151  
FXUS62 KRAH 181934  
AFDRAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RALEIGH NC  
335 PM EDT SAT AUG 18 2018  
   
SYNOPSIS
 
 
A MID AND UPPER-LEVEL TROUGH AND SURFACE COLD FRONT WILL  
APPROACH THE REGION FROM THE WEST TONIGHT. THE FRONT IS EXPECTED  
TO DROP INTO VIRGINIA AND THE WESTERN NORTH CAROLINA ON SUNDAY  
AND DRIFT INTO CENTRAL NORTH CAROLINA BY MONDAY MORNING.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 335 PM SATURDAY...  
 
NEAR TERM MODEL GUIDANCE, AND VERIFIED BY WATER VAPOR IMAGERY,  
DEPICT A MINOR S/W LIFTING NEWD FROM THE SOUTHERN APPALACHIANS INTO  
THE MID ATLANTIC. THE TAIL END OF THE S/W WAS BRUSHING OUR NORTHERN  
COUNTIES AND AIDING TO TRIGGER SCATTERED CONVECTION, PRIMARILY NORTH  
OF THE I-40/85 CORRIDOR. OTHER SCATTERED CONVECTION HAS DEVELOPED  
ACROSS THE SOUTHERN COUNTIES IN AN AXIS OF MODERATE INSTABILITY.  
OUTFLOWS PRODUCED BY THESE CLUSTERS THE MEAN FLOW WAS WESTERLY OF  
CONVECTION WILL LIKELY INITIATE ADDITIONAL CONVECTIVE CLUSTERS LATER  
THIS AFTERNOON. SCATTERED CONVECTION WILL PERSIST THROUGH THE  
EVENING AND INTO THE OVERNIGHT AS ANOTHER WEAK MID LEVEL S/W LIFTS  
NEWD ACROSS THE REGION.  
 
WHILE THE ATMOSPHERE IS MODERATELY UNSTABLE, SHEAR IS MARGINAL AND  
CONFINED TO THE FAR NORTHERN COUNTIES. THUS, APPEARS THAT ANY SEVERE  
STORMS SHOULD BE FEW IN NUMBER, AND MOSTLY LIMITED TO THE NORTHERN  
HALF OF THE REGION. OVERNIGHT TEMPERATURES 70-75.  
 

 
   
SHORT TERM /SUNDAY AND SUNDAY NIGHT/
 
 
AS OF 335 PM SATURDAY...  
 
SUNDAY, THE S/W RESPONSIBLE FOR OUR SCATTERED CONVECTION TONIGHT  
WILL BE LIFTING NEWD AWAY FROM OUR REGION SUNDAY MORNING. THIS WILL  
PLACE CENTRAL NC IN A WEAK SUBSIDENCE ZONE, AND LIKELY SUPPRESS  
CONVECTIVE DEVELOPMENT THROUGH EARLY AFTERNOON. AS THE ATMOSPHERE  
HEATS UP AND DESTABILIZES, EXPECT SCATTERED CONVECTION TO DEVELOP  
ONCE AGAIN. CONVECTIVE COVERAGE MAY BECOME ENHANCED SUNDAY NIGHT  
ANOTHER S/W AND ATTENDANT SFC BOUNDARY WILL APPROACH FROM THE WEST.  
INSTABILITY SUNDAY AFTERNOON ANTICIPATED TO BE AS STRONG IF NOT A  
LITTLE STRONGER THAN THIS AFTERNOON. WHILE INSTABILITY SUFFICIENT,  
EFFECTIVE SHEAR PROJECTED TO BE WEAKER THAN THIS AFTERNOON. WHILE A  
STRONG/SEVERE STORM POSSIBLE, MOST OF THE CONVECTION WILL REMAIN  
BELOW SEVERE CRITERIA. OF CONCERN WILL BE THE POTENTIAL FOR LOCALLY  
HEAVY DOWNPOURS WHICH MAY TRIGGER EXTENSIVE PONDING ON STREETS AND  
POOR DRAINAGE AREAS.  
 
EXTENSIVE CLOUDINESS AND SCATTERED CONVECTION WILL LIMIT THE  
TEMPERATURE RECOVERY. HIGHS SUNDAY SHOULD MAINLY BE IN THE MID-UPPER  
80S. OVERNIGHT TEMPERATURES NEAR 70-LOWER 70S.  
 

 
   
LONG TERM /MONDAY THROUGH SATURDAY/
 
 
AS OF 235 PM SATURDAY...  
 
A SFC FRONT WILL BE STALLED ACROSS CENTRAL NC AT THE START OF THE  
LONG TERM PERIOD, THANKS TO WESTERLY FLOW ABOVE IT. THE FLOW ALOFT  
WILL BECOME SW IN THE WAKE OF A SHORT WAVE RIDGE PASSING BY EARLY  
TUESDAY, SO LOOK FOR THE AFOREMENTIONED BOUNDARY TO LIFT BACK NORTH  
AS A WARM FRONT DURING THE DAYTIME TUESDAY. THESE FEATURES,  
COMBINED WITH ABUNDANT MOISTURE INVOF THEM, WILL RESULT IN A DECENT  
CHANCE FOR RAIN DURING THIS TIME.  
 
THEN FOR TUESDAY NIGHT INTO WEDNESDAY, THE NEXT SHORT WAVE TROUGH  
UPSTREAM WILL BE DIGGING ESE ACROSS THE GREAT LAKES, AND IN  
RESPONSE, A PREFRONTAL SFC TROUGH, ALONG WITH A LINE OF SHOWERS AND  
TSTMS, IS EXPECTED TO MOVE ACROSS CENTRAL NC TUESDAY NIGHT. THE  
SUBSEQUENT COLD FRONT IS EXPECTED TO FOLLOW AND MOVE ACROSS OUR AREA  
DURING THE DAYTIME WEDNESDAY, THUS WILL KEEP GOOD CHANCE POPS GOING  
DURING THAT TIME.  
 
MODELS ARE SUGGESTING THAT WE COULD SEE A DRYING TREND IN THE WAKE  
OF WEDNESDAY'S COLD FRONT, BUT WE'LL HAVE TO KEEP A CHANCE FOR  
SHOWERS IN THE FORECAST, AT LEAST ACROSS OUR EASTERN ZONES, UNTIL  
THE UPPER TROUGH AXIS MOVES ACROSS THE AREA BY MID-DAY THURSDAY.  
THEN THURSDAY NIGHT THROUGH SATURDAY IS STARTING TO LOOK LIKE IT  
COULD BE A DRY PERIOD WITH COOLER TEMPS WITH LOWER HUMIDITY.  
 

 
   
AVIATION /18Z SATURDAY THROUGH THURSDAY/
 
 
AS OF 140 PM SATURDAY...  
 
EARLY MORNING STRATUS FINALLY STARTING TO LIFT ACROSS SECTIONS OF  
THE PIEDMONT. THIS WILL LEAD TO VFR/HIGH END MVFR CEILINGS ACROSS  
CENTRAL NC THIS AFTERNOON. HEATING OF THE MOIST AIR MASS WILL LEAD  
TO DESTABILIZATION AND THE INITIATION OF SCATTERED CONVECTION, WITH  
ISOLATED STRONG-SEVERE THUNDERSTORMS POSSIBLE. WHERE THE CONVECTION  
OCCURS, ANTICIPATE MVFR CEILINGS AND MVFR/IFR VISIBILITIES DUE TO  
HEAVY DOWNPOURS. THE STRONGER STORMS WILL PRODUCE WIND GUSTS AROUND  
30KTS.  
 
THE BULK OF THE CONVECTION THROUGH 22Z WILL OCCUR IN VICINITY OF  
KINT, KGSO AND POSSIBLY KRDU. BETWEEN 22Z-03Z, MOST OF THE  
CONVECTION WILL BE IN PROXIMITY OF KRDU, KFAY AND KRWI. MOST OF THE  
CONVECTION WILL GRADUALLY DIMINISH BETWEEN 03Z-07Z. IN THE WAKE OF  
THE CONVECTION, POCKETS OF MVFR/IFR CEILINGS DUE TO STRATUS MAY  
OCCUR, THOUGH COVERAGE EXPECTED TO BE LESS COMPARED TO THIS MORNING.  
 
A MOIST AND UNSTABLE ATMOSPHERE IN CONJUNCTION WITH A SLOW MOVING  
SFC FRONT WILL CAUSE PERIODS OF CONVECTION ACROSS CENTRAL NC THROUGH  
TUESDAY. ANTICIPATE PERIODS OF MVFR CEILINGS AND VISIBILITY DUE TO  
THE CONVECTION. A STRONGER SFC FRONT MAY IMPINGE UPON CENTRAL NC  
WEDNESDAY AND THURSDAY, MAINTAINING A THREAT FOR SCATTERED  
CONVECTION AND ASSOCIATED MVFR PARAMETERS..  
 

 
   
RAH WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
SYNOPSIS...BLAES  
NEAR TERM...WSS  
SHORT TERM...WSS  
LONG TERM...NP  
AVIATION...WSS  
 
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