SPC AC 211717
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1117 AM CST MON FEB 21 2011
VALID 221200Z - 231200Z
...NO TSTM AREAS FORECAST...
...SYNOPSIS...
MODELS INDICATE THAT BLOCKING OVER THE EAST CENTRAL PACIFIC WILL
PERSIST THROUGH THIS FORECAST PERIOD...WITH A NEW RIDGE ALSO
BEGINNING TO BUILD NORTHWARD ACROSS PARTS OF THE NORTHEASTERN
PACIFIC AND ALASKA. AS THIS OCCURS...AMPLIFICATION OF A SIGNIFICANT
SHORT WAVE TROUGH APPEARS LIKELY TO ENSUE DOWNSTREAM...NEAR THE
BRITISH COLUMBIA COAST...WITHIN BROADER SCALE TROUGHING EXTENDING
EASTWARD ACROSS MUCH OF WESTERN/CENTRAL CANADA AND THE NORTHWESTERN
UNITED STATES. FARTHER TO THE SOUTH...WITHIN ANOTHER BELT OF
WESTERLIES...A FAIRLY COMPACT BUT VIGOROUS CLOSED LOW IS PROGGED TO
DIG TO THE WEST AND SOUTH OF THE SOUTHERN CALIFORNIA COAST...BEFORE
TURNING EASTWARD TOWARD NORTHERN BAJA LATE TUESDAY NIGHT INTO EARLY
WEDNESDAY. DOWNSTREAM OF THIS LATTER FEATURE...BROAD UPPER RIDGING
PROBABLY WILL DEVELOP ACROSS MUCH OF THE SOUTHERN TIER STATES.
IN CONJUNCTION WITH THE EVOLVING UPPER PATTERN...SURFACE TROUGHING
IS EXPECTED TO DEVELOP AND DEEPEN ACROSS THE HIGH PLAINS...AS
SURFACE RIDGING CONSOLIDATES AND RETREATS EAST OF THE MISSISSIPPI
VALLEY. A RETURN FLOW OFF THE WESTERN GULF OF MEXICO INTO THE
PLAINS MAY COMMENCE...BUT LOW-LEVEL MOISTENING IS NOT EXPECTED TO
BECOME SUFFICIENT TO OVERCOME MID-LEVEL INHIBITION AND SUPPORT AN
APPRECIABLE RISK FOR THUNDERSTORMS.
ELSEWHERE...A WESTERLY LOW-LEVEL ONSHORE FLOW MAY CONTRIBUTE TO WEAK
DESTABILIZATION NEAR THE PACIFIC NORTHWEST COAST INTO THE WESTERN
SLOPES OF THE CASCADES TUESDAY AND TUESDAY NIGHT. WHILE GUIDANCE
SUGGESTS THAT THIS MAY BECOME SUPPORTIVE OF MODEST CONVECTIVE
DEVELOPMENT...PARTICULARLY WITH INCREASING MID-LEVEL LIFT AND
COOLING TOWARD 12Z WEDNESDAY...THUNDERSTORM PROBABILITIES MAY NOT
REACH THE MINIMUM 10 PERCENT THRESHOLD FOR A CATEGORICAL
THUNDERSTORM OUTLOOK.
..KERR.. 02/21/2011
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0700Z
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