SWODY1
SPC AC 271250
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT FRI APR 27 2007
VALID 271300Z - 281200Z
..THERE IS A SLGT RISK OF SVR TSTMS FOR THE MID ATLANTIC STATES...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF OK AND
NORTHERN/WESTERN TX...
..SYNOPSIS...
WATER VAPOR IMAGERY FEATURES UPPER LOW CENTERED OVER MI EARLY THIS
MORNING...WITH THIS FEATURE FORECAST TO WEAKEN/LIFT NORTHEASTWARD
INTO EASTERN CANADA TODAY. WITHIN THE BROADER/EVOLVING EASTERN
STATES UPPER TROUGH...SEVERAL TRAILING SHORTWAVE IMPULSES ARE
FORECAST TO CROSS THE PLAINS AND TENNESSEE VALLEY/MID ATLANTIC
STATES AMIDST A MODERATELY STRONG BELT OF MID LEVEL FLOW. AT THE
SURFACE EARLY THIS MORNING...AN OCCLUDED/COLD FRONT WAS ANALYZED
ROUGHLY NORTH-SOUTH ALONG THE APPALACHIANS...ARCING FROM A 1002 MB
SURFACE LOW IN EASTERN LOWER MI INTO GA/FL PANHANDLE. A WEST-EAST
ORIENTED WARM FRONT WAS ANALYZED ACROSS VA...DEMARCATING 60S F
DEWPOINTS TO THE SOUTH OF THE FRONT ACROSS THE CAROLINAS. IN THE
WEST...BROAD UPPER RIDGE WILL AMPLIFY OVER MUCH OF THE WESTERN
STATES BENEATH A STRONG PACIFIC JET NOSING INTO THE PACIFIC
NORTHWEST AND WESTERN CANADIAN PROVINCES.
..MID ATLANTIC STATES THROUGH EARLY EVENING...
PRIMARY COLD FRONT WILL PUSH EASTWARD FROM THE SPINE OF THE
APPALACHIANS TOWARD THE MID ATLANTIC SEABOARD THROUGH EARLY
EVENING...WHILE THE WARM FRONT GRADUALLY LIFTS NORTHWARD ACROSS THE
DELMARVA. AHEAD OF THE COLD FRONT...GRADUAL EXIT OF EXISTING EARLY
MORNING CONVECTION AND SURGING MID LEVEL DRY SLOT WILL ALLOW FOR
SOME POCKETS OF STRONGER DAYTIME HEATING. COMBINED WITH DEWPOINTS IN
THE 60S F...AMPLE INSTABILITY WILL EXIST FOR SCATTERED STRONG/SEVERE
STORMS FROM LATE MORNING THROUGH EARLY EVENING...ESPECIALLY FROM THE
DELMARVA VICINITY TO THE COASTAL PLAIN OF THE CAROLINAS. NAM/NAMKF
FORECAST SOUNDINGS SUGGEST MLCAPE VALUES AROUND 1000 J/KG IN THE
AMBIENT WARM SECTOR...MAXIMIZED ACROSS SOUTHEAST VA INTO THE COASTAL
AREAS OF NC/SC. STRONG VERTICAL SHEAR WILL SUPPORT THE EVOLUTION OF
SOME SEMI-DISCRETE AND/OR LINE EMBEDDED SUPERCELLS THIS
AFTERNOON...WITH DAMAGING WINDS/LARGE HAIL AND A FEW TORNADOES
POSSIBLE.
..OK AND WESTERN/NORTHERN TX THIS AFTERNOON/EVENING...
WITH SHORTWAVE TROUGH AND ASSOCIATED WEAK COLD FRONT/TROUGH
ADVANCING SOUTHEASTWARD ACROSS THE SOUTH CENTRAL PLAINS
TODAY...ASSOCIATED LARGE SCALE ASCENT IS EXPECTED TO LEAD TO
INCREASING THUNDERSTORM COVERAGE ACROSS MUCH OF OK AND PORTIONS OF
NORTHERN/WESTERN TX THROUGH THE AFTERNOON. 12Z OBSERVED SOUNDINGS
SUGGEST ONLY LIMITED MOISTURE WILL GRADUALLY RETURN NORTHWESTWARD
ACROSS TX/OK AROUND THE SURFACE HIGH CENTERED OVER THE ARKLATEX.
ALTHOUGH SURFACE DEWPOINTS WILL GENERALLY BE LIMITED TO THE LOWER
50S F...AFTERNOON HEATING WILL LEAD TO MODEST CONVECTIVE INSTABILITY
WITH MLCAPES UP TO 750 J/KG. FORECAST SOUNDINGS DEPICT STRONGLY
VEERING WIND PROFILES WITH EFFECTIVE BULK SHEAR GREATER THAN 40 KT.
THIS WILL SUPPORT SOME SUPERCELL STRUCTURES WITH A RISK OF LARGE
HAIL...AS WELL AS THE POTENTIAL FOR STRONG WIND GUSTS AMIDST A WELL
MIXED BOUNDARY LAYER.
.GUYER/EDWARDS.. 04/27/2007
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