SWODY1
SPC AC 221958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT WED JUL 22 2009
VALID 222000Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL PLAINS...
--- UPDATES ---
...CENTRAL PLAINS...
MESOSCALE ADJUSTMENTS TO PROBABILITIES ACROSS THIS REGION BASED ON
CONVECTIVE/INSTABILITY TRENDS AND LATEST HIGH-RES NUMERICAL
GUIDANCE...AMIDST NEBULOUS AND SUBTLE SFC PATTERN. INITIALLY
ELEVATED TSTMS OVER S-CENTRAL NEB ARE BECOMING SFC-BASED...WITH MORE
RECENT DEVELOPMENT FARTHER NE OVER NERN NEB LIKELY ROOTED IN
BOUNDARY LAYER FROM INCEPTION. DEEP-LAYER SHEAR WILL BE FAVORABLE
FOR STG-SVR HAIL AND GUSTS...THOUGH MIDLEVEL LAPSE RATES AND THEIR
POSITIVE EFFECT ON BUOYANCY WEAKEN WITH EASTWARD EXTENT AWAY FROM
HIGHER TERRAIN AND EML.
SVR POTENTIAL ALSO APPEARS TO BE INCREASING INVOF SFC TROUGHS OVER
SWRN NEB...NEB PANHANDLE...KS/CO BORDER REGION AND ERN
MOUNTAINS/FOOTHILLS AREAS OF CO/WY. FOR NEAR-TERM FCST DETAILS REF
SPC MESOSCALE DISCUSSION 1646 AND WW 613. LATER THIS AFTERNOON AND
EVENING...COMPLEX OF CONVECTION MAY ORGANIZE FROM ACTIVITY NEAR
INTERSECTION OF E-W TROUGH AND LEE TROUGH OVER NEB/CO BORDER REGION
AND MOVE SWD. AFTER INITIAL SUPERCELL MODES...WITH LARGE HAIL AND
SVR GUSTS LIKELY...ACTIVITY MAY BUILD FORWARD-PROPAGATING COLD POOL
WITH THREAT FOR DAMAGING WIND...BEFORE DISSIPATING IN NOCTURNALLY
STABILIZING AIR MASS.
..EDWARDS.. 07/22/2009
.PREV DISCUSSION... /ISSUED 1100 AM CDT WED JUL 22 2009/
...CENTRAL HIGH PLAINS...
NWLY FLOW REGIME PERSISTS HIGH PLAINS AS UPPER RIDGE REMAINS OVER
NRN ROCKIES. SUFFICIENT MOISTURE AVAILABLE COUPLED WITH THE STRONG
DAYTIME HEATING AND STEEP LAPSE RATES TYPICAL OF NORTHWEST FLOW FOR
A RISK OF SEVERE STORM DEVELOPMENT LATER THIS AFTERNOON. SLY LOW
LEVEL FLOW CENTRAL HIGH PLAINS GENERALLY LESS THAN 20KTS...HOWEVER
EFFECTIVE DEEP LAYER SHEAR OF 30-40KT WILL FAVOR POTENTIAL FOR
SUPERCELLS ONCE SURFACE BASED THUNDERSTORMS INITIATE LATER THIS
AFTERNOON.
STORMS SHOULD FORM FIRST VICINITY HIGHER TERRAIN WY/NE BORDER AREA
AND THEN MOVE/DEVELOP SEWD INTO THE HIGH PLAINS. ANY SUPERCELL THAT
DEVELOPS WILL HAVE POTENTIAL FOR LARGE HAIL...GIVEN MLCAPES AOA 1500
J/KG AND STEEP LAPSE RATES. IN ADDITION DAMAGING DOWNBURSTS WINDS
WILL BE POSSIBLE AS DCAPE WILL BE AOA 1000 J/KG.
ACTIVITY SHOULD MOVE/PROPAGATE SEWD/SWD INTO SWRN NEB AND NWRN KS
THIS EVENING AS THE NOCTURNAL INCREASE OF THE LOW LEVEL JET OCCURS.
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