SWODY2
SPC AC 181724
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1224 PM CDT SAT SEP 18 2010
VALID 191200Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MODELS REMAIN CONSISTENT WITH THE EVOLUTION OF THE MID-UPPER LEVEL
FLOW PATTERN ACROSS THE CONUS. THE TROUGH THAT HAS BEEN LINGERING
OFF THE WRN U.S. COAST WILL MOVE INLAND TO THE GREAT BASIN/
INTERMOUNTAIN REGION ON SUNDAY. MEANWHILE...A DEEP MID-UPPER LEVEL
CYCLONE WILL TRACK SLOWLY NEWD FROM HUDSON BAY. SOME AMPLIFICATION
OF THE BASE OF THIS SYSTEM IS EXPECTED INTO NEW ENGLAND AS A
SHORTWAVE TROUGH TRACKS INTO SRN QUEBEC AND A WEAKER IMPULSE MOVES
FROM THE GREAT LAKES TO NEW ENGLAND ON DAY 2. HEIGHT RISES WILL
OCCUR OVER THE UPPER MS VALLEY AS A RIDGE BUILDS NWD BETWEEN THE
TROUGHS IN THE WRN U.S. AND NERN STATES.
IN THE LOW LEVELS...A COLD FRONT WILL MOVE EWD ACROSS THE PACIFIC NW
AND SHOULD REACH THE NRN ROCKIES TO THE GREAT BASIN BY 12Z MONDAY.
MEANWHILE...A COLD FRONT ATTENDANT TO THE HUDSON BAY LOW WILL MOVE
EWD THROUGH NEW ENGLAND AND SSEWD THROUGH THE OH VALLEY. THE
TRAILING WRN EXTENT OF THIS BOUNDARY...STALLED FROM NRN MO TO
CENTRAL KS...SHOULD RETREAT NWD DURING THE LATTER HALF OF THE PERIOD
IN RESPONSE TO SURFACE PRESSURE FALLS EXPECTED OVER THE CENTRAL/NRN
PLAINS...GIVEN STRENGTHENING LEE TROUGH AHEAD OF WRN TROUGH.
...NRN MO TO CENTRAL IL/IND...
AT 12Z SUNDAY...A COMPLEX OF MAINLY ELEVATED SHOWERS/TSTMS IS
EXPECTED TO BE ONGOING ALONG AND N OF THE COLD FRONT FROM IA/NRN MO
INTO NRN IL. THIS ACTIVITY WILL BE DRIVEN BY LOW LEVEL WAA ALONG
THE NOSE OF WSWLY LLJ EXTENDING FROM KS INTO IA...WITH SOME ASCENT
ALSO POSSIBLE ALONG SRN EXTENT OF MIDLEVEL IMPULSE TRACKING THROUGH
THE UPPER MS VALLEY/WRN GREAT LAKES REGION AT 12Z. MODERATE
INSTABILITY AND WEAK EFFECTIVE BULK SHEAR SUGGESTS SOME HAIL MAY BE
ASSOCIATED WITH THIS EARLY ACTIVITY. VEERING LLJ TO A WLY COMPONENT
SUGGESTS THE EARLY ACTIVITY SHOULD SHIFT EWD...BUT REMAIN GENERALLY
N OF THE FRONT INTO NRN IL/IND.
HOWEVER...MODELS SUGGEST THE POTENTIAL FOR SURFACE BASED TSTM
DEVELOPMENT ALONG THE SRN EXTENT OF THE MORNING TSTM COMPLEX AND/OR
ALONG THE SWD MOVING COLD FRONT...WHERE SURFACE DEWPOINTS IN THE
MID-UPPER 60S AND DIABATIC HEATING WILL SUPPORT MODERATE
INSTABILITY. THIS COMBINED WITH EFFECTIVE BULK SHEAR AROUND 30 KT
SUGGESTS MULTICELLS WOULD BE THE PRIMARY STORM MODE. ALTHOUGH THESE
PARAMETERS WOULD SUPPORT STORM ORGANIZATION WITH A SEVERE WEATHER
THREAT...THE LACK OF STRONGER MID-UPPER LEVEL FORCING EXPECTED
ACROSS THIS REGION TO SUPPORT A MORE CONCENTRATED THREAT LEADS TO
KEEPING A 5 PERCENT SEVERE WEATHER PROBABILITY FOR THIS REGION.
...PACIFIC NW...
FORCING FOR ASCENT WITH EWD MOVING MID-UPPER LEVEL TROUGH AND THE
ATTENDANT COLD FRONT WILL SUPPORT SHOWERS AND TSTMS ON SUNDAY ACROSS
PRIMARILY THE PACIFIC NW. WEAK INSTABILITY SHOULD PRECLUDE THE
THREAT FOR SEVERE WEATHER WITH THIS ACTIVITY.
..PETERS.. 09/18/2010
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