Wednesday, August 3, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 040055
SWODY1
SPC AC 040053

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0753 PM CDT WED AUG 03 2011

VALID 040100Z - 041200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
MIDDLE-UPPER LEVEL PATTERN REMAINS CHARACTERIZED BY INTENSE
ANTICYCLONE CENTERED OVER ARKLATEX REGION...WITH TROUGHING ALONG E
AND W COASTS. IN BETWEEN...SEVERAL RELATIVELY LOW-AMPLITUDE
SHORTWAVES PREVAIL. THIS INCLUDES WEAK PERTURBATIONS NOW EVIDENT IN
MOISTURE CHANNEL IMAGERY MOVING SEWD ACROSS SRN IL...AND NEWD OVER
UT. VIS AND COMPOSITE REFLECTIVITY ANIMATIONS INDICATE MCV DRIFTING
NEWD ACROSS SERN NEB.

AT SFC...23Z ANALYSIS SHOWED LOW OVER CENTRAL/NERN PA...WARM FRONT
SWD OVER ERN VA THEN EWD OFFSHORE HAMPTON ROADS REGION...AND COLD
FRONT SWWD ACROSS ERN KY TO NRN AR AND NERN OK. FRONT EFFECTIVELY
HAS BEEN SHUNTED FARTHER S THAN SYNOPTIC POSITION ACROSS CENTRAL/SRN
OK BECAUSE OF AGGREGATE OUTFLOW. FRONTAL ZONE GENERALLY W OF MS
RIVER SHOULD BECOME QUASISTATIONARY THROUGH REMAINDER PERIOD...WHILE
DRIFTING SEWD ACROSS TN VALLEY REGION AND CENTRAL/SRN APPALACHIANS.

...CENTRAL/SRN PLAINS TO SRN APPALACHIANS...
WIDELY SCATTERED TO SCATTERED TSTMS REMAIN OVERALL...WITH SOMEWHAT
MORE DENSE MESOSCALE CONCENTRATION OVER PORTIONS KS/OK.
PRE-STORM/BOUNDARY-LAYER AIR MASS ACROSS THIS REGION TRANSITIONS
FROM HIGH-PW/LARGE-CAPE REGIME OVER KY/TN TO DEEPLY MIXED AND
STRONGLY HEATED CHARACTER OVER SRN/CENTRAL PLAINS...EACH SUPPORTING
LOCALLY STG-SVR DOWNDRAFTS IN REGIME OF WEAK DEEP-TROPOSPHERIC
FLOW/SHEAR. CONVECTIVE COVERAGE/INTENSITY GENERALLY SHOULD LESSEN
THROUGH REMAINDER EVENING...DUE STABILIZING EFFECTS OF BOTH DIABATIC
SFC COOLING AND INCREASING COVERAGE OF OUTFLOW AIR.

...WRN PORTIONS SD/NEB...
WIDELY SCATTERED TO SCATTERED TSTMS ARE EVIDENT IN BAND FROM NEAR
I-90 IN WRN SD SSWWD ACROSS CENTRAL/NRN NEB PANHANDLE AND ADJACENT
PORTIONS EXTREME ERN WY. SD ACTIVITY HAS PRODUCED CONSIDERABLE
OUTFLOW ALREADY...WITH LOOSELY ORGANIZED COLD POOL EVIDENT OVER
BADLANDS REGION OF SD AND MORE ISOLATED/LOCALIZED DOWNDRAFT THREAT
FARTHER S AND SW. RELATIVELY NARROW SPATIAL/TEMPORAL CORRIDOR
REMAINS THROUGH WHICH STG/DAMAGING GUSTS ARE POSSIBLE FOR ANOTHER
FEW HOURS. MODIFIED RAOBS AND RUC SOUNDINGS SUGGEST THAT CURRENTLY
OBSERVED SFC THETAE DECREASES WITH EWD EXTENT...COMBINED WITH SFC
DIABATIC COOLING...WILL REDUCE GUST THREAT WITH TIME THIS EVENING.

...AZ...
ISOLATED TO WIDELY SCATTERED TSTMS SHOULD PERSIST FOR ANOTHER FEW
HOURS ACROSS THIS REGION...AMIDST PRE-STORM SFC TEMPS UPPER 90S TO
LOW 100S F AND DEW POINTS 50S OVER LOWER ELEVATIONS. 00Z TUS RAOB
AND MODIFIED MODEL SOUNDINGS EACH INDICATE POTENTIAL FOR ISOLATED
STG-SVR GUSTS WITH MOST INTENSE DOWNDRAFTS...GIVEN DEEP/WELL-MIXED
SUB CLOUD LAYERS AND POTENTIAL FOR EVAPORATIVE COOLING/ACCELERATION
ON STORM SCALE.

..EDWARDS.. 08/04/2011

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