SWODY1
SPC AC 090559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT MON MAY 09 2011
VALID 091200Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN IA...SW WI
AND IL...
...NRN PLAINS/NRN HIGH PLAINS...
AN UPPER-LEVEL LOW OVER THE WRN STATES WILL MOVE SWD TODAY AS A 60
TO 75 KT MID-LEVEL JET ROUNDS THE BASE OF THE TROUGH. THE EXIT
REGION OF THE MID-LEVEL JET IS FORECAST TO OVERSPREAD THE NRN PLAINS
BY EARLY THIS EVENING HELPING TO ENHANCE SHEAR PROFILES ACROSS THE
REGION. THIS WILL HELP CREATE CONDITIONS FAVORABLE FOR STRONG
THUNDERSTORM DEVELOPMENT THIS AFTERNOON. THE ECMWF...GFS AND NAM-KF
ARE IN REASONABLE AGREEMENT...INITIATING A CLUSTER OF THUNDERSTORMS
AROUND RAPID CITY AT 00Z AND MOVING THIS CONVECTION NEWD INTO CNTRL
AND NRN SD DURING THE EVENING.
FORECAST SOUNDINGS ACROSS THE SOUTH DAKOTA AT 00Z TO 03Z SHOW MLCAPE
VALUES RANGING FROM AROUND 1000 J/KG IN SWRN SD TO AROUND 3000 J/KG
IN ERN SD WITH 0-6 KM SHEAR VALUES ACROSS SD IN THE 30 TO 40 KT
RANGE. THIS ALONG WITH STEEP MID-LEVEL LAPSE RATES SHOULD BE
SUPPORTIVE OF LARGE HAIL WITH STORMS THAT HAVE ACCESS TO THE
STRONGER INSTABILITY. THE NAM IS THE OUTLIER DRIVING THE COLD FRONT
ACROSS WRN SD AND STABILIZING THE AIR MASS AROUND RAPID CITY. THIS
INTRODUCES UNCERTAINTY INTO THE FORECAST BUT AM FAVORING THE NAM-KF
WHICH DEVELOPS MORE INSTABILITY ACROSS CNTRL AND WRN SD. AT THIS
POINT...WILL MAINTAIN A SMALL 30 PERCENT PROBABILITY FOR LARGE HAIL
IN CNTRL SD WHERE CONFIDENCE IS THE GREATEST CONCERNING MODERATE TO
STRONG DESTABILIZATION. IF SUPERCELLS CAN DEVELOP IN CNTRL SD...THEN
AN ISOLATED THREAT FOR TORNADOES OR VERY LARGE HAIL COULD ALSO
EXIST. A WIND DAMAGE THREAT MAY ALSO DEVELOP BUT MAY BE FOCUSED
DURING THE MID TO LATE EVENING HOURS IF A LINE OF STORMS CAN
ORGANIZE ACROSS THE REGION.
...ERN IOWA/ILLINOIS/SW WISCONSIN...
SOUTHWEST FLOW WILL BE IN PLACE ACROSS THE MID TO UPPER MS VALLEY
JUST TO THE WEST OF AN UPPER-LEVEL RIDGE IN THE WRN GREAT LAKES AND
LOWER OH VALLEY. BENEATH THE SOUTHWEST FLOW...A BROAD LOW-LEVEL JET
SHOULD EXIST FROM THE OZARKS NWD INTO THE UPPER MS VALLEY. WARM
ADVECTION ASSOCIATED WITH THE LOW-LEVEL JET SHOULD MOVE THE
INSTABILITY AXIS QUICKLY NWD INTO ERN IA AND IL THIS AFTERNOON.
THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ALONG THE INSTABILITY
GRADIENT LATE THIS AFTERNOON IN ERN IA...SRN WI AND IL WHERE
FORECAST SOUNDINGS SHOW FAVORABLE SHEAR PROFILES FOR SEVERE STORMS.
HOWEVER...A CAPPING INVERSION IS FORECAST TO BE IN PLACE ACROSS THE
WARM SECTOR SUGGESTING STORMS WILL HAVE TROUBLE INITIATING SOUTH OF
THE WARM FRONT WHERE THE MOST FAVORABLE ENVIRONMENT IS FORECAST. IF
CONVECTION CAN INITIATE NEAR THE WARM FRONT WHERE MODERATE
INSTABILITY SHOULD EXIST...THEN SUPERCELL DEVELOPMENT WILL BE
POSSIBLE WITH A THREAT FOR ISOLATED LARGE HAIL AND WIND DAMAGE. THIS
THREAT MAY INCREASE DURING THE EVENING AND OVERNIGHT PERIOD AS THE
LOW-LEVEL JET STRENGTHENS ACROSS THE REGION AND DESTABILIZATION
OCCURS FURTHER NORTH AND EAST ACROSS THE REGION.
...ERN GULF COAST STATES/FLORIDA...
NORTHWEST FLOW WILL BE IN PLACE FROM THE SRN APPALACHIAN MTNS SEWD
ACROSS THE ERN GULF COAST STATES. AS SFC TEMPS HEAT UP THIS
AFTERNOON...ISOLATED THUNDERSTORMS SHOULD INITIATE ALONG AN AXIS OF
MODERATE INSTABILITY IN THE HIGHER TERRAN OF THE SRN APPALACHIAN
MTNS AND ACROSS THE COASTAL PLAINS OF ERN GA AND NRN FL. FORECAST
SOUNDINGS ALONG THIS CORRIDOR AT 21Z TO 00Z SUGGEST MLCAPE VALUES
WILL BE IN THE 1500 TO 2000 J/KG RANGE WITH 0-6 KM SHEAR VALUES
AROUND 30 KT. THIS ENVIRONMENT COULD SUPPORT A MARGINAL SEVERE
THREAT WITH EITHER HAIL AND/OR STRONG GUSTY WINDS POSSIBLE WITH THE
MORE INTENSE CELLS.
..BROYLES/STOPKOTTE.. 05/09/2011
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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