Area Forecast Discussion
Issued by NWS Sterling, VA

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887
FXUS61 KLWX 160827
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
427 AM EDT SAT MAY 16 2015

.SYNOPSIS...

HIGH PRESSURE IS OFF THE EAST COAST WHICH WILL PUMP SUMMERTIME
WEATHER OVER THE MID ATLANTIC OVER THE WEEKEND. A BACK DOOR COLD
FRONT WILL THEN SLIDE SOUTH TOWARD THE AREA SUNDAY NIGHT AND STALL
ACROSS THE AREA MONDAY BEFORE BECOMING DISSIPATING. A STRONGER
COLD FRONT WILL MOVE IN FROM THE WEST TUESDAY. COOL AND DRY HIGH
PRESSURE WILL FOLLOW FOR THE MIDDLE OF NEXT WEEK. LOW PRESSURE
WILL PASS SOUTH OF THE TOWARD THE END OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
A MIX OF LOW MID AND HIGH CLOUDS OVER VARIOUS PORTIONS OF THE
FORECAST AREA...A TRUE VARIABLY CLOUDY SKY. WILL HAVE TO WATCH
FOR ISOLATED CONVECTION IN THE EARLY MORNING HOURS NORTH AND WEST
OF I-95 TO THE MOUNTAINS. A CLUSTER IS ALREADY MOVING ACROSS S PA
AND SOME ISOLATED CELLS POPPING IN CENTRAL WV.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
SUMMERLIKE WEATHER THIS WEEKEND. SAT AND SUN WILL BE PRETTY
SIMILAR WITH SCATTERED (SE) TO NUMEROUS (NW) STORMS DURING THE
AFTERNOON FROM THE HEAT AND HUMIDITY COMING WITH THE 500MB RIDGE
AND NEAR BERMUDA HIGH AND THE SURFACE. MOS TEMPS ARE VERY
CONSISTENT FOR SAT...SUN HAD A LITTLE MORE SPREAD FOR MOS HIGHS
BETWEEN THE MODELS...BUT SHOULDNT BE MUCH DIFFERENT FROM SAT.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
SUN NIGHT...THE REMNANTS OF ANY ONGOING CONVECTION WILL DIMINISH
DURING THE EVENING AS 00Z MODELS SHOW A SHORT-WAVE LENGTH UPPER
RIDGE AXIS UPSTREAM OF THE CWA. THIS WILL CREATE NW FLOW IN THE LOW
LEVELS BELOW 85HPA THAT WILL HELP LOWER MOISTURE SOMEWHAT.

MON...A WEAK BACK DOOR FRONT IS HINTED BY THE 00Z/16 GFS MODEL
ALTHOUGH THE LATEST 00Z ECMWF IS MORE DIFFUSE WITH THIS FEATURE AND
FURTHER NORTH. CAN SEE THE FRONT IMPACTING EASTERN PORTIONS OF THE
CWA ON MON...WITH THE FRONT WASHING OUT SOMEWHERE ALONG THE I-95
CORRIDOR. MAX TEMPS ON MON WILL BE WARM AND SOUTHERLY FLOW AROUND
THE WRN ATLANTIC SURFACE HIGH BRINGS IN A SLIGHT REBOUND IN
MOISTURE. WITH BOUNDARIES APLENTY...AFTERNOON CONVECTION SHOULD
ONCE AGAIN FIRE THROUGHOUT THE CWA AND HAVE GONE WITH LIKELY POPS
FOR THE AFTERNOON. THIS FAR OUT...IT IS HARD TO PIN DOWN TIMING
AND COVERAGE OF CONVECTION...BUT IF 00Z GFS IS RIGHT...CONVECTION
WILL BE MORE NUMEROUS ACROSS THE WESTERN HALF OF THE CWA...WHILE
EASTERN HALF COULD BE UNDER INFLUENCE OF MORE STABLE MARITIME AIR
FROM THE AFOREMENTIONED BACK DOOR FRONT.

MON NGT...DEPENDING ON CONVECTIVE COVERAGE ON MON...THERE WILL
LIKELY BE CONVECTION GOING INTO THE EVENING HOURS...THEN BY MIDNIGHT
ON CHANCE POPS ACROSS THE CWA.

TUE-FRI ANOTHER VERY WARM AND HUMID DAY ON TAP FOR TUE...WITH PWAT
VALUES OF 1.75 INCHES ACROSS THE CWA. A WEAK UPPER LEVEL
DISTURBANCE WILL MOVE EAST ACROSS PENNSYLVANIA. MEANWHILE A COLD
FRONT EXTENDING SOUTHWARD FROM LOW PRESSURE OVER THE ST. LAWRENCERIVER
VALLEY WILL PASS ACROSS THE REGION DURING THE AFTERNOON. THE
COMBINATION OF THE TWO SYSTEM WILL LIKELY TRIGGER ANOTHER ROUND
OF AFTERNOON CONVECTION TUE AFTERNOON.

TUE NIGHT-WED...NW WINDS AND DRYING AS HIGH PRESSURE BUILDS INTO THE
REGION. MUCH COOLER TEMPS ON WED AS 85HPA TEMPS DROP A GOOD 4-8C.

THU-FRI...HIGH PRESSURE IS IN CONTROL EARLY THU...BUT A WAVE OF
LOW PRESSURE WILL FORM ALONG THE FRONTAL BOUNDARY ACROSS THE
SOUTHEAST. MOISTURE COULD SPREAD NORTHWARD AND POSSIBLE TRIGGER
SOME SHOWERS ACROSS SOUTHERN PORTIONS OF THE CWA ON THU...BEFORE
ANOTHER SURFACE HIGH IS DRIVEN SOUTH FROM THE GREAT LAKES INTO THE
MID ATLANTIC REGION BY FRI. &&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
WILL HAVE TO WATCH FOR MVFR FOG AT SOME OF THE TAF SITES DURING THE
EARLY MORNING THRU THE WEEKEND WITH INCREASING HUMIDITY. OTW JUST
NEED TO BE CONCERNED WITH TSRA THREAT...HIGHEST IN THE AFTERNOON.
HOWEVER STORMS ARE EXPECTED TO BE NON-SEVERE.

MON AND TUE WILL BE DOMINATED BY HIGH PRES...WITH SOME MVFR FOG
FOR CHO...MRB AND IAD DURING EARLY MORNINGS BOTH DAY. AFTERNOON
AND EVENING THREAT OF TSRA BOTH MON AND TUE. A STRONG COLD FRONT
WILL CROSS THE REGION LATE TUE...BRING DRIER AIR AND VFR
CONDITIONS FOR WED.

&&

.MARINE...
WILL HAVE TO WATCH CHANNELING FLOW IN THE BAY FOR POSS OF
EXCEEDING SMALL CRAFT GUSTS AND NEEDING AN ADVISORY TODAY. BUT AT
THIS POINT...EXPECTING BELOW CRITERIA AND GENERALLY 10 TO 15 KT
GUSTS TODAY. A LITTLE LESS EVEN ON SUNDAY.

SUN NIGHT THROUGH TUE...WINDS REMAIN BELOW SCA LEVELS. LATE TUE A
STRONG COLD FRONT WILL SWEEP ACROSS THE REGION. SCA LEVEL WIND
GUSTS ARE POSSIBLE BEHIND THE FRONT LATE TUE NIGHT AND THROUGHOUT
THE DAY ON WED.

&&

.TIDES/COASTAL FLOODING...

A SOUTHERLY FLOW WILL CONTINUE THROUGH THE WEEKEND. THIS WILL
LIKELY CAUSE ANOMALIES TO INCREASE A BIT...BUT THE WIND MAY BE
JUST WEST OF SOUTH...LIKELY KEEPING WATER LEVELS BELOW MINOR
FLOODING THRESHOLDS DURING THIS TIME.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...CAS
NEAR TERM...CAS
SHORT TERM...CAS
LONG TERM...SMZ
AVIATION...CAS/SMZ
MARINE...CAS/SMZ
TIDES/COASTAL FLOODING...BJL/CAS



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