SWODY2
SPC AC 110600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT WED APR 11 2012
VALID 121200Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS WRN KS...ERN OK/TX
PANHANDLES...WRN OK AND W TX...
...SYNOPSIS...
MODELS CONTINUE TO ADVERTISE THE BREAKDOWN OF THE CENTRAL U.S. RIDGE
THROUGH D2/THU AS A LEAD SHORTWAVE TROUGH...CURRENTLY APPROACHING
SRN CA...TRACKS NWD THROUGH THE NRN HIGH PLAINS...AND A LARGER
UPSTREAM PACIFIC TROUGH AMPLIFIES SE TOWARD THE WEST COAST. A
SHORTWAVE TROUGH LOCATED BETWEEN THESE TWO SYSTEMS IS EXPECTED TO
MOVE FROM THE SRN CO RIVER VALLEY TO THE SRN ROCKIES BY 13/00Z AND
THEN INTO THE CENTRAL PLAINS THU NIGHT/EARLY FRI MORNING.
...WRN PORTIONS OF THE CENTRAL AND SRN PLAINS...
HEIGHT FALLS CONTINUING OVER THE PLAINS STATES ON THU AS THE LEAD
SHORTWAVE TROUGH LIFTS NEWD INTO THE NRN PLAINS WILL ALLOW THE LEE
TROUGH/DRY LINE TO SHIFT EWD INTO WRN PORTIONS OF THE CENTRAL AND
SRN PLAINS THROUGH THU AFTERNOON. 00Z GFS/12Z ECMWF INDICATED A
SLIGHT EWD SHIFT OF THE DRY LINE THAN WAS INDICATED IN THE PREVIOUS
OUTLOOK FOR THIS REGION WITH THIS BOUNDARY FORECAST TO EXTEND FROM
NWRN KS SSEWD TO INVOF THE WRN OK/TX BORDER...AND SSWWD TO THE TX
BIG BEND REGION. MEANWHILE...A LEE CYCLONE DEEPENING OVER NERN
CO/NWRN KS BORDER AREA THU AFTERNOON IS EXPECTED TO TRACK NEWD INTO
CENTRAL NEB BY 12Z FRI AS THE SRN CO RIVER VALLEY TROUGH APPROACHES
THIS REGION.
ELEVATED CONVECTION/TSTMS MAY BE ONGOING AT THE START OF D2 ACROSS
PARTS OF THE CENTRAL/SRN PLAINS WITHIN A CORRIDOR OF WAA ALONG A
SSWLY LLJ. THIS ACTIVITY COULD PERSIST THROUGH THE DAY AS IT SPREADS
ENEWD. THE GREATEST THREAT FOR SEVERE STORMS REMAINS ALONG AND JUST
E OF THE GENERALLY N-S ORIENTED DRY LINE...WITH STORM INITIATION
EXPECTED BETWEEN 21-00Z. SLY LOW LEVEL FLOW ACROSS WRN PORTIONS OF
THE CENTRAL/SRN PLAINS WILL MAINTAIN NWD MOISTURE ADVECTION WITH A
NARROW CORRIDOR OF SURFACE DEWPOINTS IN THE LOWER 60S REACHING
CENTRAL KS /E OF DRY LINE/. THIS COMBINED WITH STRONG SURFACE
HEATING AND STEEP MIDLEVEL LAPSE RATES SHIFTING EWD ATOP THE DRY
LINE WILL SUPPORT MODERATE INSTABILITY. STRENGTHENING SWLY MIDLEVEL
WINDS /40-50 KT/ THU AFTERNOON COMBINED WITH A 30-40 KT SLY LLJ WILL
RESULT IN EFFECTIVE BULK SHEAR OF 35-45 KT WITH VECTORS ORIENTED
PERPENDICULAR TO THE SURFACE BOUNDARY. THIS WILL SUPPORT A GREATER
POTENTIAL FOR DISCRETE SUPERCELLS CAPABLE OF PRODUCING HAIL...SOME
VERY LARGE...AND DAMAGING WINDS. IN ADDITION...EFFECTIVE SRH
EXCEEDING 300 M2/S2 WITH LARGE LOW LEVEL HODOGRAPH CURVATURE WILL
SUPPORT A TORNADO THREAT...PRIMARILY FROM WRN KS INTO WRN OK/ERN TX
PANHANDLE. OVERALL SEVERE WEATHER THREAT SHOULD DIMINISH LATER THU
EVENING AS THE INSTABILITY WEAKENS.
...NEB INTO WRN IA...
AN INCREASE IN PRIMARILY ELEVATED TSTMS CAN BE EXPECTED FROM W-E
ACROSS NEB INTO WRN IA THU EVENING INTO EARLY FRI MORNING WITHIN A
WAA REGIME IN THE NOSE OF FURTHER STRENGTHENING OF THE PLAINS LLJ
INTO THIS REGION. MODERATE ELEVATED INSTABILITY AND STEEP MIDLEVEL
LAPSE RATES WILL PROMOTE A HAIL THREAT...BUT WEAKER BULK SHEAR MAY
TEND TO LIMIT THE OVERALL SEVERE WEATHER THREAT...AND THUS WARRANT
ONLY LOW SEVERE PROBABILITIES AT THIS TIME.
...S FL...
SOME TSTM DEVELOPMENT IS POSSIBLE ACROSS S FL AS A FRONT MOVES SWD
ACROSS THIS REGION ON D2/THU. 30-35 KT OF EFFECTIVE BULK SHEAR
WITHIN A NWLY FLOW REGIME AND WEAK INSTABILITY COULD PROVE FAVORABLE
FOR A FEW ORGANIZED STORMS. HOWEVER...THE WEAK INSTABILITY AND
UNCERTAINTY IN STORM COVERAGE PRECLUDES THE INCLUSION OF SEVERE
WEATHER PROBABILITIES AT THIS TIME.
..PETERS.. 04/11/2012
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