SPC AC 242013
DAY 1 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0313 PM CDT THU JUN 24 2010
VALID 242000Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN KY/NERN TN TO MID
ATLANTIC STATES AND NEWD TO NEW ENGLAND...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE NRN PLAINS
AND UPPER MS VALLEY...
CORRECTED FOR SEE TEXT LABEL ON CATEGORICAL GRAPHIC

...KY TO MID ATLANTIC STATES AND NEWD TO NEW ENGLAND...
SLIGHT RISK AREA AND SEVERE PROBABILITY LINES HAVE BEEN ADJUSTED
ACROSS THIS REGION PER REGIONAL RADAR TRENDS/EWD MOVEMENT OF COLD
FRONT SUPPORTING TRIMMING OF THE SLIGHT RISK FROM THE WEST. MINOR
NWD EXPANSION OF SLIGHT RISK/SEVERE PROBABILITIES WERE MADE OVER
NWRN MAINE TO ACCOUNT FOR ONGOING SEVERE RISK.
ALTHOUGH DEEP LAYER SHEAR WEAKENS WITH SWD EXTENT INTO ERN TN TO SRN
VA...MODERATE INSTABILITY IS EXPECTED TO SUSTAIN A POTENTIAL FOR
TSTMS AND ATTENDANT SEVERE THREAT AS THE COLD FRONT ADVANCES EWD.
THUS...SLIGHT RISK/SEVERE PROBABILITIES HAVE BEEN EXPANDED SWD INTO
THE REST OF VA TO NERN TN.
FOR SHORT TERM MESOSCALE DETAILS...PLEASE REFER TO SPC WATCHES AND
MESOSCALE DISCUSSION VALID FOR THIS PART OF THE CONUS.

...ERN ND/NRN MN...
SLIGHT RISK/SEVERE PROBABILITIES HAVE BEEN EXTENDED EWD ACROSS MUCH
OF THE REST OF NRN MN TO ACCOUNT FOR EXPECTED CONTINUATION OF TSTM
DEVELOPMENT FROM NERN/ERN ND THROUGH NRN MN WITHIN WAA REGIME
BENEATH ENTRANCE REGION OF 60-70 KT NWLY MIDLEVEL JET LOCATED OVER
NRN/WRN ONTARIO. FOR MESOSCALE DETAILS...PLEASE REFER TO SPC
MESOSCALE DISCUSSION 1113...WW 409 AND ANY SUBSEQUENT DISCUSSIONS.

...ARKLATEX WWD ACROSS N TX/FAR SRN OK...
5 PERCENT WIND PROBABILITY EXPANDED SEVERAL COUNTIES SWD ACROSS N TX
AND INTO NWRN LA TO ACCOUNT FOR ISOLATED STRONG WIND GUST POTENTIAL
ATTENDANT TO TSTMS CONTINUING TO DEVELOP ALONG NRN PERIPHERY OF WEAK
MIDLEVEL LOW. ASCENT WITHIN THIS REGIME WILL CONTINUE TO SPREAD
N/NWWD AS MIDLEVEL LOW TRACKS NW TOWARD N TX THIS FORECAST PERIOD.
MODERATE TO STRONG INSTABILITY...HIGH PW VALUES /AOA 2 INCHES/ AND
STEEP LOW LEVEL LAPSE RATES FAVOR POTENTIAL FOR A FEW STRONG
DOWNBURSTS.

...ELSEWHERE...
NO CHANGES WERE NEEDED IN THE OUTLOOK.
..PETERS.. 06/24/2010
.PREV DISCUSSION... /ISSUED 1114 AM CDT THU JUN 24 2010/

...SYNOPSIS...
FAST W TO WNW FLOW WILL PREVAIL FROM THE NRN PLNS TO THE NRN/MID
ATLANTIC CSTS TODAY...N OF ELONGATED RIDGE OVER THE SOUTH...AND
DOWNSTREAM FROM POSITIVE TILT TROUGH IN THE WEST. STRONG SHORTWAVE
IMPULSE NOW CROSSING THE LWR GRT LKS SHOULD REACH NEW ENGLAND BY EVE
AND THE CANADIAN MARITIMES EARLY FRI. AT THE SAME TIME...A SERIES
OF WEAK DISTURBANCES EXPECTED TO EJECT ENE FROM WRN TROUGH ACROSS MT
AND SRN AB/SK LATER IN THE PERIOD.
DIFFUSE COLD FRONT TRAILING SW INTO THE LWR OH VLY FROM ST LAWRENCE
VLY/NRN ME SFC LOW...AND DEVELOPING LEE TROUGH E OF THE CNTRL/NRN
APPALACHIANS...SHOULD BE THE MAIN FOCI FOR DIURNAL STORM
DEVELOPMENT/SVR THREAT TODAY.

...ERN KY/SRN OH/WV INTO NEW ENGLAND THIS AFTN/EARLY EVE...
PASSAGE OF DEBRIS FROM UPSTREAM STORMS...AND SFC HEATING...ARE
DESTABILIZING REGION ALONG AND AHEAD OF COLD FRONT ATTM FROM ERN
KY/WV NEWD INTO THE HUDSON VLY. AREA SOUNDINGS DO NOT SHOW PRESENCE
OF A WELL-DEFINED EML. BUT COMBINATION OF CONTINUED SFC HEATING
/ENHANCED BY WLY DOWNSLOPE E OF THE MOUNTAINS/ AND EXISTING LOW LVL
MOISTURE /SFC DEWPOINTS IN THE UPR 60S F AND PW AOA 1.50 IN/ SHOULD
BOOST AFTN SBCAPE TO AROUND 2500 J/KG IN ERN KY AND TO AROUND 1500
J/KG FROM ERN MD/VA NEWD INTO THE LWR HUDSON VLY/SRN NEW ENGLAND.
TSTMS SHOULD FIRST FORM/INTENSIFY ALONG COLD FRONT IN NRN/WRN PA
INTO SE OH...WITH OTHER DEVELOPMENT EXPECTED AHEAD OF FRONT BY EARLY
AFTN FROM SE NY/ERN PA SWD INTO MD/VA...AND OVER ERN KY/WV. LARGELY
UNIDIRECTIONAL 40-50 KT MEAN WLY FLOW /WITH 500 MB SPEEDS OF 50-60
KTS/ SHOULD SUPPORT SUSTAINED STORMS/SUPERCELLS FROM MD/NRN VA NWD.
THESE MAY ORGANIZE INTO SHORT BANDS/SMALL CLUSTERS. COUPLED WITH
STEEPENING LOW LVL LAPSE RATES /ESPECIALLY E OF THE MOUNTAINS/...A
THREAT WILL EXIST FOR NARROW SWATHS OF DMGG WIND AND PERHAPS
MARGINALLY SVR HAIL THROUGH EARLY EVE. GIVEN PRESENCE OF A FEW
SUSTAINED SUPERCELLS AND STRENGTH OF SHEAR...ONE OR TWO TORNADOES
CANNOT BE RULED OUT. THIS THREAT APPEARS GREATEST FROM THE CT RVR
VLY INTO ME...WHERE SLIGHTLY BACKED LOW LVL FLOW WILL EXIST CLOSER
TO UPR VORT/SFC LOW. WEAKER SHEAR WILL EXIST FARTHER SW INTO ERN
KY/WV. BUT COMBINATION OF MODERATE WNW SHEAR WITH SUBSTANTIAL
SBCAPE LIKELY WILL YIELD A FEW BANDS/CLUSTERS OF MULTICELLS WITH
LOCALLY DMGG WIND.

...ND/NW MN THIS AFTN/EVE...
MODIFIED POLAR AIR /WITH SFC DEWPOINTS IN THE 50S F/ WILL PREVAIL AT
LWR LVLS OVER THE NRN PLNS THIS PERIOD...N OF WEAK FRONT MARKING SRN
EDGE OF THE WLYS. LOW LVL WAA ALSO WILL PERSIST...AHEAD OF
AFOREMENTIONED DISTURBANCES IN WLY FLOW ALOFT. THIS SETUP MAY
SUPPORT AN INCREASING POTENTIAL FOR SLIGHTLY ELEVATED STORMS TO
MOVE/DEVELOP SE ACROSS ND AND INTO THE UPR MS VLY LATER
TODAY/TONIGHT. THESE STORMS MAY INTENSIFY/BECOME MORE NEARLY
SFC-BASED AS THE BOUNDARY LAYER DESTABILIZES. SELY LOW LVL WINDS
VEERING TO 30-40 KT WLY FLOW AT MID LVLS MAY SUPPORT A FEW
SUPERCELLS WITH LARGE HAIL AND LOCALLY DMGG WIND...MAINLY THIS AFTN
THROUGH MID EVE.