SWODY2
SPC AC 061730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT MON JUL 06 2009
VALID 071200Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE NRN
PLAINS AND UPPER MS VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF THE NERN
STATES...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF W CNTRL MT...
...SYNOPSIS...
TUESDAYS LARGE SCALE UPPER PATTERN WILL REMAIN DOMINATED BY AN UPPER
TROUGH OVER THE PACIFIC AND NWRN U.S. COASTS AND A RIDGE AXIS FROM
THE SRN HIGH PLAINS THROUGH THE NRN PLAINS. BY 12Z TUESDAY...PRIMARY
SYNOPTIC FRONT WILL EXTEND FROM A SURFACE LOW IN SERN CANADA INTO
THE NERN STATES THEN WNWWD THROUGH SD AND NERN MT. A LEE TROUGH WILL
STRETCH N-S THROUGH THE CNTRL AND SRN HIGH PLAINS. A QUASISTATIONARY
FRONT WILL REMAIN ACROSS THE GULF COAST STATES.
...CNTRL THROUGH NRN PLAINS AND PORTIONS OF UPPER MS VALLEY...
A FEW STORMS MAY BE ONGOING EARLY TUESDAY FROM PORTIONS OF ND INTO
THE UPPER MS VALLEY REGION WITHIN ZONE OF WARM ADVECTION NORTH OF
NW-SE ORIENTED FRONT. IN-SITU MOISTURE AND EVAPOTRANSPIRATION WILL
RESULT IN MIXED LAYER DEWPOINTS GENERALLY IN THE 50S TO AROUND 60
FARTHER SOUTH IN WARM SECTOR. AXIS OF STEEPER MID LEVEL LAPSE RATES
WILL HAVE OVERSPREAD A PORTION OF THE CNTRL-NRN PLAINS AND IN
CONJUNCTION WITH DIABATIC WARMING WILL CONTRIBUTE TO 1000-2000 J/KG
MLCAPE.
THE BULK OF SHORTWAVE TROUGH CURRENTLY MOVING THROUGH THE PACIFIC NW
WILL LIKELY LIFT NWD INTO SRN ALBERTA/SASKATCHEWAN. HOWEVER...MODELS
SUGGEST SRN END VORT MAX OR REMNANT MCV FROM MONDAYS STORMS MAY
CONTINUE OVER TOP OF UPPER RIDGE THROUGH THE NRN PLAINS AND UPPER MS
VALLEY. THE WEAK LARGE SCALE FORCING ALONG WITH PLUME OF WARM AIR IN
THE 850-700 MB LAYER ASSOCIATED WITH EML COULD BE PROBLEMATIC FOR
THUNDERSTORM INITIATION IN MUCH OF THE WARM SECTOR. HOWEVER...AS
BOUNDARY LAYER WARMS AND MIXES THE POTENTIAL WILL EXIST FOR STORMS
TO INTENSIFY ALONG CONVECTIVELY ENHANCED BAROCLINIC ZONE. FARTHER
SOUTH MORE ISOLATED DEVELOPMENT MAY OCCUR IN VICINITY OF PRE-FRONTAL
CONVERGENCE BOUNDARY ACROSS CNTRL SD BY LATE AFTERNOON.
STRENGTHENING SSWLY LOW LEVEL JET MAY SUPPORT ADDITIONAL STORMS
DEVELOPING PRIMARY NORTH OF BOUNDARY DURING THE EVENING. BULK SHEAR
OF 25-35 KT WILL SUPPORT BOTH MULTICELL AND SUPERCELL STRUCTURES
WITH STORMS EVOLVING INTO ONE MORE CLUSTERS OVERNIGHT. ISOLATED
LARGE HAIL AND DAMAGING WIND GUSTS WILL BE THE MAIN THREATS
PRIMARILY FROM LATE AFTERNOON TO MID EVENING.
...NERN STATES...
COLD AIR ALOFT WITH TEMPERATURES OF -15 TO -17C AT 500 MB WILL EXIST
ABOVE AXIS MODEST LOW LEVEL MOISTURE EAST OF FRONTAL BOUNDARY
RESULTING IN 500-1000 J/KG MLCAPE AS THE BOUNDARY LAYER WARMS DURING
THE AFTERNOON. THIS REGION WILL EXIST WITHIN EXIT REGION OF A
MID-UPPER LEVEL JET THAT WILL MOVE SEWD THROUGH BASE OF UPPER
TROUGH. STORMS ARE EXPECTED TO INCREASE IN COVERAGE AND INTENSITY
INTO THE AFTERNOON WITH BULK SHEAR OF 40+ KT SUPPORTIVE OF ORGANIZED
STRUCTURES. ISOLATED DAMAGING WIND AND LARGE HAIL WILL BE THE
PRIMARY THREATS.
...WRN AND CNTRL MT...
ANOTHER IN A SERIES OF SHORTWAVE TROUGHS WILL MOVE THROUGH BASE OF
UPPER TROUGH AND INTO MT DURING THE AFTERNOON. STORMS WILL LIKELY
DEVELOP OVER THE HIGHER TERRAIN BY LATE AFTERNOON AND SPREAD NEWD
INTO THE HIGH PLAINS OF CNTRL MT DURING THE EVENING. STRONG BULK
SHEAR WILL FAVOR SUPERCELLS WITH INVERTED-V BOUNDARY LAYERS AND
STEEP LAPSE RATES SUPPORTING ISOLATED DAMAGING WIND AND HAIL. THERE
STILL REMAINS SOME QUESTION REGARDING QUALITY OF AIRMASS SINCE
INSTABILITY/MOISTURE WILL LIKELY BE SOMEWHAT LIMITED IN POSTFRONTAL
REGIME...BUT WILL BE COMPENSATED FOR TO SOME EXTENT BY COOL
TEMPERATURES ALOFT.
...SRN AND CNTRL HIGH PLAINS...
A FEW STORMS WILL BE POSSIBLE ALONG LEE TROUGH OVER THE CNTRL AND
SRN HIGH PLAINS WITHIN NWLY FLOW REGIME WHERE BULK SHEAR WILL BE
SUFFICIENT FOR ORGANIZED STORMS WITH LARGE HAIL AND ISOLATED
DAMAGING WIND POSSIBLE. HOWEVER...CAPPING INVERSION AND PROXIMITY TO
UPPER RIDGE SUGGEST IT MAY BE DIFFICULT TO INITIATE MORE THAN VERY
ISOLATED STORMS...WLL THEREFORE MAINTAIN 5% SEVERE PROBABILITIES AT
THIS TIME.
..DIAL.. 07/06/2009
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