864  
FXUS62 KRAH 201438  
AFDRAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RALEIGH NC  
1030 AM EDT WED JUN 20 2018  
   
SYNOPSIS
 
 
A RIDGE OF HIGH PRESSURE OVER THE SOUTHEASTERN UNITED STATES WILL  
SHIFT SOUTH BUT LARGELY PERSIST THROUGH THE WORK WEEK. A WEAK COLD  
FRONT WILL DRIFT INT THE REGION ON WEDNESDAY AND LINGER THROUGH  
THURSDAY BEFORE LIFTING NORTH LATE FRIDAY.  
 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 1030 AM WEDNESDAY...  
 
...HEAT ADVISORY REMAINS IN EFFECT FROM 11 AM TO 8 PM WEDNESDAY FOR  
THE SANDHILLS, THE SOUTHERN COASTAL PLAIN AND THE EASTERN  
PIEDMONT...  
 
MORNING STRATUS ACROSS THE NORTHEAST FROM CONVECTIVE OUTFLOW LAST  
EVENING SUPPRESSED THE EARLY MORNING DIURNAL TEMP RISE A FEW  
DEGREES. THIS OUTFLOW MIGRATING SOUTH COULD INITIATE CONVECTION A  
LITTLE EARLIER THIS AFTERNOON ACROSS THE EAST AND ESPECIALLY IN THE  
SOUTHEAST WHERE INSTABILITY WILL BE MAXIMIZED. OTHERWISE, ONGOING  
FORECAST FOR CONVECTIVE ACTIVITY COURTESY OF THE SHORT WAVE MOVING  
ACROSS THE MOUNTAINS IS ON TRACK FOR EARLY AFTERNOON AS ARE HIGHS IN  
THE MID 90S WITH ASSOCIATED TRIPLE DIGIT HEAT INDICES.  
 
PREVIOUS DISCUSSION: LOW-LEVEL THICKNESSES AND H8 TEMPS BEGIN TO  
WANE TODAY IN RESPONSE TO THE SOUTHWARD SUPPRESSION OF THE THE  
MID/UPPER LEVEL RIDGE INTO THE DEEP SOUTH/EASTERN GOM. THUS, HIGHS  
TODAY SHOULD AVERAGE A GOOD 2 TO 3 DEGREES COOLER THAN YESTERDAY,  
RANGING FROM NEAR 90 NE TO TO MID 90S SOUTH. WHEN COMBINED WITH  
LOWER TO MID 70 DEGREE DEWPOINTS HEAT INDICES WILL APPROACH HEAT  
ADVISORY CRITERIA(105 DEGREES) AGAIN ACROSS THE EASTERN PIEDMONT,  
SANDHILLS AND SOUTHERN AND CENTRAL COASTAL PLAIN COUNTIES.  
 
ANOTHER BENEFIT OF THE ABATING RIDGE WILL BE INCREASING/SCATTERED  
CONVECTIVE RAIN CHANCES, AS THE QUASI-ZONAL FLOW ALOFT WILL  
ALLOW THE PASSAGE OF THE LOW-AMPLITUDE SHORTWAVE DISTURBANCE,  
CURRENTLY ACROSS WESTERN TN, TO TRACK EAST THROUGH THE MID-ATLANTIC  
STATES DURING THE LATE AFTERNOON THROUGH LATE EVENING.  
ENHANCED 0-6KM SHEAR OF 20-30 KTS ACROSS SOUTHERN VA/NORTHERN NC  
COULD RESULT IN SOME WEAK ORGANIZATION IN THE FORM OF SOME  
MULTICELLS AND CLUSTERS AND THE RISK OF A FEW STRONG TO SEVERE  
STORMS ACROSS THE NORTHEASTERN COUNTIES.  
 
MUGGY OVERNIGHT LOWS IN THE LOWER TO MID 70S.  
 

 
   
SHORT TERM /THURSDAY AND THURSDAY NIGHT/
 
 
AS OF 410 AM WEDNESDAY...  
 
IN ADVANCE OF THE CLOSED UPPER LOW DIGGING SOUTHEAST INTO THE  
MID MS VALLEY, THE FLAT UPPER RIDGE EXTENDING NORTH OVER THE SE US  
WILL SHIFT OFFSHORE LATE IN THE DAY.  
 
INDIVIDUAL SHORTWAVE DISTURBANCES(LIKELY TO BE CONVECTIVELY  
ENHANCED) EJECTING ENE AHEAD OF THE UPPER LOW ALONG THE LEADING  
EASTERN FRINGES OF THE BROAD CYCLONIC FLOW, WILL INTERACT WITH THE  
BACK-DOOR COLD FRONT FORECAST TO SAG SOUTH INTO THE AREA LATE  
THURSDAY EVENING/NIGHT. THIS WILL RESULT IN MORE ROBUST RAIN CHANCES  
LATE THURSDAY AFTERNOON/EVENING AND INTO THE OVERNIGHT HOURS,  
ESPECIALLY ACROSS THE NORTHERN PORTIONS OF THE FORECAST AREA, WHERE  
MODELS HINT AT THE POTENTIAL STALL OUT OF THE BOUNDARY. DEEP LAYER  
SHEAR OF 25-30KTS COULD SUPPORT A FEW STRONG TO SEVERE MULTICELLS OR  
CONVECTIVE CLUSTERS, THAT SHOULD WEAKEN IN INTENSITY AS NIGHT FALLS  
AND BL COOLS AND STABILIZES. HOWEVER, WITH THE FRONT POTENTIALLY  
BISECTING THE AREA, RAIN CHANCES WILL PERSIST THROUGH-OUT THE NIGHT.  
 
HIGHS THURSDAY RANGING FROM UPPER 80S/NEAR 90 NORTH TO MID  
90S SOUTH. HEAT INDICES OF 100 TO 105 SHOULD REMAIN CONFINED  
ACROSS THE FAR SOUTHERN ZONES ON THURSDAY. OVERNIGHT LOWS  
IN THE 70S.  
 

 
   
LONG TERM /FRIDAY THROUGH TUESDAY/
 
 
AS OF 355 AM WEDNESDAY...  
 
TO BEGIN THE PERIOD, A COMPLEX MID TO UPPER LEVEL CLOSED LOW OVER  
THE CORN BELT OF THE US WILL WEAKEN AND PROGRESS EASTWARD ACROSS THE  
GREAT LAKES, BEFORE DISSIPATING. IN IT'S WAKE, LEE-SIDE TROUGHING  
REESTABLISHES OVER THE WEEKEND, ONLY TO BE INTERRUPTED BY AN  
EJECTING SHORTWAVE TROUGH AND SUBSEQUENT FRONTAL PASSAGE MONDAY  
NIGHT INTO TUESDAY.  
 
THIS PATTERN SHOULD PROVIDE SOME DISRUPTION TO THE CONSISTENTLY  
WARM/WET WEATHER PATTERN. BY FRIDAY AFTERNOON, MUCH OF THE REGION  
WILL FIND ITSELF WITH SHOWERS/STORMS ONGOING, FOCUSED IN LARGE PART  
BY A QUASI-STATIONARY FRIENDLILY BOUNDARY WHICH LOOKS TO RETURN BACK  
NORTH OF THE VA/NC BORDER BY SUNRISE SATURDAY. STORM CHANCES  
DECREASE SATURDAY AFTERNOON INTO EARLY SUNDAY AS A WAA REGIME AND  
SOUTHERLY/SOUTHWESTERLY FLOW REESTABLISHES ACROSS THE CAROLINAS.  
THIS TREND WILL CONTINUE TO MOISTEN/WARM THE AREA AHEAD OF A  
SECONDARY FRONT, WHICH IS EXPECTED TO DRAG THROUGH THE REGION MONDAY  
NIGHT WITH A COOLER AND DRIER AREA OF HIGH PRESSURE WEDGING SOUTH  
ALONG THE APPALACHIANS BY TUESDAY MORNING. SOME UNCERTAINTY REMAINS  
ON JUST HOW FAR SOUTH THIS FRONT WILL PUSH, WITH BOTH THE 00Z  
GFS/CAN MODELS CLEARING THE AREA OF PRECIPITATION, WHILE THE 00Z  
ECMWF STALLS THE BOUNDARY ALONG OUR SOUTHERN DOORSTEP, KEEPING  
SHOWER/STORM CHANCES TOO CLOSE FOR COMFORT. FOR NOW, HAVE SIDED WITH  
CONSENSUS, KEEPING BEST SHOWER/STORM CHANCES SOUTH OF THE AREA  
WEDNESDAY.  
 
TEMPERATURE WISE, EXPECT A PRETTY GOOD TEMP GRADIENT FRIDAY  
AFTERNOON, WITH HIGHS IN THE MID 90S (SOUTH) TO LOW 80S (NORTH).  
SOUTHERLY FLOW REESTABLISHES SAT - MON, ALLOWING A GRADUAL WARMING  
TREND TO TAKE HOLD, ALLOWING TEMPS TO RETURN TO THE MID TO UPPER  
90S. WIDESPREAD 80S RETURN BY MID WEEK AS THE FRONT DROPS TO OUR  
SOUTHEAST. OVERNIGHT LOWS WILL DROP INTO THE LOW TO MID 70S EACH  
NIGHT, WITH A FEW READINGS IN THE 60S POSSIBLE BY THE MIDDLE OF NEXT  
WEEK.  
 

 
   
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
 
 
AS OF 723 AM WEDNESDAY...  
 
24 HOUR TAF PERIOD: ISOLATED TO SCATTERED SHOWERS AND STORMS ARE  
EXPECTED THIS AFTERNOON AND EVENING, WITH THE BEST CHANCE ACROSS THE  
EASTERN TAF SITES (KRDU/KRWI/KFAY) THROUGH 00Z THURSDAY. AGAIN, SUB  
VFR CONDITIONS AND GUSTY WINDS WILL BE POSSIBLE WITH THE STRONGEST  
STORMS. A PERIOD OF SUB-VFR CEILINGS AND/OR FOG IS POSSIBLE ACROSS  
THE NORTHERN COASTAL PLAIN DURING THE PRE-DAWN HOURS THURSDAY  
MORNING, HOWEVER CONFIDENCE IS TOO LOW TO INCLUDE AT THIS TIME.  
 
OUTLOOK: THE CHANCES OF ADVERSE AVIATION CONDITIONS WITH SCATTERED,  
MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS WILL INCREASE  
LATE WEEK THROUGH THE WEEKEND AS A COLD FRONT APPROACHES AND THEN  
LINGERS NEAR OR JUST NORTH OF THE REGION.  
 

 
   
CLIMATE
 
 
MAX TEMPERATURE AND HIGH-MINIMUM TEMPERATURE RECORDS...  
 
GSO:  
REC HI  
DAY MAX YR MIN YR  
 
06/20 100 1924 75 2009  
06/21 100 1933 75 1924  
06/22 100 1914 75 1981  
 
-------------------------------------  
 
RDU:  
REC HI  
DAY MAX YR MIN YR  
 
06/20 102 1887 77 1924  
06/21 101 1933 75 1933  
06/22 100 1981 78 1933  
 
-------------------------------------  
 
FAY:  
REC HI  
DAY MAX YR MIN YR  
 
06/20 102 1970 77 2009  
06/21 105 1933 84 1928  
06/22 101 1990 84 1928  
 

 
   
RAH WATCHES/WARNINGS/ADVISORIES
 
 
HEAT ADVISORY FROM 11 AM TO 8 PM EDT WEDNESDAY FOR NCZ041>043-  
075>078-085-086-088-089.  
 

 
 

 
 
SYNOPSIS...BLAES  
NEAR TERM...MLM/CBL  
SHORT TERM...CBL  
LONG TERM...JJM  
AVIATION...CBL/BLAES  
CLIMATE...KCP  
 
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