Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 011438
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
1038 AM EDT FRI AUG 1 2014

.SYNOPSIS...
A FRONTAL BOUNDARY WILL DEVELOP ALONG THE SOUTHEAST COAST TODAY
AS HIGH PRESSURE BECOMES CENTERED WELL OFFSHORE. THE FRONT STAYS
ALONG THE COAST OR JUST INLAND OVER THE MID ATLANTIC REGION...KEEPING
UNSETTLED CONDITIONS IN PLACE THROUGH THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATE...THE COMBINATION OF ENHANCED SHORTWAVE ENERGY AND
ISENTROPIC LIFT IS ENHANCING RAINFALL RATES IN ERN NC...SOUTH OF
ALBEMARLE SOUND. THIS SWATH OF PRECIP WILL MOVE NWD INTO NE NC AND
SE VA AS THE DAY PROGRESSES WITH MODERATE TO HEAVY RAINFALL RATES
AND EMBEDDED THUNDERSTORMS. FLASH FLOOD GUIDANCE REQUIRES AROUND
3.00 INCHES OF RAIN IN ONE HOUR AND AROUND 4.00-4.50 INCHES IN A
6 HOUR PERIOD. ALTHOUGH FLASH FLOODING IS NOT ANTICIPATED IN NE
NC/SE VA (BASED ON UPSTREAM OBSERVATIONS TODAY)...IF AN EMBEDDED
THUNDERSTORM ENHANCES HOURLY RAINFALL RATES...THEN LOCALIZED FLOOD
ADVISORIES MAY BE NEEDED. WILL NEED TO SEE HOW DAYTIME HEATING
DESTABILIZES THE ATMOSPHERE ALOFT AND SUBSEQUENTLY AFFECTS PRECIP
COVERAGE AND RATES. WILL ALSO MAINTAIN POTENTIAL FOR FLOODING IN
HWO ATTM. MEANWHILE...A SECONDARY SWATH OF PRECIP IS CURRENTLY
LOCATED OVER FAR NW AND NRN COUNTIES OF THE WAKEFIELD CWA WITH A
RELATIVELY DRY AREA (OR AT LEAST VERY LIGHT SPRINKLES) OCCURRING
BTWN THE TWO MAIN AREAS OF PRECIP. AGAIN AS DAYTIME HEATING
DESTABILIZES THE ATMOSPHERE ALOFT (IN ADDITION TO ISENTROPIC
LIFT)...AM EXPECTING THIS SO-CALLED DRY AREA TO FILL BACK IN WITH
SHOWERS AND POSSIBLY EMBEDDED THUNDERSTORMS. HAVE ADJUSTED POPS TO
FOCUS ON CURRENT PRECIP AREAS AND THEN GRADUALLY
INCREASING/FILLING IN COVERAGE BY THIS AFTN. ALSO ADDED MODERATE
TO HEAVY RAINFALL WORDING. ASIDE FROM ADJUSTMENTS TO POP...THE
REST OF THE FORECAST APPEARS TO BE ON TRACK.

PREVIOUS DISCUSSION...
LATEST SFC ANALYSIS REVEALS ~1023 MB HI PRES OFF THE MID
ATLANTIC/NE CST AND AN INVERTED TROF OF LO PRES OFF THE CAROLINA
CST. THIS TROF WILL SLIDE TOWARDS THE MID ATLANTIC CST THRU THE
DAY...AND IN ASSOCIATION WITH APPROACHING MID-LEVEL ENERGY AND
INCREASING MOISTURE WILL LEAD TO RAIN LIKELY OVR MUCH OF THE AREA
(EXCEPTION IS THE LWR ERN SHORE WITH 30-50% POPS). NO SVR WX
ANTICIPATED WITH PARAMETERS NOT FAVORABLE. MAY TAKE A WHILE FOR
PRECIP TO START IN SOME AREAS WITH STILL DRY LOW LEVELS WHICH WILL
MOISTEN TOP DOWN. CLOUDS WILL CONTINUE TO STREAM INTO THE REGION
RESULTING IN MOSTLY CLOUDY TO CLOUDY SKIES. TEMPS WILL ONLY MAX
OUT IN THE UPR 70S TO MID 80S WITH THE CLOUDS AND PRECIP IN THE
AREA.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
UNSETTLED/RATHER WET PATTERN WILL DOMINATE THE FCST AREA TNGT THRU
AT LEAST SUN...AS TROF ALOFT SITS OVR THE OH/TN/MS VALLEYS WHILE A
FRNTL BOUNDARY SETS UP RIGHT ALONG THE CST OR JUST INLAND OVR THE
MID ATLC REGION. THIS SCENARIO WILL RESULT IN A MOIST SFC-ALOFT
FLO OVR THE AREA. THAT COMBINED WITH GOOD CONVERGENCE/LIFT...ESPLY
WHEN WEAK LO PRES AREAS MOVE NNE ALONG THE FRNTL BOUNDARY...WILL
PROVIDE AN IDEAL SETUP FOR PERIODS OF SHOWERS AND POSSIBLY A TSTM
ALL LOCATIONS FM THIS EVENG THRU AT LEAST SUN. SEVERE WX IS NOT
EXPECTED DURING THIS TIME PERIOD...BUT HEAVY RAIN WILL BE
POSSIBLE...ESPLY OVR ERN/SERN CNTIES...TNGT THRU SUN AS PWATS ARE
FCST TO BE BETWEEN 1.75 AND 2.25 INCHES IN THESE AREAS. WILL
HIGHLIGHT IN HWO.

PLENTY OF CLOUDS AND LIKELIHOOD OF PCPN WILL HOLD MAX TEMPS DOWN
OVR THE WEEKEND. HIGHS WILL BE MAINLY IN THE UPR 70S TO LWR
80S...WITH LOWS RANGING FM THE MID 60S TO LWR 70S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A STALLED FRONT AND ASSOCIATED PLUME OF ATLANTIC MOISTURE IS
FORECAST TO REMAIN IN VICINITY OF THE ATLANTIC COASTAL PLAIN SUNDAY
NIGHT AND MONDAY. THIS BOUNDARY WILL BE TRAPPED BETWEEN A STRONG
RIDGE OVER THE WESTERN ATLANTIC...AND A TROUGH OVER THE MIDWEST.
THERE ARE SUBTLE MODEL DIFFERENCES AMONGST MEDIUM RANGE
GUIDANCE...WHICH WILL ULTIMATELY AFFECT THE PROBABILITY OF RAIN
DURING THIS TIMEFRAME. 31/12Z GFS REMAINS THE WESTERN-MOST AND HENCE
WETTEST SOLUTION...WHILE THE 31/12Z ECMWF/CMC HAVE THE BOUNDARY
CLOSER TO THE COAST. AT THIS TIME...30-40% POPS (HIGHEST E) WILL BE
MAINTAINED SUNDAY NIGHT AND MONDAY. A COLD FRONT DROPS THROUGH THE
GREAT LAKES MONDAY NIGHT AND TUESDAY...AND THEN INTO THE OHIO VALLEY
BY MIDWEEK. THIS WILL SHOVE THE PLUME OF MOISTURE OFFSHORE...WITH
POPS GRADUALLY DIMINISHING NW-SE THROUGH MIDWEEK. HIGHS SHOULD
AVERAGE IN THE MID 80S MONDAY...AND TREND UPWARD TO THE MID/UPPER
80S TUESDAY...AND UPPER 80S TO AROUND 90 WEDNESDAY/THURSDAY. LOW
TEMPERATURES SHOULD AVERAGE IN THE UPPER 60S TO LOW 70S.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
ALTHOUGH COPIOUS AMOUNTS OF MOISTURE NOTED ON RADAR...NOT MUCH
MEASURABLE PCPN HAS FALLEN EAT OF I95 CORRIDOR OVERNIGHT. SHORT
RANGE MODELS CONTINUE TO OVERSPREAD THE PCPN N & E THRU OUT THE
DAY...BUT CONFIDENCE ONLY HIGH ENOUGH TO PUT A TEMPO IN AT RIC
FOR NEXT SVRL HRS. ADDED VCSH TO COASTAL TAF SITES AS ONLY LIGHT
RAIN XPCTD THERE.

SCT SHWRS WILL BE PSBL WITH ISLTD LATE AFTN/EVE TSTMS DVLPNG...BUT
TIMING THESE RATHER PROBLEMATIC ATTM GIVEN THE MODEL DIFFERENCES.
THUS...KEPT PCPN OUT OF FCST ATTM WITH VFR CIGS XPCTD DURING THE
DAY (CU BTWN 4-5K FT). ADDNTL MOISTURE OVERSPREADS THE FA AFTER
00Z BUT INDICATED CIGS INTO THE MVFR RANGE FOR THE LAST 6 HOURS OF
THE FCST PRD. NAM/GFS INDICATING SOME IFR CIGS WITH RAIN PSBL LATE
IN THE FCST PRD.

OUTLOOK...THREAT FOR SHOWERS/TSTMS CONTINUE INTO THE WEEKEND AS
MOISTURE CONTINUES TO INCREASE ALONG AND AHEAD OF A STALLED
COASTAL BOUNDARY. EXPECT GRADUAL INCREASE IN AREAL COVERAGE OF
SHOWERS SAT/SUN AS MOISTURE RAMPS UP. PERIODIC FLIGHT RESTRICTIONS
WILL BE POSSIBLE IN SHRAS AND TSTMS SAT AFTN AND SUN.

&&

.MARINE...
AN INVERTED TROUGH BECOMES THE DOMINANT FEATURE ALONG THE MID
ATLANTIC COAST TODAY BEFORE SHIFTING INLAND THIS WEEKEND. NO FLAGS
EXPECTED AS BOTH WINDS AND SEAS EXPECTED TO REMAIN BELOW CRITERIA.
THAT BEING SAID...A PERSISTENT SE FLOW RESULTS IN SEAS BUILDING TO
BETWEEN 2-4 FT...HIGHEST 20-40 NM OUT. WINDS BECOME S-SW BY MONDAY
AS ENTIRE SYSTM PUSHES OFFSHORE WITH HIGH PRESSURE BUILDING BACK
INTO THE REGION.

WILL GO WITH A MODERATE RIP CURRENT RISK OVER SOUTHERN BEACHES TODAY
GIVEN A E-SE SWELL AND 2 FT OR SLIGHTLY HIGHER NEARSHORE WAVES. THE
MODERATE THREAT WILL LIKELY WORK ITS WAY NORTH TONIGHT AND SATURDAY.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...MODERATE RIP CURRENT RISK UNTIL 8 PM EDT THIS EVENING FOR
     NCZ102.
VA...MODERATE RIP CURRENT RISK UNTIL 8 PM EDT THIS EVENING FOR
     VAZ098.
MARINE...NONE.

&&

$$
SYNOPSIS...MAS
NEAR TERM...BMD/MAS
SHORT TERM...MAS/TMG
LONG TERM...AJZ
AVIATION...MPR
MARINE...MPR







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