SWODY1
SPC AC 100541
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1241 AM CDT SAT APR 10 2010
VALID 101200Z - 111200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MODELS INDICATE THAT A VIGOROUS DIGGING SHORT WAVE TROUGH WILL
CONTRIBUTE TO LARGE-SCALE UPPER TROUGH AMPLIFICATION OFF THE PACIFIC
COAST DURING THIS FORECAST PERIOD. SIGNIFICANT LOW/MID LEVEL
CYCLOGENESIS IS FORECAST TO ACCOMPANY THIS FEATURE...WHICH IS
EXPECTED TO REMAIN GENERALLY OFFSHORE THROUGH AT LEAST 12Z SUNDAY.
MID-LEVEL-LEVEL HEIGHT FALLS APPEAR LIKELY...HOWEVER ...TO ACCOMPANY
AN IMPULSE LIFTING OUT OF THE LARGER SCALE TROUGH THROUGH NORTHERN
CALIFORNIA AND THE PACIFIC NORTHWEST COAST STATES.
DOWNSTREAM...UPPER RIDGING IS PROGGED TO BUILD THROUGH THE NORTHERN
INTERMOUNTAIN REGION/ROCKIES AND PLAINS...WHILE BROAD TROUGHING
LINGERS FROM THE UPPER MISSISSIPPI VALLEY THROUGH NEW ENGLAND...IN
THE WAKE OF THE DEAMPLIFYING UPPER TROUGH LIFTING THROUGH THE
CANADIAN MARITIMES.
MEANWHILE...ACROSS THE NORTHERN MEXICAN PLATEAU AND SOUTHERN TIER
STATES...A COUPLE OF SHORT WAVE IMPULSES...EMANATING FROM A STRONG
SUBTROPICAL CENTRAL/EASTERN PACIFIC UPPER JET...ARE PROGGED TO
PROGRESS THROUGH A GENERALLY ZONAL REGIME.
IN ASSOCIATION WITH THE EVOLVING UPPER PATTERN...A RETREATING
SURFACE RIDGE IS EXPECTED TO ALLOW A RETURN FLOW OFF THE GULF OF
MEXICO THROUGH THE LOWER RIO GRANDE VALLEY AND SOUTHERN PLAINS.
HOWEVER...GULF BOUNDARY LAYER MOISTENING OVER THE NORTHWESTERN GULF
OF MEXICO IS STILL ONGOING...AND INLAND MOISTURE RETURN SHOULD
REMAIN WEAK. THIS...COUPLED WITH THE NORTHEASTWARD ADVECTION OF
WARM AND CAPPING ELEVATED MIXED LAYER AIR OFF THE MEXICAN PLATEAU
AND ROCKIES...WILL LIMIT CONVECTIVE POTENTIAL TODAY AND TONIGHT.
IN FACT...LOW MOISTURE LEVELS ACROSS MUCH OF THE NATION WILL
PROBABLY CONTINUE TO RESULT IN LOW CONVECTIVE POTENTIAL. BUT
THUNDERSTORM PROBABILITIES MAY REACH AT LEAST THE MINIMUM 10%
THRESHOLD FOR A CATEGORICAL THUNDERSTORM OUTLOOK ACROSS PARTS OF THE
WEST...THE CENTRAL PLAINS...RIO GRANDE VALLEY AND SOUTHERN FLORIDA.
...WEST/INTERMOUNTAIN WEST...
WEAK DESTABILIZATION ASSOCIATED WITH SURFACE HEATING...AND
LARGE-SCALE FORCING DOWNSTREAM OF UPPER TROUGH...AND ALONG A
WEST-EAST ZONE OF LOW/MID-LEVEL WARM ADVECTION...MAY CONTRIBUTE TO
SCATTERED THUNDERSTORM ACTIVITY THIS AFTERNOON AND EVENING.
COVERAGE PROBABLY WILL BE RATHER SPARSE...BUT RELATIVELY HIGHER
CONCENTRATIONS OF STORMS MAY BECOME FOCUSED IN FAVORABLE OROGRAPHIC
FORCING ACROSS THE SOUTHERN CASCADES/SHASTAS AND SISKIYOUS INTO
PARTS OF THE NORTHERN SIERRA...AND ACROSS THE CENTRAL ROCKIES.
...SOUTHERN AND CENTRAL PLAINS...
DESPITE WEAK MOISTURE RETURN...SREF GUIDANCE SUGGESTS MIXED LAYER
CAPE MAY REACH 500-1000 J/KG NEAR THE DEVELOPING DRY LINE ACROSS THE
SOUTHERN HIGH PLAINS BY LATE AFTERNOON. ONE OR TWO STORMS IS NOT
COMPLETELY OUT OF THE QUESTION SOMEWHERE ACROSS NORTHWEST TEXAS AND
WESTERN OKLAHOMA...BUT A SOMEWHAT BETTER PROBABILITY SEEMS TO EXIST
LATER THIS EVENING/OVERNIGHT ACROSS KANSAS... WITHIN A ZONE OF
STRENGTHENING LOW-LEVEL WARM ADVECTION.
...RIO GRANDE VALLEY...
STRONG CAPPING IS EXPECTED TO INHIBIT CONVECTIVE POTENTIAL THROUGH
THE DAY EAST OF THE RIVER. HOWEVER...GIVEN INCREASING LOW-LEVEL
MOISTURE...LARGE-SCALE ASCENT ASSOCIATED WITH A SHORT WAVE TROUGH
MAY SUPPORT THUNDERSTORM DEVELOPMENT OFF THE MEXICAN PLATEAU THROUGH
THE TEXAS BIG BEND REGION...AND INTO THE VICINITY OF THE RIO GRANDE
RIVER FARTHER SOUTH...TONIGHT. ACTIVITY IS EXPECTED TO BE IN THE
PROCESS OF WEAKENING AS THIS OCCURS.
...SRN FLORIDA...
WITH A FRONT LINGERING NEAR THE SOUTHERN PENINSULA AND KEYS...THE
APPROACH OF A SHORT WAVE TROUGH THIS EVENING INTO TONIGHT WILL
SUPPORT A RISK FOR THUNDERSTORM ACTIVITY.
..KERR/STOPPKOTTE.. 04/10/2010
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