657  
FXUS62 KRAH 210555  
AFDRAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RALEIGH NC  
155 AM EDT FRI SEP 21 2018  
   
SYNOPSIS
 
 
SURFACE HIGH PRESSURE WILL EXTEND INTO THE REGION FROM THE NORTHEAST  
THROUGH FRIDAY. A COLD FRONT WILL MOVE SOUTH INTO VA ON SATURDAY  
NIGHT AND SUNDAY, THEN STALL OVER OUR AREA ON MONDAY.  
 

 
   
NEAR TERM /OVERNIGHT/
 
 
AS OF 940 PM THURSDAY...  
 
00Z UPPER AIR ANALYSIS REVEALS A STRONG AREA OF HIGH PRESSURE ALOFT  
OVER THE CAROLINAS WITH A SFC RIDGE STRETCHING BASICALLY SOUTH-NORTH  
OVER THE COASTAL PLAIN. THIS SET UP WILL MAINTAIN WARM AND DRY  
CONDITIONS ACROSS CENTRAL NC OVERNIGHT.  
 
THE POSITION/ORIENTATION OF THE SFC RIDGE WILL PERMIT A LIGHT SLY  
RETURN FLOW OVER THE WESTERN PIEDMONT. THIS FLOW MAY LEAD TO THE  
FORMATION BY DAYBREAK OF A LAYER OF LOW CLOUDS. ELSEWHERE PATCHY MID  
LEVEL CLOUDS MAY OCCUR, ALONG WITH POCKETS OF FOG. CANNOT RULE OUT  
THE POSSIBILITY OF LOCALLY DENSE FOG IN A FEW SPOTS, THOUGH  
CURRENTLY DO NO THINK THAT A DENSE FOG ADVISORY WILL BE NEEDED DUE  
TO THE EXPECTED LIMITED COVERAGE.  
 
OVERNIGHT TEMPERATURES GENERALLY IN THE MID-UPPER 60S.  
 

 
   
SHORT TERM /FRIDAY THROUGH SATURDAY/
 
 
AS OF 220PM THURSDAY...  
 
DEEP LAYER RIDGING WILL PEAK OVER THE AREA FRIDAY MORNING,  
SHIFTING SLOWLY EAST THROUGH FRIDAY NIGHT AND SATURDAY. THE EARLY  
MORNING STRATUS/FOG WILL BURN OFF QUICKLY, EXCEPT IN THE NW PIEDMONT  
WHERE THE STRATUS WILL GRADUALLY LIFT OUT BY LATE MORNING LEAVING  
PARTLY SUNNY SKIES. OTHER THAN AN ISOLATED (20 PERCENT CHANCE)  
SHOWER OR AFTERNOON THUNDERSTORM (MAINLY NW) ON FRIDAY  
AFTERNOON/EARLY EVENING, EXPECT PARTLY SUNNY SKIES AND LESS THAN A  
15 PERCENT CHANCE OF A SHOWER ELSEWHERE. HIGHS ARE FORECAST TO BACK  
OFF A FEW DEGREES DUE TO THE INCREASE IN THE LIGHT E-SE FLOW  
TEMPERING CONDITIONS. EXPECT MOSTLY MID 80S FOR HIGHS. LOWS FRIDAY  
NIGHT WITH PARTLY CLOUDY SKIES WILL BE IN THE UPPER 60S TO LOWER  
70S.  
 
SATURDAY, THERE IS A CHANCE OF MAINLY AFTERNOON AND EVENING  
THUNDERSTORMS ACROSS THE NORTHERN PIEDMONT AS A COLD FRONT  
APPROACHES FROM WVA/VA LATE IN THE DAY. THE LOW LEVEL WINDS WILL  
BECOME S TO SW WITH A RETURN FLOW AS HIGH PRESSURE SHIFTS OFFSHORE.  
THIS WILL LEAD TO HIGHS IN THE MID 80S TO AROUND 90 (SANDHILLS).  
 

 
   
LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
 
 
AS OF 400 PM THURSDAY...  
 
THE LONG TERM LOOKS TO BE CHARACTERIZED BY MOSTLY ABOVE NORMAL  
TEMPERATURES AND PRECIPITATION WITH THE LATEST RUNS OF THE GEFS  
AND GEPS SHOWING MOSTLY ABOVE NORMAL HEIGHT ANOMALIES.  
 
THE LONG TERM WILL OPEN UP WITH A SURFACE COLD FRONT NEAR THE  
NC/ VA BORDER WITH A POTENTIAL COLD AIR DAMMING SITUATION  
SETTING UP. DURING THE DAY SUNDAY THE COLD FRONT WILL SLOWLY SAG  
SOUTH AND WASH OUT AS A WEAK SHORTWAVE MOVES INTO WESTERN NORTH  
CAROLINA. BY SUNDAY EVENING, THE GFS, ECMWF, NAM, AND CMC ALL  
HAVE THE FRONT THROUGH THE TRIAD. AS THE FRONT PASSES, PWATS  
WILL REMAIN ONLY AROUND 1.3" WITH INSTABILITY RATHER LACKING.  
DUE TO THE ABOVE, HAVE KEPT POPS IN THE CHANCE CATEGORY. DURING  
THE DAY MONDAY ISENTROPIC UPGLIDE ALONG WITH UPSLOPE FLOW LOOKS  
TO FAVOR HIGHER POPS. CONDENSATION PRESSURE DEFICITS ALSO AT  
THIS TIME DO START TO LOWER.  
 
PWATS THROUGH THE REMAINDER OF THE EXTENDED REMAIN AROUND 1.70"  
WITH MID-LEVEL RIDGING SLOWLY BEGINNING TO BREAK DOWN. WEDNESDAY  
INTO THURSDAY A PATTERN CHANGE WILL BEGIN TO DEVELOP ACROSS THE  
UNITED STATES WITH A LONG WAVE TROUGH BEGINNING TO SETUP.  
WEDNESDAY INTO THURSDAY A SHORTWAVE WILL EJECT NORTHEAST WITH A  
WEAK COLD FRONT CROSSING THE ZONES THURSDAY. THE LATEST RUN OF  
THE ECMWF HAS THE FRONT STALLING NORTH OF THE AREA IN VIRGINIA,  
WHILE THE GFS AND CMC HAVE THE FRONT WASHING OUT ACROSS THE  
VIRGINIA/ NORTH CAROLINA BORDER. THURSDAY INTO FRIDAY OF NEXT  
WEEK A MORE POTENT SHORTWAVE WILL TRAVERSE THROUGH THE LONG WAVE  
TROUGH AS THE GROUP VELOCITY OF THE LONG WAVE SLOWS. THIS  
LIKELY MEANS OUR FIRST FALL COLD FRONT WILL PROBABLY CROSS AT  
THE END OF NEXT WEEK.  
 

 
   
AVIATION /06Z FRIDAY THROUGH TUESDAY/
 
 
AS OF 155 AM FRIDAY...  
 
MVFR TO LOW-END VFR CEILINGS ARE EXPECTED ACROSS THE AREA OVERNIGHT,  
WITH THE LOWEST CEILINGS MORE LIKELY IN PROXIMITY OF THE TRIAD  
TERMINALS. OTHERWISE, THIS CLOUD COVER SHOULD LIMIT FOG DEVELOPMENT  
OVERNIGHT, WITH THE EXCEPTION FOR FOG PRONE AREA LIKE KRWI. THE BULK  
OF THE LOW CLOUDS WILL LIFT AND SCATTER OUT BETWEEN 12Z-15Z, THOUGH  
MAY LINGER UNTIL 16Z IN VICINITY OF THE TRIAD. OUTSIDE OF SOME  
ISOLATED CONVECTION INVOF THE TRIAD TERMINALS THIS AFTERNOON, EXPECT  
VFR CONDITIONS THROUGH THE REMAINDER OF THE TAF PERIOD.  
 
LOW-LEVEL FLOW VEERS AROUND TO A MORE SWLY COMPONENT FRIDAY NIGHT,  
AHEAD OF A COLD FRONT APPROACHING FROM THE NORTH. THIS SHOULD RESULT  
IN LOWER PROBABILITIES FOR SUB-VFR CONDITIONS IN FOG AND/OR STRATUS  
SATURDAY MORNING. A BACK-DOOR COLD FRONT WILL PUSH SOUTH INTO THE  
AREA LATE SATURDAY AND INTO SUNDAY. OWING TO THE APPROACH OF THE  
FRONT, THE CHANCE OF SHOWERS AND STORMS WILL INCREASE ACROSS THE  
AREA, ESPECIALLY ACROSS THE NORTHERN TERMINALS SATURDAY AFTERNOON AND  
SATURDAY NIGHT. ADDITIONALLY, A PROLONGED PERIOD OF SUB-VFR CEILINGS  
ASSOCIATED WITH COLD AIR DAMMING EAST OF THE MTNS LOOKS INCREASINGLY  
LIKELY SUNDAY, LINGERING INTO EARLY NEXT WEEK.  
 

 
   
RAH WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
SYNOPSIS...BADGETT/CBL  
NEAR TERM...WSS  
SHORT TERM...BADGETT  
LONG TERM...HAINES  
AVIATION...CBL  
 
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