SWODY1
SPC AC 090601
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0101 AM CDT SAT AUG 09 2008
VALID 091200Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SERN LOWER MI INTO THE
LOWER GREAT LAKES...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN ID INTO WRN MT...
...SYNOPSIS...
AN AMPLIFIED UPPER FLOW PATTERN WILL PERSIST OVER NORTH AMERICA THIS
FORECAST PERIOD...WITH A TROUGH OVER MUCH OF THE ERN CONUS...
RIDGING FROM THE SRN ROCKIES INTO CANADIAN PRAIRIES AND A MORE
PROGRESSIVE TROUGH TRACKING THROUGH THE PACIFIC NW INTO WRN CANADA.
IN THE LOW LEVELS...A LEE CYCLONE WILL SLOWLY DEVELOP SWD FROM THE
CNTRL HIGH PLAINS TO WRN OK WITH ATTENDANT FRONTAL ZONE EXTENDING
SEWD THROUGH ERN TX. A COLD FRONT ACCOMPANYING PACIFIC NW TROUGH
WILL PUSH EWD THROUGH THE NRN INTERMOUNTAIN REGION INTO THE NRN HIGH
PLAINS. FINALLY...A COLD FRONT ASSOCIATED WITH A SHORT WAVE TROUGH
DIGGING SEWD ACROSS THE GREAT LAKES WILL MOVE SWD REACHING THE LOWER
GREAT LAKES TO SRN WI/NRN IL BY LATE AFTERNOON...WHILE WRN EXTENSION
OF THIS BOUNDARY REMAINS MORE QUASI-STATIONARY OVER THE NRN PLAINS.
...SERN LOWER MI INTO LOWER GREAT LAKES...
SURFACE HEATING IN ADVANCE OF THE SWD MOVING COLD FRONT COMBINED
WITH SURFACE DEWPOINTS IN THE MID-UPPER 50S WILL SUPPORT MARGINAL
INSTABILITY. STRONGER FORCING FOR ASCENT WITH A SEWD MOVING SHORT
WAVE TROUGH SHOULD COMPENSATE FOR THE WEAKER INSTABILITY AND SUPPORT
A THREAT FOR A LINE OF TSTMS SPREADING SEWD ACROSS SERN LOWER MI
INTO ADJACENT PARTS OF SWRN ONTARIO...AND REACHING WRN NY/UPPER OH
VALLEY THIS EVENING. COOLER MID LEVEL TEMPERATURES WILL SUPPORT A
HAIL THREAT...WITH AN ADDITIONAL THREAT FOR STRONG WIND GUSTS.
...ERN ID/WRN MT...
A MOIST AIR MASS /PW VALUES OF 0.75-1.00 INCH/ COUPLED WITH STEEP
LAPSE RATES WILL CONTRIBUTE TO AN INCREASINGLY UNSTABLE AIR MASS BY
AFTERNOON AHEAD OF COLD FRONT WITH MLCAPES APPROACHING 1000-1500
J/KG. TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND INTENSITY BY
LATE AFTERNOON OR EVENING AS OROGRAPHIC ASCENT COMBINES WITH FRONTAL
FORCING AND HEIGHT FALLS ASSOCIATED WITH UPPER TROUGH. EFFECTIVE
BULK SHEAR OF 35-45 KT WILL BE SUPPORTIVE OF ORGANIZED
STORMS...INCLUDING POTENTIAL FOR BOWING AND SUPERCELL STRUCTURES.
HAIL AND DAMAGING WINDS WILL BE THE PRIMARY SEVERE WEATHER THREATS
THROUGH THE EVENING HOURS AS ACTIVITY SPREADS ENEWD.
...CENTRAL NEB TO CENTRAL OK INTO THE OZARKS...
MUCH UNCERTAINTY EXISTS WITH THE POTENTIAL FOR SEVERE STORMS AND THE
PLACEMENT OF ANY STRONGER ACTIVITY ACROSS THE CENTRAL PLAINS INTO
PART OF NRN OK TODAY. ONGOING CONVECTIVE COMPLEX...CURRENTLY
LOCATED OVER NERN CO...AND A SEPARATE AREA OF WAA TSTMS NE OF THE
BAROCLINIC ZONE OVER NWRN KS SHOULD BE MAINTAINED INTO THIS
MORNING...GIVEN ASCENT ATTENDANT TO SLY LLJ VEERING TO SWLY BY 12Z.
LEFT OVER CLOUD DEBRIS...ANY ONGOING TSTM ACTIVITY THIS MORNING OVER
KS/NRN OK...AND THE POTENTIAL FOR A STABILIZED BOUNDARY LAYER IN THE
WAKE OF THIS SYSTEM OVER THE WRN PART OF THE CENTRAL PLAINS HAVE
REDUCED THE FORECAST CONFIDENCE FOR A SLIGHT RISK IN THIS REGION.
MODELS DO TEND TO AGREE WITH THE DEVELOPMENT OF MODERATE INSTABILITY
ALONG THE SW THROUGH NW PERIPHERY OF CLOUD DEBRIS... WITH THIS ZONE
POTENTIALLY EXTENDING FROM CENTRAL/NW OK TO SW NEB. A MOIST...WARM
AIR MASS WOULD RESULT IN MODERATE INSTABILITY IN THIS
REGION...DESPITE WEAK MID LEVEL LAPSE RATES. 20-35 KT OF NWLY MID
LEVEL WINDS ATOP SWLY LOW LEVEL FLOW WILL SUPPORT DEEP SHEAR VALUES
FAVORING ORGANIZED STORMS...SOME SUPERCELLS. DAMAGING WIND GUSTS
WILL BE THE PRIMARY THREAT...GIVEN WEAK MID LEVEL LAPSE RATES
LIMITING THE HAIL POTENTIAL. AFOREMENTIONED UNCERTAINTIES WARRANT
LOW SEVERE WEATHER PROBABILITIES AT THIS TIME...WITH POTENTIAL FOR
PART OF THIS REGION TO BE UPGRADED TO A SLIGHT RISK.
SWLY LLJ IS EXPECTED TO RE-STRENGTHEN THIS EVENING/OVERNIGHT NRN TX
INTO NERN OK/NWRN AR RESULTING IN A TSTM CLUSTER TO TRACK SEWD FROM
SERN KS/NRN OK INTO AR. STRONG EFFECTIVE BULK SHEAR AND MARGINAL
ELEVATED INSTABILITY WOULD SUPPORT AN ISOLATED SEVERE WEATHER THREAT
WITH THIS EVENING/OVERNIGHT ACTIVITY.
...SRN AZ/SWRN NM...
WATER VAPOR IMAGERY INDICATED A CIRCULATION CENTER CURRENTLY LOCATED
FROM SERN AZ/SWRN NM INTO NERN SONORA. MODELS SUGGEST THIS IMPULSE
SHOULD TRACK WNWWD INTO SRN AZ TODAY AIDING IN TSTM DEVELOPMENT AS
THE AIR MASS OVER THIS REGION BECOMES MODERATELY UNSTABLE. WEAK
FLOW AND DEEP LAYER SHEAR WILL PRECLUDE THE POTENTIAL FOR STORM
ORGANIZATION. HOWEVER...STEEP LOW LEVEL LAPSE RATES SUGGEST
ISOLATED WIND GUSTS WILL BE THE PRIMARY THREAT.
...NRN HIGH PLAINS...
MOIST UPSLOPE FLOW INTO SERN MT/ERN WY BENEATH ERN EXTENT OF STEEPER
MID LEVEL LAPSE RATES WILL SUPPORT MARGINAL INSTABILITY WITH
AFTERNOON CONVECTIVE DEVELOPMENT INITIALLY LIKELY OVER THE HIGHER
TERRAIN. EFFECTIVE BULK SHEAR OF 25-30 KT SHOULD TEND TO LIMIT
STORM ORGANIZATION AND OVERALL SEVERE WEATHER THREAT...WITH ISOLATED
HAIL/STRONG WIND GUSTS POSSIBLE AS ACTIVITY SPREADS ESEWD INTO WRN
DAKOTAS...WRN NEB AND NERN CO THIS EVENING.
...SRN FL...
UPPER TROUGH MOVING SWD ACROSS CENTRAL/SRN FL WILL SUPPORT TSTM
DEVELOPMENT ACROSS THE SRN HALF OF THE FL PENINSULA TODAY WHERE THE
AIR MASS WILL BE MODERATELY UNSTABLE. DESPITE WEAK DEEP LAYER
SHEAR...30 KT OF WLY MID LEVEL FLOW AND STEEP LOW LEVEL LAPSE RATES
SUGGEST SOME POTENTIAL FOR AN ISOLATED SEVERE WEATHER THREAT.
..PETERS/HURLBUT.. 08/09/2008
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