SPC AC 180559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT TUE MAY 18 2010
VALID 181200Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL/SOUTHERN
HIGH PLAINS...
...SYNOPSIS...
SPLIT UPPER FLOW REGIME WILL REMAIN OVER NORTH AMERICA DURING THE
PERIOD. LARGELY CUT-OFF UPPER LOW CURRENTLY OVER THE OH RIVER VALLEY
WILL CONTINUE TO WEAKEN/MIGRATE EAST-NORTHEASTWARD...WHILE A
SOUTHERN STREAM SHORTWAVE TROUGH CURRENTLY OVER CA/NV ADVANCES
EASTWARD OVER THE FOUR CORNERS VICINITY TODAY...AND THE
SOUTH-CENTRAL HIGH PLAINS LATE TONIGHT.
AT THE SURFACE...IN RESPONSE TO UPSTREAM HEIGHT FALLS...LEE
CYCLOGENESIS WILL FAVOR A MORE PROMINENT LOW LEVEL UPSLOPE REGIME
ACROSS A BROAD-NORTH SOUTH EXTENT OF THE ROCKIES FRONT RANGE/HIGH
PLAINS...WHILE A CONVECTIVELY MODIFIED FRONTAL ZONE OTHERWISE
RETREATS NORTHWARD ACROSS TX. IN THE EAST...A COLD
FRONT/OCCLUSIONARY FRONTAL ZONE WILL REMAIN A FOCUS FOR
SHOWERS/TSTMS ACROSS PORTIONS OF THE SOUTHEAST STATES/CAROLINAS.
...CENTRAL/SOUTHERN HIGH PLAINS TO SOUTH TX...
MULTIPLE MCS/S WILL LIKELY BE ONGOING AT THE BEGINNING OF THE PERIOD
THIS MORNING ACROSS NORTHWEST TX/PERHAPS ADJACENT OK...AS WELL AS
SOUTH TX. A FEW SEVERE TSTMS MAY REMAIN POSSIBLE EARLY THIS MORNING
IN ASSOCIATION WITH THIS ACTIVITY.
LATER THIS AFTERNOON...LEADING BRUNT OF LARGE SCALE HEIGHT FALLS AND
STRENGTHENING/DIFFLUENT FLOW ALOFT...COMBINED WITH SURFACE
CYCLOGENESIS ACROSS EASTERN NM/SOUTHEAST CO AND NNW-WARD MOISTURE
RETURN...WILL LEAD TO AN APPRECIABLE SEVERE POTENTIAL ACROSS THE
CENTRAL/SOUTHERN HIGH PLAINS. STRONG/SEVERE TSTMS SHOULD INCREASE
THROUGH MID/AFTERNOON...VIA MOIST SOUTHEASTERLY UPSLOPE AND
DIFFERENTIAL HEATING ALONG THE EASTERN CO/NORTHEAST NM HIGHER
TERRAIN...AS WELL AS THE NORTH-SOUTH EXTENT OF THE DRYLINE ACROSS
FAR EASTERN NM/FAR WEST TX. VERY STEEP LAPSE RATES/MODERATE
INSTABILITY AND STRONG VERTICAL SHEAR/VEERING WIND PROFILES WILL BE
MORE THAN ADEQUATE FOR SUPERCELLULAR DEVELOPMENT...WITH LARGE HAIL
AND SOME TORNADOES ESPECIALLY DURING THE LATE AFTERNOON/EARLY
EVENING HOURS ACROSS SOUTHEAST CO/FAR EASTERN NM AND MUCH OF WEST
TX. WITH A MODERATE LOW LEVEL JET EXPECTED TO INCREASE DURING THE
EVENING...THE RELATIVELY GREATEST TORNADO THREAT MAY EXIST ACROSS
PORTIONS OF THE TX PANHANDLE/ADJACENT TX SOUTH PLAINS IN VICINITY OF
A SURFACE LOW/WARM FRONT/DRYLINE /AND PERHAPS CONVECTIVE OUTFLOW/
FOCUSED TRIPLE POINT.
OTHERWISE...THE NOCTURNALLY INCREASING/MODERATELY STRONG SOUTHERLY
LOW LEVEL JET SHOULD CONTRIBUTE TO THE ORGANIZATION/SUSTENANCE OF
ONE OR MORE SOUTHEAST MOVING MCS/S TONIGHT...WITH CONTINUED BOUTS OF
SEVERE HAIL ALONG WITH THE POSSIBILITY OF AN INCREASING DAMAGING
WIND THREAT DURING THE EVENING /MOST PROBABLE ACROSS NORTHWEST TX
AND PERHAPS ADJACENT WESTERN OK/.
...MT AND ADJACENT NORTHERN HIGH PLAINS...
BOUNDARY LAYER MOISTURE /MAINLY 40S F SURFACE DEWPOINTS/ WILL
INCREASE ACROSS THE HIGH PLAINS OF MT TODAY AS LEE SIDE
CYCLOGENESIS/TROUGHING OCCURS. WITH TSTMS EXPECTED TO INCREASE
DURING THE AFTERNOON OWING TO ONE OR MID LEVEL
DISTURBANCES/OROGRAPHIC FORCING...STEEP LAPSE RATES AND AS MUCH AS
500-1000 J/KG OF SBCAPE /HIGHEST ACROSS SOUTHEAST MT/ WILL
CONTRIBUTE TO A FAVORABLE ENVIRONMENT FOR SOME STRONG/SEVERE
TSTMS...WITH HAIL THE PRIMARY HAZARD.
...FL...
SLIGHT COOLING ALOFT IN ASSOCIATION WITH CYCLONIC MID/UPPER FLOW
WILL CONTRIBUTE TO FAVORABLE THERMODYNAMIC PROFILES FOR ISOLATED
STRONG/SEVERE TSTMS THIS AFTERNOON. A FEW DOWNBURSTS/MARGINALLY
SEVERE HAIL WILL BE POSSIBLE MAINLY ACROSS THE EASTERN PORTIONS OF
THE FL PENINSULA.
..GUYER/ROGERS.. 05/18/2010
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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