DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 121948
SWODY1
SPC AC 121946

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0246 PM CDT FRI OCT 12 2012

VALID 122000Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN HIGH PLAINS
REGION...

...DISCUSSION...
ONGOING FORECAST REMAINS GENERALLY ON TRACK...WITH ONLY MINOR TWEAKS
MADE TO OUTLOOK LINES FROM THE HIGH PLAINS EWD. CONVECTION IS
INCREASING ATTM ACROSS THE REGION...AND EXPECT THIS TREND TO
CONTINUE OVER THE NEXT SEVERAL HOURS. WITH CAPE/SHEAR COMBINATION
SUFFICIENT FOR ORGANIZED/ROTATING STORMS -- PARTICULARLY ACROSS THE
HIGH PLAINS OF ERN NM/W TX...WILL MAINTAIN HIGHER PROBABILITY THREAT
FOR HAIL/WIND AND A COUPLE OF TORNADOES ACROSS THIS AREA. ELEVATED
STORM DEVELOPMENT -- AND MARGINAL HAIL POTENTIAL -- STILL APPEARS
LIKELY TO INCREASE NNEWD ACROSS THE CENTRAL PLAINS LATER THIS
EVENING.

THE MAIN CHANGE TO THE FORECAST IS BEING MADE TO THE FOUR CORNERS
AREA...WITH SEVERE POTENTIAL NOW PRIMARILY E OF THE PRIOR SLIGHT
RISK AREA. WHILE A SMALL/NARROW AREA OF SLIGHTLY HIGHER SEVERE RISK
EXISTS OVER A PORTION OF N CENTRAL NM AND ADJACENT SRN CO...WILL OPT
NOT TO EXPAND THE SLIGHT RISK EWD AND MAINTAIN ONLY SEE TEXT/LOW
PROBABILITY RISK ACROSS THIS REGION OVER THE NEXT COUPLE OF HOURS.

..GOSS.. 10/12/2012

.PREV DISCUSSION... /ISSUED 1130 AM CDT FRI OCT 12 2012/

...SRN HIGH PLAINS THROUGH TONIGHT...
THE CLOSED LOW OVER THE LOWER CO RIVER VALLEY WILL EVOLVE INTO MORE
OF AN OPEN WAVE AND PROGRESS ENEWD TO THE FOUR CORNERS THIS EVENING
AND ERN CO/NM BY SATURDAY MORNING. A SURFACE FRONT IS NOW STALLING
ACROSS NE NM...THE TX SOUTH PLAINS...AND NW OK. THE EJECTING
MIDLEVEL TROUGH APPROACHING CO/NM WILL CONTRIBUTE TO CYCLOGENESIS IN
THE LEE OF THE CENTRAL ROCKIES...THOUGH RAINFALL REINFORCING THE
FRONT ACROSS NM/TX/OK WILL LIMIT EROSION OF THE COOL/STABLE AIR AND
NWD PROGRESS OF THE SURFACE FRONT. S OF THE FRONT...RICH BOUNDARY
LAYER MOISTURE IS PRESENT /DEWPOINTS IN THE MID-UPPER 60S/...AND
REGIONAL 12Z SOUNDINGS SUPPORT MLCAPE VALUES OF 1500-2500 J/KG WITH
AFTERNOON TEMPERATURES IN THE 70S NEAR THE FRONT.

OTHER THAN THE POSITION OF THE SURFACE FRONT...THE PRIMARY
UNCERTAINTY THIS AFTERNOON THROUGH TONIGHT CONCERNS THE IMPACTS OF
ONGOING CONVECTION. RELATIVELY WIDESPREAD CLOUDS AND CONVECTIVE
OUTFLOW WILL INHIBIT DAYTIME HEATING NEAR THE FRONT...WITH THE
POSSIBLE EXCEPTION OF A SMALL AREA OF E CENTRAL NM. THUS...THE MOST
PROBABLE SCENARIO WILL BE FOR ADDITIONAL STORM DEVELOPMENT LATER
THIS AFTERNOON/EVENING NEAR THE ERN NM/TX BORDER...POSSIBLY AS FAR S
AS SE NM/W CENTRAL TX. STRENGTHENING MID-UPPER SWLY FLOW AND
MAINTENANCE OF THE LOW-LEVEL WAA REGIME WILL RESULT IN HODOGRAPHS
FAVORABLE FOR SUPERCELLS. POTENTIALLY MODERATE INSTABILITY IN THE
MOIST ENVIRONMENT...IN COMBINATION WITH EFFECTIVE BULK SHEAR OF
40-50 KT AND EFFECTIVE SRH NEAR 250 M2/S2...WILL SUPPORT THE RISK
FOR A FEW TORNADOES AND LARGE HAIL/DAMAGING WINDS.

...FOUR CORNERS THROUGH MID AFTERNOON...
AN EMBEDDED SPEED MAX IS ROTATING NEWD OVER AZ THIS MORNING...WITH
THE DOWNSTREAM ZONE OF ASCENT EXPECTED TO SPREAD NEWD OVER THE FOUR
CORNERS THROUGH EARLY-MID AFTERNOON. SOME SURFACE HEATING IN CLOUD
BREAKS...AND SURFACE DEWPOINTS IN THE MID 40S AT A RELATIVELY HIGH
ELEVATION...WILL SUPPORT SBCAPE VALUES OF 500-1000 J/KG. VERTICAL
SHEAR WILL BE FAVORABLE FOR ORGANIZED SEVERE STORMS...WHERE COOL
MIDLEVEL TEMPERATURES AND STEEP LOW-MIDLEVEL LAPSE RATES WILL
SUPPORT A RISK FOR ISOLATED SEVERE GUSTS AND LARGE HAIL.

...KS/NE/MO/IA AREA THROUGH TONIGHT...
THE RESIDUAL COOL/STABLE AIR MASS WILL BE SLOW TO ERODE TODAY GIVEN
WIDESPREAD CLOUDS AND PRECIPITATION FARTHER TO THE S IN TX/OK.
THOUGH THE COOL AIR SHOULD RETREAT SOME OVERNIGHT IN RESPONSE TO
HIGH PLAINS CYCLOGENESIS...THE SHORT-TERM MODEL FORECASTS APPEAR A
LITTLE TOO AGGRESSIVE IN WARMING/MOISTENING THE LOW LEVELS.
THUS...THE RISK FOR SEVERE STORMS OVERNIGHT IS IN QUESTION...WITH
LARGELY SUB-SEVERE/ELEVATED CONVECTION EXPECTED.

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