Thursday, November 11, 2010

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 110547
SWODY1
SPC AC 110545

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1145 PM CST WED NOV 10 2010

VALID 111200Z - 121200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
IN MID-UPPER LEVELS...EXPECT WRN MEAN TROUGHING TO BE MAINTAINED
THROUGH PERIOD...ALONG WITH WELL-DEFINED RIDGING E OF MS RIVER AND
ACROSS LOWER GREAT LAKES. SHORTWAVE ANALYZED ATTM OVER GREAT BASIN
IS FCST TO PIVOT EWD ACROSS SRN ROCKIES BY 12/12Z...RESULTING IN
PROGRESSIVE AND HIGHLY AMPLIFIED TROUGH FROM BLACK HILLS TO NEAR ELP
AT THAT TIME.

IN RESPONSE...SFC LEE TROUGHING ALREADY UNDERWAY OVER SRN HIGH
PLAINS WILL LEAD TO NWD RETREAT OF STALLED FRONTAL ZONE NOW ANALYZED
FROM S-CENTRAL OK ACROSS SERN NM...THROUGH ABOUT 12/06Z. THIS FRONT
WILL SHIFT/REDEVELOP NWD TO DEVELOPING SFC LOW OVER NERN NM BY
12/00Z...EXTENDING ENEWD AT THAT TIME ACROSS NRN OK AND CENTRAL/SRN
MO. FRONT WILL PROGRESS SEWD OVER SRN HIGH PLAINS OVERNIGHT...NEAR
MKC-ICT-CDS-MAF LINE. DRYLINE...NOW ANALYZED FROM S-CENTRAL OK SWWD
ACROSS SW TX...SHOULD REORIENT MERIDIONALLY BY MID-LATE
AFTERNOON...EXTENDING FROM SW TX NWD ACROSS SWRN/W-CENTRAL OK TO
INTERSECTION WITH FRONTAL ZONE.

...CENTRAL/SRN PLAINS...LOWER MO VALLEY...IA...
TWO PRIMARY TEMPORAL CONVECTIVE EPISODES ARE EXPECTED.
FIRST...ELEVATED CONVECTION SHOULD BUILD INTO ISOLATED TO WIDELY
SCATTERED TSTMS OVER PORTIONS KS/OK AND PERHAPS SWRN MO BEFORE
18Z...AS MRGL MOISTURE BEGINS TO ACCOMPANY INCREASINGLY WARM
TRAJECTORIES ABOVE BOUNDARY LAYER THAT WILL BE RAISED TO LFC. NET
STEEPENING OF LOW-MIDDLE LEVEL LAPSE RATES WILL RESULT...COMBINING
WITH ENOUGH MOISTURE TO BOOST DEPTH OF BUOYANCY PAST
SLOWLY-DESTABILIZING WEAKNESS IN LAPSE RATES AROUND 500-MB LEVEL.
BOTH CAPE AND SHEAR SHOULD BE TOO WEAK FOR SVR THREAT WITH THIS
ACTIVITY.

LATER...BANDS OF TSTMS ARE FCST TO INCREASE IN COVERAGE INVOF
FRONTAL ZONE THROUGH EVENING AND OVERNIGHT HOURS AS MOISTURE AND
DEEP-LAYER ASCENT EACH STRENGTHEN...BUT BEGINNING PERHAPS IN
AFTERNOON WITH SFC DIABATIC HEATING AND CONVERGENCE NEAR BOUNDARY.
E OF DRYLINE AND SE OF FRONT...RETURN OF INCOMPLETELY MODIFIED AIR
MASS FROM GULF COAST REGION WILL SUPPORT CONVECTIVE POTENTIAL.
EXPECT INCREASING COVERAGE OF 50S F SFC DEW POINTS NOW ANALYZED IN
NARROW CORRIDOR FROM NW TX TO NRN MO...WITH LOW 60S F AT LEAST INTO
PORTIONS SRN/CENTRAL OK. STEADILY INCREASING WARM-SECTOR MOISTURE
OVERNIGHT ACCOMPANYING 40-45 KT LLJ...ALONG WITH STRENGTHENING
FRONTOGENETIC FORCING...SHOULD ASSIST WITH CONVECTIVE BACKBUILDING
SWD TOWARD UPPER RED RIVER VALLEY REGION NEAR CDS AND
SPREADING/DEVELOPING NEWD TOWARD WRN PORTIONS OF CORN BELT.

FRONTAL TSTMS OVER SRN PLAINS SHOULD SHIFT EWD AMIDST MRGL
DEEP-LAYER INSTABILITY...WITH MUCAPES REMAINING GENERALLY AOB 500
J/KG MOST AREAS...AND SHALLOW/DIABATICALLY COOLED STABLE LAYER AT
SFC THAT SHOULD DAMPEN DOWNDRAFT GUSTS. GIVEN LINEAR MODE AND LACK
OF ROBUST LAPSE RATES ALOFT...AS WELL AS FCST EFFECTIVE SHEAR
MAGNITUDES LESS THAN 30 KT...HAIL THREAT APPEARS MINIMAL. LACK OF
MORE ROBUST LOW-LEVEL THETAE AND LAPSE RATES ALOFT ALSO SHOULD
PRECLUDE APPRECIABLE SVR THREAT WITH ELEVATED CONVECTION FROM
CENTRAL PLAINS TO IA.

...4-CORNERS AREA...
ISOLATED TO WIDELY SCATTERED...SHALLOW AND HIGH-BASED TSTMS MAY
DEVELOP DURING DAY AS STG DCVA AND RELATED COOLING ALOFT SPREAD OVER
THIS REGION...WHILE DIABATIC SFC HEATING OFFSETS CAA ENOUGH TO
GENERATE MUCAPE AOB 200 J/KG.

..EDWARDS/HURLBUT.. 11/11/2010

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