DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 091957
SWODY1
SPC AC 091955

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0155 PM CST SAT FEB 09 2013

VALID 092000Z - 101200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF CNTRL AND NRN
TX...SWRN OK AND THE ERN TX PANHANDLE...

ONLY MINOR CHANGES TO THE PREVIOUS OUTLOOK.

EXPANDED LOW HAIL PROBS NEWD ACROSS OK AS COOL AIR ALOFT MAY SUPPORT
MARGINALLY SEVERE HAIL WITH INTENSE WARM ADVECTION AT 850 MB. ALSO
REDUCED HAIL PROBS ACROSS KS/CO/NEB AS IT APPEARS PRECIPITABLE WATER
MAY BE TOO LOW TO SUPPORT SEVERE HAIL...ALTHOUGH SMALLER HAIL IS
LIKELY.

FARTHER S...EXPANDED THE SRN EDGE OF THE SLIGHT RISK A BIT TO
ACCOUNT FOR POSSIBLE NOCTURNAL DEVELOPMENT ON THE NRN EDGE OF THE
CAPPING GRADIENT.

..JEWELL.. 02/09/2013

.PREV DISCUSSION... /ISSUED 1021 AM CST SAT FEB 09 2013/

...SYNOPSIS...

THE PRIMARY FEATURE OF INTEREST THIS PERIOD IS A MIDLEVEL LOW OVER
THE GREAT BASIN INTO LOWER CO VALLEY WHICH WILL DEVELOP INTO THE
CNTRL PLAINS BY 10/12Z. THIS SYSTEM WILL BE ATTENDED BY A 100 KT
JET STREAK AND A CORRIDOR OF 12-HR HEIGHT FALLS AT 500 MB OF 150-200
M. IN THE LOW LEVELS...A LEE CYCLONE WILL DEEPEN TODAY OVER ERN CO
BEFORE DEVELOPING EWD ALONG THE NEB-KS BORDER TONIGHT. AN
ASSOCIATED DRYLINE WILL BECOME ESTABLISHED BY MID/LATE AFTERNOON
FROM THE SURFACE LOW SWD THROUGH THE CNTRL OK/TX PNHDLS INTO W-CNTRL
TX. A PACIFIC FRONT EMERGING FROM THE ROCKIES WILL OVERTAKE THE
DRYLINE TONIGHT WITH THIS FEATURE REACHING CNTRL PARTS OF KS/OK/TX
BY SUNDAY MORNING. MEANWHILE...A WARM FRONT WILL GRADUALLY
STRENGTHEN WHILE LIFTING SLOWLY NWD THROUGH PORTIONS OF THE RED
RIVER INTO LOWER MS VALLEY REGIONS.

...SRN PLAINS LATE THIS AFTERNOON THROUGH TONIGHT...

12Z OBSERVED SOUNDINGS AND GPS PW DATA INDICATE A MODIFIED CP AIR
MASS /CHARACTERIZED BY PW VALUES OF 1.0-1.3 INCHES/ CONFINED TO SRN
PORTIONS OF THE TX HILL COUNTRY INTO DEEP SOUTH TX. THE LOW-LEVEL
MASS RESPONSE TO THE APPROACHING MIDLEVEL TROUGH --MANIFEST AS A
40-50 KT SLY LLJ-- WILL ENHANCE THE NWD FLUX OF THIS MOISTURE
THROUGH THE REGION WITH BOUNDARY LAYER DEWPOINTS RISING THROUGH THE
50S BY TONIGHT ALONG THE RED RIVER WITH LOWER/MID 60S BECOMING
COMMON ACROSS THE HILL COUNTRY INTO SERN TX. THIS NWD MOISTURE
RETURN WILL COINCIDE WITH THE EWD ADVECTION OF AN EML FROM THE SRN
ROCKIES AND ADJACENT HIGH PLAINS...CONTRIBUTING TO THE GRADUAL
DESTABILIZATION OF THE AIR MASS AHEAD OF THE DRYLINE/PACIFIC FRONT.

LATEST CONVECTION-PERMITTING AND MESOSCALE MODEL GUIDANCE INDICATE
AN INCREASING LIKELIHOOD FOR SURFACE-BASED TSTM DEVELOPMENT BY LATE
AFTERNOON OR EARLY EVENING ALONG THE DRYLINE OVER THE CNTRL/ERN
OK/TX PNHDLS...PERHAPS INTO NWRN AND W-CNTRL TX. THIS ACTIVITY IS
FORECAST WITHIN A WEAKLY UNSTABLE...BUT STRONGLY SHEARED
ENVIRONMENT...SUGGESTING SOME POTENTIAL FOR UPDRAFT ROTATION WITH AN
ATTENDANT RISK FOR MARGINALLY SEVERE HAIL AND LOCALLY STRONG WIND
GUSTS.

MORE ROBUST TSTM DEVELOPMENT IS NOT ANTICIPATED UNTIL LATER TONIGHT
ACROSS PORTIONS OF N-CNTRL INTO CNTRL TX AS LOW-LEVEL UPLIFT ALONG
THE PACIFIC FRONT AND INCREASING MIDLEVEL HEIGHT FALLS INTERCEPT A
MORE MOIST...UNSTABLE BOUNDARY LAYER DEVELOPING NWD. A FAIRLY RAPID
EVOLUTION OF STORMS INTO A QLCS IS ANTICIPATED WITH THE RISK FOR
DAMAGING WINDS AND SOME HAIL CONTINUING THROUGH THE REMAINDER OF THE
DAY 1 PERIOD.

...CNTRL PLAINS LATE THIS AFTERNOON INTO TONIGHT...

DRY BOUNDARY LAYER CONDITIONS WILL BE OFFSET BY STEEPENING LAPSE
RATES WHICH WILL CONTRIBUTE TO A WEAKLY UNSTABLE ENVIRONMENT AHEAD
OF THE DRYLINE/PACIFIC FRONT. STRONG HEIGHT FALLS/DCVA IN ADVANCE
OF THE MIDLEVEL LOW ARE EXPECTED TO FOSTER A BROKEN BAND OF
LOW-TOPPED STORMS BY LATE AFTERNOON/EARLY EVENING FROM NERN CO/SWRN
NEB INTO WRN KS. THIS ACTIVITY MAY PERSIST THROUGH ABOUT
10/06Z...AS THE STRONG FORCING FOR ASCENT SPREADS ACROSS THE CNTRL
HIGH PLAINS.

MODEL-DERIVED FORECAST SOUNDINGS SHOW THAT DESPITE BOUNDARY LAYER
DEWPOINTS OF AROUND 40 F...COLD MIDLEVEL TEMPERATURES WILL PROMOTE
MLCAPE VALUES OF 300-400 J/KG INVOF SURFACE LOW ALONG THE NEB-KS
BORDER. GIVEN THE PRESENCE OF A STRONGLY SHEARED...VERTICALLY
VEERING WIND PROFILE...THE POTENTIAL WILL EXIST FOR UPDRAFT ROTATION
WITH A LOW-PROBABILITY RISK FOR SEVERE WEATHER.

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