lundi 9 mars 2015

Mar 9, 2015 2000 UTC Day 1 Convective Outlook



 DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0300 PM CDT MON MAR 09 2015

   VALID 092000Z - 101200Z

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS SOUTHEAST LA AND FAR SRN
   MS FOR LATE TONIGHT/EARLY TUESDAY MORNING...

   ...SUMMARY...
   A FEW STRONG TO POSSIBLY SEVERE THUNDERSTORMS MAY AFFECT PORTIONS OF
   SOUTHEAST LOUISIANA AND FAR SOUTHERN MISSISSIPPI TONIGHT. OTHER
   THUNDERSTORMS ARE POSSIBLE OVER THE SOUTHERN ROCKIES INTO FAR
   WESTERN TEXAS...AND ACROSS PARTS OF SOUTH AND EAST TEXAS.

   ...SRN/ERN TX TO THE LOWER MS VALLEY...
   TSTMS ARE EXPECTED TO DEVELOP INTO TONIGHT ACROSS PORTIONS OF THE TX
   GULF COAST INTO THE LOWER MS VALLEY.  ALTHOUGH INSTABILITY IS
   EXPECTED TO REMAIN MARGINAL THROUGH 12Z...ESPECIALLY GIVEN POOR
   LAPSE RATES...18Z RAP AND RECENT HRRR SUGGEST THE POTENTIAL FOR
   TSTMS TO BECOME SURFACE-BASED FROM SERN LA INTO FAR SRN MS TOWARD
   12Z.  A SLY LLJ IS EXPECTED TO STRENGTHEN TONIGHT FROM EAST TX INTO
   THE ADJACENT LOWER MS VALLEY RESULTING IN ENHANCED LOW-LEVEL
   HODOGRAPH CURVATURE.  THIS WOULD SUPPORT A MARGINAL SEVERE RISK FOR
   LOCALLY STRONG WIND GUSTS AND A BRIEF TORNADO COULD NOT BE RULED
   OUT.

   ...SOUTHERN ROCKIES EAST INTO FAR WEST TEXAS...
   NO CHANGES ARE NEEDED ACROSS THIS REGION.  TSTMS HAVE DEVELOPED AS
   EXPECTED ACROSS THE HIGHER TERRAIN OF NEW MEXICO INTO SOUTHWEST
   TX...WITH THIS TSTM THREAT FORECAST TO BE PRIMARILY DIURNAL.

   ..PETERS.. 03/09/2015

   .PREV DISCUSSION... /ISSUED 1119 AM CDT MON MAR 09 2015/

   ...SYNOPSIS...
   A BROAD SOUTHERN-STREAM UPPER TROUGH WILL REMAIN ESSENTIALLY
   STATIONARY THROUGH 12Z TUESDAY AS TWO VORTICITY MAXIMA OF PROMINENCE
   ROTATE THROUGH THE TROUGH. THE FIRST WILL LIFT NORTHEAST ACROSS
   TEXAS TODAY AND INTO THE OZARK PLATEAU TONIGHT.  THE SECOND WILL
   MOVE SOUTHWARD THROUGH THE SOUTHERN GREAT BASIN INTO THE
   SONORA/CHIHUAHUA PROVINCES REGION OF NORTHERN MEXICO BY TUESDAY
   MORNING.

   A WEAK SURFACE LOW ASSOCIATED WITH THE LEAD DISTURBANCE WILL MOVE
   NORTHEAST FROM SOUTHERN TEXAS THIS MORNING INTO SOUTHERN ARKANSAS BY
   THE END OF THE PERIOD AS A COLD FRONT MOVES EAST TO NEAR THE
   TEXAS/LOUISIANA BORDER.

   ...SOUTHERN/EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY...
   WIDESPREAD CLOUDS/RAIN PERSISTS THIS MORNING WITHIN A ZONE OF
   ISENTROPIC ASCENT FROM MUCH OF CENTRAL/EASTERN TEXAS INTO THE LOWER
   MISSISSIPPI VALLEY REGION...AND THIS WILL LIKELY PERSIST THROUGH
   MUCH OF THE DAY. WITH TIME...PARTIALLY MODIFIED GULF MOISTURE SHOULD
   BEGIN TO ADVECT NORTHWARD ON STRENGTHENING LOW-LEVEL FLOW AS THE
   WEAK SURFACE LOW LIFTS NORTHEAST...WITH LOWER TO MID 60S DEW POINTS
   AS FAR NORTH AS CENTRAL MS BY 12Z TUE.  

   A FEW THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON AND
   TONIGHT ALONG AND EAST OF THE COLD FRONT FROM SOUTHERN/SOUTHEAST
   TEXAS INTO THE LOWER MISSISSIPPI VALLEY AS MOISTURE ADVECTION
   CONTRIBUTES TO WEAK INSTABILITY /MUCAPE 200-300 J/KG/ AND MODEST
   LARGE-SCALE FORCING FOR ASCENT WITH THE LEAD SHORTWAVE GLANCES THE
   AREA. A WEAK CONFLUENCE ZONE EXPECTED TO EXTEND FROM FAR SOUTHEAST
   LOUISIANA NORTHWARD INTO SOUTHWESTERN MISSISSIPPI TONIGHT MAY ALSO
   FOCUS ADDITIONAL DEVELOPMENT IN THAT AREA. WEAK LAPSE RATES AND THE
   LIKELIHOOD THAT THUNDERSTORMS WILL BE SLIGHTLY ELEVATED SUGGEST THAT
   ORGANIZED SEVERE WEATHER IS UNLIKELY...HOWEVER A COUPLE OF
   WEAKLY-ROTATING STRONG STORMS WITH GUSTY WINDS WILL BE POSSIBLE.  

   ...SOUTHERN ROCKIES EAST INTO FAR WEST TEXAS...
   DAYTIME HEATING COUPLED WITH THE COOL MID-LEVEL TEMPERATURES WITH
   THE UPSTREAM SHORTWAVE WILL RESULT IN SUFFICIENT INSTABILITY FOR A
   FEW THUNDERSTORMS MAINLY THIS AFTERNOON AND EVENING...AIDED IN PART
   BY TOPOGRAPHIC FORCING.

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