038
FXUS61 KAKQ 230756
AFDAKQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
356 AM EDT WED AUG 23 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 PM THIS EVENING/
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 PM THIS EVENING THROUGH FRIDAY/
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 /FRIDAY 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 /08Z WEDNESDAY THROUGH SUNDAY/
EARLY THIS MORNING, A COLD FRONT WAS MOVING INTO NRN/NW
PORTIONS OF THE CWA. THAT FRONT WILL SLOWLY PUSH SE ACRS THE
REGION AND OFF THE COAST TODAY INTO THU MORNING. FLIGHT
RESTRICTIONS WILL BE POSSIBLE ALONG AND BEHIND THE FRONT THIS
AFTN INTO THU MORNING FM SHOWERS AND TSTMS. THE FRONT SHOULD
PUSH SE OF NE NC DURING THU, WITH LINGERING SHOWERS POSSIBLE
OVER EXTRM SE VA/NE NC. CONDITIONS ARE EXPECTED TO IMPROVE
THU AFTN THRU FRI, AS THE FRONT SHIFTS FARTHER SE AND HIGH
PRESSURE BUILDS NORTH OF THE REGION. BREEZY NE WINDS EXPECTED
NEAR THE COAST THU AND FRI.
MARINE
A COLD FRONT WILL APPROACH THE WATERS FROM THE NORTHWEST AND
CROSS THE AREA LATE THIS AFTN THROUGH TONIGHT. SW FLOW STILL
AVEARGES 15-20 KT OVER THE BAY AND COASTAL WATERS, HAVE THE SCA
HEADLINES THROUGH 7 AM FOR THE ENTIRE BAY AND FOR THE NRN COATL
WATERS. WAVES AVG 2 TO 3 FEET IN THE BAY AND SEAS ACRS THE N ARE
4-5 FT. WINDS SHIFT TO THE N/NE 10 TO 15 KNOTS BEHIND THE FRONT
BY LATE THIS MORNING N AND BY AFTN FARTHER S (AND WITH
CONVECTION THIS AFTN WINDS WILL BE LOCALLY MUCH STRONGER BUT
THIS WILL BE HANDLED W/ MWS/SMW'S AS NEEDED).
STRONG HIGH PRESSURE BUILDS NORTH OF THE REGION THURSDAY AND
INTO THE WEEKEND. GIVEN THE WARM WATERS AND SOME COLD ADVECTION
LATE TONIGHT/THU MORNING, EXPECT A MARGINAL SCA EVENT OVER AT
LEAST SOME OF THE BAY AND PROBABLY THE LOWER JAMES THU MORNING.
DID NOT RAISE ANY SCA HEADLINES AS THIS WILL BE MAINLY A 3RD
PERIOD EVENT (AND STILL FAIRLY MARGINAL). OTHERWISE EXPECT
DIMINISHING WINDS LATER THU AFTN THROUGH FRI AS SFC HIGH
PRESSURE BUILDS A LITTLE FARTHER SOUTH AND THE PRESSURE GRADIENT
WEAKENS. WAVES IN THE LOWER BAY MAY BRIEFLY BUILD TO 3-4 FT THU
MORNING, THEN WILL SUBSIDE TO 1-2 FT WITH COASTAL SEAS 3-4 FT.
ONSHORE (E-NE) FLOW FOR THE WEEKEND AS HIGH PRESSURE BUILDS NNW
OF THE LOCAL AREA AND THEN SHIFTS EAST TO NEW ENGLAND. WINDS
REMAIN ELEVATED 10 TO 15, OCCASIONAL GUSTS TO ~20 KT SAT, AND
THEN INCREASE MORE SIGNIFICANTLY SUNDAY INTO NEXT WEEK AS
STALLED FRONT TO THE SOUTH LIFTS BACK N WITH LOW PRESSURE
DEVELOPING ALONG THE BOUNDARY. SEAS REMAIN CHOPPY SAT, AND THEN
WILL BUILD TO 5-7 FT OR GREATER LATE SUN INTO NEXT WEEK.
AKQ WATCHES/WARNINGS/ADVISORIES
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EDT THIS MORNING FOR
ANZ630>632-634-650-652.
SYNOPSIS...TMG
NEAR TERM...TMG
SHORT TERM...LKB/SAM/TMG
LONG TERM...MAM
AVIATION...TMG
MARINE...LKB
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