909  
FXUS62 KRAH 191751  
AFDRAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RALEIGH NC  
151 PM EDT FRI OCT 19 2018  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL EXTEND OVER CENTRAL NORTH CAROLINA TODAY, THEN  
MOVE OFF THE MID ATLANTIC COAST TONIGHT. A COLD FRONT WILL CROSS THE  
AREA LATE SATURDAY. MUCH COOLER AND DRIER AIR WILL ARRIVE FOR SUNDAY  
AND MONDAY.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 1030 AM FRIDAY...  
 
FORECAST IS IN GOOD SHAPE. ISOLATED FOG PATCHES NEAR BODIES OF WATER  
HAVE VANISHED WITH HEATING, AND PLENTIFUL SUNSHINE IS EXPECTED FOR  
MUCH OF THE DAY, ALTHOUGH CLOUDS WILL BEGIN TO INCREASE THIS  
AFTERNOON. ISOLATED SPRINKLES NOW LOCATED JUST OFF THE GA AND S SC  
COAST IS ASSOCIATED WITH A DEVELOPING BUT WEAK INVERTED TROUGH, AND  
AS THIS RIDES NE JUST OFF THE S NC COAST LATE TODAY, A FEW SPRINKLES  
MAY WORK INTO OUR FAR SE, BUT OTHERWISE A DRY FORECAST WILL BE  
MAINTAINED. SHEARED VORTICITY STREAMING OUT AHEAD OF THE BROAD MID  
LEVEL TROUGH CROSSING THE MIDWEST/GREAT LAKES APPEARS UNLIKELY TO  
GATHER ENOUGH MOISTURE FOR ANY PRECIP OVER CENTRAL NC UNTIL AFTER  
MIDNIGHT AT THE EARLIEST, SO HAVE BACKED OFF/SLOWED THE  
EVENING/NIGHT POPS. UNDER MOSTLY SUNNY SKIES (BECOMING PARTLY SUNNY  
FAR SE), AND WITH THICKNESSES THIS MORNING SUGGESTING TEMPS AROUND A  
CATEGORY WARMER THAN YESTERDAY, EXPECT HIGHS IN THE MID 60S TO LOWER  
70S. -GIH  
 
EARLIER DISCUSSION FROM 330 AM: A BROAD UPPER LEVEL HIGH CENTERED  
OVER THE EASTERN GULF EARLY THIS MORNING IS SUPPORTING A SFC RIDGE  
OVER CENTRAL NC. THE BROAD HIGH ALOFT WILL DRIFT SWD TODAY AND  
TONIGHT AS A SERIES OF S/W DIVE SEWD FROM THE UPPER MIDWEST INTO THE  
GREAT LAKES AND BEGIN THE PROCESS OF DIGGING A L/W TROUGH OVER THE  
EASTERN THIRD OF THE U.S. THE SWD DRIFT OF THE UPPER HIGH WILL CAUSE  
THE SFC RIDGE OVERHEAD TO MOVE EAST, RESULTING IN A RETURN SLY FLOW  
OVER THE FORECAST AREA TODAY AND TONIGHT. UNDER SUNNY SKIES,  
TEMPERATURES WILL REBOUND QUICKLY, WARMING FROM THE 40S (WITH A FEW  
30S AT THE NORMALLY COLDER SPOTS) EARLY THIS MORNING INTO THE UPPER  
50S-LOWER 60S BY NOON, AND SOLIDLY IN THE 60S TO AROUND 70 BY MID  
AFTERNOON.  
 
THE S/WS CROSSING THE GREAT LAKES WILL PROPEL A SFC COLD FRONT  
TOWARD CENTRAL NC TONIGHT. SOUTHWESTERLY FLOW AHEAD OF THE FRONT  
WILL ADVECT A MARGINALLY MOIST AIR MASS INTO CENTRAL NC, LEADING TO  
INCREASING/THICKENING MID/HIGH LEVEL CLOUDINESS. A NARROW ZONE OF  
ISENTROPIC LIFT IN THE 290-300K LAYER MAY SUPPORT A FEW SPRINKLES OR  
PATCHY LIGHT RAIN EARLY THIS EVENING OVER THE SOUTHERN COASTAL  
PLAIN, AND THEN SHIFT AND FOCUS MORE OVER THE NORTHERN PIEDMONT  
CLOSER TO MIDNIGHT. APPEARS THAT THE ATMOSPHERE WILL BE MOIST ENOUGH  
AND MID-UPPER LEVEL LIFT STRONG ENOUGH TO PERMIT SPOTTY LIGHT RAIN  
TO OCCUR ALONG AND NORTH OF THE I-40/85 CORRIDOR OVERNIGHT. THE MILD  
SLY FLOW AND INCREASING CLOUDINESS WILL RESULT IN MILDER  
TEMPERATURES COMPARED TO THIS MORNING. IN FACT, SOME, IF NOT MOST,  
PLACES WILL LIKELY SEE THEIR OVERNIGHT LOW TEMPERATURES OCCURRING  
AROUND MIDNIGHT WITH TEMPERATURES EITHER HOLDING STEADY OR SLOWLY  
RISING OVERNIGHT. MIN TEMPS GENERALLY IN THE MID-UPPER 50S.  
 

 
   
SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/
 
 
AS OF 330 AM FRIDAY...  
 
THE SFC COLD FRONT WILL BE POISED IMMEDIATELY TO OUR NORTH-NORTHWEST  
SATURDAY MORNING, AND PROJECTED TO GLIDE SEWD ACROSS THE REGION  
DURING THE LATE MORNING THROUGH THE AFTERNOON HOURS. A PRONOUNCED  
WLY FLOW IN THEW 850-700MB LAYER MAY RESULT IN THE PRECIP BECOMING  
PATCHY AND RELATIVELY LIGHT. STILL PLAN TO ADVERTISE HIGH CHANCE-  
LIKELY POPS FOR SATURDAY, THOUGH DO NOT EXPECT THE RAIN TO PERSIST  
ANY ONE LOCATION FOR MORE THAN A COUPLE OF HOURS AND TOTAL AMOUNTS  
GENERALLY LESS THAN A QUARTER OF AN INCH. THE SOUTHWEST FLOW AHEAD  
OF THE FRONT WILL ADVECT A WARMER AIR MASS INTO THE REGION,  
ESPECIALLY THE SOUTHERN COUNTIES WHERE THE SHOWERS/PATCHY RAIN MAY  
NOT BE AS PROMINENT AS COMPARED ACROSS THE NORTH. HIGHS SATURDAY  
SHOULD VARY FROM THE UPPER 60S NORTH TO THE LOW-MID 70S SOUTH.  
 
LOW LEVEL FLOW WILL VEER TO A NWLY DIRECTION BEHIND THE FRONT,  
INITIATING A TREND TOWARD DRIER AND MORE STABLE CONDITIONS. EXPECT  
CLEARING SKIES TO COMMENCE IN THE NW PIEDMONT BY MID AFTERNOON, WITH  
THE CLEARING TREND PROGRESSING SEWD INTO THE CENTRAL-SOUTHERN  
COASTAL PLAIN AROUND SUNSET-EARLY EVENING. THE PASSAGE OF THE 850MB  
TROUGH DURING THE EVENING WILL COMMENCE THE TRUE COLD AIR ADVECTION.  
THE PASSAGE OF THE 850MB TROUGH WILL BE NOTED BY THE NW SFC WINDS  
BECOMING BLUSTERY WITH GUSTS 18-23KTS PROBABLE DURING THE LATE  
EVENING AND THROUGH THE OVERNIGHT HOURS. MIN TEMPS BY EARLY SUNDAY  
SHOULD RANGE FROM THE LOWER 40S/NEAR 40 NW TO THE MID-UPPER 40S EAST  
AND SOUTH.  
 

 
   
LONG TERM /SUNDAY THROUGH THURSDAY/
 
 
AS OF 150 PM FRIDAY...  
 
SUNDAY AND SUNDAY NIGHT: THE CLEAR, COOL AND BREEZY CONDITIONS WILL  
CONTINUE THROUGH SUNDAY AS NC REMAINS SANDWICHED BETWEEN THE FRONT  
OFFSHORE AND THE SURFACE HIGH OVER THE MIDWEST. THE RESULTANT  
PRESSURE GRADIENT WILL BE RESPONSIBLE FOR THE WINDY CONDITIONS,  
WHILE SUBSIDENCE IN NW FLOW WILL YIELD THE CLEAR SKIES. DESPITE THE  
CLEAR SKIES, STRONG COLD ADVECTION WILL RESULT IN HIGHS TOPPING OUT  
IN THE MID 50S NW TO AROUND 60 DEGREES SE, WITH THE WIND MAKING THE  
TEMPERATURE FEEL A FEW DEGREES LOWER. AS THE SURFACE HIGH BUILDS  
EASTWARD INTO AND OVER THE CAROLINAS SUNDAY NIGHT, THE PRESSURE  
GRADIENT WILL RELAX, RESULTING IN ABATING WINDS, CLEAR SKIES AND  
EXCELLENT RADIATIONAL COOLING CONDITIONS. LOWS SUNDAY NIGHT WILL BE  
THE COOLEST OF THE SEASON, MID 30 NW TO UPPER 30S SE.  
 
MONDAY THROUGH THURSDAY: COOL, DRY WEATHER WILL CONTINUE THROUGH MID-  
WEEK. ALTHOUGH THE SURFACE HIGH IS EXPECTED TO SHIFT OFFSHORE, IT  
WILL CONTINUE TO RIDGE WESTWARD INTO THE CAROLINAS THROUGH MID-WEEK.  
AN UPPER LEVEL SHORTWAVE TROUGH IS EXPECTED TO PASS OVER THE REGION  
ON TUESDAY/TUESDAY NIGHT, BUT THE ONLY IMPACT EXPECTED IS SOME  
INCREASED CLOUD COVERAGE. THE SURFACE REFLECTION OF THE TROUGH WILL  
SWING THROUGH AS WELL, BRINGING A REINFORCING SHOT OF COLD AIR INTO  
THE REGION WEDNESDAY NIGHT/THURSDAY. TEMPERATURES WILL MODERATE TO  
NEAR NORMAL ON TUESDAY, WITH HIGHS IN THE MID 60S TO LOW 70S AND  
LOWS TUESDAY NIGHT IN THE MID TO UPPER 40S. (FOR REFERENCE, NORMAL  
HIGHS ARE IN THE UPPER 60S TO LOW 70S AND NORMAL LOWS ARE IN THE MID  
TO UPPER 40S). TEMPERATURES WILL THEN DECREASE ONCE AGAIN WEDNESDAY  
AND THURSDAY (BY APPROXIMATELY A CATEGORY/DAY) IN RESPONSE TO THE  
REINFORCING SHOT OF COLD AIR.  
 

 
   
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
 
 
AS OF 1245 PM FRIDAY...  
 
HIGH CONFIDENCE IN VFR CONDITIONS HOLDING AT ALL SITES THROUGH AT  
LEAST THIS EVENING, AS HIGH PRESSURE RIDGING AND DEEP DRY AIR  
PERSISTS OVER THE REGION. AS THE SURFACE HIGH SHIFTS EAST AND OFF  
THE MID ATLANTIC COAST LATE THIS AFTERNOON, LOW LEVEL FLOW WILL  
REMAIN LIGHT BUT SWING AROUND TO SE AND S. THIS, AS WELL AS  
INCREASING HIGH LEVEL MOISTURE AS AN UPPER TROUGH APPROACHES FROM  
THE W, WILL CAUSE CLOUDS TO OVERSPREAD THE AREA FROM THE S AND W  
OVERNIGHT. A PERIOD OF MVFR CIGS IS POSSIBLE AT FAY 08Z-13Z, AND A  
PERIOD OF IFR/LIFR FOG IS POSSIBLE AT RWI 06Z-13Z. ELSEWHERE,  
THOUGH, CIGS/VSBYS SHOULD REMAIN VFR THROUGH THE END OF THE TAF  
VALID PERIOD. PATCHY SPRINKLES OR LIGHT RAIN ARE POSSIBLE LATE  
TONIGHT INTO SAT, STARTING AT INT/GSO AFTER 09Z, AND AT RDU AFTER  
12Z, AHEAD OF A COLD FRONT THAT WILL MOVE IN FROM THE NW. RAIN  
CHANCES ARE MUCH SMALLER AT RWI/FAY.  
 
LOOKING BEYOND 18Z SAT, THE COLD FRONT WILL SHIFT E OUT OF THE AREA  
SAT AFTERNOON, WITH THE SHOWER RISK ENDING W TO E. VFR CONDITIONS  
AND COOL HIGH PRESSURE WILL DOMINATE THROUGH WED, EXCEPT WE'LL SEE A  
CHANCE FOR SUB-VFR CONDITIONS MON NIGHT/TUE AS AN UPPER DISTURBANCE  
AND SECONDARY COLD FRONT CROSSES THE CAROLINAS. ALSO: AS THE COLD  
FRONT CROSSES THE AREA LATE SAT, WE'LL SEE A SHIFT OF SURFACE WINDS  
TO WNW WITH INCREASING SPEEDS TO 15-20 KTS AND GUSTS UP TO 20-25 KTS  
POSSIBLE FROM LATE SAT AFTERNOON THROUGH EARLY SUN MORNING. -GIH  
 

 
   
RAH WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
SYNOPSIS...WSS  
NEAR TERM...HARTFIELD/WSS  
SHORT TERM...WSS  
LONG TERM...KC  
AVIATION...HARTFIELD  
 
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