEVEL FRONTAL
BOUNDARY...AND A MOIST AIRMASS/STRONG LOW LEVEL CAPE SHOULD SUPPORT
SOME TRANSIENT SUPERCELLS/FAIRLY ORGANIZED MULTICELLS WITH POTENTIAL
FOR A FEW BRIEF TORNADOES ALONG WITH DAMAGING WINDS/SOME HAIL. SEE
MESOSCALE DISCUSSION 946 AND TORNADO WATCH 327 FOR ADDITIONAL
DETAILS.
...CENTRAL/SOUTHERN HIGH PLAINS...
SEE MESOSCALE DISCUSSION 947.
...PACIFIC NORTHWEST/NORTHERN INTERMOUNTAIN WEST...
SEE MESOSCALE DISCUSSION 945.
OTHERWISE...CHANGES TO PREVIOUS OUTLOOK ARE MINIMAL...SEE PREVIOUS
DAY 1 OUTLOOK TEXT AND LATEST WATCHES/MESOSCALE DISCUSSIONS FOR
GUIDANCE.
..GUYER.. 06/04/2009
.PREV DISCUSSION... /ISSUED 1127 AM CDT THU JUN 04 2009/
..SYNOPSIS...
BROAD CYCLONIC FLOW WILL REMAIN EAST OF THE ROCKIES THROUGH THE
PERIOD. WEAK DISTURBANCES ROTATING WITHIN THIS FLOW WERE INDICATED
BY SATELLITE/RADAR OVER NEB...WRN MS AND SERN AL. AN UPPER LOW OFF
THE CA COAST IS FORECAST TO MOVE INLAND FRI MORNING. STRONG
SHORTWAVE IMPULSE OVER SASKATCHEWAN IS EXPECTED TO MOVE SEWD INTO
NRN MN BY 12Z FRI. AT THE SURFACE...A COLD FRONT ASSOCIATED WITH THE
CANADIAN IMPULSE WILL DROP SEWD INTO THE NRN PLAINS/UPPER MS
VALLEY...WHILE WEAK COLD FRONT FROM VA SEWD INTO THE LOWER MS VALLEY
EDGES SLOWLY SEWD.
...CENTRAL/SRN HIGH PLAINS...
AS SURFACE RIDGE OVER THE CENTRAL PLAINS SHIFTS EWD INTO THE MS
VALLEY...WINDS WILL BECOME SELY AND INCREASE THE UPSLOPE FLOW ACROSS
THE REGION. ALTHOUGH DEWPOINTS ARE EXPECTED TO ONLY BE IN THE 40S TO
LOWER 50S F...STEEP LAPSE RATES ABOVE BOUNDARY LAYER WILL SUPPORT
SBCAPES TO NEAR 1000 J/KG THIS AFTERNOON. ALTHOUGH REGION WILL BE
LOCATED ON THE ERN SIDE OF UPPER RIDGE...STORMS ARE EXPECTED TO BE
PRIMARILY DRIVEN BY STRONG DIFFERENTIAL HEATING NEAR THE EASTERN
FOOTHILLS. BEST POTENTIAL FOR A GREATER STORM COVERAGE SHOULD BE
ACROSS SERN CO/NERN NM AND SERN WY WHERE SUNSHINE/HEATING HAS BEEN
STRONGER THIS MORNING.
ALTHOUGH VERTICAL WIND PROFILES ARE NOT PARTICULARLY STRONG IN THE
LOWER 2-3 KM...STRONGLY VEERING WINDS WITHIN THIS LAYER AND 30-50 KT
WNWLY WINDS BETWEEN 600-200 MB SHOULD PROVIDE SUFFICIENT SHEAR FOR
SOME MID LEVEL ROTATION IN STORMS. THE LACK OF RICHER BOUNDARY LAYER
MOISTURE INDICATES THAT HAIL SHOULD BE THE PRIMARY THREAT.
...PACIFIC NW AND NRN ROCKIES...
STRONGLY DIFFLUENT FLOW ALOFT AND APPROACHING MID LEVEL JET MAX
SHOULD PROVIDE SUFFICIENT LIFT FOR SCATTERED TO NUMEROUS
THUNDERSTORMS...ESPECIALLY THIS AFTERNOON AND EVENING. RELATIVELY
MOIST SOUNDINGS...PW VALUES AROUND 1 INCH...AND SBCAPES NEAR 1000
J/KG...COMBINED WITH MOSTLY SLY FLOW ALOFT WILL BE FAVORABLE FOR
LINE SEGMENTS AND LOCALLY DAMAGING WINDS/HAIL. A FEW SUPERCELLS ALSO
APPEAR POSSIBLE...ESPECIALLY ACROSS ERN ORE/NRN NV/SRN ID...WHERE
DEEP LAYER SHEAR WILL BE THE GREATEST AT 40-45 KT.
...SERN U.S...
VERY MOIST AND UNSTABLE AIR MASS...COMBINED WITH BROAD LIFT
ASSOCIATED WITH UPPER TROUGH...SHOULD RESULT IN NUMEROUS
STORMS.PRESENCE OF STRONGER WINDS NEAR SERN AL UPPER TROUGH AND
MOIST BOUNDARY LAYER COULD YIELD A BRIEF TORNADO OR TWO FROM NRN
FL/ERN GA NEWD INTO THE CAROLINAS. HOWEVER...CONSIDERABLE
CLOUDS/PCPN AND POOR LAPSE RATES ARE EXPECTED TO LIMIT THE SEVERE
POTENTIAL.
...NERN ND/NWRN MN...
ALTHOUGH DEWPOINTS WILL ONLY BE IN THE 40S...STEEPER MID LEVEL LAPSE
RATES MAY SUPPORT ENOUGH INSTABILITY FOR STORMS TO DEVELOP ALONG
COLD FRONT BY LATE AFTERNOON. IF STORMS DEVELOP...DEEP LAYER SHEAR
AT 40 KT WOULD SUPPORT SUSTAINED STORMS WITH ISOLATED WIND GUSTS
POSSIBLE.
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