SPC AC 231733
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1233 PM CDT MON APR 23 2007
VALID 241200Z - 251200Z
...THERE IS A MDT RISK OF SVR TSTMS TUE/TUE NIGHT ACROSS MUCH OF THE
CNTRL/SRN PLAINS...INCLUDING MUCH OF KS/ERN OK...CNTRL/NRN TX AND
PARTS OF WRN MO/WRN AR...WHERE POTENTIAL EXISTS FOR A WIDESPREAD
OUTBREAK OF SEVERE THUNDERSTORMS...INCLUDING A FEW TORNADOES....
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
AREA...ACROSS MUCH OF THE CNTRL/S CNTRL STATES....
...SYNOPSIS...
LARGE UPPER TROUGH EMBEDDED WITHIN THE SOUTHERN BRANCH OF SPLIT
POLAR WESTERLIES APPEARS LIKELY TO PROGRESS EASTWARD INTO THE PLAINS
TUESDAY...MUCH AS HAS BEEN SUGGESTED BY MODEL FORECASTS THE PAST
SEVERAL DAYS. THIS IS EXPECTED TO OCCUR AS ANOTHER SIGNIFICANT
SHORT WAVE TROUGH...EMANATING FROM STRONG ZONAL PACIFIC
JET...PROGRESSES INTO BRITISH COLUMBIA/PACIFIC NORTHWEST COASTAL
AREAS. SMALLER SCALE DETAILS OF THIS EVOLUTION ARE STILL A BIT
UNCERTAIN. BUT...IT CURRENTLY SEEMS MOST PROBABLE THAT AN INITIAL
MID-LEVEL JET STREAK/IMPULSE ASSOCIATED WITH THE SOUTHERN BRANCH
SYSTEM WILL ALREADY BE IN THE PROCESS OF LIFTING OUT OF THE SOUTHERN
ROCKIES INTO THE CENTRAL HIGH PLAINS BY 12Z TUESDAY. THIS FEATURE
IS EXPECTED TO CONTINUE PIVOTING ACROSS THE CENTRAL PLAINS DURING
THE DAY TUESDAY...AROUND THE EASTERN/NORTHEASTERN PERIPHERY OF A
BROADER SCALE MID-LEVEL CIRCULATION. THEN...ON THE SOUTHERN
PERIPHERY OF THE CIRCULATION...ANOTHER SIGNIFICANT IMPULSE IS
PROGGED TO DIG SOUTHEAST OF THE SOUTHERN ROCKIES THROUGH CENTRAL
TEXAS...LATER TUESDAY INTO 12Z WEDNESDAY.
IN RESPONSE TO THE EVOLVING UPPER FLOW PATTERN...A FAIRLY DEEP
/NEAR OR JUST BELOW 1000 MB/ SURFACE CYCLONE SHOULD FORM TO THE LEE
OF THE CENTRAL ROCKIES. THIS WILL CONTRIBUTE TO STRENGTHENING DEEP
LAYER SHEAR ACROSS A BROAD AREA OF THE CENTRAL U.S...WHERE A
SIGNIFICANT MOISTURE RETURN FROM THE WESTERN GULF OF MEXICO IS
ALREADY WELL UNDERWAY. WARM SECTOR SURFACE DEW POINTS IN THE
MID/UPPER 60S SHOULD BE COMMON...PERHAPS NEAR 70F ACROSS PARTS OF
SOUTHERN/EASTERN TEXAS. SOME CONCERN EXISTS ABOUT THE POSSIBILITY
OF CONSIDERABLE CLOUD COVER...AND ITS INFLUENCE ON INSOLATION...BUT
MIXED LAYER CAPE OF 1000-2000 J/KG SEEMS PROBABLE BY TUESDAY
AFTERNOON. THIS IS EXPECTED TO BE MORE THAN SUFFICIENT...GIVEN
FAVORABLE LARGE SCALE FORCING...TO SUPPORT WIDESPREAD CONVECTIVE
DEVELOPMENT...INCLUDING AN OUTBREAK OF SEVERE THUNDERSTORMS WITH THE
POTENTIAL FOR TORNADOES...VERY LARGE HAIL...AND DAMAGING WINDS.
...CENTRAL PLAINS INTO THE OZARKS...
FORCING IN THE EXIT REGION OF A 70+ KT 500 MB JET STREAK LIKELY WILL
OVERSPREAD THE CENTRAL HIGH PLAINS BY/SHORTLY AFTER 12Z
TUESDAY...BEFORE SHIFTING EASTWARD ACROSS KANSAS DURING THE DAYTIME
HOURS. ELEVATED CONVECTIVE DEVELOPMENT IS EXPECTED TO BE ONGOING AT
THE OUTSET OF THE FORECAST PERIOD TO THE NORTH OF WARM FRONT ACROSS
NORTHERN KANSAS...AND INITIATION OF BOUNDARY LAYER BASED STORMS MAY
NOT TAKE MUCH HEATING NEAR SURFACE LOW/WARM FRONT/DRY LINE
INTERSECTION. THIS MAY OCCUR BY MIDDAY ACROSS WEST CENTRAL
KANSAS...BEFORE ACTIVITY SPREADS EASTWARD ALONG DEVELOPING FRONTAL
OCCLUSION...ROUGHLY NEAR THE INTERSTATE 70 CORRIDOR...INTO WEST
CENTRAL MISSOURI BY TUESDAY EVENING. RISK OF TORNADOES WITH
SUPERCELLS APPEARS HIGHEST WITH THIS ACTIVITY...AS WELL AS WELL AS
WITH DISCRETE SUPERCELLS LIKELY TO DEVELOP SOUTHWARD ALONG DRY LINE
THROUGH SOUTHERN KANSAS INTO NORTH CENTRAL/EASTERN OKLAHOMA ...AND
POSSIBLY SOUTHWEST MISSOURI...BY THE 25/00-03Z TIME FRAME. ISOLATED
STRONG TORNADOES ARE POSSIBLE...ALONG WITH POTENTIAL FOR VERY LARGE
HAIL AND ISOLATED DAMAGING DOWNBURSTS.
...SOUTHERN PLAINS...
CONSIDERABLE CONVECTIVE INHIBITION AND LATE ARRIVAL OF STRONGER
MID/UPPER FORCING MAY DELAY ONSET OF PRIMARY CONVECTION. BUT...
ISOLATED TO WIDELY SCATTERED STORMS APPEAR POSSIBLE ALONG DRY
LINE/PACIFIC FRONT ACROSS PARTS OF CENTRAL/NORTHERN TEXAS BY LATE
AFTERNOON. IF THIS OCCURS...POTENTIAL FOR VERY LARGE HAIL/DAMAGING
WINDS WILL EXIST...IN ADDITION TO ISOLATED TORNADOES. MODELS ARE
SUGGESTIVE THAT LARGE-SCALE FORCING WILL BE SUPPORTIVE OF A BROKEN
SQUALL LINE DURING THE EVENING HOURS... WHICH MAY PERSIST WELL INTO
THE NIGHT...SPREADING THROUGH NORTHEAST TEXAS/SOUTHEAST OKLAHOMA
INTO THE PARTS OF THE LOWER MIDDLE MISSISSIPPI VALLEY. LARGE
HAIL/DAMAGING WIND GUSTS COULD BECOME QUITE NUMEROUS...ALONG WITH A
CONTINUING RISK FOR ISOLATED TORNADOES.
..KERR.. 04/23/2007
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