SWODY2
SPC AC 221710
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1210 PM CDT FRI OCT 22 2010
VALID 231200Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID-MO VALLEY/CORN
BELT SWWD INTO CENTRAL TX......
...SYNOPSIS...
A SHORTWAVE TROUGH CURRENTLY MOVING EWD WITHIN SRN BRANCH OF WRN
CONUS SPLIT FLOW REGIME ACROSS NRN BAJA REGION IS EXPECTED TO REACH
NM/NRN MEXICO BY 12Z SATURDAY. THIS FEATURE WILL PHASE WITH A
MID-UPPER LEVEL TROUGH LIFTING NEWD INTO THE CENTRAL PLAINS DURING
DAY 1...AND EVOLVE INTO A BROAD LONGWAVE TROUGH ACROSS THE MIDDLE
PART OF THE COUNTRY.
A LEAD IMPULSE...CURRENTLY LOCATED WITHIN THE NRN BAJA TROUGH... IS
FORECAST TO TRACK FROM KS TO THE GREAT LAKES REGION. MEANWHILE...
THE SRN EXTENT OF A WEAKER/SHEARED IMPULSE TRAVERSING CA EARLY DAY 1
IS EXPECTED TO TRACK FROM NRN MEXICO INTO TX SATURDAY AFTERNOON AND
REACH MID MS VALLEY BY 12Z SUNDAY. EACH OF THESE IMPULSES AND
ATTENDANT JET STREAM DYNAMICS WILL BE THE FOCI FOR A BIMODAL SEVERE
EVENT EXPECTED TO UNFOLD ON DAY 2 ALONG AND AHEAD OF A FRONT
SPREADING EWD ACROSS THE CENTRAL/SRN PLAINS. A SURFACE LOW...
ATTENDANT TO THE CENTRAL PLAINS TROUGH...WILL TRACK ENEWD FROM NWRN
KS/SWRN NEB THIS FORECAST PERIOD...REACHING NWRN IA BY 12Z SUNDAY.
...W CENTRAL/CENTRAL TX NEWD INTO ERN OK...
TSTMS...SOME SEVERE...SHOULD BE ONGOING ACROSS W CENTRAL TX REGION
AND EDWARDS PLATEAU /SEE DAY 1 CONVECTIVE OUTLOOK FOR DETAILS
REGARDING THIS SEVERE THREAT/. GIVEN A SOMEWHAT MORE SWWD/WWD
EXTENT OF THE LATE DAY 1/EARLY DAY 2 SEVERE THREAT...THE SEVERE
PROBABILITIES AND CATEGORICAL SLIGHT RISK HAVE BEEN ADJUSTED
ACCORDINGLY. MODELS REMAIN CONSISTENT SUGGESTING A RAMP-UP IN
SEVERE STORM PROBABILITIES SATURDAY MORNING INTO THE AFTERNOON AS
SRN EXTENT OF UPPER TROUGH SWINGS ACROSS THE REGION. MORNING STORMS
IN W CENTRAL TX WILL GRADUALLY GROW UPSCALE IN INTENSITY/NUMBER OVER
CNTRL TX TO SRN OK BY EARLY AFTERNOON AMIDST MODERATE INSTABILITY
AND 45-50 KTS OF EFFECTIVE SHEAR. CLUSTERS OF STORMS...INCLUDING
EMBEDDED SUPERCELLS AND POSSIBLE BOWS/LEWPS...WILL DEVELOP NE INTO
ERN OK BY EVENING WITH RISKS FOR LARGE HAIL...DAMAGING WINDS AND
PERHAPS A TORNADO OR TWO. ACTIVITY WILL THEN MOVE INTO THE ARKLATEX
REGION TO SRN MO OVERNIGHT...BUT WITH A LESSENING SEVERE THREAT AS
STORMS ENCOUNTER A MORE STABLE NOCTURNAL BOUNDARY LAYER.
...MID/LOWER MO RIVER VALLEY/CORN BELT...
A STRONG SSWLY LLJ DEVELOPING FRIDAY NIGHT INTO THE LOWER MO VALLEY
TO IA COMBINED WITH A SECOND LLJ STRENGTHENING FROM OK TO LOWER MO
VALLEY SATURDAY WILL SUPPORT A NWD SURGE OF LOW-LEVEL MOISTURE INTO
THIS REGION. MORNING WARM CONVEYOR-DERIVED CONVECTION SHOULD MOVE
INTO THE MS VALLEY/WRN GREAT LAKES BY AFTERNOON WITH A NARROW ZONE
OF MODERATE INSTABILITY /MLCAPE TO 1500 J PER KG/ DEVELOPING IN ITS
WAKE FROM THE NEB/IA BORDER SWD INTO WRN MO BY MID-AFTERNOON.
AS A NEW WARM CONVEYOR FORMS DURING THE AFTERNOON TSTMS SHOULD FORM
BOTH TO THE N-E OF THE SURFACE LOW IN NERN NEB/WRN IA AND SEWD INTO
NERN KS/NWRN MO. SLIGHT RISK HAS BEEN EXPANDED WWD SOME ACROSS SERN
NEB/FAR NERN KS TO ACCOUNT FOR STORMS DEVELOPING INTO THIS REGION
PER LATEST MODELS. BACKED LOW-LEVEL FLOW... ATTENDANT TO SURFACE
LOW...AND POTENTIAL FOR STEEP LOW-LEVEL LAPSE RATES WILL SERVE TO
MAXIMIZE AN ISOLATED TORNADO THREAT WITH DISCRETE CELLS DURING THE
MID-LATE AFTERNOON. FAIRLY SUBSTANTIAL INCREASE IN STORMS SHOULD
EVOLVE BY LATE AFTERNOON/EARLY EVENING ACROSS NRN MO/IA AS FORCING
FOR ASCENT/STEEP MIDLEVEL LAPSE RATES ATTENDANT TO AFOREMENTIONED KS
IMPULSE SPREAD ACROSS THIS REGION. A FEW STORMS WILL POSSIBLY
CONTAIN LARGE HAIL OR DAMAGING WINDS. THIS ACTIVITY SHOULD DEVELOP
EWD TOWARD THE CENTRAL GREAT LAKES REGION OVERNIGHT...BUT WITH A
DECREASING SEVERE THREAT AFTER DARK.
...UPPER MS VALLEY/UPPER GREAT LAKES...
GENERAL TSTM AREA HAS BEEN EXPANDED NWD SOME TO ACCOUNT FOR LATEST
MODEL CONSENSUS INDICATING WAA INTO THIS REGION SUPPORTING ELEVATED
TSTM ACTIVITY. THE COMBINATION OF WEAK INSTABILITY THIS FAR N AND
WEAK SHEAR ARE EXPECTED TO PRECLUDE A SEVERE WEATHER THREAT ACROSS
THIS REGION.
..PETERS.. 10/22/2010
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