997  
FXUS61 KAKQ 230141  
AFDAKQ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE WAKEFIELD VA  
941 PM EDT TUE AUG 22 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE REMAINS CENTERED OFF THE MID ATLANTIC COAST  
THROUGH TONIGHT AS A COLD FRONT BEGINS TO APPROACH FROM THE  
WEST. THE FRONT CROSSES THE AREA LATE WEDNESDAY AFTERNOON  
THROUGH WEDNESDAY NIGHT, WITH STRONG HIGH PRESSURE BUILDING  
NORTH OF THE AREA FROM THURSDAY INTO THE UPCOMING WEEKEND.  
 

 
   
NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/
 
 
NO MAJOR CHANGES NECESSARY TO THE PREVIOUS FORECAST. STILL  
EXPECTING A DRY NIGHT ASIDE FROM A STRAY SHOWER LATE OVER  
NORTHERN AREAS.  
 
PREVIOUS DISCUSSION...  
WARM/HUMID TONIGHT WITH LITTLE CHANCE FOR ANY RAIN UNDER A SW  
WIND OF 10 MPH. LOWS MAINLY IN THE MID TO UPPER 70S. CLOUDS  
INCREASE ACROSS THE NORTH AHEAD OF THE APPROACHING COLD FRONT  
AND LEAD SHORTWAVE. HAVE INTRODUCED A SLIGHT CHANCE POP FOR THE  
MARYLAND EASTERN SHORE LATE TONIGHT, BUT BEST CHANCES FOR  
MEASURABLE PRECIPITATION REMAIN NORTH AND WEST OF THE LOCAL  
AREA.  
 

 
   
SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/
 
 
MODELS IN GOOD AGREEMENT WITH DROPPING THE COLD FRONT INTO THE  
LOCAL AREA WEDNESDAY MORNING, THEN PUSHING THE FRONT ACROSS THE  
AREA THROUGH WEDNESDAY AFTERNOON. SHEARING VORT LOBE PROGGED TO  
RIDE ALONG THE FRONT AS WINDS INCREASE ALOFT. THE ADDED FORCING  
ALONG THE BOUNDARY ALONG A NARROW RIBBON OF HIGH PRECIPITABLE  
WATERS WILL RESULT IN SCATTERED TO NUMEROUS SHOWERS AND  
THUNDERSTORMS WEDNESDAY AFTERNOON. DOWNSLOPE FLOW FROM 1-3KM  
WILL LIMIT THE COVERAGE OVER THE PIEDMONT, BUT HI-RES AND COURSE  
RESOLUTION GUIDANCE INDICATES THAT THE ACTIVITY SHOULD BECOME  
MORE ORGANIZED CENTRAL VIRGINIA EASTWARD AS IT INTERACTS A  
MODERATELY UNSTABLE AIR MASS (MIXED-LAYER CAPE VALUES 500-1500  
J/KG) AND MARGINAL SHEAR (25-30 KNOTS). DRY MID LEVELS AND AN  
INVERTED V SOUNDING INDICATE THE MAIN THREAT WILL BE DAMAGING  
WINDS AND FREQUENT LIGHTNING. SPC MAINTAINS A MARGINAL RISK FOR  
SEVERE WEATHER ACROSS THE SOUTHEAST HALF OF THE LOCAL AREA.  
HEAVY RAINFALL IS ALSO POSSIBLE AS THE COLD FRONT SLOWS AS IT  
REACHES SOUTHEAST VIRGINIA AND NORTHEAST NORTH CAROLINA  
WEDNESDAY AFTERNOON. PRECIPITABLE WATER VALUES PROGGED AROUND 2  
TO 2.25 INCHES. WESTERLY FLOW IN THE MID LEVELS INDICATES THAT  
THE MOTION SHOULD PREVENT WIDESPREAD HEAVY RAINFALL, BUT SOME  
AREAS COULD SEE PERIODS OF HEAVY RAINFALL. NO HEADLINES PLANNED  
AT THIS TIME. FLOW BECOMES NORTH TO NORTHEAST BEHIND THE FRONT,  
AS DRY AIR SPREADS INTO THE AREA FROM THE NORTHWEST. THE FRONT  
AND UPPER WAVE PUSH OFFSHORE WEDNESDAY EVENING. GUIDANCE  
INDICATES A WAVE OF LOW PRESSURE DEVELOPS ALONG THE FRONT OVER  
THE CAROLINAS, KEEPING RAIN CHANCES IN NORTHEAST NORTH CAROLINA  
AND FAR SOUTHEAST VIRGINIA THROUGH WEDNESDAY NIGHT. HIGHS  
WEDNESDAY RANGE FROM THE MID 80'S NORTHWEST TO AROUND 90  
SOUTHEAST. LOWS WEDNESDAY NIGHT IN THE LOW TO MID 60'S INLAND TO  
THE LOW 70'S NEAR THE COAST.  
 
HIGH PRESSURE BUILDS IN FROM THE NORTHWEST THURSDAY AS THE FRONT  
STALLS ALONG THE SOUTHEAST COAST. WILL KEEP LOW CHANCE POPS  
ACROSS NORTHEAST NORTH CAROLINA THURSDAY NEAREST THE FRONT AND  
DEEPEST MOISTURE. OTHERWISE, DRY, COOLER AND LESS HUMID  
CONDITIONS EXPECTED. HIGHS THURSDAY FORECAST IN THE LOW TO MID  
80'S UNDER A PARTLY CLOUDY SKY.  
 

 
   
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
 
 
COOLER AND DRIER FOR THE LATE WEEK PERIOD COURTESY OF BUILDING  
LONGWAVE UPPER LEVEL TROUGH OVER THE EASTERN UNITED STATES.  
MEANWHILE, BROAD 1024+ MB SURFACE HIGH PRESSURE BUILDS SOUTH OVER  
THE INTERIOR NORTHEAST FROM GREAT LAKES THURSDAY AND FRIDAY,  
EVENTUALLY SETTING UP OVER NEW ENGLAND AND RIDGING DOWN THE EAST  
COAST OVER THE WEEKEND INTO EARLY NEXT WEEK. FORECAST REMAINS MOSTLY  
DRY, ALTHOUGH A FEW SHOWERS POSSIBLE ALONG THE COAST IN PERSISTENT  
ONSHORE FLOW.  
 
MEDIUM RANGE GUIDANCE IN RELATIVELY GOOD AGREEMENT WITH DEVELOPING A  
TROPICAL SYSTEM ALONG AND OFFSHORE OF THE SOUTHEAST COAST ALONG THE  
OLD FRONTAL BOUNDARY EARLY NEXT WEEK. KEPT WEEKEND DRY, WITH LOW  
RAIN CHANCES ALONG THE SE COAST BY MONDAY. LOOKING AHEAD, RAIN  
CHANCES LOOK TO IMPROVE INTO THE MIDDLE OF NEXT WEEK, WITH MOISTURE  
FROM THE REMNANTS OF HARVEY LOOMING TO THE SW. FOR TEMPERATURES,  
HIGH TEMPERATURES FRI-MON WILL BE AT OR JUST SLIGHTLY BELOW NORMAL  
THROUGH THE PERIOD, MAINLY IN THE UPPER 70S TO LOW 80S. EARLY  
MORNING LOWS IN THE 50S INLAND TO MID 60S ALONG THE COAST.  
 

 
   
AVIATION /01Z WEDNESDAY THROUGH SUNDAY/
 
 
VFR AND DRY CONDITIONS CONTINUE AT THE 00Z TAF PERIOD WITH  
HIGH PRESSURE JUST OFFSHORE. SKIES ARE MOSTLY CLEAR WITH A FEW  
CU THAT ARE GENERALLY DISSIPATING. SOUTH TO SOUTHWEST WINDS  
10-15 KNOTS WILL PREVAIL THROUGH THE OVERNIGHT.  
 
A COLD FRONT APPROACHES THE REGION LATE TONIGHT INTO WED  
AFTERNOON AND EVENING. FLIGHT RESTRICTIONS WILL BE POSSIBLE  
WITH THE FRONT LATER ON WEDNESDAY...MAINLY IN THE LATE AFTERNOON  
INTO WEDNESDAY NIGHT FROM SHOWERS AND THUNDERSTORMS. THE FRONT  
SHOULD EXIT THE COAST EARLY THURSDAY MORNING WITH LINGERING  
SHOWERS POSSIBLE ACROSS FAR SE VA/NE NC. CONDITIONS ARE  
ANTICIPATED TO IMPROVE THURSDAY AFTERNOON INTO FRIDAY AS THE  
FRONT SHIFTS FARTHER SOUTHEAST AND HIGH PRESSURE BUILDS NORTH OF  
THE REGION. BREEZY NE WINDS EXPECTED NEAR THE COAST THURSDAY  
AND FRIDAY.  
 

 
   
MARINE
 
 
A COLD FRONT WILL APPROACH THE WATERS FROM THE NORTHWEST TONIGHT,  
CROSSING THE AREA WEDNESDAY THROUGH WEDNESDAY NIGHT. WINDS WILL  
INCREASE TONIGHT AHEAD OF THE COLD FRONT WITH SSW WINDS OF 15 TO 20  
KNOTS POSSIBLE ACROSS BOTH THE BAY AND OCEAN. A FEW WIND GUSTS OF 25  
KNOTS WILL ALSO BE POSSIBLE ACROSS THE NORTHERN OCEAN AND BAY ZONES.  
AS A RESULT, WENT AHEAD AND ISSUED A SMALL CRAFT ADVISORY FOR THE  
CHESAPEAKE BAY TONIGHT INTO EARLY WEDNESDAY MORNING. WAVES WILL  
BUILD TO 2 TO 3 FEET IN THE BAY AND SEAS WILL BUILD TO 3 TO 5 FEET  
IN THE NORTHERN ZONES. WINDS SHIFT TO THE N/NE 10 TO 15 KNOTS BEHIND  
THE FRONT BY WEDNESDAY AFTERNOON THROUGH EARLY THURSDAY MORNING.  
 
STRONG HIGH PRESSURE BUILDS NORTH OF THE REGION THURSDAY AND INTO  
THE WEEKEND. EXPECT WIND SPEEDS OF 10 TO 15 KNOTS WITH A FEW  
OCCASIONAL GUSTS TO 20 KNOTS, PARTICULARLY EARLY THURSDAY MORNING AS  
THE GRADIENT TIGHTENS. WAVES WILL BE 1 TO 3 FEET AND SEAS WILL BE 2  
TO 4 FEET.  
 
ONSHORE (E-NE) FLOW FOR THE LATE WEEK PERIOD AS HIGH PRESSURE BUILDS  
NNW OF THE LOCAL AREA. WINDS REMAIN ELEVATED 10 TO 15, OCCASIONAL  
GUSTS TO ~20 KT THROUGH THE LATE WEEK PERIOD AS A COUPLE OF WAVES  
MOVE ACROSS THE STALLED FRONT TO THE SOUTH ACROSS THE CAROLINAS.  
SEAS REMAIN CHOPPY FOR THE LATE WEEK PERIOD INTO THE WEEKEND WITH  
THE PERSISTENT ONSHORE FLOW, REMAINING 2-4 FT NORTHERN WATERS...4-  
5FT SOUTHERN WATERS.  
 

 
   
AKQ WATCHES/WARNINGS/ADVISORIES
 
 
MD...NONE.  
NC...NONE.  
VA...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ630>632-  
634-650-652.  
 

 
 

 
SYNOPSIS...LKB  
NEAR TERM...LKB/MAS/SAM  
SHORT TERM...LKB/SAM  
LONG TERM...MAM  
AVIATION...SAM/JEF  
MARINE...MAM  
 
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