676  
FXUS62 KRAH 260718  
AFDRAH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RALEIGH NC  
315 AM EDT FRI MAY 26 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL EXTEND ACROSS THE SOUTHEAST STATES TODAY INTO  
SATURDAY, AS A WEAK TROUGH EXTENDS DOWN THROUGH WESTERN AND CENTRAL  
NORTH CAROLINA. AN UPPER LEVEL DISTURBANCE WILL CROSS THE REGION  
LATE SATURDAY THROUGH SATURDAY NIGHT, FOLLOWED BY ANOTHER  
DISTURBANCE SUNDAY AFTERNOON.  
 

 
   
NEAR TERM /THROUGH FRIDAY/
 
 
AS OF 955 PM THURSDAY...  
 
A MID-UPPER LOW CENTERED NEAR THE MID-ATLANTIC COAST WILL CONTINUE  
TO LIFT NORTHEASTWARD AND AWAY FROM THE AREA OVERNIGHT. GIVEN THIS  
ALONG WITH THE MAIN TROUGH AXIS NOW TO THE EAST OF THE AREA EXPECT  
DRY CONDITIONS FOR THE REST OF THE NIGHT. THUS, EXPECT CLEARING  
SKIES OVERNIGHT WITH A COOLER AND DRIER AIR MASS IN PLACE FOR  
TONIGHT. EXPECT WE WILL MAINTAIN A WSW TO SOUTHWESTERLY BREEZE  
OVERNIGHT AS THE MSLP GRADIENT SHOULD CONTINUE TO REMAIN SOMEWHAT  
TIGHT. GIVEN THIS EXPECT TEMPS WILL FALL INTO THE 50S OVERNIGHT AT  
MOST SPOTS, WITH A FEW LOCATIONS ACROSS THE SOUTHEASTERN REACHES OF  
THE AREA ONLY BOTTOMING OUT NEAR 60.  
 
RIDGING AND DRIER AIRMASS ON FRIDAY WILL SUPPORT CLEAR TO SCATTERED  
CLOUDS WITH MAX TEMPERATURES 80 TO 85.  
 

 
   
SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/
 
 
AS OF 430 PM THURSDAY...  
 
THE MID AND UPPER LEVEL LOW OVER NEW ENGLAND AT THE START OF THE  
PERIOD WILL DEPART AS THE UPPER LEVEL FLOW OVER THE MID-ATLANTIC  
BECOMES MORE WESTERLY FRIDAY NIGHT AS AN UPPER LEVEL RIDGE  
DEVELOPS ACROSS THE NORTHERN GULF OF MEXICO. INCREASING MID AND  
AND HIGH LEVEL MOISTURE WILL RESULT IN SOME HIGH CLOUDINESS.  
LOWS WILL RANGE IN THE LOWER TO MID 60S.  
 
A GENERAL WESTERLY TO WEST-NORTHWESTERLY FLOW ALOFT IS EXPECTED  
FOR SATURDAY AND SATURDAY NIGHT ACROSS THE MID-ATLANTIC. A GOOD  
WARM ADVECTION PATTERN WILL DEVELOP ACROSS THE DEEP SOUTH AND  
SOUTHEAST. THIS WILL RESULT IN THE DEVELOPMENT OF A WARM FRONT  
THAT EXTENDS FROM THE SOUTHERN APPALACHIANS INTO THE VA AND NC  
AND SUBSEQUENT SCATTERED CONVECTION. THE BEST CHANCE OF  
THUNDERSTORMS WILL BE ACROSS THE NORTHEAST HALF OF THE CWA,  
PRIMARILY SATURDAY AFTERNOON AND EVENING. IT WILL BE NOTICEABLY  
WARMER AND A BIT MORE HUMID WITH HIGHS IN THE MID 80S TO LOWER  
90S ACROSS THE SOUTHEAST. LOWS WILL RANGE IN THE MID 60S TO NEAR  
70.  
 

 
   
LONG TERM /SUNDAY THROUGH THURSDAY/
 
 
AS OF 315 AM FRIDAY...  
 
SUN/SUN NIGHT: TOUGH FORECAST BEHIND THE MCV SHIFTING OFF THE MID  
ATLANTIC COAST LATE SAT NIGHT. MODELS INDICATE A WEAK SHORTWAVE  
RIDGE SHIFTING OVER THE AREA FROM THE WEST, WITH A WARM 850-700 MB  
LAYER, HIGH CLOUDS TO LIMIT INSOLATION (LIKELY CONVECTIVE DEBRIS  
CLOUDS RESULTING FROM LATE-SAT STORM COMPLEX OVER THE MID MISS  
VALLEY), AND WEAK MID LEVEL LAPSE RATES DURING THE FIRST HALF OF THE  
DAY. MODELS SHOW AN EVENTUAL RECOVERY OF THIS AIR MASS THROUGH THE  
DAY, WITH LOW LEVEL WARMING AND MIXING ALLOWING FOR LATE-DAY  
DESTABILIZATION TO 500-2000 J/KG OF MUCAPE (HIGHEST SW, LOWEST NE)  
AND DEEP LAYER SHEAR OF 45-50 KTS. AND AN EXPECTED CLUSTER OF  
CONVECTION OVER TN EARLY SAT MAY WORK WITH THIS DESTABILIZATION TO  
PROMPT ORGANIZED STORMS OVER CENTRAL NC LATE SUN, A DEVELOPMENT  
SHARED BY THE NAM/NAM NEST/GFS/ECMWF. AFTER A MOSTLY DRY MORNING,  
WILL BRING IN SCATTERED TO NUMEROUS SHOWERS/STORMS LATE SUN INTO SUN  
EVENING. HIGHS 84-90. CONVECTION CHANCES SHOULD DWINDLE SUN NIGHT  
WITH MODELS SHOWING A BATCH OF DRIER AIR BETWEEN THE EXITING STORMS  
AND WELL OUT AHEAD OF THE APPROACHING MID LEVEL TROUGH, WHICH SHOULD  
FEATURE STRONGLY FORCED CONVECTION FROM THE EASTERN GREAT LAKES  
THROUGH THE MID/LOWER MISS VALLEY TO TX. WARM LOWS OF 66-72.  
 
MON/MON NIGHT: A MID LEVEL SHEAR AXIS AND ACCOMPANYING COLD FRONT  
AND CONVECTIVE BAND WILL APPROACH FROM THE W AND NW MON, AS OUR  
STEERING FLOW GRADUALLY BECOMES MORE CYCLONIC AS A DEEP MID LEVEL  
LOW WOBBLES EASTWARD OVER SOUTHERN ONTARIO. DEEP LAYER SHEAR AND  
CAPE VALUES ARE BOTH EXPECTED TO IMPROVE THROUGH MON, ESPECIALLY  
ALONG AND EAST OF HIGHWAY 1 WHERE THE GFS DEPICTS 1500-2500 J/KG OF  
MUCAPE AND 40-50 KTS OF 0-6 KM SHEAR MON AFTERNOON. WILL BRING IN  
HIGH POPS, ESPECIALLY CENTRAL/EAST, DURING THE DAY, TRAILING OFF  
LATE MON NIGHT AS THE SURFACE FRONT PUSHES TO COASTAL AND SE NC.  
THICKNESSES REMAIN ELEVATED ABOVE NORMALS, FAVORING HIGHS OF 84-91.  
LOWS 63-70 WITH SOME COOLING IN THE NW BEHIND THE FRONT.  
 
TUE-THU: MID LEVEL FLOW DECREASES AND FLATTENS A BIT AS HEIGHTS RISE  
OVER THE ST LAWRENCE VALLEY REGION, AND WITH THE DIFFUSE SURFACE  
FRONT HAVING SETTLED NEAR THE EASTERN AND SOUTHERN EDGES OF THE CWA  
TUE AND MUCH LOWER PW ADVECTING INTO THE NW, WILL CARRY CHANCE POPS  
IN THE SE CWA ONLY TUE. AS THE MID LEVEL TROUGH AXIS SHIFTS EASTWARD  
THROUGH THE MID ATLANTIC AND NORTHEAST BY EARLY WED, THE BELOW-  
NORMAL PW AND WEAK MID LEVEL LAPSE RATES SHOULD CONTINUE TO SPREAD  
IN FROM THE WEST, AND WILL HAVE A DRY FORECAST FOR WED/THU AS WEAK  
SURFACE HIGH PRESSURE BUILDS OVER THE REGION WITH RISING HEIGHTS AND  
MID LEVEL SUBSIDENCE DOMINATING. HIGHS MOSTLY IN THE LOWER TO MID  
80S, NEAR SEASONAL NORMALS. -GIH  
 

 
   
AVIATION /00Z FRIDAY THROUGH TUESDAY/
 
 
AS OF 220 AM FRIDAY...  
 
STRONG SUBSIDENCE, BEHIND THE UPPER LEVEL TROUGH AND ACCOMPANYING  
HAIL STORMS THAT CROSSED CENTRAL NC ON THU, WILL RESULT IN VFR  
CONDITIONS THROUGH THE 24 HOUR TAF PERIOD. SWLY SURFACE WINDS WILL  
BE THE PRIMARY AVIATION CONCERN AS THEY INCREASE INTO THE LOW TO MID  
TEENS KTS, WITH GUSTS AROUND 20 KTS, MAINLY BETWEEN 14-20Z - HIGHEST  
EAST/AT RWI.  
 
OUTLOOK: AT LEAST A COUPLE OF CLUSTERS OF SHOWERS AND STORMS, SOME  
SEVERE, WILL RETURN TO PORTIONS OF CENTRAL NC THIS WEEKEND - ONE  
MAINLY OVER THE NORTHERN HALF OF THE FORECAST AREA BUT WITH GUSTY  
OUTFLOW WINDS SURGING WELL AWAY FROM THEM LATE SAT AND EARLY SAT  
NIGHT, THEN ANOTHER ON SUN. THE APPROACH AND STALL OF A COUPLE OF  
COLD FRONTS EAST OF THE APPALACHIANS WILL RESULT IN A SMALL CHANCE  
OF DIURNAL CONVECTION MON AND TUE AFTERNOON.  
 

 
   
RAH WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
SYNOPSIS...HARTFIELD  
NEAR TERM...BSD/JF  
SHORT TERM...BLAES  
LONG TERM...HARTFIELD  
AVIATION...MWS  
 
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