SWODY1
SPC AC 191958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT SUN JUN 19 2011
VALID 192000Z - 201200Z
...THERE IS A MDT RISK OF SVR TSTMS FROM NERN CO INTO NEB...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS ESEWD
ACROSS THE MIDDLE MS VALLEY INTO THE CAROLINAS...
...NERN CO INTO NEB...
A LOW LEVEL BOUNDARY EXTENDS FROM NORTH CENTRAL NEB SWWD INTO NERN
CO WHERE A DEN CYCLONE/VORTICITY ZONE IS EVIDENT FROM SURFACE DATA.
TO THE SE OF THIS CONVERGENCE ZONE...MOIST SELY LOW LEVEL FLOW
CONTINUES FROM NRN KS ACROSS NEB INTO NERN CO. A SMALL CLUSTER OF
STRONG/SEVERE STORMS HAS DEVELOPED NEAR THE BOUNDARY NEAR THE
CO/NEB/WY BORDER INTERSECTION...AND ADDITIONAL CONVECTION IS LIKELY
TO DEVELOP WITHIN THE NEXT SEVERAL HOURS NEAR THE SURFACE BOUNDARY.
SWLY WINDS ALOFT ARE EXPECTED TO GRADUALLY INCREASE INTO TONIGHT IN
ADVANCE OF THE UPSTREAM UPPER LOW OVER THE GREAT BASIN...MAINTAINING
STRONG VERTICAL SHEAR OVER THE REGION WHERE MODERATELY STEEP LAPSE
RATES ARE ENHANCING INSTABILITY WITH MLCAPE OF 1500-2500 J/KG. THIS
WILL SUPPORT AN INCREASE IN SEVERE STORM POTENTIAL AS CONVECTION
MOVES NEWD INTO THE PLAINS THIS EVENING WITH A THREAT FOR VERY LARGE
HAIL...A FEW TORNADOES AND DAMAGING WIND GUSTS. STORMS ARE EXPECTED
TO GROW UPSCALE INTO ONE OR TWO BOWING MCS/S TONIGHT IN RESPONSE TO
A STRENGTHENING NOCTURNAL LOW LEVEL JET...WITH THE PRIMARY SEVERE
THREAT TRANSITIONING TO DAMAGING WIND GUSTS ALONG THE LEADING EDGE
OF THE MCS OUTFLOW.
ELSEWHERE...ONLY MINOR CHANGES HAVE BEEN MADE TO PREVIOUS OUTLOOK
...PRIMARILY TO ADJUST NRN EDGE OF SEVERE THREAT SWD OVER PARTS OF
THE OH VALLEY IN THE WAKE OF THE MCV MOVING EWD OVER SWRN OH.
..WEISS.. 06/19/2011
.PREV DISCUSSION... /ISSUED 1123 AM CDT SUN JUN 19 2011/
...SYNOPSIS...
UNSEASONABLY STRONG TROUGH DIGGING SEWD ACROSS INTERMOUNTAIN REGION
TO SRN ROCKIES BY TONIGHT. DOWNSTREAM ANOTHER MCV HAS DEVELOPED
OVERNIGHT FROM MCS ACTIVITY AND CURRENTLY MOVING EWD OH VALLEY TO
REACH THE MID ATLANTIC COAST LATER TONIGHT.
SURFACE LOW WILL DEEPEN CENTRAL HIGH PLAINS THIS AFTERNOON/TONIGHT
WITH APPROACHING STRONG UPPER TROUGH. E/W WARM FRONT CENTRAL PLAINS
WILL SHIFT NWD TO VICINITY NEB/KS BORDER THIS AFTERNOON AND BE A
PRIMARY FOCUS FOR THE EXPECTED SEVERE THUNDERSTORM OUTBREAK
BEGINNING LATER THIS AFTERNOON AND TONIGHT.
DRY LINE WILL AGAIN BECOME ACTIVE LATE THIS AFTERNOON FROM WRN OK
INTO W CENTRAL TX WHERE VERY HOT/STEEP LAPSE RATES WILL RESIDE ALONG
WITH MORE THAN SUFFICIENT INSTABILITY TO FUEL PULSE STORM
DEVELOPMENT.
...CENTRAL PLAINS...
ONLY ADJUSTMENTS TO THE MDT RISK WAS TO INCLUDE A LITTLE MORE OF
NERN CO AS VEERING WIND PROFILES ON THE N SIDE OF DEEPENING SURFACE
LOW ALONG WITH MLCAPES AOA 1500 J/KG FAVOR SUPERCELLS WITH VERY
LARGE HAIL POTENTIAL. ADDITIONALLY TORNADOES WILL BE POSSIBLE WITH
ANY SUPERCELL THAT DEVELOPS.
FURTHER E THE AIR MASS VICINITY E/W WARM FRONT BECOMES VERY UNSTABLE
WITH MLCAPES RANGING UPWARDS TO 3-4000 J/KG ACROSS NRN KS/SRN NEB.
CAP WILL WEAKEN SUFFICIENTLY BY LATE AFTERNOON TO ALLOW RAPID
DEVELOPMENT OF SEVERE THUNDERSTORMS INCLUDING SUPERCELLS. ALONG
WITH VERY LARGE HAIL...TORNADOES WILL BE POSSIBLE...PARTICULARLY
ALONG AND JUST N OF WARM FRONT WHERE BACKED SURFACE FLOW WILL
ENHANCE THE SHEAR.
DURING THE EVENING...STORMS ARE LIKELY TO DEVELOP UPSCALE INTO A
FORWARD PROPAGATING MCS ACROSS NEB. THIS ACTIVITY WOULD THEN SPREAD
EASTWARD INTO PARTS OF IA/MO WITH A THREAT OF WIDESPREAD DAMAGING
WINDS.
...LWR OH/TN VALLEYS INTO CAROLINAS...
IMPRESSIVE MCV DEVELOPED OVERNIGHT AND CURRENTLY MOVING EWD ACROSS
IND. A BAND OF STRONG WESTERLIES DEVELOPED S OF MCV AND WILL PROVIDE
FAVORABLE SHEAR FOR REDEVELOPMENT OF SEVERE THUNDERSTORMS THIS
AFTERNOON FROM TN VALLEY EWD TO MID ATLANTIC STATES BY TONIGHT. AIR
MASS CURRENTLY RECOVERING FROM W TO E ACROSS TN VALLEY IN THE WAKE
OF MORNING MCS AND BY EARLY AFTERNOON WILL BECOME MDTLY UNSTABLE
WITH MLCAPES AOA 2000 J/KG EWD ACROSS TN VALLEY AND SRN
APPALACHIANS.
THUNDERSTORMS WILL INCREASE RAPIDLY BY MID AFTERNOON AND FORM INTO
LINE SEGMENTS/BOWS GIVEN THE 40-50KT OF WLY SHEAR ACROSS TN VALLEY.
WIND DAMAGE WILL BE THE PRIMARY THREAT AS STORMS CONTINUE TO DEVELOP
UPSCALE AS THEY SPREAD EWD ACROSS TN VALLEY TO CAROLINAS.
ADDITIONAL SEVERE STORMS POSSIBLE BY MID AFTERNOON FURTHER S INTO
NRN GA WHERE AIR MASS BECOMES MDTLY UNSTABLE WITH SOMEWHAT WEAKER
SHEAR THAN FURTHER N.
...OK/TX...
THE SURFACE DRYLINE IS EXPECTED TO EXTEND FROM WESTERN OK INTO WEST
TX BY LATE AFTERNOON. HOT SURFACE TEMPERATURES AND STEEP LOW LEVEL
LAPSE RATES ALONG AND WEST OF THE DRYLINE...COUPLED WITH AFTERNOON
MLCAPE VALUES OF 1500-2000 J/KG RANGE EAST OF THE DRYLINE...WILL
PROMOTE ISOLATED THUNDERSTORM DEVELOPMENT. THE STORMS THAT FORM
WILL LIKELY REMAIN WITHIN A FEW COUNTIES OF INITIATION DUE TO
INCREASING INHIBITION FARTHER EAST. HOWEVER WITH NEAR DRY ADIABATIC
LAPSE RATES TO 500MB...MLCAPES AOA 2000 J/KG AS WELL AS DCAPE TO
ALMOST 2000 J/KG...STORMS THAT DO FORM WILL POSE A RISK OF DAMAGING
WINDS AND HAIL.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment