SWODY2
SPC AC 010730
DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT THU APR 01 2010
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SRN/E-CENTRAL PLAINS
TO OZARKS AND ARKLATEX...
CORRECTED FOR 15% LINE
...SYNOPSIS...
ERN CONUS MEAN RIDGING AND WRN TROUGHING WILL DOMINATE UPPER AIR
PATTERN OVER CONUS THROUGH PERIOD. STG MID-UPPER LEVEL SHORTWAVE
TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER NRN/CENTRAL
CA AND JUST OFFSHORE SRN CA AS OF 01/05Z -- IS FCST TO MOVE EWD
ACROSS WRN CONUS DAY-1...REACHING NM AND CHIHUAHUA BY BEGINNING OF
DAY-2. THIS FEATURE WILL MOVE EWD ACROSS SRN HIGH PLAINS DURING
DAY...REACHING W-CENTRAL TX AND WRN OK BY 3/00Z...THEN TURNING
NEWD...ASSUMING SLGT NEGATIVE TILT...AND MOVING OVER ARKLATEX AND
OZARK REGIONS BY END OF PERIOD. REASONABLY STG CONSENSUS IS
SOMEWHAT FASTER THAN GUIDANCE FROM PREVIOUS DAYS WITH THIS
SYSTEM...SFC AND ALOFT.
MEANWHILE...LEADING SHORTWAVE TROUGH NOW OVER SRN NV WILL EJECT NEWD
TO DAKOTAS BY 2/12Z...CONTRIBUTING TO REGIME OF HIGH-AMPLITUDE
TROUGHING. QUASISTATIONARY UPPER LEVEL TROUGH AND WEAK EMBEDDED LOW
ARE EVIDENT IN MOISTURE CHANNEL IMAGERY OVER S-CENTRAL GULF NEAR
YUCATAN PENINSULA...SURROUNDED BY STG DRYING ALOFT AND ACCORDINGLY
IMPLIED SUBSIDENCE. NRN STREAM TROUGH - NOW EVIDENT S OF
ALEUTIANS...WILL MOVE SEWD AND AMPLIFY THROUGH PERIOD...REACHING
COASTAL PAC NW AND PERHAPS INLAND CASCADES BY 3/00Z.
AT SFC...FRONTAL ZONE IS ANALYZED FROM WY ACROSS SERN NEB AND SWRN
KS...CURVING NWWD INTO SERN CO..WHERE WEAK CYCLONE IS DRAWN AT ITS
INTERSECTION WITH LEE TROUGH THAT EXTENDS SSEWD ACROSS ERN NM/TX
BORDER REGION. MAIN SFC LOW SHOULD CONSOLIDATE OVER CO DAY-1...THEN
EJECT NEWD AS FRONTAL-WAVE CYCLONE LATE DAY-1 INTO EARLY DAY-2...IN
ADVANCE OF LEAD SHORTWAVE. THIS LOW SHOULD BE LOCATED OVER MN
AROUND BEGINNING OF PERIOD...WITH COLD FRONT SWWD ACROSS ERN
NEB...CENTRAL KS AND NWRN OK. WEAKER/PACIFIC ORIGIN FRONTAL ZONE
AND EFFECTIVE DRYLINE WILL EXTEND SSWWD ACROSS NWRN/WRN OK TO BIG
BEND REGION...WHILE MORE PURE DRYLINE BOUNDARY SPLITS OFF OVER SW TX
AND EXTENDS SSEWD ACROSS ERN COAHUILA. BY 3/00Z...EXPECT COLD FRONT
FROM IA TO CENTRAL MO TO SRN OK AND NW TX...WITH PRECEDING
FRONT/DRYLINE FROM N-CENTRAL TX SWD/SSWWD OVER LOWER RIO GRANDE
VALLEY. BY END OF PERIOD...LATTER BOUNDARY SHOULD REACH ROUGHLY
FROM MID MS VALLEY SWWD ACROSS ERN AR...CENTRAL/SRN LA AND NWRN
GULF.
...SRN/E-CENTRAL PLAINS TO OZARKS AND ARKLATEX...
MULTI-MODAL SVR EPISODE POSSIBLE THROUGH PERIOD...BUT WITH ENOUGH
LIMITING FACTORS STILL EVIDENT TO KEEP PROBABILISTIC MAXIMA WITHIN
CATEGORICAL SLGT-RISK BIN. WRN PART OF OUTLOOK OVER OK/KS
REPRESENTS CONTINUING SVR POTENTIAL FROM LATE DAY-1 PERIOD...AS LINE
OF TSTMS MOVES EWD ACROSS PORTIONS OF THIS REGION WITH POTENTIAL FOR
SVR GUSTS/HAIL. THIS ACTIVITY SHOULD MOVE NEWD EARLY IN PERIOD
WHILE BACKBUILDING SWD...EFFECTIVELY EXPANDING INTO NARROW CORRIDOR
OF ADEQUATE --- BUT NOT IDEAL -- RETURN-FLOW MOISTURE PLUME AHEAD OF
SFC FRONT. ANTECEDENT CLOUD COVER COULD LIMIT FAVORABLE DIURNAL
HEATING TO NARROW CORRIDOR AHEAD OF MAIN CONVERGENCE ZONE...HOWEVER
STRENGTH OF DEEP-LAYER WIND FIELDS SUGGESTS SVR THREAT EVEN AMIDST
WEAK MLCAPE UNDER 1000 J/KG. POSSIBLE DEVELOPMENT OF WEAK
FRONTAL-WAVE LOW OVER OK DURING MIDDAY...WHICH THEN WOULD MOVE
NEWD...ALSO MAY FOCUS ADDITIONAL LOW-LEVEL LIFT.
GREATEST JUXTAPOSITION OF SHEAR AND BUOYANCY MAY BE DURING AFTERNOON
FROM ERN/SRN OK SWD ACROSS CENTRAL TX. IN THAT CORRIDOR...STRONGER
AND LONGER-DURATION SFC HEATING...ALONG WITH SFC DEW POINTS REACHING
60S F AND LIFT INVOF FRONT/DRYLINE...MAY BE SUFFICIENT TO OVERCOME
INITIALLY STRONG CAPPING THAT IS LIKELY AT BASE OF ELEVATED MIXED
LAYER. SUPERCELLS AS WELL AS LINEAR MODES ARE POSSIBLE...WITH LARGE
HAIL...SVR GUSTS AND PERHAPS THREAT OF TORNADOES. SVR THREAT WILL
TRANSLATE EWD INTO WRN AR AND NE TX DURING NIGHTTIME
HOURS...POSSIBLY BUILDING SWD INTO E-CENTRAL/SE TX. SWD EXTENT OF
SUCH DEVELOPMENT WILL BE LIMITED BY STG CINH. SVR POTENTIAL WILL
DIMINISH WITH TIME DURING MID-LATE OVERNIGHT HOURS -- I.E. AFTER
ABOUT 03/06Z...AS UPPER SYSTEM BEGINS TO EJECT AND AS ZONE OF
STRONGEST LOW-LEVEL FORCING EFFECTIVELY OUTPACES EWD SHIFT OF
FAVORABLY UNSTABLE CORRIDOR OF SFC-BASED INFLOW.
....LOWER MO VALLEY TO UPPER MS VALLEY...
BAND OF STG-SVR TSTMS MAY DEVELOP DURING DAY AS FRONTAL FORCING
IMPINGES UPON INCREASING LOW-LEVEL THETAE IN NARROW CORRIDOR FROM
MO-MN. DEEP-LAYER WIND FIELDS WILL BE STG...WITH 50-60 KT EFFECTIVE
SHEAR...BUT ALSO...LIMITED DIABATIC DESTABILIZATION AND MEAN WIND
NEARLY PARALLEL TO BOUNDARY. MLCAPE 500-700 J/KG APPEARS
POSSIBLE...WITH PREDOMINANT LINEAR CONVECTIVE MODE...WITH BOW/LEWP
DEVELOPMENT POSING SOME RISK OF STG-SVR GUSTS OR A BRIEF TORNADO.
SVR POTENTIAL APPEARS TOO CONDITIONAL TO EXTEND CATEGORICAL RISK
THIS FAR N ATTM.
...INLAND PAC NW...
ISOLATED AND PERHAPS WIDELY SCATTERED TSTMS WILL BE POSSIBLE IN
ZONES OF STG LOW-LEVEL WAA AND MID-UPPER LEVEL DPVA PRECEDING
LANDFALLING SHORTWAVE TROUGH. FCST DEEP-LAYER SHEAR PROFILES ALONE
WOULD INDICATE SOME POTENTIAL FOR STG-SVR TSTMS...AND POCKETS OF
SUPPORTIVE SFC HEATING MAY DEVELOP. FCST SOUNDINGS SUGGEST RATHER
MEAGER LOW-LEVEL THETAE...LIMITING BUOYANCY SIGNIFICANTLY.
HOWEVER...ONLY SLGT INCREASE VERSUS CONSENSUS OF CURRENT PROGS WOULD
BE NEEDED TO SUPPORT SOME SVR POTENTIAL. ATTM...THREAT APPEARS TOO
CONDITIONAL TO INTRODUCE PROBABILITIES.
..EDWARDS.. 04/01/2010
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