SWODY1
SPC AC 210558
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT WED MAY 21 2008
VALID 211200Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE CNTRL HIGH
PLAINS...
...SYNOPSIS...
LARGE-SCALE OMEGA BLOCK WILL PERSIST ACROSS NORTH AMERICA THROUGH
THE DAY ONE PERIOD WITH THE PRIMARY FEATURE OF INTEREST BEING
EVOLVING UPPER LOW OVER THE INTERMOUNTAIN WEST. IN THE LOW
LEVELS...PRIMARY LEE CYCLONE IS FORECAST TO DEVELOP SEWD FROM CNTRL
OR ERN WY INTO ERN CO. AS THIS OCCURS...BAROCLINIC ZONE CURRENTLY
QUASI-STATIONARY ACROSS CNTRL TX WILL LIFT NWD AS A WARM
FRONT...LIKELY EXTENDING FROM SURFACE LOW SEWD THROUGH THE ERN TX
PNHDL INTO SRN OK BY EARLY EVENING. THIS BOUNDARY WILL THEN
CONTINUE SEWD THROUGH CNTRL LA AND THEN EWD ALONG THE GULF COAST TO
NEAR THE GA/FL BORDER. FINALLY...A DRYLINE WILL BECOME INCREASINGLY
WELL DEFINED OVER WRN TX TODAY WITH THIS BOUNDARY INTERSECTING THE
WARM FRONT OVER NWRN TX OR THE SERN TX PNHDL LATER THIS AFTERNOON.
...CNTRL PLAINS...
STRENGTHENING LOW-LEVEL FLOW E OF SURFACE LOW WILL AID IN THE NWWD
RETURN OF AN INCREASINGLY MOIST BOUNDARY LAYER WITH DEWPOINTS
INCREASING INTO THE 50S OVER KS...AND MID/UPPER 40S INTO CNTRL/ERN
WY. THIS MOISTURE RETURN WILL OCCUR BENEATH A PLUME OF STEEP
MIDLEVEL LAPSE RATES RESIDING ON ERN PERIPHERY OF EVOLVING UPPER
LOW...CONTRIBUTING TO AFTERNOON MLCAPES OF 500-1000 J/KG INVOF WARM
FRONT/LEE TROUGH.
SUSTAINED CONVERGENCE NEAR SURFACE LOW AND INCREASING UPSLOPE FLOW
TO THE N OF IT WILL PROMOTE SCATTERED TSTM DEVELOPMENT BY MID/LATE
AFTERNOON OVER CNTRL/ERN WY WITH STORMS PROGRESSIVELY BUILDING SWD
INTO NERN CO. DESPITE LARGELY MERIDIONAL MID AND HIGH-LEVEL WIND
FIELDS...BACKED LOW-LEVEL WINDS TO THE N OF SURFACE LOW WILL RESULT
IN SUFFICIENT DEEP-LAYER SHEAR FOR ORGANIZED/ROTATING STORMS WITH
THE PRIMARY SEVERE WEATHER THREATS BEING LARGE HAIL AND LOCALLY
DAMAGING WINDS.
A NW-SE ORIENTED BAND OF ELEVATED TSTMS IS EXPECTED TO DEVELOP LATER
TONIGHT FROM WRN PARTS OF SD/NEB SEWD TOWARD THE LOWER MO VALLEY AS
WAA/ISENTROPIC UPGLIDE ARE ENHANCED TO THE N OF RETREATING WARM
FRONT AND ALONG STRENGTHENING/EXPANDING LLJ AXIS. SOME OF THE MORE
INTENSE STORMS WILL BE CAPABLE OF MARGINALLY SEVERE HAIL.
...SRN PLAINS...
AIR MASS E OF DRYLINE AND ALONG RETREATING WARM FRONT IS EXPECTED TO
BECOME MODERATELY UNSTABLE THIS AFTERNOON WITH MLCAPES INCREASING TO
1000-2000 J/KG. WHILE DEEP LAYER SHEAR WILL NOT BE PARTICULARLY
STRONG /0-6 KM SHEAR AOB 30-35 KT/...LOW-LEVEL HODOGRAPHS ARE
FORECAST TO REMAIN FAIRLY LARGE...NAMELY ALONG WARM FRONT. ANY
SEVERE WEATHER THREAT WILL BE CONDITIONAL ON WHETHER A STORM CAN
DEVELOP AND BECOME SUSTAINED. GIVEN THE HIGH UNCERTAINTY...ONLY LOW
SEVERE WEATHER PROBABILITIES WILL BE INCLUDED ATTM.
...SRN GA/NRN FL...
SURFACE FRONT IS EXPECTED TO BECOME QUASI-STATIONARY NEAR THE FL/GA
BORDER...LIKELY PROVIDING THE FOCUS FOR SCATTERED TSTM DEVELOPMENT
THIS AFTERNOON. WHILE MIDLEVEL LAPSE RATES WILL BE SOMEWHAT WEAKER
THAN TUESDAY...BOUNDARY LAYER WILL REMAIN MOIST WITH DEWPOINTS IN
THE 60S...CONTRIBUTING TO MLCAPES OF 1000-1500 J/KG. MARGINALLY
LARGE-SCALE FORCING FOR ASCENT AND LOW-LEVEL CONVERGENCE MAY TEND TO
LIMIT A MORE ORGANIZED SEVERE WEATHER THREAT...HOWEVER GIVEN THE
MODERATE INSTABILITY AND 40-45 KT OF DEEP LAYER SPEED SHEAR...A FEW
SEVERE STORMS ARE POSSIBLE WITH A THREAT OF HAIL AND DAMAGING WIND
GUSTS.
..MEAD/SMITH.. 05/21/2008
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@PO.UIUC.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment