SWODY2
SPC AC 220526
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1226 AM CDT SUN MAR 22 2009
VALID 231200Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MO VALLEY SWD TO
THE RED RIVER VALLEY...
...SYNOPSIS...
A DYNAMIC LARGE-SCALE PATTERN WILL EXIST OVER THE CNTRL CONUS DURING
THE DAY TWO PERIOD AS INTENSE MID/UPPER-LEVEL LOW SHIFTS NEWD FROM
THE CNTRL HIGH PLAINS INTO SD/NEB. AS THIS PROCESS
OCCURS...SIGNIFICANT HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT WILL
SPREAD EWD THROUGH THE CNTRL/SRN PLAINS...AND EVENTUALLY MORE NEWD
THROUGH THE DAKOTAS INTO UPPER MS VALLEY.
AT THE SURFACE...LOW PRESSURE INITIALLY OVER NERN CO WILL DEEPEN
SLIGHTLY EARLY MONDAY BEFORE SLOWLY FILLING DURING THE OCCLUSION
PROCESS WHILE DEVELOPING NEWD THROUGH CNTRL NEB INTO ERN SD.
TRAILING PACIFIC FRONT/DRYLINE WILL PUSH EWD INTO CNTRL PARTS OF
NEB/KS BEFORE BEING OVERTAKEN BY POLAR COLD FRONT SURGING SEWD FROM
THE NRN HIGH PLAINS. FARTHER S...DRYLINE WILL MIX EWD INTO WRN OK
AND NWRN TX BY AFTERNOON/EARLY EVENING BEFORE MERGING WITH POLAR
FRONT LATER MONDAY NIGHT OVER CNTRL OK INTO N-CNTRL TX.
...GREAT PLAINS...
RECENT TRENDS IN GOES TPW DATA INDICATE THAT SLOW AIR MASS
MODIFICATION IS NOW OCCURRING OVER THE FAR WRN GULF OF MEXICO WITH
LOWER TO MID 60S DEWPOINTS NOW OBSERVED AS FAR N AS DEEP S TX.
HOWEVER...LATEST MODEL GUIDANCE CONTINUES TO CONFIRM THAT DEEPER
CONTINENTAL PBL MIXING WILL LIMIT MOISTURE QUALITY WITH DEWPOINTS
REMAINING LARGELY IN THE 50S ACROSS SYSTEM WARM SECTOR.
THIS MOISTURE WILL COMBINE WITH A RESERVOIR OF STEEP MIDLEVEL LAPSE
RATES /7-8 C PER KM/ SITUATED ON CYCLONIC SIDE OF MID AND HIGH-LEVEL
JET CORES TO SUPPORT POCKETS OF MODERATE INSTABILITY OVER THE CNTRL
PLAINS BY AFTERNOON WHERE MLCAPE WILL APPROACH 1000 J/KG.
OVER THE SRN PLAINS...MIDLEVEL LAPSE RATES WILL TEMPORARILY WEAKEN
MONDAY WHICH WILL HAVE AN IMPACT ON AIR MASS DESTABILIZATION INTO
THE AFTERNOON. HOWEVER...MODEL DATA CONTINUE TO INDICATE THAT A
SECONDARY PLUME OF STEEPER LAPSE RATES WILL ACCOMPANY A TRAILING JET
STREAK/VORTICITY MAXIMUM SHIFTING EWD ACROSS THE TX PNHDL AND
OK...BOOSTING MLCAPE TO AROUND 1000 J/KG TOWARD 24/00Z FROM SRN KS
INTO OK.
INITIAL SURFACE-BASED TSTM ACTIVITY WILL LIKELY OCCUR MONDAY
AFTERNOON INVOF SURFACE LOW AND IMMEDIATELY TO THE S ALONG OCCLUDING
PACIFIC AND POLAR FRONTS OVER PARTS OF NEB/KS. WHILE HAIL/DAMAGING
WINDS WILL BE THE PRIMARY SEVERE WEATHER THREATS...SETUP WILL BE
FAVORABLE FOR LOW-TOPPED SUPERCELL DEVELOPMENT NEAR OCCLUDING
SURFACE LOW OVER N-CNTRL/NERN NEB INTO SERN SD WHERE ISOLATED
TORNADOES ARE POSSIBLE. RAPIDLY BACKING DEEP-LAYER SHEAR VECTORS
WITH TIME ACROSS NEB INTO NRN KS SUGGESTS THAT STORMS MAY EVOLVE
INTO A LINEAR SYSTEM WITH THE THREAT FOR HAIL AND DAMAGING WINDS
CONTINUING EWD THROUGH THE MID AND LOWER MO VALLEYS MONDAY NIGHT.
FROM CNTRL KS INTO THE RED RIVER VALLEY...MORE NORMAL ORIENTATION OF
DEEP-LAYER SHEAR VECTORS TO THE DRYLINE AND GENERALLY WEAKER
LARGE-SCALE FORCING MAY BE MORE FAVORABLE FOR BROKEN LINE SEGMENTS
OR DISCRETE STORMS MONDAY AFTERNOON INTO MONDAY NIGHT. WHILE
ENVIRONMENT WILL NOT BE PARTICULARLY UNSTABLE...THE PRESENCE OF
RATHER STRONG LOW AND DEEP-LAYER SHEAR /I.E. 0-1 KM SHEAR OF 25-35
KT AND EFFECTIVE BULK SHEAR OF 50-60 KT/ SUGGESTS THE THREAT FOR A
FEW SUPERCELLS CAPABLE OF DAMAGING WINDS...HAIL AND PERHAPS
TORNADOES. HERE TOO...STORMS MAY TEND TO GROW UPSCALE INTO A LINEAR
SYSTEM MONDAY NIGHT WITH A HAIL/WIND THREAT PERSISTING EWD ACROSS OK
PERHAPS INTO PARTS OF THE OZARK PLATEAU AND NRN TX. EMBEDDED
SUPERCELLS WILL REMAIN POSSIBLE HOWEVER...AND GIVEN THAT BOUNDARY
LAYER MOISTURE WILL CONTINUE TO INCREASE IN AN ENVIRONMENT OF STRONG
LOW-LEVEL SHEAR...ISOLATED TORNADOES CANNOT BE RULED OUT.
..MEAD.. 03/22/2009
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