SWODY1
SPC AC 201956
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0256 PM CDT TUE OCT 20 2009
VALID 202000Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS SHIFTING EWD THIS AFTERNOON AND
EVENING FROM PORTIONS SERN AND EXTREME E-CENTRAL AZ...ACROSS
CENTRAL/SRN NM...AND FAR W TX...
...SERN AZ TO SRN HIGH PLAINS...
SCATTERED TSTMS...AMIDST BROADER FIELD OF DEEPENING TCU AND SMALL
CB...HAVE DEVELOPED ALREADY ACROSS MUCH OF EXTREME E-CENTRAL AND
SERN AZ AND W-CENTRAL TROUGH S-CENTRAL NM. THIS ACTIVITY IS
EXPECTED TO MOVE NEWD AND BUILD SWD...WITH NET EWD SHIFT ACROSS
OUTLOOK AREA THROUGH REMAINDER AFTERNOON/EVENING HOURS. SVR HAIL
AND DAMAGING GUSTS ARE POSSIBLE. REF WW 770 AND RELATED MESOSCALE
DISCUSSIONS FOR COVERAGE OF NEAR-TERM SVR THREAT FROM CENTRAL NM TO
SERN AZ THROUGH 00Z.
IN ADDITION TO THREAT SPREADING EWD FROM WW 770 LATER THIS
AFTERNOON/EVENING...DEEP CONVECTION IS BECOMING EVIDENT IN VIS
IMAGERY INVOF HIGHER TERRAIN OF S-CENTRAL/SERN NM. ORGANIZED SVR
THREAT WILL CONTINUE TO DIMINISH AND BECOME MORE CONDITIONAL WITH
EWD EXTENT ACROSS SERN NM AND W TX...IN CONCORDANCE WITH SIMILAR EWD
DROP-OFF IN DEEP-LAYER SHEAR. STILL...ISOLATED SVR HAIL AND
DAMAGING WIND ARE POSSIBLE THROUGH REMAINDER AFTERNOON AS ACTIVITY
MOVES OVER DEEPLY-MIXED BOUNDARY LAYER. REF SPC MESOSCALE
DISCUSSION 2117 FOR NEAR-TERM DETAILS.
GUST POTENTIAL WILL DIMINISH WITH TIME AFTER DARK AS DIABATIC
COOLING OCCURS AND SFC STATIC STABILITY STRENGTHENS. THIS
TRANSITION MAY BE GRADUAL DUE TO SOMEWHAT OFFSETTING INFLUENCE OF
MOIST/WARM ADVECTION...OCCURRING ALONG WRN RIM OF MODIFIED GULF OF
MEXICO RETURN FLOW REGIME. AS INCREASINGLY MOIST PARCELS ARE LIFTED
ISENTROPICALLY TO LFC...TSTMS WILL INCREASE IN COVERAGE OVERNIGHT
AND OVERSPREAD MORE OF CORRIDOR FROM SWRN KS TO PERMIAN BASIN.
ISOLATED HAIL AND DMGG GUST POTENTIAL WILL EXIST THROUGHOUT TONIGHT
AS UPPER TROUGH AND PRECEDING CONVECTION CONTINUE TO SHIFT EWD...PER
PREVIOUS OUTLOOK DISCUSSION BELOW.
..EDWARDS.. 10/20/2009
.PREV DISCUSSION... /ISSUED 1044 AM CDT TUE OCT 20 2009/
...SERN AZ/NM/FAR WRN TX
VIGOROUS UPPER LOW OVERNIGHT HAS TRACKED SEWD TO CURRENT LOCATION
NWRN AZ. MODELS MOVE THE LOW CENTER TO CENTRAL NM BY 12Z WED WITH
STRONG PVA/MID LEVEL COOLING SPREADING EWD ACROSS ERN AZ INTO WRN NM
THIS AFTERNOON...REACHING SRN HI PLAINS BY WED AM.
VERY MOIST AIR WHICH HAS WORKED NWD THRU WRN MEXICO PAST COUPLE DAYS
IS BEING DRAWN NEWD IN THE STRONGER SWLY FLOW IN ADVANCE OF UPPER
LOW ACROSS SERN AZ INTO SRN NM/FAR WRN TX. PRONOUNCED DRYING NOTED
ON W/V IMAGERY SPREADING EWD ACROSS CENTRAL AZ IN ADVANCE OF UPPER
LOW EXPECTED TO BE ZONE OF STRONGER ASCENT FOR THUNDERSTORM
DEVELOPMENT BY EARLY AFTERNOON.
WITH DEWPOINTS RISING INTO THE MID/UPPER 50S PRIOR TO THE ARRIVAL OF
DRYING AND TROUGH...SURFACE TEMPERATURES RISING INTO THE MID 70S
SERN AZ VALLEYS EXPECTED TO BE SUFFICIENT TO INITIATE SURFACE BASED
THUNDERSTORMS. WITH STEEP LAPSE RATES...7-8C/KM...MLCAPES UP TO
1000 J/KG...AND DEEP LAYER SHEAR OF 40-50KT...CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS. STORMS SHOULD INITIATE VICINITY
HIGHER TERRAIN FROM ERN RIM/WHITE MTNS SWD IN SERN AZ AND QUICKLY
MOVE/DEVELOP EWD ACROSS LOWER ELEVATIONS AND INTO SWRN NM/FAR WRN
TX.
LARGE HAIL AND LOCALLY DAMAGING WINDS WILL BE LIKELY WITH THE
STRONGEST ACTIVITY...WITH PARAMETERS FAVORABLE FOR ROTATING
STORMS...ENHANCING THE SEVERE CONCERN...PARTICULARLY FOR LARGE HAIL.
WITH GREATER INSTABILITY NOW EXPECTED...THIS AREA HAS BEEN UPGRADED
TO A SLIGHT RISK FOR THIS AFTERNOON AND EVENING.
...SRN/CNTRL HI PLNS...
A MODIFIED CP AIR MASS /WITH SFC DEW POINTS IN THE LOW 50S/ WILL
CONTINUE TO RETURN NWD ACROSS THE SRN AND CNTRL HI PLNS TODAY IN
STRENGTHENING SLY FLOW AHEAD OF LEE TROUGH. SIMILAR TO MON...
HEATING/BOUNDARY LAYER DEEPENING WILL ERODE CIN NOW PRESENT OVER
REGION TO SUPPORT ISOLD/SCTD STORMS BY MID/LATE AFTN ALONG LEE
TROUGH...WHERE SBCAPE WILL BE AROUND 500 J/KG.
THE STRONGER MID/HI LVL FLOW/SHEAR ASSOCIATED WITH AZ UPR TROUGH
WILL REMAIN W OF THE REGION THROUGH THE DAY. THUS...ENVIRONMENT
WILL BE MOST SUPPORTIVE OF MULTICELL CLUSTERS CAPABLE OF GUSTY WINDS
AND POSSIBLY MARGINALLY SVR HAIL. STRENGTHENING NOCTURNAL LLJ AND
INCREASING FORCING FOR ASCENT SHOULD RESULT IN AN INCREASE IN STORM
COVERAGE AND LARGER SCALE ORGANIZATION TONIGHT FROM ERN NM/WRN TX
NEWD INTO WRN KS/S-CNTRL NEB. THIS ACTIVITY MAY CONTINUE TO POSE A
THREAT FOR ISOLD DMGG WIND AND MARGINALLY SVR HAIL.
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