SPC AC 210554
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1254 AM CDT FRI JUL 21 2006
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE MID-ATLANTIC
REGION SWWD TO ERN TX...
...SYNOPSIS...
A SIGNIFICANT PATTERN CHANGE WILL CONTINUE THIS WEEKEND AS THE
LONGWAVE TROUGH DEEPENS ACROSS THE ERN STATES...FORCING THE UPPER
RIDGE WWD INTO THE WRN PART OF THE COUNTRY. AS A RESULT...A COLD
FRONT...SITUATED FROM SRN NEW ENGLAND SWWD ACROSS THE OH VLY TO THE
SRN ROCKIES AT THE START OF THE PERIOD WILL SETTLE TO A
NJ...NC...SRN LA...S TX AND SERN AZ LINE BY 12Z SUN. THE FRONT WILL
BE THE FOCUS FOR POSSIBLE SEVERE TSTMS.
...MID-ATANTIC STATES TO THE SRN APPALACHIANS...
AN MCS IS EXPECTED TO BE ONGOING EARLY SATURDAY MORNING ACROSS
PORTIONS OF THE OH VLY SWWD TO THE MID-SOUTH. THIS ACTIVITY SHOULD
WEAKEN THROUGH EARLY SATURDAY AS IT MOVES NEWD INTO NRN PARTS OF THE
OH VLY/MID-ATLANTIC REGION.
A STRONG H5 SHORTWAVE TROUGH IS EXPECTED TO TRANSLATE ALONG THE BASE
OF THE DIGGING LONGWAVE TROUGH FROM THE MID-SOUTH EARLY SATURDAY TO
ERN PA BY SATURDAY NIGHT. LARGE SCALE FORCING FOR ASCENT PROVIDED
BY THIS FEATURE /AND LEFT-OVER MCV/S/ WILL SPREAD NEWD ALONG THE
FRONTAL ZONE DURING PEAK HEATING. AIR MASS ALONG/SE OF THE COLD
FRONT WILL BE VERY MOIST AND UNSTABLE AND TSTMS WILL LIKELY
INTENSIFY ALONG THE SRN EDGE OF THE MORNING MCS DEBRIS FROM PARTS OF
SERN PA SWWD TO THE SRN APPALACHIANS BY EARLY SATURDAY AFTN. H5
FLOW OF 40-50 KTS WILL BOOST VERTICAL SHEAR VALUES SUFFICIENT FOR
SUPERCELLS...THOUGH MEAGER MID-LEVEL LAPSE RATES AND WEAK CINH
SUGGEST EVOLUTION INTO MAINLY SHORT-LINE SEGMENTS WILL BE PREFERRED
WITH DAMAGING WINDS THE PRIMARY SEVERE THREAT. HIGHEST PROBABILITY
FOR SEVERE TSTMS SHOULD OCCUR FROM PARTS OF SERN PA SWWD TO THE
MOUNTAINS/FOOTHILLS OF NC/VA.
ACTIVITY COULD DEVELOP INTO ONE OR MORE MCS/S OVERNIGHT. 30-40 KT
SWLY H85 JET WILL LIKELY DEVELOP ACROSS THE MID-ATLANTIC INTO SRN
NEW ENGLAND. THIS MAY SUPPORT ISOLD STRONG-SEVERE TSTMS AS FAR N AS
PARTS OF SRN NEW ENGLAND...THOUGH NRN EDGE OF THE SEVERE THREAT IS
UNCERTAIN ATTM.
...DEEP S WWD INTO CNTRL/S TX...
TAIL END OF THE COLD FRONT WILL LIKELY BE THE IMPETUS FOR SCT TSTMS
SATURDAY AFTN/EVE. VERTICAL SHEAR WILL BE MUCH WEAKER ALONG THIS
PORTION OF THE FRONT COMPARED TO FARTHER NE. BUT...HOT AND MOIST
BOUNDARY LAYER AND LOCALIZED CONVERGENCE WILL CONTRIBUTE TO
MULTICELL STORM CLUSTERS. FORECAST SOUNDINGS SHOW INVERTED-V TYPE
SUB-CLOUD STRUCTURES THAT WILL INCREASE THE THREAT FOR DAMAGING WIND
GUSTS ALONG WITH THE RISK OF HAIL.
...UPPER MS VLY...
WEAK UPPER SHORTWAVE TROUGHS WILL MOVE SEWD FROM THE CANADIAN
PRAIRIES INTO THE UPPER MS VLY/CORN BELT ON SATURDAY. RELATIVELY
COOL MID-LEVEL TEMPERATURES ATOP RESIDUAL SFC DEW POINTS IN THE MID
50S TO MID 60S WILL CONTRIBUTE TO MLCAPES OF 1000-1500 J/KG. SCT
TSTMS WILL LIKELY DEVELOP WITHIN THE CYCLONIC FLOW ALOFT BY AFTN.
THOUGH VERTICAL SHEAR WILL BE SOMEWHAT WEAK...ON THE ORDER OF 30
KTS...TSTMS WILL PROBABLY DEVELOP INTO QUICK MOVING LINE
SEGMENTS...INCREASING THE RISK FOR DAMAGING WIND GUSTS ALONG WITH
THE THREAT FOR HAIL.
..RACY.. 07/21/2006
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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