SPC AC 051721
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1221 PM CDT MON OCT 05 2009
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE TUE AFTN ACROSS PARTS OF
TX INTO LWR MS VALLEY...
...SYNOPSIS...
AS A SIGNIFICANT SHORT WAVE IMPULSE/JET STREAK TOPS THE CREST OF THE
NORTHEAST PACIFIC RIDGE...UPPER FLOW APPEARS LIKELY TO AMPLIFY
ACROSS THE NORTHEAST PACIFIC INTO WESTERN CANADA THROUGH THIS
FORECAST PERIOD. MODELS INDICATE THAT THE JET STREAK WILL DIG
SOUTHWARD THROUGH THE CANADIAN ROCKIES TUESDAY/TUESDAY NIGHT. AS
THIS OCCURS...A SIGNIFICANT IMPULSE/CLOSED LOW...EMANATING FROM THE
SPLITTING DOWNSTREAM POSITIVELY TILTED TROUGH OVER THE WESTERN
U.S...IS PROGGED TO ACCELERATE EASTWARD THROUGH THE GREAT LAKES
REGION BY EARLY WEDNESDAY. AT THE SAME TIME...ANOTHER CLOSED LOW IS
EXPECTED TO FORM WITHIN THE DEVELOPING SOUTHERN STREAM...NEAR
SOUTHERN CALIFORNIA COASTAL AREAS...WITH CORRESPONDING MID/UPPER
HEIGHT RISES DOWNSTREAM ACROSS PARTS OF THE CENTRAL/SOUTHERN ROCKIES
AND PLAINS.
IN RESPONSE TO THE EVOLVING PATTERN...STRONG CYCLOGENESIS APPEARS
LIKELY TO ACCOMPANY THE IMPULSE EMERGING FROM THE WEST...ACROSS THE
UPPER MIDWEST THROUGH THE GREAT LAKES REGION...WHILE MID/HIGH LEVEL
FLOW INTENSIFIES IN A BROADLY CYCLONIC BELT ACROSS THE MIDDLE
MISSISSIPPI VALLEY THROUGH THE NORTHEAST. DESPITE FAVORABLE LARGE
SCALE FORCING FOR UPWARD VERTICAL MOTION...IN THE PRESENCE OF
INCREASING FAVORABLE DEEP LAYER SHEAR FOR STRONG/SEVERE STORM
DEVELOPMENT...GUIDANCE CONTINUES TO INDICATE THAT PROBABILITIES FOR
SUBSTANTIVE BOUNDARY LAYER DESTABILIZATION ARE NEARLY NEGLIGIBLE TO
THE NORTHEAST OF THE OZARK PLATEAU/LOWER MISSISSIPPI VALLEY REGION.
THIS...COUPLED WITH THE LIKELIHOOD THAT LAPSE RATES WILL REMAIN
GENERALLY WEAK ABOVE THE ELEVATED MOISTURE RETURN...SUGGESTS THAT
CONVECTIVE POTENTIAL WILL REMAIN LIMITED.
...TEXAS INTO THE LOWER MISSISSIPPI VALLEY...
HIGH MOISTURE LEVELS...CHARACTERIZED BY 70F+ SURFACE DEW POINTS AND
PRECIPITABLE WATER NEAR OR IN EXCESS OF 2 INCHES...WILL LINGER
BENEATH SUBTROPICAL RIDGING TUESDAY ACROSS THE GULF STATES. BEFORE
STRONGER SOUTHERLY LOW-LEVEL FIELDS SHIFT OFF TO THE NORTHEAST EARLY
IN THE DAY...A TONGUE OF HIGHER MOISTURE CONTENT AIR COULD ADVECT
NORTHWARD ACROSS NORTHERN TEXAS INTO PARTS OF THE OZARK
PLATEAU...AHEAD OF A SOUTHWARD ADVANCING COLD FRONT TRAILING FROM
THE DEEPENING SURFACE CYCLONE. DESPITE SOMEWHAT WEAK MID-LEVEL
LAPSE RATES...SREF GUIDANCE INDICATES THAT MOISTURE WILL BE
SUPPORTIVE OF MODERATE POTENTIAL INSTABILITY AND CONVECTIVE
DEVELOPMENT AS FRONTAL FORCING STRENGTHENS DURING THE AFTERNOON. IN
THE PRESENCE OF LINGERING MODERATELY STRONG WEST SOUTHWESTERLY
MID/UPPER FLOW...DEEP LAYER SHEAR PROBABLY WILL BE SUFFICIENT TO
ENHANCE THE RISK FOR SEVERE STORMS CAPABLE OF LARGE HAIL AND LOCALLY
DAMAGING WIND GUSTS. THE WINDOW OF OPPORTUNITY FOR SEVERE STORMS
MAY NOT BE PARTICULARLY LONG-LIVED...HOWEVER...GIVEN THE EXPECTED
TENDENCY FOR THE FRONT TO UNDERCUT THE STRONGER CONVECTION...AND THE
PROBABLE ONSET OF MID/UPPER HEIGHT RISES...BY THE EVENING HOURS.
..KERR.. 10/05/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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