SWODY1
SPC AC 050509
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1209 AM CDT SAT SEP 05 2009
VALID 051200Z - 061200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
IN MID-UPPER LEVELS...NRN STREAM PATTERN SHIFT IS UNDERWAY AS
BROAD/PERSISTENT CYCLONIC GYRE OVER GULF OF AK MOVES TOWARD NWRN PAC
NW AND BC COAST. BY 6/12Z...CENTER OF VORTEX STILL SHOULD BE
OFFSHORE...ALTHOUGH STG SHORTWAVE TROUGH WILL BE MOVING AROUND SERN
QUADRANT OF CYCLONE AND INLAND ACROSS WRN PORTIONS WA/ORE.
WEAKER/LEADING SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL
IMAGERY OFFSHORE WA/ORE INVOF 133W -- IS FCST TO MOVE NEWD ACROSS
WA/ORE BETWEEN 5/18Z-6/06Z...DEAMPLIFYING AND REACHING W-CENTRAL AB
BY 6/12Z.
MEANWHILE...SMALL PERTURBATION AND INTERMITTENTLY CLOSED LOW -- NOW
OVER MO -- IS EXPECTED TO BECOME ISOLATED FROM NRN STREAM FLOW BELT
AS HEIGHTS RISE OVER GREAT LAKES...RESULTING IN ERRATIC DRIFT AND
LITTLE NET MOTION OF THIS FEATURE THROUGH PERIOD.
IN LOW LEVELS...DIFFUSE BAROCLINIC ZONE IS FCST TO BECOME
QUASISTATIONARY FROM OZARKS REGION GENERALLY WWD ACROSS NRN
OK...NNWWD ACROSS CENTRAL HIGH PLAINS...THEN NWWD AGAIN FROM WRN SD
ACROSS ERN MT AS WARM FRONT. THIS FEATURE WAS BETTER DEFINED AT
5/00Z IN 850/825 MB ANALYSES THAN AT SFC...WHERE NUMEROUS SMALLER
SCALE CONVECTIVE BOUNDARIES HAVE BECOME PREDOMINANT. FRONTAL ZONE
AND OUTFLOW BOUNDARIES WILL SUPPORT GEN TSTM POTENTIAL DAY-1 OVER
PORTIONS OZARKS...SRN PLAINS AND CENTRAL HIGH PLAINS...HOWEVER
AMBIENT FLOW/SHEAR WILL BE TOO WEAK FOR ORGANIZED SVR RISK. STG
LEESIDE TROUGHING...WITH ONE OR TWO EMBEDDED/MESOSCALE CYCLONES --
IS EXPECTED TODAY FROM SRN AB SEWD ACROSS WRN MT...AS AFOREMENTIONED
WARM FRONT LIFTS NWD OVER CENTRAL/ERN MT.
...SRN GREAT BASIN TO AZ...
WEAK MID-UPPER TROUGH NOW OVER SRN NV WILL HAVE EJECTED NEWD AWAY
FROM THIS AREA...LEAVING DIABATIC HEATING...ADEQUATE LOW LEVEL
MOISTURE FROM GULF OF CA INTRUSION...AND OROGRAPHIC FORCING AS
PRIMARY CONTRIBUTORS TO CONVECTIVE ENVIRONMENT OVER THIS AREA.
WIDELY SCATTERED TO SCATTERED TSTMS SHOULD DEVELOP...AT FIRST OVER
HIGHER TERRAIN...MOVING ERRATICALLY OVER LOWER ELEVATIONS WHERE
DEEP/WELL-MIXED BOUNDARY LAYERS WILL SUPPORT POTENTIAL FOR STG GUSTS
FROM SOME ACTIVITY. WEAK DEEP-LAYER FLOW IS FCST...INCLUDING LACK
OF ELY COMPONENT IN LOW-MIDDLE LEVELS TO ASSIST IN MOVING CONVECTION
OFF RIM MORE EXPEDITIOUSLY. THIS ALSO WILL YIELD VERY WEAK SHEAR
VIA ALMOST ANY LOW-LEVEL OR DEEP-LAYER MEASURE. THEREFORE...SVR
THREAT APPEARS MRGL AND SOMEWHAT DISORGANIZED ATTM.
...NRN ROCKIES REGION...
DEEP-LAYER ASCENT FCST TO SPREAD/DEVELOP NEWD ACROSS REGION THIS
AFTERNOON AHEAD OF EJECTING PAC NW TROUGH. ISOLATED STG TSTMS ARE
POSSIBLE WITHIN POTENTIAL CORRIDOR OF HIGH-BASED CONVECTION FORMING
THIS AFTERNOON OVER MOUNTAINS...AND MOVING NEWD ACROSS FOOTHILLS
TOWARD ADJOINING HIGH PLAINS. NEARLY UNIDIRECTIONAL DEEP-LAYER WIND
PROFILES AND PRESENCE OF MRGL SPEED SHEAR SUGGEST SOME POTENTIAL FOR
LINEAR/BOWING MODES OF HIGH-BASED TSTMS...WITH STG/ISOLATED SVR
GUSTS POSSIBLE. PRIMARY LIMITING FACTOR WILL BE LACK OF MORE ROBUST
MOISTURE. DESPITE ANTECEDENT WARM/MOIST ADVECTION BOOSTING THETAE
ABOVE VALUES FROM PREVIOUS DAY...NEAR AND S OF WARM FRONT...SFC DEW
POINTS SHOULD REACH ONLY 30S TO MID 40S F MOST AREAS E OF HIGHER
TERRAIN OVER CENTRAL/ERN MT. ACCORDINGLY MODIFIED SOUNDINGS YIELD
MLCAPE ONLY IN 100-400 J/KG RANGE.
..EDWARDS/HULRBUT.. 09/05/2009
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