933  
FXUS62 KRAH 261901  
AFDRAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RALEIGH NC  
300 PM EDT WED JUL 26 2017  
   
SYNOPSIS
 
 
A STALLED SURFACE FRONT DRAPED ACROSS SC WILL RETURN NORTH AS A WARM  
FRONT LATER TONIGHT, THEN DISSIPATE OVER CENTRAL NC ON THURSDAY. A  
COLD FRONT WILL APPROACH FROM THE NORTHWEST THURSDAY NIGHT AND CROSS  
OUR REGION FRIDAY NIGHT.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 255 PM WEDNESDAY...  
 
A RETURN TO A TYPICAL SUMMERTIME WEATHER PATTERN TO OCCUR THIS  
PERIOD WITH AN INCREASING CHANCE FOR SCATTERED CONVECTION IN THE  
SHORT TERM.  
 
A STRONG UPPER LEVEL RIDGE EXTENDS WEST-TO-EAST ACROSS THE SOUTHERN  
TIER OF THE U.S., WITH THE EASTERN EXTENSION ACROSS THE CAROLINAS  
THIS AFTERNOON. THIS UPPER RIDGE EXTENSION WILL WEAKEN/RETREAT WEST  
AS A SERIES OF DISTURBANCES IN THE JET STREAM ACROSS THE NORTHERN  
TIER OF THE U.S. BEGIN TO CARVE OUT AN UPPER LEVEL TROUGH ALONG THE  
EASTERN SEABOARD. THE ATTENDANT SFC HIGH WILL CONTINUE TO DRIFT  
OFFSHORE TONIGHT THROUGH EARLY THU. THE RETURN SLY FLOW WILL ADVECT  
A MORE HUMID AIR MASS RESIDING ACROSS GA/SC, CHARACTERIZED BY  
DEWPOINTS IN THE LOWER 70S, INTO CENTRAL NC BY THU. THE STALLED  
BOUNDARY DELINEATING THE NORTHERN EXTENT OF THE HUMID AIR MASS WILL  
ADVANCE NORTHWARD OVERNIGHT INTO CENTRAL NC, THEN BECOME ILL-  
DEFINED. THIS FEATURE MAY TRIGGER AN ISOLATED SHOWER OR STORM THIS  
EVENING OVER THE SOUTHERN PIEDMONT. OVERNIGHT TEMPERATURES WILL BE  
WITHIN A DEGREE OR TWO OF 70 DEGREES.  
 

 
   
SHORT TERM /THURSDAY AND THURSDAY NIGHT/
 
 
AS OF 255 PM WEDNESDAY...  
 
THE ATMOSPHERE OVER CENTRAL NC WILL BECOME INCREASINGLY MOIST AND  
UNSTABLE AS THE UPPER LEVEL RIDGE DEPARTS AND HEIGHT FALLS OCCUR  
AHEAD OF THE APPROACHING UPPER DISTURBANCES AND SFC COLD FRONT.  
WHILE AN ISOLATED STORM OR TWO POSSIBLE IN VICINITY OF THE VA ORDER  
THU AFTERNOON, BETTER FORCING/SUPPORT ALOFT DOESN'T ARRIVE UNTIL THU  
EVENING/THU NIGHT. THE ATMOSPHERE BY LATE THU PROJECTED TO BE  
SLIGHTLY UNSTABLE WITH MLCAPE VALUES APPROACHING 1000 J/KG ACROSS  
THE NORTHERN COUNTIES. MEANWHILE, BULK SHEAR NOT TOO SHABBY FOR THIS  
TIME OF YEAR, IN THE NEIGHBORHOOD OF 25-30 KTS. THIS COULD BE  
SUPPORTIVE OF BROKEN LINE SEGMENTS AND POTENTIAL STRONG WIND GUSTS.  
THIS THREAT FOR STRONG STORMS SHOULD BE ISOLATED, HOWEVER, AND  
PRIMARILY CONFINED TO LOCATIONS ALONG AND WEST OF I-85 THU EVENING.  
 
THE THREAT FOR ISOLATED/SCATTERED CONVECTION WILL PERSIST WELL INTO  
THE OVERNIGHT THU NIGHT ACROSS OUR NORTHERN COUNTIES, PARTICULARLY  
NEAR THE VA BORDER AS THE INITIAL DISTURBANCE CROSSES VA. WILL  
MAINTAIN CHANCE POPS FOR NOW ROUGHLY NORTH OF HIGHWAY 64 BUT MAY  
NEED TO BUMP UP POPS IN PROXIMITY OF THE VA BORDER TO LIKELY AFTER  
06Z FRI, ESPECIALLY IF THE GFS VERIFIES.  
 
THE WARMING/MODIFYING AIR MASS WILL RESULT IN AFTERNOON TEMPS THU  
NEAR 90-LOWER 90S. VARIABLY CLOUDY SKIES AND CONTINUED LIGHT SLY SFC  
WIND WILL MAINTAIN WARM/MUGGY CONDITIONS THU NIGHT. MIN TEMPS  
GENERALLY IN THE LOWER 70S.  
 

 
   
LONG TERM /FRIDAY THROUGH WEDNESDAY/
 
 
AS OF 300 PM WEDNESDAY...  
 
A VIGOROUS MID-LEVEL SHORTWAVE WILL DIG SE ACROSS THE OHIO VALLEY  
AND SLOW AS IT STARTS TO CUT OFF AND REACHES THE MID ATLANTIC EARLY  
THIS WEEKEND. IT WILL CONTINUE DIGGING AT THIS SLOWED PACE SE ACROSS  
THE AREA, EXITING THE COAST ON SUNDAY.  
 
A SURFACE LOW WILL DEVELOP OVER NORTHERN VIRGINIA ALONG THE COLD  
FRONT ASSOCIATED WITH THIS SYSTEM ON FRIDAY, WITH NC REMAINING IN  
STRONG WARM AND MOIST ADVECTION AHEAD OF THE FRONT THROUGH THE DAY.  
CONVECTION WILL BECOME LIKELY BY FRIDAY AFTERNOON WITH LOW LEVEL  
FLOW INCREASING CONVERGENCE ALONG THE PIEDMONT TROF AHEAD OF THE  
FRONT, WITH LIKELY POPS LINGERING THROUGH FRONTAL PASSAGE...WHICH  
WILL BE AROUND MIDNIGHT IN THE NORTHWEST, AND NEAR DAYBREAK SATURDAY  
IN THE COASTAL PLAIN. STRONGER SHEAR WILL REMAIN NORTH OF THE AREA  
IN THE VICINITY OF THE TRIPLE POINT LOW AND STRONGER UPPER  
DIFFLUENCE ASSOCIATED WITH THE UPPER SHORT WAVE AS THEY SKIRT  
NORTHERN VIRGINIA. STRONG INSTABILITY WITH DEEP MOISTURE COULD  
POTENTIALLY PRODUCE A FEW SEVERE STORMS CAPABLE OF DAMAGING  
DOWNDRAFTS. STILL A LOT OF UNCERTAINTY AS TO WHERE IT WILL  
CONCENTRATE, BUT CONVECTION WILL BE WIDESPREAD, SO STAY TUNED. HIGHS  
FRIDAY WILL BE HINDERED BY CLOUD AND PRECIP COVERAGE, WITH THE  
NORTHERN TIER STALLING OUT IN THE MID 80S, WHILE SOME MORNING SUN  
SHOULD PRODUCE SOME LOW 90S ACROSS THE SOUTH.  
 
COULD SEE PATCHY SHOWERS AND MAYBE AN ISOLATED STORM ON SATURDAY AS  
THE UPPER TROF SWINGS THROUGH, OTHERWISE CLEARING WITH A DRIER AND  
COOLER AIRMASS SETTLING INTO PLACE WHICH WILL LINGER AT LEAST  
THROUGH EARLY NEXT WEEK. LOWER HUMIDITY WILL ADD TO THE COMFORT  
LEVEL AS HIGHS SATURDAY THROUGH TUESDAY TOP OUT MOSTLY IN THE MID  
80S, WITH A POSSIBLE WARMUP TOWARDS MIDWEEK BUMPING HIGHS BACK INTO  
THE UPPER 80S WEDNESDAY. MINS WILL BE IN THE MID TO UPPER 60S.  
 

 
   
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
 
 
AS OF 1230 PM WEDNESDAY...  
 
AN AREA OF HIGH PRESSURE EXTENDING ACROSS CENTRAL NC THIS AFTERNOON  
WILL PROVIDE VFR CONDITIONS THROUGH THURSDAY. THE EXCEPTION WILL BE  
POCKETS OF MVFR/IFR VISIBILITY DUE TO FOG OVERNIGHT TONIGHT THROUGH  
DAYBREAK THURSDAY OR PATCHES OF MVFR CEILINGS. THE FOG APPEARS MOST  
PROBABLE IN VICINITY OF OF KFAY AND KRWI BETWEEN 09Z-12Z THU.  
 
WHILE VFR PARAMETERS ANTICIPATED FOR MUCH OF THURSDAY, AN  
APPROACHING COLD FRONT WILL INCREASE THE RISK OF SCATTERED  
CONVECTION ACROSS THE NORTHERN COUNTIES LATE THURSDAY BUT MORE SO  
THURSDAY NIGHT. AT THIS TIME, IT APPEARS SCATTERED CONVECTION MAY BE  
IN THE VICINITY OF THE TRIAD TERMINALS AND KRDU AFTER 02Z FRIDAY,  
PERSISTING INTO FRIDAY MORNING.  
 
ADDITIONAL SCATTERED CONVECTION AND ASSOCIATED MVFR PARAMETERS  
APPEAR PROBABLE ACROSS CENTRAL NC FRIDAY THROUGH FRIDAY NIGHT AS THE  
SFC COLD FRONT DRIFTS SOUTHWARD. A DRIER, MORE STABLE ATMOSPHERE AND  
ATTENDANT VFR PARAMETERS EXPECTED SATURDAY THROUGH MONDAY.  
 

 
   
RAH WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
SYNOPSIS...WSS  
NEAR TERM...WSS  
SHORT TERM...WSS  
LONG TERM...MLM  
AVIATION...WSS  
 
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