WFO RAH Logo

FXUS62 KRAH 161651
 AFDRAH
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE RALEIGH NC
 1030 AM EDT SAT APR 16 2011
 
 .SYNOPSIS...
 A STRONG LOW PRESSURE SYSTEM WILL CROSS OUR REGION TODAY....THEN 
 MOVE OFFSHORE THIS EVENING. HIGH PRESSURE WILL FOLLOW FOR TONIGHT 
 THROUGH SUNDAY.
 
 &&
 
 .NEAR TERM /THROUGH TONIGHT/...
 AS OF 1030 AM SATURDAY...
 
      SEVERE WEATHER OUTBREAK WITH A HIGH RISK FOR SEVERE STORMS
 SATURDAY...
 
 A 16Z RAOB HAS BEEN SCHEDULED FOR KGSO. THE GARNER NOAA WEATHER 
 RADIO IS OFF THE AIR DUE TO PHONE LINE PROBLEMS. TECHNICIANS ARE 
 WORKING ON THE PROBLEM. 
 
 LOOKING OVER RECENT TRENDS AND 12Z SOUNDINGS EVERYTHING REMAINS 
 PRIMED FOR A SIGNIFICANT SEVERE WEATHER OUTBREAK ACROSS CENTRAL NC 
 FROM NOON THROUGH 7 PM TODAY. SATELLITE IMAGERY ALONG WITH LIGHTNING 
 DATA SHOW A BAND OF DEVELOPING STORMS ALREADY STARTING TO ORGANIZE 
 THEMSELVES EAST OF THE MOUNTAINS. THIS IS OCCURRING IN  A REGION 
 JUST AHEAD OF THE MID LEVEL DRY AIR WHERE MID LEVEL LAPSE RATES ARE 
 BEST. BEST SURFACE BASED AND MIXED LAYER CAPE IS STILL OVER SC THIS 
 MORNING...BUT WITH TEMPS WARMING INTO THE MID 70S AND DEWPOINTS INTO 
 THE LOWER 60S THIS HIGHER INSTABILITY AIR WILL ADVECT NORTH INTO 
 CENTRAL NC. LOW LCLS AND HIGH SHEAR FROM THE LOW TO MID LEVELS IS 
 ALREADY IN PLACE. AS THE INSTABILITY INCREASES AND THE DYNAMICS AND 
 UPDRAFT VELOCITIES INCREASE AS THE UPPER LOW APPROACHES FROM THE 
 WEST THE DANGER OF SEVERE WEATHER WILL INCREASE GREATLY. 
 
 THE COMBINATION OF ATMOSPHERIC VARIABLES WILL LIKELY RESULT IN 
 SUPERCELLS DEVELOPING THIS AFTERNOON AHEAD OF A QLCS SQUALL LINE ALL 
 CAPABLE OF PRODUCING TORNADOES...DAMAGING WINDS IN EXCESS OF 60 MPH 
 AND LARGE HAIL. TIMING OF THE MOST SIGNIFICANT SEVERE THREAT IN THE 
 TRIAD IS FROM NOON THROUGH 3 PM...THE TRIANGLE FROM 1 PM THROUGH 5 
 PM...THE I-95 CORRIDOR AND THE COASTAL PLAIN FROM 2 PM THROUGH 7 PM.
 
 FLOOD THREAT LOOKS MINIMAL AS SOILS HAVE HAD TIME TO DRY FROM THE 
 LAST SIGNIFICANT RAINS AND TRAINING OF STORMS IS NOT LIKELY. BRIEF 
 HEAVY RAINS WILL HOWEVER CAUSE AT LEAST SOME PONDING OF WATER IN 
 MORE URBAN LOCATIONS AND LOW LYING AREAS. 
 
 SHOWERS ENDING IN THE EAST THIS EVENING AS THE FRONT EXITS TO THE 
 EAST. CLEARING BEHIND THE FRONT OF CLOUDS AND MUCH OF THE NIGHT 
 SHOULD BE CLEAR. 
 
 HIGH TEMPERATURES MID 60S IN THE TRIAD TO MID 70S IN THE TRIANGLE 
 SOUTH AND EAST WITH LOW TEMPERATURES MID 40S TO LOWER 50S.
 
 &&
 
 .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
 AS OF 1230 PM SATURDAY...
 
 SURFACE HIGH PRESSURE WILL BE IN CONTROL OF THE WEATHER ACROSS 
 CENTRAL NC THROUGH THE SHORT TERM AS IT PROGRESSES FAIRLY QUICKLY 
 EASTWARD ACROSS THE SOUTHEASTERN US. THIS WILL RESULT IN FAIR 
 WEATHER AND THEN AS RETURN FLOW SETS BY SUNDAY AFTERNOON...A WARMING 
 TREND THROUGH THE PERIOD. THICKNESS VALUES WILL REBOUND TO NEAR 
 1380M BY MONDAY AFTERNOON WHICH SHOULD TRANSLATE TO HIGH TEMPS IN 
 THE MID/UPPER 70S TO NEAR 80 DEGREES (A GOOD FIVE DEGREES WARMER 
 THAN WHAT IS EXPECTED ON SUNDAY). OVERNIGHT LOWS WILL ALSO BE ON A 
 MODERATING TREND...WITH UPPER 40S TO NEAR 50 DEGREES EXPECTED SUNDAY 
 NIGHT AND MID 50S EXPECTED BY MONDAY NIGHT.     
 
 &&
 
 .LONG TERM /TUESDAY THROUGH SATURDAY/...
 AS OF 1245 PM SATURDAY...
 
 DURING THE BEGINNING OF THE LONG TERM PERIOD...THE SUBTROPICAL RIDGE 
 IS PROGGED TO STRENGTHEN OVER THE SOUTHWESTERN ATLANTIC AND THE 
 SOUTHEASTERN US. THIS FEATURE IS EXPECTED TO PUSH THE NEXT STORM 
 SYSTEM MOVING OUT OF THE PLAINS NEXT WEEK NORTH OF THE FORECAST AREA 
 AS IT TRACKS INTO THE UPPER GREAT LAKES REGION. THEREFORE THE 
 TRAILING FRONTAL ZONE AND ASSOCIATED PRECIP IS EXPECTED TO INITIALLY 
 REMAIN NORTH OF THE REGION THROUGH AT LEAST WEDNESDAY...RESULTING IN 
 DRY CONDITIONS AND A CONTINUED WARMING TREND. HIGH TEMPS ARE 
 EXPECTED TO RISE FROM THE LOW/MID 80S ON TUESDAY TO THE MID/UPPER 
 80S BY WEDNESDAY. THE AFOREMENTIONED SUBTROPICAL RIDGE IS THEN 
 PROGGED TO BECOME SUPPRESSED TO THE SOUTH WHICH SHOULD ALLOW THE 
 FRONTAL ZONE TO DRIFT SOUTHWARD INTO THE REGION THURSDAY INTO 
 FRIDAY. MODELS HAVE TRENDED TOWARDS A STRONGER SOUTHWARD PUSH OF 
 THIS FRONT WHICH SHOULD RESULT IN BETTER PRECIP CHANCES WEDNESDAY 
 INTO THURSDAY. WILL ALSO SHOW A SLIGHT CHANCE OF PRECIP FRIDAY INTO 
 SATURDAY AS THE FRONTAL BOUNDARY. SLIGHTLY COOLER TEMPS ARE ALSO 
 EXPECTED FOR THE END OF THE FORECAST PERIOD..  
 
 &&
 
 .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
 AS OF 755 AM SATURDAY...
 
 WINDY CONDITIONS IN SOUTHEAST THEN SOUTHERLY FLOW WILL DEVELOP 
 TODAY...AHEAD OF A STRONG LOW PRESSURE SYSTEM THAT WILL CROSS OUR 
 REGION LATER THIS AFTERNOON. OTHERWISE...EXPECT CURRENT IFR-MVFR 
 CEILINGS (IN NUMEROUS SHOWERS) AT KINT/KGSO TO RISE TO AROUND 2000 
 FT THROUGH MIDDAY...WHILE GENERALLY LOW VFR OR HIGH MVFR CEILINGS 
 DEVELOP AT THE REMAINDER OF CENTRAL NC TAF SITES. SHOWERS AND 
 THUNDERSTORMS WILL BECOME MORE NUMEROUS WITH DAYTIME 
 HEATING/DESTABILIZATION AND THE APPROACH OF A VERY DYNAMIC STORM 
 SYSTEM FROM THE WEST BETWEEN 15-19Z. SHOWERS AND STORMS -- -- 
 WITH DAMAGING WINDS...ISOLATED TORNADOES...AND LARGE HAIL -- WILL BE 
 MOST CONCENTRATED ALONG AND IMMEDIATELY AHEAD OF A COLD FRONT THAT 
 WILL CROSS CENTRAL NC THIS AFTERNOON. THE PROJECTED TIMING OF THE 
 MOST CONCENTRATED AND INTENSE STORMS WILL BE APPROXIMATELY BETWEEN 
 18-20Z AT KINT/KGSO...20-22Z AT KRDU/KFAY...AND 21-23Z AT KRWI. 
 DRY...VFR CONDITIONS WILL FOLLOW QUICKLY ON THE HEELS OF THE COLD 
 FRONT AND ASSOCIATED SHOWERS AND THUNDERSTORMS...AS HIGH PRESSURE 
 WILL BUILD INTO OUR REGION FROM THE WEST TONIGHT. 
 
 LOOKING AHEAD: THE HIGH PRESSURE RIDGE WILL CONTINUE TO EXTEND 
 ACROSS THE SOUTHEASTERN US AND MAINTAIN VFR CONDITIONS THROUGH THE 
 MIDDLE OF NEXT WEEK.
 
 &&
 
 .RAH WATCHES/WARNINGS/ADVISORIES...
 NONE.
 
 &&
 
 $$
 
 SYNOPSIS...MWS
 NEAR TERM...JO
 SHORT TERM...KRR
 LONG TERM...KRR
 AVIATION...MWS