SWODY3
SPC AC 250701
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0201 AM CDT TUE MAR 25 2008
VALID 271200Z - 281200Z
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SRN/ERN OK...EXTREME
N-CENTRAL TX...WRN AR...
..SYNOPSIS...
MID/UPPER LEVEL SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL
IMAGERY IN SRN RIM OF GULF OF AK VORTEX...IS EXPECTED TO TURN EWD
ACROSS PACIFIC NW AND NRN ROCKIES DAY-2...THEN EWD ACROSS N-CENTRAL
PLAINS AND UPPER MS VALLEY THIS PERIOD. OPERATIONAL SPECTRAL AND A
COUPLE SPECTRAL/WRF SREF MEMBERS REPRESENT SLOWEST OUTLIERS AND
ALREADY APPEAR TOO SLOW BASED ON CURRENT SATELLITE TRENDS.
MEANWHILE OPERATIONAL NAM IS FAST OUTLIER...WITH SREF CONSENSUS PROG
OF PERTURBATION PREFERRED ATTM.
SFC COLD FRONT SHOULD MOVE SWD ACROSS CENTRAL AND PERHAPS PORTIONS
SRN PLAINS IN WAKE OF EJECTING FRONTAL/WAVE LOW...DECELERATING AT
LEAST TEMPORARILY DURING MIDDLE PART OF PERIOD AS PRESSURE FALLS
OCCUR OVER SRN/CENTRAL HIGH PLAINS. STRENGTH/POSITION OF SUCH
FALLS...AND OTHER ASPECTS OF BOUNDARY LAYER MASS FIELDS...VARY
CONSIDERABLY IN NUMERICAL GUIDANCE BUT ARE ABSOLUTELY CRITICAL TO
PLACEMENT/MAGNITUDE OF SVR POTENTIAL THIS PERIOD. BY
28/00Z...VARIOUS OPERATIONAL/SREF SOLUTIONS INDICATE CONSIDERABLE
DIVERSITY OF FRONTAL POSITIONS -- ANYWHERE FROM S-CENTRAL KS TO I-20
AREA IN N-CENTRAL TX. GIVEN TENDENCY OF MANY PROGS TO UNDER-FCST
LATE WINTER/EARLY SPRING SFC FRONTAL SURGES...FCST FOR LATE
AFTERNOON IS WEIGHTED TOWARD SRN PORTION OF ENSEMBLE
CONSENSUS...WHICH WOULD BE SWRN/S-CENTRAL OK NEWD ACROSS OZARKS TO
FRONTAL-WAVE LOW OVER IL/INDIANA. EXPECT CONTINUED GULF AIR MASS
MODIFICATION AND ADVECTION OF RESULTANT MOISTURE NWD/NEWD OVER SRN
PLAINS...OZARKS AND LOWER OH VALLEY. AS THIS OCCURS...DRYLINE
SHOULD BECOME INCREASINGLY WELL DEFINED THROUGH PERIOD...FROM
S-CENTRAL TX NNEWD TO FRONTAL INTERSECTION OVER SRN OK.
..OH VALLEY TO SRN PLAINS...
WIDELY SCATTERED TO SCATTERED TSTMS MAY DEVELOP INVOF FRONT DURING
AFTERNOON...AS FAR SW AS DRYLINE INTERSECTION. NERN PORTION OF THIS
CORRIDOR WOULD TREND MORE TOWARD WIND THREAT...WITH LARGE HAIL MORE
PROBABLE OVER RED RIVER REGION. ACTIVITY SHOULD BE SUPPORTED BY
INFLOW LAYER EMANATING FROM NARROW PLUME OF WARM-SECTOR MOISTURE
RETURN...COMBINED WITH FRONTAL ASCENT AND DIABATIC/DIURNAL HEATING.
STRONGER CAPPING IS EXPECTED WITH SWWD EXTENT DOWN FRONTAL
ZONE...RELATED TO ELEVATED MIXED LAYER. HOWEVER...ALSO EXPECT
STEEPER LAPSE RATES ALOFT...MORE MOISTURE...STRONGER HEATING AND
LARGER BUOYANCY ACROSS OK/N TX PORTION OF OUTLOOK AREA THAN FARTHER
NE...LEADING TO CONDITIONAL/SIGNIFICANT SVR POTENTIAL. GIVEN
STRENGTH/PERSISTENCE OF ANTECEDENT EML...DRYLINE PROBABLY WILL
REMAIN TOO CAPPED TO SUPPORT MORE THAN VERY ISOLATED CONVECTIVE
THREAT.
VERTICAL SHEAR PROFILES WILL BE FAVORABLE ALONG MOST OF FRONTAL
ZONE...WITH ACTUAL SVR THREAT STRONGLY DICTATED BY MESOSCALE AND
SMALLER INFLUENCES ON CONVECTIVE MODE. GIVEN AFOREMENTIONED SPATIAL
AND MODAL UNCERTAINTIES...UNCONDITIONAL SVR PROBABILITIES ARE KEPT
AT MRGL THRESHOLDS FOR CATEGORICAL SLGT RISK OVER SRN PLAINS...AND
JUST BELOW THAT FARTHER NE.
.EDWARDS.. 03/25/2008
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