DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 210055
SWODY1
SPC AC 210053

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0653 PM CST TUE NOV 20 2012

VALID 210100Z - 211200Z

...NO SVR TSTM AREAS FORECAST...

...PACIFIC NORTHWEST/NORTHERN INTERMOUNTAIN REGION...
A LARGE COLD UPPER TROUGH IS IN THE PROCESS OF MIGRATING INLAND OFF
THE PACIFIC...WITH A NUMBER OF SMALLER SCALE IMPULSES PROGRESSING
THROUGH BROADER SCALE CYCLONIC FLOW AROUND A LINGERING MID-LEVEL
CIRCULATION TO THE WEST OF THE BRITISH COLUMBIA COAST. ONE OF THE
MORE SIGNIFICANT OF THESE IMPULSES IS RAPIDLY TURNING EASTWARD
TOWARD THE OREGON COAST...AND APPEARS LIKELY TO ADVANCE
INLAND...ACROSS THE CASCADES...BY THE END OF THE PERIOD.

THOUGH RATHER SPARSE IN COVERAGE...SOME THUNDERSTORM ACTIVITY IS
ALREADY OCCURRING IN ASSOCIATION WITH WEAK DESTABILIZATION BENEATH
COLD AIR ALOFT. NOT MUCH CHANGE IS EXPECTED THROUGH THE 06-08Z TIME
FRAME...WHEN STRONGER MID-LEVEL FORCING FOR UPWARD VERTICAL MOTION
MAY BEGIN IMPACTING THE OREGON COAST...SUPPORTING SOMEWHAT HIGHER
/AROUND 10-30 PERCENT/ THUNDERSTORM PROBABILITIES. DEEP LAYER WIND
FIELDS AND SHEAR NEAR A 40-50 KT SOUTHERLY 850 MB JET OVERSPREADING
THE REGION OVERNIGHT MAY ACTUALLY BECOME FAVORABLE FOR ORGANIZED
STRONG/SEVERE STORM DEVELOPMENT. QUESTIONS LINGER CONCERNING THE
EVOLUTION OF THERMODYNAMIC PROFILES...WHICH DO NOT APPEAR
PARTICULARLY LIKELY TO BECOME CONDUCIVE TO VIGOROUS UPDRAFTS. BUT
THE POTENTIAL FOR CONVECTIVELY ENHANCED SURFACE WIND GUSTS DOES NOT
SEEM COMPLETELY NEGLIGIBLE WEST OF THE OREGON CASCADES...MAINLY
DURING THE 07-11Z TIME FRAME.

ADDITIONAL THUNDERSTORM ACTIVITY ALSO DOES NOT APPEAR OUT OF THE
QUESTION FARTHER INLAND...EAST OF THE CASCADES...PARTICULARLY ACROSS
PARTS OF NORTHEASTERN OREGON/SOUTHEASTERN WASHINGTON INTO THE
MOUNTAINS OF NORTH CENTRAL IDAHO BY 12Z.

..KERR.. 11/21/2012

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