[SWODY1] SWODY1

[SWODY1 at goshenarc.org]

ACUS01 KWNS 200619
SWODY1
SPC AC 200617

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1217 AM CST SUN FEB 20 2005

VALID 201200Z - 211200Z

THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 40 S
PRX 20 ENE FSM 30 W JEF DEC 40 SSW BMG 25 SW CKV 35 N GWO 20 SSE ELD
15 NE GGG 40 S PRX.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 40 ENE DRA 50 ESE U24
EGE 45 W ALS 50 NW GUP 50 NE PHX 40 NW GBN 30 NNW EED 40 ENE DRA.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 30 WNW UKI 50 WSW FAT
PMD 45 S RAL.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 15 SE DAL 35 NNW PGO
10 ENE CNU 30 WNW BIE 20 N OMA 40 SSE LNR 35 SSE MTC 20 ESE BUF 30 W
AVP 20 S DCA 45 NNE RDU LGC 40 S MLU 35 NNE VCT 10 S SAT 45 ENE JCT
15 SE DAL.

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE ARKLATEX NEWD INTO THE
MID MS / LOWER OH VALLEYS...

...SYNOPSIS...
BROAD / MODERATELY FAST SWLY FLOW ALOFT WILL PREVAIL E OF THE
ROCKIES...WITH LOW-AMPLITUDE SHORT-WAVE TROUGH NOW MOVING INTO THE
HIGH PLAINS FORECAST TO BE THE MAIN FEATURE WITH REGARDS TO
CONVECTIVE / SEVERE THREAT THIS PERIOD.  MEANWHILE...UPPER PATTERN
IN THE WEST IS FORECAST TO AMPLIFY...AS UPPER LOW EVOLVES / MOVES
SSEWD ALONG THE CA COAST.

AT THE SURFACE...LOW NOW OVER FAR WRN KS IS EXPECTED OVER NERN KS AT
THE START OF THE PERIOD.  THE LOW IS THEN FORECAST TO MOVE ENEWD
WITH TIME...REACHING THE MID MS VALLEY AROUND SUNSET AND THEN
CONTINUING EWD ACROSS THE OH VALLEY STATES TOWARD THE LOWER GREAT
LAKES REGION THROUGH THE END OF THE PERIOD.  ASSOCIATED COLD
FRONT...INITIALLY EXTENDING SWWD INTO FAR W TX...SHOULD BECOME
INCREASINGLY W-E ORIENTED WITH TIME AS LOW RACES ENEWD ACROSS THE MS
/ OH VALLEYS.

...ARKLATEX NEWD INTO THE MID MS / LOWER OH VALLEYS...
DIFFICULT FORECAST THIS PERIOD AS NAM FORECASTS APPEAR TO REMAIN
MUCH TOO OPTIMISTIC WITH REGARDS TO AIRMASS DESTABILIZATION ACROSS
THE MID MS / OH VALLEYS.

LATEST SURFACE ANALYSIS SHOWS GENERALLY 30S DEWPOINTS ACROSS
MO...AND UPPER 30S TO LOW 40S ACROSS AR...WRN TN...AND MS.  LOW
CLOUDS AND LIGHT PRECIPITATION REMAIN ACROSS THIS REGION...AS COOL /
VERY STABLE BOUNDARY LAYER PERSISTS BENEATH STRONG LOW- TO MID-LEVEL
WARM ADVECTION.  WITH HIGH PRESSURE NOSING W-E ACROSS THE GULF COAST
REGION...ADVECTION OF HIGHER THETA-E AIRMASS -- NOW OVER TX -- WILL
BE SLOW TO OCCUR GIVEN TRAJECTORIES INTO THE OZARKS REGION
PERSISTING FROM WITHIN SURFACE RIDGE THROUGH MIDDAY.

WITH UPPER TROUGH FORECAST TO WEAKEN AS IT MOVES INTO REGION OF
CONFLUENT FLOW ALOFT...AND WITH STRONGEST LOW-LEVEL WARM ADVECTION /
LIFT EXPECTED TO SHIFT RAPIDLY NEWD ACROSS THIS REGION AND INTO THE
UPPER OH VALLEY / GREAT LAKES BY AFTERNOON...SIGNIFICANT QUESTIONS
PERSIST ATTM WITH REGARD TO SEVERE THREAT.

SHOWERS AND ELEVATED THUNDERSTORMS ARE FORECAST TO BE ONGOING AT THE
START OF THE PERIOD ACROSS ERN KS / ERN OK INTO THE OZARKS...WITHIN
LARGER AREA OF LIGHT PRECIPITATION.  THE CONVECTION -- DRIVEN BY
STRONG WARM ADVECTION -- SHOULD SHIFT ENEWD WITH TIME ACROSS THE OH
VALLEY.

BEHIND THIS PRECIPITATION...LOW CLOUDS SHOULD BE SLOW TO ERODE AS
MENTIONED ABOVE -- PARTICULARLY ACROSS MO AND SRN IL.  FURTHER S
ACROSS AR INTO THE ARKLATEX...GREATER DESTABILIZATION IS EXPECTED. 
HOWEVER...WITH UPPER FORCING FORECAST TO REMAIN WELL NE OF THE
ARKLATEX AND CONVERGENCE AT LOW LEVELS FORECAST TO BE WEAK...STORM
DEVELOPMENT IS FORECAST TO BE ISOLATED AT BEST.  

ATTM...IT APPEARS THAT A FEW SURFACE BASED STORMS SHOULD DEVELOP BY
LATE AFTERNOON FROM NERN TX NEWD ACROSS AR...WITH COVERAGE LIMITED
BY WEAK CAP AND LIMITED BOUNDARY-LAYER CONVERGENCE.  WITH SWLY
LOW-LEVEL FLOW VEERING TO WSWLY AT AROUND 60 KT...SHEAR WILL BE
SUFFICIENT FOR SUPERCELLS.  THOUGH AN ISOLATED TORNADO WILL BE
POSSIBLE...LARGE HAIL AND LOCALLY DAMAGING WINDS SHOULD BE THE MAIN
THREATS WITH ANY STORM WHICH DEVELOPS ACROSS THIS REGION.  STORMS
WILL MOVE ENEWD WITH TIME...BUT SEVERE THREAT SHOULD DIMINISH DURING
THE EVENING AS BOUNDARY LAYER STABILIZES.

FURTHER N...SEVERE THREAT WILL BE CONDITIONAL UPON BOUNDARY LAYER
WARMING / MOISTENING AND SUBSEQUENT DESTABILIZATION.  UNDER THE MOST
FAVORABLE SCENARIO FOR SEVERE WEATHER...CLEARING / BOUNDARY LAYER
HEATING ALONG REAR SIDE OF LOW CLOUD FIELD MAY ALLOW AIRMASS TO
DESTABILIZE SUFFICIENTLY TO ALLOW STORM DEVELOPMENT BY AFTERNOON. 
FAVORABLE WIND FIELD WOULD SUGGEST SUPERCELLS...WITH LARGE HAIL AND
DAMAGING WINDS...ALONG WITH ISOLATED TORNADOES.  HOWEVER...WHAT
APPEARS TO BE A MORE LIKELY SCENARIO WOULD BE THAT ANY CLEARING /
HEATING WOULD OCCUR LATE...AND JUST AHEAD OF LOW / FRONT...WITH
INSUFFICIENT BOUNDARY LAYER DESTABILIZATION FOR SURFACE-BASED
STORMS.  ATTM...WILL MAINTAIN SLIGHT RISK FORECAST NWD ACROSS MO
INTO THE SRN HALF OF IL...BUT THIS FORECAST WILL HAVE TO BE ADJUSTED
AS EVOLUTION OF LOW CLOUDINESS / BOUNDARY LAYER STABILIZATION
BECOMES MORE APPARENT.

..GOSS.. 02/20/2005

...NOTICE...
FOR USERS DECODING THE POINTS PARAGRAPH HEREIN...LATITUDE AND
LONGITUDE POINTS FOR THE CATEGORICAL AND PROBABILISTIC OUTLOOK
GRAPHICS ALSO ARE LOCATED IN A SEPARATE PRODUCT UNDER THE WMO
HEADINGS WUUS01 PTSDY1...WUUS02 PTSDY2...AND WUUS03 PTSDY3.  THE
INCLUSION OF POINTS IN THIS PRODUCT WILL EVENTUALLY BE DISCONTINUED.