Sunday, September 23, 2012

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 231939
SWODY1
SPC AC 231938

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0238 PM CDT SUN SEP 23 2012

VALID 232000Z - 241200Z

...NO SVR TSTM AREAS FORECAST...

...SE TX/SRN LA...
VISIBLE SATELLITE IMAGERY SHOWED CU FORMATION ACROSS PARTS OF E TX
THROUGH CENTRAL LA TO SWRN MS...WITH LESS COVERAGE FARTHER S AND
INLAND OF THE UPPER TX COAST AND IN SERN LA. HOWEVER...THE LACK OF
STRONGER LOW LEVEL CONVERGENCE AND UPPER LEVEL FORCING SUGGEST THE
POTENTIAL FOR DEEPER MOIST CONVECTION RESULTING IN TSTM DEVELOPMENT
THIS AFTERNOON/EARLY EVENING IS RATHER LOW. THUS...THIS OUTLOOK HAS
REMOVED THE GENERAL TSTM AREA FORECAST EARLIER FOR PARTS OF SE TX
INTO SRN LA.

...PARTS OF COASTAL S TX...
TRENDS IN SATELLITE/RADAR IMAGERY...AND THE INTRUSION OF DRIER AIR
FROM THE NORTHEAST...SUGGEST ANY NEW TSTM DEVELOPMENT YET THIS
AFTERNOON SHOULD BE CONFINED TO THE WWD MOVING SEA BREEZE BOUNDARY.
THUS...THE COASTAL AREAS FROM INVOF CRP TO 60 N BRO HAVE BEEN
REMOVED FROM THE GENERAL TSTM FORECAST.

...ELSEWHERE...
THE PREVIOUS FORECAST REMAINS ON TRACK WITH NO CHANGES NEEDED.

..PETERS.. 09/23/2012

.PREV DISCUSSION... /ISSUED 1108 AM CDT SUN SEP 23 2012/

...SYNOPSIS...
MEAN TROUGH WHICH COVERS A LARGE PORTION OF THE ERN CONUS WILL
REMAIN THE DOMINATE SYNOPTIC FEATURE DURING THE PERIOD. A SHORTWAVE
TROUGH...CURRENTLY ACROSS THE UPPER MS VALLEY PER LATEST WATER VAPOR
IMAGERY...AND ATTENDANT MID-LEVEL SPEED MAX WILL QUICKLY MOVE
CYCLONICALLY THROUGH THE BASE OF THE TROUGH...PROGRESSING THROUGH
THE UPPER AND LOWER GREAT LAKES AND INTO THE NORTHEAST. THIS
SHORTWAVE TROUGH WILL RESULT IN LITTLE SENSIBLE WEATHER AS THE AREA
WILL REMAIN IN A COOL AND DRY POST-FRONTAL ENVIRONMENT. FARTHER
W...A COMPACT UPPER LOW WILL CONTINUE TO SLOWLY MOVE SEWD ACROSS THE
PACIFIC NW AND INTO THE GREAT BASIN AND CONTRIBUTE TO THE BREAKDOWN
OF AN UPPER RIDGE.

AT THE SFC...A COLD FRONT CURRENTLY EXTENDS FROM JUST OFF THE
NORTHEAST COAST SSWWD INTO S-CNTRL GA THEN WNWWD ACROSS THE
SOUTHEAST AND INTO THE TX PANHANDLE...DEMARCATED PRIMARILY BY A
MOISTURE GRADIENT. A LARGE SFC HIGH COVER MOST OF THE NRN/CNTRL
PLAINS AND MIDWEST. THIS SFC HIGH WILL DEVELOP ESEWD AND BECOME
CENTERED OVER THE OH/TN VALLEYS. THIS TRANSLATION IN CONJUNCTION
WITH SFC PRESSURE FALLS OVER THE SRN/CNTRL PLAINS ASSOCIATED WITH
LEE TROUGH DEVELOPMENT WILL FAVOR SLY FLOW ACROSS THE SRN PLAINS.
SUBSEQUENT NRN PROGRESSION OF THE FRONTAL BOUNDARY NOW ALONG THE RED
RIVER IS ANTICIPATED.

...INTERMOUNTAIN WEST...
ISOLATED TSTMS ARE EXPECTED ACROSS THE AREA AS THE AFOREMENTIONED
UPPER LOW MOVES SEWD. MEAGER MOISTURE /PW AROUND 0.6 INCH ON THE 12Z
LKN AND BOI RAOBS/ SHOULD KEEP TSTM COVERAGE ISOLATED AND NO SEVERE
TSTMS ARE EXPECTED.

...S TX...
SATELLITE-DERIVED PW VALUES SHOW AN INCREASING TREND AS A WEAK
INVERTED TROUGH MOVES OVER THE AREA. ADDITIONALLY...TEMPERATURES
REMAIN COOL ENOUGH ALOFT TO SUPPORT MODEST INSTABILITY. DRY AIR IS
EXPECTED TO SPREAD ACROSS THE AREA DURING THE LATE AFTERNOON BUT
THERE SHOULD STILL BE ENOUGH TIME BEFORE THIS OCCURS FOR SCATTERED
TSTMS DEVELOPMENT DURING THE EARLY AFTERNOON FOR AREAS S OF CRP.
SOME GUSTY WINDS WILL BE POSSIBLE WITH THIS ACTIVITY BUT THE CHANCE
OF SEVERE WINDS IS TOO LOW TO INCLUDE ANY PROBABILITIES.

...SE TX/SRN LA...
A SUBTLE SHORTWAVE TROUGH ASSOCIATED WITH THE CURRENT ACTIVITY OVER
AR WILL CONTINUE SEWD...SUPPORTED BY AN AREA OF ENHANCED MID-LEVEL
WINDS...ACROSS LA. 12Z SOUNDINGS DEPICTED A POCKET OF COOLER TEMPS
ALOFT AT LCH AND LIX. THE COMBINATION OF WEAK LIFT AND MODEST
INSTABILITY MAY RESULT IN A FEW TSTMS OVER THE AREA THIS AFTERNOON.
THE NMM4 AND NSSL WRF SHOW SOME ACTIVITY BUT MOST OTHER GUIDANCE
DOES NOT GENERATE CONVECTION. IF ACTIVITY DOES DEVELOP...SOME GUSTY
WINDS WILL BE POSSIBLE BUT THE CHANCE OF SEVERE WINDS IS TOO LOW TO
INCLUDE ANY PROBABILITIES.

...OZARKS...
A SWLY LOW LEVEL JET IS EXPECTED TO DEVELOP ACROSS NRN PORTIONS OF
THE SRN PLAINS OVERNIGHT...AIDING ISENTROPIC ASCENT ALONG A WEAK
FRONTAL BOUNDARY. ELEVATED INSTABILITY WILL PROMOTE THE POTENTIAL
FOR A FEW TSTMS BUT MEAGER COVERAGE AND LOW SEVERE PROBABILITY
PRECLUDE THE INCLUSION OF ANY PROBABILITIES.

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