SWODY2
SPC AC 090618
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1218 AM CST TUE NOV 09 2010
VALID 101200Z - 111200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
LARGE-SCALE TROUGHING IS EXPECTED TO PERSIST ACROSS MUCH OF THE
WESTERN AND CENTRAL U.S. DURING THIS FORECAST PERIOD...AS BLOCKING
PERSISTS DOWNSTREAM ACROSS PARTS OF THE EASTERN U.S. AND THE
ATLANTIC. HOWEVER...MODELS DO INDICATE THAT SHORT WAVE RIDGING MAY
BUILD AND SHIFT EASTWARD INTO BRITISH COLUMBIA AND THE U.S. PACIFIC
COAST...AHEAD OF A PROGRESSIVE SPLITTING SHORT WAVE TROUGH ACROSS
THE NORTHEAST PACIFIC. AS THIS OCCURS...A VIGOROUS SHORT WAVE
IMPULSE MAY BEGIN TO DIG MORE SHARPLY WITHIN THE WESTERN
TROUGH...ACROSS THE SOUTHERN GREAT BASIN AND FOUR CORNERS
REGION...WHILE A STRONG DOWNSTREAM PERTURBATION LIFTS NORTHWARD OUT
OF THE PLAINS TOWARD THE CENTRAL CANADIAN/U.S. BORDER AREA.
MOST GUIDANCE HAS TRENDED SLOWER...AND FARTHER TO THE SOUTH... WITH
THE MORE PROMINENT MID-LEVEL FORCING ACCOMPANYING THE LEAD FEATURE.
WHILE THIS DOES NOT APPEAR TO BE IMPACTING THE SOMEWHAT MODEST
PROGGED STRENGTH OF A DEVELOPING CYCLONE OVER THE NORTHERN
PLAINS...THE NORTHWARD MIGRATION OF THE MAIN LOW CENTER...OUT OF THE
DAKOTAS INTO SOUTHERN CANADA...IS NOW SUBSTANTIALLY SLOWER...PERHAPS
NOT UNTIL WEDNESDAY NIGHT. THE TRAILING SURFACE FRONT WILL ALSO
PROBABLY BE SLOWER TO ADVANCE INTO THE UPPER MISSISSIPPI
VALLEY...BUT IT IS STILL EXPECTED TO STALL OR SLOWLY RETREAT ACROSS
THE SOUTH CENTRAL PLAINS LATE IN THE PERIOD.
FAVORABLE LARGE-SCALE FORCING ASSOCIATED WITH THE EVOLVING PATTERN
STILL APPEARS TO SUPPORT AT LEAST A RELATIVE INCREASE IN CONVECTIVE
POTENTIAL ACROSS PARTS OF THE PLAINS AND UPPER MISSISSIPPI VALLEY.
HOWEVER...MOISTURE INFLUX OFF THE GULF OF MEXICO IS LIKELY TO REMAIN
WEAK...MINIMIZING POTENTIAL FOR SUBSTANTIVE DESTABILIZATION...AND
LIMITING THE RISK FOR SEVERE THUNDERSTORMS.
...UPPER MISSISSIPPI VALLEY...
GIVEN THE SLOWER NORTHWARD PROGRESSION OF THE SURFACE CYCLONE... AND
THE POSSIBILITY OF SLIGHTLY STRONGER DEEP LAYER MEAN FLOW FIELDS AND
SHEAR WEDNESDAY AFTERNOON AND EVENING...A WINDOW OF OPPORTUNITY
APPEARS TO EXIST FOR CONVECTIVE DEVELOPMENT CAPABLE OF SUPPORTING AT
LEAST LOW SEVERE PROBABILITIES. GUIDANCE STILL SUGGESTS THAT A
PRE-FRONTAL TONGUE OF LOWER 50S DEW POINTS ADVECTING ACROSS THE
REGION WILL CONTRIBUTE TO MIXED LAYER CAPE ON THE ORDER OF 100 TO
250 J/KG. WHILE WEAK...THIS IS EXPECTED TO BE SUFFICIENT TO SUPPORT
SCATTERED THUNDERSTORMS...PERHAPS A NARROW BROKEN LINE...IN THE
PRESENCE OF STRONG VERTICAL SHEAR...INCLUDING SIZABLE AND CLOCKWISE
CURVED LOW-LEVEL HODOGRAPHS. THERE APPEARS TO BE SOME POTENTIAL FOR
AN ISOLATED TORNADO OR TWO AND LOCALLY DAMAGING WIND GUSTS WITH
ACTIVITY ACROSS MINNESOTA...NORTH CENTRAL/NORTHEAST IOWA AND PARTS
OF WESTERN WISCONSIN...BEFORE STORMS DIMINISH WEDNESDAY EVENING.
...CENTRAL PLAINS INTO LOWER MISSOURI VALLEY...
SCATTERED STORMS APPEAR POSSIBLE LATE WEDNESDAY NIGHT IN THE
PRESENCE OF STRENGTHENING LOWER/MID TROPOSPHERIC WARM ADVECTION AND
CONTINUED LOW-LEVEL MOISTURE RETURN.
...GREAT BASIN AND ROCKIES...
MID-LEVEL COOLING AND LIFT ALONG/NORTH OF A VIGOROUS DIGGING JET
STREAK AND ASSOCIATED IMPULSE IS EXPECTED TO CONTRIBUTE TO WEAK
DESTABILIZATION AND CONVECTIVE DEVELOPMENT. A FEW WEAK
THUNDERSTORMS APPEAR POSSIBLE...THOUGH COVERAGE MAY BE NEAR THE 10
PERCENT MINIMUM THRESHOLD.
..KERR.. 11/09/2010
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