Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 222022
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
422 PM EDT WED APR 22 2015

.SYNOPSIS...
A COLD FRONT CROSSES THE MID ATLANTIC REGION THIS AFTERNOON AND
EARLY EVENING. CANADIAN HIGH PRESSURE BUILDS INTO THE REGION FOR
THURSDAY AND FRIDAY. LOW PRESSURE APPROACHES THE REGION FROM THE
WEST ON SATURDAY...CROSSING THE REGION SATURDAY NIGHT INTO SUNDAY.
HIGH PRESSURE RETURNS EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
LATEST REGIONAL RADAR MOSAIC DEPICTS ISOLATED-SCATTERED SHOWERS
WITH EMBEDDED THUNDER STRETCHING FROM THE DELMARVA SWWD INTO THE
PIEDMONT THIS AFTERNOON. COLD FRONT CURRENTLY EXTENDING FROM NEAR
DCA TO WRN VA. LIMITED FACTOR FOR BETTER COVERAGE AND DEVELOPMENT
CONTINUES TO BE THE DRY...WELL MIXED SUBCLOUD LAYER. PER BLENDED
TOTAL PRECIP WATER...PWATS GENERALLY AROUND HALF AN INCH ACROSS
THE MID-ATLANTIC REGION. DEWPOINTS HAVE MIXED INTO THE 30S-LOW
40S. BETTER COVERAGE OF SHOWERS OBSERVED NORTH OF THE LOCAL
AREA...CLOSEST TO SHORTWAVE ENERGY TRAVERSING THE NE STATES.

COLD FRONT WILL CONTINUE TO PUSH ACROSS THE LOCAL AREA THIS
AFTERNOON THRU EARLY EVENING IN FAST WLY FLOW ALOFT. LATEST RAP
ANALYSIS DEPICTS VERY LITTLE MLCAPE OVER THE LOCAL
AREA...GENERALLY AOB 400 J/KG. HENCE ANY TSTMS ARE NOT EXPECTED
TO CONTAIN STRONG LONG-LIVED UPDRAFTS. HOWEVER...THE 700MB FLOW IS
STILL PROGGED TO BE ~60KT...AND THIS WILL BE ABOVE A WELL MIXED
CONVECTIVE BOUNDARY LAYER SO ANY TSTMS HAVE THE POTENTIAL TO
PRODUCE STRONG TO PERHAPS DAMAGING WIND GUSTS. DEEP LAYER SHEAR
WILL ALSO EXIST...WHICH MAY RESULT IN BETTER ORGANIZATION ACROSS
THE NE PORTION OF THE LOCAL AREA AS THE FRONT SWEEPS ACROSS. WILL
MAINTAIN ISOLATED-SCATTERED WORDING. SW WINDS OF 20-25 MPH WITH
GUSTS ~35 KT PERSIST AHEAD OF THE FRONT...BECOMING WLY POST
FRONTAL AND DIMINISHING.

NRN PORTION OF THE FRONT PUSHES OFF THE ERN SHORE COAST EARLY
THIS EVENING...WITH THE SRN PORTION PUSHING THRU SE VA/NE NC THRU
LATE EVENING. EXPECT ANY ISOLATED ACTIVITY ALONG THE SRN PORTION
TO DIMINISH WITH THE LOSS OF HEATING. OTHERWISE...HIGH PRESSURE
BUILDS IN FROM THE NW TONIGHT BEHIND THE COLD FRONT. SKY BECOMES
MOSTLY CLEAR AFTER MIDNIGHT...WITH OVERNIGHT LOWS RANGING FROM THE
LOW 40S NW...TO AROUND 50 SE.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
UPPER/SFC LOW PRESSURE REMAINS VIC OF NEW ENGLAND THRU THE SHORT
TERM PERIOD. CONFLUENCE OVER THE REGION WILL ALLOW WEAK HIGH
PRESSURE TO BUILD INTO THE REGION THURSDAY...REMAINING OVER THE MID-
ATLANTIC THRU FRIDAY NIGHT. ASSOCIATED AIRMASS WILL BE CANADIAN IN
ORIGIN. THE RESULT WILL BE DRY CONDITIONS/LOW DEWPOINTS...MOSTLY
CLEAR/SUNNY CONDITIONS AND BELOW NORMAL TEMPS. PER GEFS STD
ANOMALIES...H85 TEMPS WILL RANGE FROM -1 TO -2 STD DEV THURS AND
FRI. HOWEVER...BREEZY WLY/DOWNSLOPE FLOW THURS WILL HELP KEEP TEMPS
IN THE LOW-MID 60S NORTH TO UPPER 60S SOUTH. TEMPS THURS NIGHT
FORECAST TO DROP INTO THE MID-UPPER 30S INLAND AND UPPER 30S-LOW 40S
NEAR THE COAST. SHORTWAVE MOVING ACROSS THE MID-ATLANTIC THURS-THURS
NIGHT WILL RESULT IN A PARTLY CLOUDY SKY ACROSS THE N-NERN LOCAL
AREA...WHICH WILL LIKELY KEEP TEMPS SLIGHTLY WARMER. FEW LOCALS IN
THE PIEDMONT MAY BE ABLE TO DROP INTO THE LOW 30S...BUT FROST IS NOT
EXPECTED DUE TO THE DRY AIRMASS (DEWPOINTS IN THE 20S). COOLER FRI
WITH HIGHS GENERALLY IN THE LOW-MID 60S.

SFC HIGH PRESSURE SLIDES OFFSHORE SAT AS A SRN STREAM SYSTEM LIFTS
FROM THE PLAINS INTO THE MIDWEST. ASSOCIATED SFC LOW LOCATES OVER
THE MID MS VALLEY LATE SAT. MODELS IN GOOD AGREEMENT NOW WITH SFC
LOW PLACEMENT. FRONTAL BOUNDARY OVER THE GULF STATES WILL BEGIN TO
LIFT NWD IN AMPLIFYING FLOW AS MOISTURE INCREASES FROM THE GULF OF
MEX. EXPECT BEST ISENTROPIC LIFT TO COMMENCE OVER THE REGION LATE
SAT. BETTER UPPER LEVEL SUPPORT FROM THE UPPER WAVE ARRIVES SAT
NIGHT...SO ONLY EXPECT LIGHT RAIN RICHMOND SOUTH AND WEST LATE SAT.
CLOUDS ALSO INCREASE THRU THE DAY...RESULTING IN A MOSTLY CLOUDY SKY
BY SAT AFTERNOON. COOL...WITH HIGHS GENERALLY IN THE LOW 60S (-1 STD
DEV).

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
WEAKENING UPPER SHORTWAVE WILL PIVOT OFF THE CAROLINA COAST LATE
SAT, WHICH WILL ALLOW FOR SCT SHRAS TO DEVELOP ACROSS THE AREA
SATURDAY NIGHT. GREATEST COVERAGE EXPECTED ACROSS SE ZONES WHERE
W-SW FLOW WILL BRING PW VALUES AOA 1" SAT NIGHT AND EARLY SUNDAY,
SO WILL GO WITH HIGH END CHC IN THESE ZONES, 30-40% POP ACROSS THE
NORTH, WITH A NARROW WINDOW OF SOME VERY SHALLOW LIFT SAT NIGHT
SUNDAY MORNING. UPPER LOW AND PERTURBATIONS PINWHEELING AROUND IT WILL
SERVE TO FLATTEN FLOW ALOFT SUNDAY AND ERY MON, THEREBY SUPPRESSING
MOST OF THE ADDITIONAL WEAK DISTURBANCES RIDING ALONG THE
WEAK/WAVY FRONTAL BOUNDARY TO THE SOUTH. DESPITE WHAT WILL LIKELY
BE A COOL/CLOUDY DAY ON SUNDAY, WOULD EXPECT MUCH OF THE ACTIVITY
WOULD REMAIN TO THE SOUTH. GIVEN SATURATED LLVLS WILL KEEP SLIGHT
CHC POP IN PLACE EARLY IN THE DAY SUNDAY (THROUGH THE DAY SOUTH),
WITH THE EXPECTATION OF LITTLE MORE THAN SOME PATCHY DRIZZLE/FEW
SHRAS IN COOL W-NW FLOW. DID GO ABOUT A CATEGORY BELOW MOS GIVEN
THIS MOIST SETUP...HIGHS IN THE L/M60S. ERY MORNING LOWS MONDAY IN
THE 40S.

DRY AND A BIT WARMER MONDAY AS HIGH PRESSURE TO THE NORTH OF THE
REGION BUILDS A BIT FARTHER SOUTH. HIGHS 65-70. LOWS M40S-L50S.
SHOULD REMAIN DRY THROUGH MONDAY NIGHT, BUT EXPECT INCREASING SLY
FLOW/OVERRUNNING IN ASSOCIATION WITH NUMEROUS DISTURBANCES PUSHING
EAST FROM DEEP UPPER LOW THAT WILL SET UP OVER THE
CENTRAL/SOUTHERN PLAINS EARLY NEXT WEEK. THIS WILL SERVE TO KEEP
UNSETTLED, COOL CONDITIONS IN PLACE ACROSS THE LOCAL AREA THROUGH
MIDWEEK, WITH DAILY POP CHANCES IN THE SLIGHT TO LOW END CHC
RANGE TO END THE PERIOD. DAYTIME HIGHS REMAIN IN THE 60S TO NR
70, WITH EARLY MORNING LOWS IN THE 40S TO AROUND 50.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
BREEZY/WINDY S/SW WINDS THIS AFTN ACRS THE ENTIRE REGION AHEAD OF
AN APPROACHING COLD FRONT. HAVE INCLUDED GUSTS TO 30 KT AT
KRIC/KSBY...GENLY 25-30 KT ELSEWHERE THROUGH THE NEXT FEW HRS.
RADAR SHOWS A LINE OF SHOWERS ENTERING CENTRAL VA AS OF 18Z...BUT
THUS FAR UPSTREAM OBS SHOW LITTLE TO NONE OF THIS REACHING THE
GROUND DUE TO DRY AIRMASS IN PLACE. FARTHER NORTH IN MD/FAR NRN VA ALONG
THIS BROKEN LINE OF SHOWERS HAS EMBEDDED TSTMS AND PRECIP IS
REACHING THE GROUND. HAVE INCLUDE "VCTS" AT KSBY AND "VCSH" AT
KRIC AFTER 20Z...DID NOT INCLUDE THIS AT OTHER TERMINALS AS
CONFIDENCE IS QUITE LOW THAT THIS LINE WILL HOLD TOGETHER AS
SUPPORT WEAKENS FARTHER TO THE SE. MAIN IMPACTS WOULD BE ERRATIC/STRONG
GUSTY WINDS WITH MINIMAL OR VERY BRIEF LOWERING OF CIGS/VSBYS.

THIS EVENING...WINDS SHIFT TO THE W AND EVENTUALLY THE NW
OVERNIGHT IN THE WAKE OF THE COLD FRONT. GENLY EXPECT WINDS TO
DIMINISH TO 10-15 KT IN THE EVENING...BUT WITH A BRIEF INCREASE IN
WIND SPEEDS/GUSTS TO 20-25 KT LIKELY AS WIND DIRECTIONS SHIFT
FROM W TO NW BETWEEN 03-06Z. OTHERWISE DRY/VFR CONDS OVERNIGHT AND
THROUGH THE NEXT SEVERAL DAYS AS HIGH PRESSURE BUILDS IN FROM THE
WNW. WINDS REMAIN SOMEWHAT ELEVATED FROM THE W/NW THU AND FRI
AFTN. CHANCE FOR RAIN LATER SAT INTO SUNDAY.

&&

.MARINE...
LATEST OBS/BUOY REPORTS REFLECT PREFRONTAL S-SW FLOW 15-25 KT ACROSS
THE MARINE AREA THIS AFTERNOON. PRES GRADIENT BETWEEN SFC HIGH
PRESSURE TO THE SOUTH AND SFC TROUGH APPROACHING FROM THE WEST HAS
TIGHTENED ENOUGH TO ALLOW INCREASING WINDS OVER THE PAST FEW HOURS,
WITH GUSTS TO AROUND 30 KTS IN THE CENTRAL/LOWER BAY AND COASTAL
ZONES. EXPECT A POST FRONTAL (NORTH) SURGE TONIGHT, AND THUS SCA
FLAGS REMAIN IN EFFECT THROUGH LATE TONIGHT FOR THE BAY/NORTHERN
COASTAL ZONES.

WINDS VEER TO THE W-NW FOR THURSDAY/FRIDAY, WITH WINDS
DIMINISHING SUB-SCA/SEAS SUBSIDING TO 2-4FT RANGE (HIGHEST OUT 20NM)
AS HIGH PRESSURE BUILDS IN FROM THE WEST. SUB-SCA MARINE CONDITIONS
CONTINUE ON SATURDAY, WITH WEAK FLOW PERSISTING AS SFC LOW PRESSURE
DEVELOPS TO THE SOUTH AND MOVES OFFSHORE OF THE CAROLINA COAST BY
MIDDAY SUNDAY. LIGHT SLY WINDS BACK TO THE E-NE BY EARLY SUNDAY.
THERE IS A SLIGHT CHC THAT WINDS COULD INCREASE TO LOW END SCA
ACROSS SOUTHERN ZONES BY SUNDAY MORNING, BUT EXPECT PREDOMINATE SUB-
SCA CONDITIONS THROUGHOUT THIS PERIOD. FOR THAT REASON, HAVE
FOLLOWED CLOSELY TO WAVEWATCH TROUGH THE WEEKEND.

&&

.FIRE WEATHER...
A COOL AND DRY AIRMASS WILL SPREAD OVER THE REGION THURS AND FRI AS
CANADIAN HIGH PRESSURE BUILDS IN FROM THE WEST. MINIMUM RH VALUES
ARE FORECAST TO RANGE FROM 20-30 PCT BOTH THURS AND FRI. A WEST WIND
IS EXPECTED TO AVERAGE 10-15 MPH WITH GUSTS TO 20-25 MPH
THURS...DIMINISHING TO AROUND 10 MPH WITH GUSTS TO 20 FRI. GOOD
OVERNIGHT RECOVERY IS EXPECTED WITH OVERNIGHT RH VALUES BTWN 65-75
PCT. WHILE DRY/BREEZY CONDITIONS ARE EXPECTED...RECENT RAINFALL AND
GREEN-UP WILL BE THE PRIMARY LIMITING FACTORS WITH RESPECT TO FIRE
WEATHER CONCERNS.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR ANZ633-
     635>638-656-658.
     SMALL CRAFT ADVISORY UNTIL 7 AM EDT THURSDAY FOR ANZ630>632-
     634.
     SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ650-
     652-654.

&&

$$
SYNOPSIS...AJZ/SAM
NEAR TERM...AJZ/SAM
SHORT TERM...AJZ/SAM
LONG TERM...MAM
AVIATION...LKB
MARINE...MAM
FIRE WEATHER...


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