Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 020200
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
1000 PM EDT FRI AUG 1 2014

.SYNOPSIS...
A FRONTAL BOUNDARY ALONG THE SOUTHEAST COAST WILL SLOWLY DRIFT
NORTH TOWARDS THE MID ATLANTIC COAST TONIGHT. THE FRONT THEN
STALLS ALONG THE COAST OR JUST INLAND OVER THE MID ATLANTIC
REGION...KEEPING UNSETTLED CONDITIONS IN PLACE THROUGH AT LEAST
MONDAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
HIGHLY AMPLIFIED FLOW OVER THE CONUS AND WRN ATLANTIC ONGOING THIS
EVENING...HIGHLIGHTED BY LONGWAVE TROUGHING OVER THE CNTRL CONUS AND
LONGWAVE RIDGING OVER THE WRN ATLANTIC. PLUME OF ANOMALOUS MOISTURE
VISIBLE ON WATER VAPOR STREAMING NWD IN SWLY FLOW FROM THE ERN GULF
AND OFF THE SE COAST OVER THE MID-ATLANTIC REGION. AT THE SFC...LOW
PRESSURE RESIDES OVER SE GA/NRN FL WITH A STATIONARY BOUNDARY
EXTENDING NEWD ALONG THE SE AND MID-ATLANTIC COASTS. WAA/OVERRUNNING
OF THE FRONTAL BOUNDARY AS WELL AS SMALL AMPLITUDE SHORTWAVES
LIFTING IN SWLY FLOW ARE PRODUCING A BROAD AREA OF LIGHT-MODERATE
PRECIP OVER THE LOCAL AREA THIS EVENING. RAINFALL RATES HAVE BEEN
LIGHT...WITH STORM TOTAL AMOUNTS THROUGH 930PM RANGING FROM A FEW
TENTHS TO JUST OVER HALF AN INCH. LATEST GFS 310K OMEGA IS HANDLING
THE CURRENT PRECIP OVER THE PIEDMONT AND CNTRL VA WELL. DRY SLOT
OVERSPREAD SE VA/NE NC EARLIER THIS EVENING...RESULTING IN A BRIEF
LULL IN THE PRECIP. HOWEVER...THE LOCATION OF THE INVERTED
TROUGH/CONVERGENCE AND MODEST INSTABILITY/SHEAR...HAS RESULTED IN
SCT-NUMEROUS SHOWERS IN THAT REGION. WILL MAINTAIN HIGH POPS THROUGH
THE EVENING...BUT EXPECT THE PRECIP TO BEGIN LIFTING NWD FROM THE
PIEDMONT AND CNTRL VA BY LATE THIS EVENING. ALREADY BEGINNING TO SEE
SIGNS OF THE PRECIP LIFTING FROM THE N CTNRL NC.

MODELS CONTINUE TO INDICATE FAVORABLE FORCING FOR ASCENT AND
ABUNDANT MOISTURE (PWATS AOA 2 INCHES) OVER THE REGION TONIGHT.
FRONTAL BOUNDARY/INVERTED TROUGH IS EXPECTED TO NUDGE TO THE EAST AS
THE UPPER RIDGE RETROGRADES SLIGHTLY. THIS PLACES THE BEST
LIFT/OMEGA OVER SE VA/NE NC AND OVER THE COASTAL WATERS. WILL
MAINTAIN CATEGORICAL POPS ALONG THE COAST WITH LIKELY POPS EAST OF
INTERSTATE 95 (TAPERING OFF TO LOW END CHANCE POPS OVER THE PIEDMONT
AFTER MIDNIGHT). QPF AMOUNTS OF ONE HALF INCH UP TO ONE INCH
EXPECTED. OUTSIDE OF URBAN AND LOW LYING AREAS...FLOODING IS NOT
ANTICIPATED AS HEAVIEST PRECIP WILL FALL IN FAVORABLE LOCATIONS.
RAINFALL RATES ALSO EXPECTED TO REMAIN LOW. TEMPS WILL GENERALLY
HOLD STEADY OVERNIGHT...GENERALLY IN THE MID-UPPER 60S TO LOW 70S.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
FRONTAL BOUNDARY IS PROGGED TO STRADDLE THE COAST FROM THE
DELMARVA DOWN ALONG THE SE COAST. THE INTERACTION OF A STEADY
INFLUX OF MOISTURE AND SHORTWAVE ENERGY WITH THE FRONTAL BOUNDARY
WILL MAINTAIN HIGH PRECIP CHANCES...ONCE AGAIN WITH THE MAIN FOCUS
ALONG THE COAST AND ESPECIALLY NE NC/SE VA. MODEL SOUNDINGS FOR
KECG AND KORF ARE VERY MOIST...WITH SFC CAPES OF 700-1500 J/KG...
AND UNIDIRECTIONAL SW FLOW WHERE WINDS ARE VERY LIGHT BELOW
700-500MB (AT OR BELOW 20 KT). THIS IS A FAVORABLE SET-UP FOR
TRAINING PRECIPITATION ESPECIALLY ALONG THE STALLED BOUNDARY. THE
POTENTIAL FOR EMBEDDED THUNDERSTORMS ALSO INCREASES ON SATURDAY
NEAR THE COAST. IT IS VERY POSSIBLE THAT 3-6 HOUR PRECIP TOTALS
COULD BE UPWARDS OF 2.00 INCHES...ESPECIALLY IN CONVECTION. IF
THIS OCCURS ON TOP OF RAINFALL RECEIVED ON FRI/FRI NIGHT...THEN
THE POTENTIAL FOR A FLOOD WATCH BECOME INCREASINGLY LIKELY. WILL
NEED TO MONITOR TRENDS AND TOTALS FRI EVENING/OVERNIGHT TO
DETERMINE IF ADDITIONAL TOTALS ON SATURDAY WILL EXACERBATE MINOR
FLOODING POTENTIAL IN URBAN AREAS...LOW LYING AREAS...AREAS OF
POOR DRAINAGE...AND IN THE VICINITY OF SMALL STREAMS/CREEKS.
PLEASE REFER TO HYDROLOGY SECTION BELOW AND HWO FOR ADDITIONAL
DETAILS. ADDITIONAL RAINFALL AND THREAT FOR MINOR FLOODING
CONTINUES INTO SUNDAY AS OVERALL SYNOPTIC CONDITIONS REMAIN
UNCHANGED. PRECIPITATION COVERAGE STARTS TO DIMINISH FROM WEST TO
EAST ON MONDAY AS THE FRONT GETS PULLED OFFSHORE BY TROPICAL STORM
BERTHA.

HIGH TEMPERATURES WILL RUN ABOUT 5-10 DEGREES BELOW NORMAL DUE TO
PRECIP AND CLOUDY SKIES. HIGHS SAT MID-UPPER 70S...SUN AROUND 80...
MON LOW-MID 80S. LOWS WILL BE NEAR NORMAL WITH READINGS IN THE
MID 60S NW TO LOWER 70S SE.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
THE NEARLY STATIONARY FRONT AND ASSOCIATED PLUME OF ATLANTIC
MOISTURE SHOULD FINALLY NUDGE OFFSHORE MONDAY NIGHT AS A FINAL
WAVE OF LOW PRESSURE LIFTS NE ALONG THE BOUNDARY. THIS WAVE THEN
PULLS OFF THE COAST TUESDAY. 30-40% POPS WILL BE MAINTAINED OVER
SE PORTIONS IN CLOSER PROXIMITY TO THE SURFACE BOUNDARY. A BRIEF
DRY PERIOD IS EXPECTED TUESDAY NIGHT INTO EARLY WEDNESDAY AS
SHORTWAVE RIDGING PASSES OVERHEAD. A COLD FRONT THEN APPROACHES
FROM THE NW WEDNESDAY AND DROPS INTO THE AREA WEDNESDAY NIGHT.
THIS WILL BRING A CHC OF AFTERNOON/EVENING SHOWERS/TSTMS. THE
FRONT IS PROGGED TO DROP INTO NC THURSDAY. 20-30% POPS WILL BE
INCLUDED FOR SRN PORTIONS TO ACCOUNT FOR ANY UNCERTAINTY WITH
RESPECT TO THE FRONTAL LOCATION. THE FRONT SHOULD EVENTUALLY LIFT
BACK N LATER IN THE WEEK...BUT CONFIDENCE WITH RESPECT TO TIMING
AND LOCATION IS LOW...SO MINIMAL POPS WILL BE CONTINUED. HIGHS
TUESDAY SHOULD AVERAGE IN THE UPPER 80S...WITH UPPER 80S/
AROUND 90 WEDNESDAY AHEAD OF THE FRONT. HIGHS SHOULD DROP BACK
INTO THE MID/UPPER 80S THURSDAY AND FRIDAY BEHIND THE FRONT. LOW
TEMPERATURES SHOULD AVERAGE FROM THE MID 60S TO LOW 70S.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
SHOWERS WITH LIGHT/OCCASIONALLY MODERATE RAIN CONTINUE TO PUSH N
INTO THE REGION...AFFECTING ALL AKQ TAF SITES. CIGS CONTINUE TO
LOWER OVERNIGHT AND COULD SEE SEVERAL HRS WHERE THEY DROP TO 1-2
K FT OVERNIGHT...WITH KRIC/KSBY HAVING HIGHEST CHANCE FOR IFR
CIGS/ BELOW 1 KFT. SOME BRIEF EMBEDDED TSTMS POSSIBLE AS
WELL...MOST LIKELY AT KECG/KORF/KPHF...BUT PROBABILITY TOO LOW TO
INCLUDE IN TAFS.

OUTLOOK...THREAT FOR SHOWERS/TSTMS PERSIST SAT/SUN AS MOISTURE
WITH STALLED BOUNDARY ALONG/JUST INLAND FROM THE COAST. PERIODIC
FLIGHT RESTRICTIONS WILL BE POSSIBLE IN HEAVIER SHOWERS/TSTMS BOTH
DAYS. OVERALL COVERAGE OF PRECIP WILL GRADUALLY DIMINISH MON/MON
NIGHT.

&&

.MARINE...
AN INVERTED TROUGH WILL REMAIN OFF THE COAST TONIGHT AND STEADILY
DRIFT INLAND THROUGH THE WEEKEND. NO FLAGS ARE EXPECTED AS WIND
SPEEDS SHOULD REMAIN AOB 15KT (DIRECTION AVERAGING E/SE) AND
SEAS/WAVES SHOULD REMAIN BELOW 5FT/4FT. NEVERTHELESS...PERSISTENT
ONSHORE FLOW SHOULD BUILD SEAS TO AROUND 3FT...WITH OCCASIONAL 4FT
SEAS OUT NEAR 20NM. WAVES IN THE MOUTH OF THE BAY SHOULD BUILD TO
2-3FT...WITH 1-2FT ELSEWHERE IN THE BAY. THE SYSTEM PUSHES
OFFSHORE EARLY NEXT WEEK AS HIGH PRESSURE RETURNS TO THE REGION. A
COLD FRONT APPROACHES FROM THE NW DURING THE MIDDLE OF NEXT WEEK.
OVERALL SUB-SCA CONDITIONS ARE EXPECTED TO PREVAIL DURING THE
EARLY TO MIDDLE PORTION OF NEXT WEEK. HOWEVER...SOME LONG PERIOD
SWELL COULD ENCROACH THE AREA DEPENDING ON THE STRENGTH/TRACK OF
TS BERTHA. CURRENT 01/12Z WAVEWATCH GUIDANCE BRINGS 3-4FT SWELL
OUT NEAR 20NM TUESDAY/WEDNESDAY OF NEXT WEEK.

&&

.HYDROLOGY...
PERSISTENT RAINFALL ALONG A SLOW-MOVING FRONTAL BOUNDARY WILL
BRING STEADILY ACCUMULATING PRECIPITATION TO THE REGION THE REST
OF TODAY THROUGH AT LEAST MONDAY...WITH BEST ACCUMULATIONS FOCUSED
OVER NE NC AND SE VA. ACROSS THE AFOREMENTIONED SOUTHEAST AREAS...
STORM TOTAL PRECIPITATION AMOUNTS OF 2.50 TO 3.50 INCHES (LOCALLY
UP TO 4.00 INCHES) ARE ANTICIPATED OVER THE NEXT 48-72 HOURS. THIS
MAY POTENTIALLY CAUSE MINOR FLOODING OF URBAN AREAS...AREAS OF
POOR DRAINAGE...LOW LYING AREAS...AND TO RISES OF SMALL
STREAMS/CREEKS. A FLOOD WATCH MAY BE NEEDED LATER THIS EVENING OR
OVERNIGHT DEPENDING ON UPSTREAM PRECIPITATION TRENDS. WILL
CONTINUE TO HIGHLIGHT FLOODING POTENTIAL IN THE HWO (WBCHWOAKQ).

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...MODERATE RIP CURRENT RISK FROM 8 AM EDT SATURDAY THROUGH
     SATURDAY EVENING FOR MDZ025.
NC...MODERATE RIP CURRENT RISK FROM 8 AM EDT SATURDAY THROUGH
     SATURDAY EVENING FOR NCZ102.
VA...MODERATE RIP CURRENT RISK FROM 8 AM EDT SATURDAY THROUGH
     SATURDAY EVENING FOR VAZ098>100.
MARINE...NONE.

&&

$$
SYNOPSIS...BMD
NEAR TERM...SAM
SHORT TERM...BMD
LONG TERM...AJZ
AVIATION...LKB/DAP
MARINE...AJZ
HYDROLOGY...BMD





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