SPC AC 150600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1200 AM CST MON DEC 15 2014
VALID 161200Z - 171200Z
...NO SVR TSTM AREAS FORECAST...
...SUMMARY...
THE RISK FOR SEVERE STORMS APPEARS NEGLIGIBLE TUESDAY THROUGH
TUESDAY NIGHT.
...SYNOPSIS...
THE MID-LEVEL CLOSED LOW...WITHIN A NEGATIVELY TILTED SHORT WAVE
TROUGH THAT HAS EMERGED FROM THE SOUTHWEST...MAY GENERALLY MAINTAIN
STRENGTH WHILE PROGRESSING EAST NORTHEASTWARD INTO SOUTHERN PORTIONS
OF THE GREAT LAKES AND ADJACENT OHIO VALLEY BY 12Z TUESDAY.
THEREAFTER...MODELS CONTINUE TO SUGGEST IT MAY UNDERGO CONSIDERABLE
DEFORMATION WHILE PIVOTING NORTHEASTWARD TOWARD NEW ENGLAND...AS AN
ELONGATING UPSTREAM CLOSED LOW DIGS INTO THE UPPER GREAT LAKES
REGION...TO THE SOUTH OF A PROMINENT NORTHERN STREAM HIGH CENTER
SHIFTING ACROSS THE CENTRAL CANADIAN PROVINCES. AS THIS IS
OCCURRING...IT ALSO APPEARS THAT A SEPARATE IMPULSE WILL SPLIT OFF
THE INITIAL PERTURBATION WHILE PROGRESSING ACROSS THE MID ATLANTIC
COAST. IN RESPONSE TO THESE DEVELOPMENTS...AN ASSOCIATED WEAKENING
OCCLUDED SURFACE CYCLONE IS FORECAST TO MIGRATE NORTHEASTWARD
THROUGH THE LOWER GREAT LAKES REGION...WHILE A NEW SURFACE LOW
BEGINS TO FORM ALONG A TIGHTENING BAROCLINIC ZONE SOUTH/EAST OF LONG
ISLAND.
MEANWHILE...ACROSS THE FAR EASTERN PACIFIC INTO WESTERN NORTHERN
AMERICA...WHERE THE SPLIT BELTS OF STRONGER FLOW ARE EXPECTED TO
REMAIN SOMEWHAT IN PHASE...AMPLIFIED LARGE-SCALE UPPER TROUGHING MAY
PERSIST THROUGH THIS PERIOD. WITHIN THIS REGIME...IT DOES APPEAR
THAT ANOTHER SIGNIFICANT SHORT WAVE TROUGH WILL DIG INTO THE
SOUTHERN STREAM...PROBABLY REACHING THE CALIFORNIA COAST BY LATE
TUESDAY NIGHT.
...APPALACHIANS INTO MID ATLANTIC COAST...
MODELS CONTINUE TO SUGGEST THAT MID/UPPER FORCING FOR ASCENT AHEAD
OF THE REMNANT CLOSED LOW MAY REMAIN FAIRLY STRONG ACROSS AND EAST
OF THE APPALACHIANS INTO THE DAY TUESDAY. COUPLED WITH CONTINUING
NORTHWARD MOISTURE ADVECTION...AT LEAST IN LOWER TO MID TROPOSPHERIC
LEVELS...MODEL FORECAST SOUNDINGS STILL INDICATE SUFFICIENT
STEEPENING OF LAPSE RATES TO YIELD WEAK CAPE THROUGH THE FAVORABLE
MIXED PHASE LAYER FOR THE DEVELOPMENT OF CHARGE SEPARATION. WHILE
THIS IS EXPECTED TO OCCUR ABOVE A FAIRLY DEEP NEAR SURFACE OR
SURFACE BASED STABLE LAYER...WIDELY SCATTERED TO SCATTERED WEAK
THUNDERSTORM ACTIVITY WILL BE POSSIBLE.
...CALIFORNIA...
VARIABILITY LINGERS AMONG THE MODELS AND MODEL ENSEMBLES CONCERNING
THE EVOLUTION OF THE APPROACHING SHORT WAVE TROUGH. HOWEVER...THE
ENVIRONMENT MAY BECOME CONDUCIVE TO AT LEAST SCATTERED WEAK
THUNDERSTORMS...WITHIN AN ASSOCIATED FRONTAL CONVECTIVE BAND
FORECAST TO ADVANCE INLAND ACROSS THE NORTHERN CALIFORNIA COAST
TUESDAY AFTERNOON. THIS ACTIVITY MAY PERSIST WHILE SPREADING
SOUTHWARD...INLAND ACROSS MUCH OF THE REMAINDER OF THE CENTRAL AND
SOUTHERN CALIFORNIA COAST TUESDAY NIGHT...WITH ADDITIONAL ISOLATED
TO WIDELY SCATTERED THUNDERSTORMS ALSO POSSIBLE IN THE POST-FRONTAL
REGIME...ALONG COASTAL AREAS.
..KERR.. 12/15/2014
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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