SWODY1
SPC AC 080553
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1153 PM CST SAT FEB 07 2009
VALID 081200Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS FAR NERN NM...MUCH OF
WEST TX...WRN OK INCLUDING THE PANHANDLE...AND FAR SERN CO/SW KS...
...SYNOPSIS...
MODELS REMAIN CONSISTENT SHOWING CLOSED LOW OVER THE LOWER CO RIVER
VALLEY AT 12Z SUNDAY EVOLVING INTO AN OPEN WAVE AND TRACKING EWD
THROUGH THE SWRN STATES/NRN MEXICO SUNDAY AFTERNOON...AND THEN
TRACKING MORE NEWD INTO THE CENTRAL/SRN PLAINS BY 12Z MONDAY. A
FAIRLY STRONG RIDGE EXTENDING NWD FROM THE GULF OF MEXICO COMBINED
WITH A PACIFIC TROUGH DIGGING SEWD TOWARD THE WEST COAST WILL BOTH
BE KEY IN THE SWRN SYSTEM BECOMING NEGATIVELY-TILTED THIS FORECAST
PERIOD...AND TAKING A NEW TRACK.
SURFACE CYCLOGENESIS IS EXPECTED OVER ERN NM THIS AFTERNOON WITH THE
LOW DEEPENING AS IT TRACKS NEWD INTO NW KS LATE IN THE PERIOD. SLY
LOW LEVEL FLOW WILL INCREASE ACROSS THE FULL EXTENT OF THE PLAINS
TODAY WITH FURTHER STRENGTHENING /50-70 KT/ EXPECTED SUNDAY
NIGHT...IN RESPONSE TO STRONG HEIGHT FALLS /90-150 METERS/ ATTENDANT
TO APPROACHING UPPER TROUGH. A PACIFIC COLD FRONT ACCOMPANYING THE
SW U.S. TROUGH IS EXPECTED TO BE THE PRIMARY FOCUS FOR TSTM
DEVELOPMENT BY LATE SUNDAY AFTERNOON/EARLY EVENING AS IT MOVES EWD
THROUGH THE SRN HIGH PLAINS AND REACHES CENTRAL KS TO CENTRAL TX BY
12Z MONDAY.
...SRN PLAINS...
DESPITE AN INCREASE IN SLY LOW LEVEL WINDS TODAY...MOISTURE RETURN
IN ADVANCE OF THE PACIFIC FRONT IS NOT EXPECTED TO BE VERY ROBUST
DUE TO RECENT SERIES OF COLD INTRUSIONS INTO THE GULF. SURFACE
DEWPOINTS IN THE MID-UPPER 50S SHOULD REMAIN CONFINED TO SRN/ERN
TX...WHILE DEWPOINTS IN THE MID-UPPER 40S WILL BE MORE COMMON ACROSS
MUCH OF W TX. MODELS REMAIN CONSISTENT INDICATING LOW CLOUDS...
ASSOCIATED WITH MOISTURE RETURN BENEATH A CAPPING ELEVATED MIXED
LAYER...WILL LIMIT SURFACE HEATING AS FAR WEST AS THE TX SOUTH
PLAINS AND PANHANDLE REGION TODAY. ALTHOUGH STEEP LAPSE RATES ARE
ALREADY IN PLACE ACROSS THIS REGION...THE WEAK BOUNDARY LAYER
THERMAL/MOISTURE FIELDS WILL PRECLUDE THE DEVELOPMENT OF STRONG
INSTABILITY WITH MUCAPE VALUES FORECAST TO BE 250-500 J/KG.
THUS..TSTM INITIATION IS NOT EXPECTED UNTIL LATE SUNDAY AFTERNOON
ACROSS NERN NM WHERE LOW LEVEL CONVERGENCE WILL BE MAXIMIZED IN
VICINITY OF SURFACE LOW. ADDITIONAL ACTIVITY WILL THEN DEVELOP
ALONG THE ADVANCING COLD FRONT FROM SERN CO TO W TX AS STRONG
FORCING FOR ASCENT SPREADS ACROSS THE SRN HIGH PLAINS WITH THE
APPROACH OF THE NEGATIVELY TILTED UPPER TROUGH. THE DEEP LAYER
FORCING IS EXPECTED TO WEAKEN THE CAP FOR SURFACE BASED STORMS
PRODUCING HAIL AND STRONG WIND GUSTS AS THE PRIMARY THREATS. BACKED
SLY MID-UPPER LEVEL WINDS ATOP A LOW LEVEL WAA PROFILE SUGGEST TSTMS
SHOULD EVOLVE INTO A QUASI-LINEAR MCS BY EARLY SUNDAY EVENING AS
ACTIVITY PROGRESSES EWD...REACHING SRN KS TO CENTRAL TX BY 12Z
MONDAY. INSTABILITY WILL REMAIN WEAK INTO THE OVERNIGHT PERIOD...
WITH STRONG WIND GUSTS EXPECTED TO BE THE PRIMARY THREAT.
HOWEVER...FORECAST SOUNDINGS SUGGEST AT LEAST A MARGINAL TORNADO
THREAT WILL EXIST WITH THIS LINEAR FORCED SYSTEM AS LOW LEVEL
HODOGRAPH CURVATURE WILL BE LARGE WITH THE INCREASE IN THE SLY LLJ.
EMBEDDED LOW LEVEL ROTATION IN THE TSTM LINE CAN NOT BE RULED OUT.
..PETERS.. 02/08/2009
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