SWODY2
SPC AC 080553
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1153 PM CST SUN NOV 07 2010
VALID 091200Z - 101200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
LATEST MODEL RUNS CONTINUE TO INDICATE THE EVOLUTION OF A
LARGE-SCALE TROUGH OVER THE WESTERN AND CENTRAL U.S. DURING THIS
FORECAST PERIOD. ALTHOUGH VARIABILITY LINGERS CONCERNING THE SHORT
WAVE DEVELOPMENTS WITHIN THIS REGIME...IT IS BECOMING MORE CERTAIN
THAT AN INITIAL SURFACE LOW CENTER...WITHIN THE LEE SURFACE TROUGH
OVER THE NORTH CENTRAL HIGH PLAINS AT 12Z TUESDAY...WILL WEAKEN
THROUGH THE DAY...WITH A NEW LOW CENTER DEVELOPING OVER THE DAKOTAS
LATE TUESDAY INTO TUESDAY NIGHT. AS THIS OCCURS...A SURFACE COLD
FRONT IS EXPECTED TO ADVANCE THROUGH THE NORTHERN AND CENTRAL
PLAINS.
DESPITE THE STRENGTH OF THE LEE CYCLONE AND ASSOCIATED SURFACE
TROUGH /SUB 1000 MB/...A PERSISTENT BLOCKING PATTERN OVER THE
ATLANTIC...INCLUDING A LOW/MID-LEVEL CYCLONE OFF NORTHERN/MID
ATLANTIC COASTAL AREAS...WILL REMAIN UNFAVORABLE FOR STRONG BOUNDARY
LAYER MOISTENING OVER THE GULF OF MEXICO. WEAK INLAND MOISTURE
RETURN COULD COMMENCE OFF THE SLOWLY MODIFYING WESTERN GULF...AROUND
THE WESTERN PERIPHERY OF AN ELONGATED SURFACE RIDGE EXTENDING FROM
SOUTHEASTERN CANADA INTO THE CENTRAL AND EASTERN GULF. BUT
GENERALLY DRY AND STABLE CONDITIONS ARE EXPECTED TO CONTINUE ACROSS
MOST AREAS EAST OF THE ROCKIES...AND MUCH OF THE NATION...WITH LOW
CONVECTIVE POTENTIAL.
...NORTHERN AND CENTRAL ROCKIES/PLAINS...
THE RISK FOR WEAK THUNDERSTORM ACTIVITY MAY NOT BE COMPLETELY
NEGLIGIBLE TUESDAY IN ASSOCIATION WITH BROADER SCALE COLD UPPER
TROUGHING GRADUALLY LIFTING ACROSS THE REGION...AHEAD OF A STRONG
IMPULSE PROGGED TO DIG ACROSS THE PACIFIC NORTHWEST.
HOWEVER...GUIDANCE GENERALLY INDICATES THE DEVELOPMENT OF ONLY VERY
WEAK CAPE ON THE ORDER OF A COUPLE HUNDRED J/KG...AT BEST...WHICH
COULD OCCUR IN SCATTERED POCKETS OVER A SIZABLE AREA. PROBABILITIES
APPEAR TOO LOW FOR A CATEGORICAL THUNDERSTORM OUTLOOK AT THE PRESENT
TIME...EXCEPT PERHAPS NEAR THE PALMER DIVIDE...WHERE THE EASTWARD
PROGRESSION OF THE MID-LEVEL COLD CORE AND FORCING FOR UPWARD
VERTICAL MOTION MAY BE FAVORABLY TIMED WITH STRONGER SURFACE HEATING
AND STEEPENING OF LOW-LEVEL LAPSE RATES.
...PACIFIC NORTHWEST...
MODELS INDICATE AT LEAST A MODEST ONSHORE FLOW DEVELOPING BY TUESDAY
AFTERNOON...AS A VIGOROUS UPPER IMPULSE WITH A -24 TO -28C 500 MB
COLD CORE ADVANCES INLAND. THIS PROBABLY WILL CONTRIBUTE TO
SUFFICIENT DESTABILIZATION FOR SCATTERED WEAK THUNDERSTORM ACTIVITY.
..KERR.. 11/08/2010
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