Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 220153
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
953 PM EDT THU AUG 21 2014

.SYNOPSIS...
A FRONTAL BOUNDARY REMAINS NEARLY STATIONARY ACROSS THE AREA INTO
THE UPCOMING WEEKEND. HIGH PRESSURE FROM NEW ENGLAND IS SLOW TO
BUILD OVER THE REGION FROM SUNDAY INTO EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
UPDATE THIS EVENING TO MAKE MINOR TWEAK TO TIMING AND LONATION
OVERNIGHT POPS. MORE WIDESPREAD SHOWERS BREAKING OUT ACROSS
CENTRAL VA ARE IN RESPONSE TO THE SHORTWAVE JUST MOVING INTO THE
REGION FROM THE NW. THE RAP IS HANDLING THIS FEATURE AND FORCING
VERY WELL. EXPECT THE PRECIP TO CONTINUE TO EXPAND SOMEWHAT IN
COVERAGE AND SPREAD EAST ACROSS CENTRAL VA AND THEN THE COAST
INCLUDING MD...EASTERN SHORE AND SOUTHEAST VA. THUNDER ACTIVITY
WITH THIS SHOULD BE LIMITED THOUGH CANNOT RULE OUT A FEW RUMBLES
ESPECIALLY ACROSS NORTH CENTRAL VA...MD AND THE EASTERN SHORE.
OVERALL TEMP FORECASTS REMAIN ON TRACK.


PREVIOUS DISCUSSION...
THE CURRENT SURFACE ANALYSIS INDICATES WEAK BROAD LOW PRESSURE IN
VICINITY OF THE GREAT LAKES WITH A BOUNDARY EXTENDING SOUTHWARD FROM
E-CENTRAL PA THROUGH THE WESTERN SHORE OF THE CHESAPEAKE BAY.
THUNDERSTORMS HAVE DEVELOPED ALONG THE BOUNDARY OVER PA AHEAD OF A
~100KT UPPER JET DIVING ACROSS THE ERN GREAT LAKES. SPC MESOANALYSIS
INDICATES 35-40KT OF EFFECTIVE SHEAR FROM SE PA THROUGH THE LOWER MD
ERN SHORE ALONG WITH AN AXIS OF 1500J/KG OF MLCAPE. THUNDERSTORM
COVERAGE IS EXPECTED TO INCREASE OVER THE ERN SHORE LATER THIS
AFTERNOON INTO THE EVENING HOURS AS THE JET DIVES SE. A FEW STRONGER
STORMS ARE POSSIBLE BASED ON FAVORABLE DYNAMIC AND THERMODYNAMIC
PARAMETERS...WITH THE PRIMARY THREAT BEING STRONG WIND GUSTS. THE
MAIN LIMITING FACTOR WILL BE RATHER WEAK LAPSE RATES. OTHERWISE...A
CHC (30-40%) OF GENERAL THUNDER IS EXPECTED OVERNIGHT AS THE UPPER
JET ENERGY PASSES OVER THE AREA AND THE SURFACE BOUNDARY REMAINS IN
PLACE. LESS FOG IS EXPECTED DUE TO THE PRESENCE OF MID/UPPER LEVEL
CLOUD COVER. OVERNIGHT LOWS SHOULD RANGE FROM THE UPPER 60S TO LOW
70S.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
MID/UPPER NW FLOW REMAINS OVER THE REGION FRIDAY INTO THE WEEKEND. A
MORE VIGOROUS WAVE DROPS THROUGH THE FLOW ACROSS THE AREA FRIDAY
NIGHT. THIS WILL PROVIDE BEST CHC OF AND GREATEST AREAL COVERAGE OF
SHOWERS/TSTMS ACROSS THE LOCAL AREA DURING THE SHORT-TERM PERIOD DUE
TO MORE FAVORABLE/STRONGER UPPER JET SUPPORT. POCKETS OF MODERATE TO
HEAVY RAIN ARE POSSIBLE GIVEN MODEST MOISTURE AND FAVORABLE UPPER
SUPPORT. HIGH PRESSURE BUILDS OVER NEW ENGLAND SATURDAY AND SLOWLY
PUSHES INTO THE REGION BY SUNDAY. THIS WILL PUSH THE REMNANT FRONT S
OF THE AREA. CHC POPS WILL CONTINUE EARLY SATURDAY...WITH A STEADY
DRYING TREND COMMENCING SATURDAY AFTERNOON FROM NNE-SSW AS THE HIGH
BUILDS INTO THE REGION.

HIGHS FRIDAY SHOULD BE MAINLY 85-90...AND THEN FROM THE LOW TO MID
80S SATURDAY (UPPER 70S ALONG THE ATLANTIC BEACHES)...WITH UPPER 70S
TO LOW 80S SUNDAY. LOWS SHOULD BE IN THE UPPER 60S TO LOW 70S
SATURDAY...AND IN THE 60S SUNDAY MORNING.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
EXTENDED FORECAST PERIOD WILL CONSIST OF MAINLY NE FLOW AS HIGH
PRESSURE TO THE NORTH RIDGES SOUTH WHILE AN AREA OF LOW PRESSURE
EMERGES FROM THE BAHAMAS. THIS PATTERN WILL MAINTAIN A COOLER
MARITIME AIRMASS IN PLACE OVER THE AREA THROUGH WED BEFORE HIGH
PRESSURE AT THE SURFACE AND ALOFT BEGIN TO CENTER THEMSELVES OVER
THE FA. AT THIS POINT SUBSIDENCE WILL PREVAIL AND WILL HELP TO DRY
THE ATMOSPHERE. PRECIP ALONG THE VA/NC COAST CAN NOT BE COMPLETELY
RULED OUT DUE TO THE INFLUX OF MOISTURE NORTH AS THE SURFACE LOW
FORMS TO THE SOUTH. THERE IS SOME MODEL DISCREPANCY IN REGARDS TO
THE POSITION AND STRENGTH OF THE LOW OVER THE TROPICAL ATLANTIC. AND
DUE TO THE LARGE DEGREE OF CHANGE IN MODEL RUNS...AT THIS POINT...
WILL NOT MODIFY THE PREVIOUS FORECAST TOO MUCH.

TEMPS WILL REMAIN BELOW AVERAGE FOR MUCH OF THE EXTENDED PERIOD
WITH HIGHS AROUND 80 MON AND TUES...WARMING SLIGHTLY INTO THE MID 80S
WED AND THUR. SEASONAL LOW TEMPS IN THE LOW TO MID 60S ARE LIKELY
AS THE MARITIME AIRMASS WILL LIMIT SIGNIFICANT OVERNIGHT COOLING.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
AS OF 23Z...A WARM FRONT EXTENDED FROM NEAR WASHINGTON DC THROUGH
EASTERN VIRGINIA (BETWEEN RICHMOND AND HAMPTON ROADS) AND INTO
EASTERN NORTH CAROLINA. WINDS WERE MAINLY FROM THE W/SW WEST OF THE
BOUNDARY AND FROM THE E/SE TO THE EAST OF IT. THIS FRONT WILL MOVE
TOWARD THE COAST OVERNIGHT. LOW PRESSURE MAY DEVELOP JUST OFF THE
COAST FRIDAY WHICH WOULD HELP SHIFT THE WINDS BRIEFLY TO NW/N DURING
THE DAY.

WIDELY SCT TSTMS WERE OVER THE MID ATLANTIC STATES BUT NONE WERE A
THEREAT TO THE TAF SITES. A BAND OF LIGHT RAIN MAY AFFECT SOME
LOCATIONS LATER THIS EVENING. SBY HAS A T/TD SPREAD OF AROUND 5
DEGREES AND WITH RAIN HAVING FALLEN LATE THURSDAY...THERE MAY BE
SOME MVFR/IFR FOG THERE. AN OVERCAST HIGH CEILING SHOULD LIMIT FOG
FORMATION AT ALL LOCATIONS AND PRESENTLY NONE IS FORECAST AT THE
OTHER TAF SITES.

FRIDAY SHOULD BE A DRY AT THE BEGINNING BUT AN UPPER LEVEL SHORT
WAVE MAY BRING A ROUND OF TSTMS LATE IN THE DAY OR FRIDAY NIGHT.

OUTLOOK...THUNDERSTORM CHANCES CONTINUE INTO SATURDAY WITH DRY
WEATHER FORECAST BEGINNING SUNDAY. MVFR/IFR DUE TO STRATUS OR FOG
WILL BE A POTENTIAL A FEW HOURS AROUND SUNRISE THROUGH SUNDAY
MORNING.

&&

.MARINE...
LOW PRESSURE FORMS ALONG A STATIONARY BOUNDARY THAT IS CURRENTLY
POSITIONED OVER THE EASTERN PORTIONS OF THE FORECAST AREA OVERNIGHT.
THIS WEAK AREA OF LOW PRESSURE WILL MOVE OFF THE COAST FRIDAY AFTN.
EARLY SAT MORNING...HIGH PRESSURE NOSES SOUTH FROM THE NORTHEASTERN
US CAUSING A BACKDOOR COLD FRONT TO MOVE THROUGH THE AREA. ENERGY
STREAMING SE WILL HELP FORM AN AREA OF LOW PRESSURE OFF THE CAROLINA
COAST. THIS SYNOPTIC SETUP WILL ENHANCE THE PRESSURE GRADIENT ACROSS
THE WATERS CAUSING NEAR SCA WIND GUST OVER THE BAY(18-20KT) AND THE
COASTAL WATERS(23-25KT) ON SATURDAY. DUE TO THE WIND DIRECTION AND
FETCH...EXPECT WAVES TO BUILD TO 4-6FT ACROSS MOST OF THE COASTAL
WATERS LASTING EARLY SATURDAY THROUGH MONDAY NIGHT. HIGH PRESSURE
BEGINS TO POSITION OVER THE AREA BY TUESDAY BUT LOW PRESSURE
EMERGING FROM THE SOUTH MAY HELP TO MAINTAIN THE PRESSURE GRADIENT
AND ONSHORE FLOW THROUGH WED.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...MODERATE RIP CURRENT RISK FROM 8 AM EDT FRIDAY THROUGH FRIDAY
     EVENING FOR MDZ025.
NC...NONE.
VA...MODERATE RIP CURRENT RISK FROM 8 AM EDT FRIDAY THROUGH FRIDAY
     EVENING FOR VAZ099.
MARINE...NONE.

&&

$$
SYNOPSIS...AJZ/ALB
NEAR TERM...AJZ/JAO
SHORT TERM...AJZ/ALB
LONG TERM...DAP
AVIATION...LSA
MARINE...DAP






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