Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 130820
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
420 AM EDT SUN APR 13 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN ANCHORED OFF THE EAST COAST THROUGH
MONDAY. A COLD FRONT WILL GRADUALLY MOVE THROUGH THE REGION LATE
MONDAY NIGHT INTO TUESDAY...WITH HIGH PRESSURE BUILDING INTO THE
AREA FOR THE SECOND HALF OF THE WEEK.

&&

.NEAR TERM /THROUGH MONDAY/...
HIPRES IS PARKED OVER THE WRN ATLANTIC. A WARM FRONT IS LOCATED
OVER THE NORTHEAST STATES. THE MID-ATLANTIC REGION WILL BE
SITUATED DEEP INTO THE WARM/MOIST SECTOR AND IN SLY RETURN FLOW
AROUND THE HIGH. SFC DEWPOINTS HAD INCREASED INTO THE 50S OVNGT.
11-3.9U SAT AND SFC OBS AT NAK/NHK CAPTURED THE DEVELOPMENT OF
STRATUS ALONG THE WRN SHORE OF THE CHSPK. THE HRRR AND LOCAL ARW-
WRF4N MODELS HAVE HAD A DECENT HANDLE ON THE LOW CLOUDS THOUGH
APPEAR TO BE TOO AGGRESSIVE WITH LOW VSBYS AND FOG. STRATUS SHOULD
BE CONFINED TO THE WRN SHORE AND WILL MIX OUT BY MID MRNG.

YDA WAS WARM BUT FCST H8-H9 TEMPS TDA ABOUT 3C WARMER...WHICH SHOULD
TRANSLATE TO HIGHS IN THE UPPER 70S AND LOWER 80S ACROSS MUCH OF THE
REGION. A BAY BREEZE SHOULD DEVELOP THIS AFTN DUE TO A SIGNIFICANT
TEMP/DENSITY GRADIENT INLAND AND OVER THE CHSPK BAY WHERE WATERS
TEMPS ARE STILL IN THE 50S. SYNOPTIC SLY WINDS WILL BE STRONG ENOUGH
TO PREVENT THE COOL MARINE AIR FROM ADVECTING MUCH INLAND. TRIED TO
REFLECT THIS IN FCST TEMP/WIND GRIDS- HIGHS STRUGGLE TO REACH 70F
ALONG THE IMMEDIATE WRN SHORE OF MD. LOW- AND MID-LVL SUBSIDENCE
UNDER THE RIDGE WILL YIELD DRY CONDITIONS TDA.

HIPRES WILL RETREAT FURTHER OFFSHORE TNGT AS A COLD FRONT ADVANCES
EWD INTO THE MIDWEST/GREAT LAKES REGIONS TNGT. MOIST SLY WINDS 5-15
MPH WILL PERSIST AFTER SUNSET...KEEPING TEMPS MILD TNGT AND FOG
POTENTIAL LOW. FCST MIN TEMPS IN THE UPPER 50S/LOWER 60S FAVORED THE
WARMER BIAS CORRECT MET/NAM GUIDANCE. STRATUS MAY DEVELOP AGAIN NEAR
THE CHSPK BAY.

THE COLD FRONT WILL APPROACH THE WRN SIDE OF THE APPALACHIANS ON
MON. HEIGHT FALLS ALOFT AHEAD OF THE AMPLIFY CENTRAL CONUS TROUGH
WILL SPREAD EWD TOWARD THE ERN SEABOARD DURING THE DAY AND SLY LLVL
JET WILL TRANSPORT MOISTURE INTO THE REGION. HOWEVER...POPS WERE
KEPT LOW AND COVERAGE LIMITED TO THE MTS AS THE MAIN SYNOPTIC LIFT
REMAINS UPSTREAM OF THE CWA. NOT MUCH INSTABILITY PRESENT ON MON DUE
TO THE PRESENCE OF A MID-LVL CAPPING INVERSION. THE MID-LVL
SUBSIDENCE INVERSION WEAKENS LATE IN THE DAY ACROSS THE WRN
HIGHLANDS...WHERE SLIGHT CHANCE OF TSTMS WERE MENTIONED. TEMPS
EXPECTED TO REACH THE MID TO UPPER 70S ACROSS MUCH OF THE AREA
DESPITE INCREASING CLOUD COVER.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
MON NIGHT...THE 00Z/03Z ENSEMBLE MODEL GUIDANCE IN GENERALLY GOOD
AGREEMENT ON POSITION OF THE APPROACHING COLD FRONT MOVING THROUGH
THE GREAT LAKES/OHIO/TENNESSEE VALLEY EARLY IN THE PERIOD. MODELS
ARE SLOWER WITH FRONTAL PASSAGE THEN WAS ADVERTIZED YESTERDAY...SO
THE CWA WILL STILL BE IN A MILD SOUTHERLY REGIME THIS PERIOD.

TUE AND TUE NIGHT...THE COLD FRONT WILL MOVE THROUGH DURING THE
DAYTIME. STRONG COLD ADVECTION BEHIND THE FRONT WILL USHER IN MUCH
COLDER CONDITIONS. RAIN WILL DEVELOP JUST AHEAD AND ALONG THE FRONT
WITH AMOUNTS OF BETWEEN ONE HALF TO ONE INCH CWA WIDE...WITH SOME
HIGHER AMOUNTS UP TO ONE AND ONE-HALF INCH POSSIBLE IN CONVECTION.
INSTABILITY NOT HIGH OWING TO AMPLE CLOUD COVER...BUT SOME ELEVATED
CONVECTION INSTABILITY OF 100-500 J/KG...SO THUNDERSTORMS POSSIBLE.

TUE NIGHT...THERE COULD BE LINGERING POST-FRONTAL SHOWERS...AND
ALONG AND WEST OF THE BLUE RIDGE...COLD AIR ALOFT COULD MEAN SOME
SNOW MIXED IN WITH SHOWERS...BUT NOTHING APPRECIABLE EXPECTED FOR
ACCUMULATIONS. 85H TEMPS FALL TO -6C TO -10C RANGE LATE TUE NIGHT.
STRONG CAA WILL KEEP NW WINDS

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
WED...HIGH PRESSURE CENTER OVER THE OHIO VALLEY WILL MOVE EAST
AND AND BE OVER THE REGION BY THE END OF WED. TEMPERATURES ON WED
WILL BE UNSEASONABLY COOL BY A GOOD 10 TO 15 DEGF WITH BLUSTRY
WINDS TO START THE DAY...GRADUALLY DIMINISHING BY LATE AFTERNOON.

THU-FRI...HIGH PRESSURE WILL MOVE NORTHEAST AND FORM A RIDGE ALONG
THE EASTERN SEABOARD BRINGING DRY WEATHER AND NORTH TO NORTHEAST
WINDS. COOL TEMPS EXPECTED THUR...ALTHOUGH NOT QUITE AS COOL AS WED.
TEMPS MODERATE A BIT MORE ON FRI.

SAT...LOTS OF UNCERTAINTY AS WE HEAD TOWARD THE WEEKEND. RIGHT NOW
IT LOOKS DRY FOR SAT...BUT VARIOUS MODEL SOLNS ARE SHOWING LOW
PRESSURE SOMEWHERE OF THE EASTERN SEABOARD...OR GREAT LAKES...
DEPENDING ON WHAT MODEL GUIDANCE ONE LOOKS AT. FOR NOW WILL DOWNPLAY
PRECIP CHANCES AS UNCERTAINTY IS HIGH.


&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
LOW CLOUDS HAVE DEVELOPED OVNGT ALONG THE WRN SHORE OF THE MD CHSPK
BAY...RESULTING IN MVFR CIGS AT MTN. CIGS MAY LOWER TO IFR TOWARD
DAYBREAK AT MTN AND TO MVFR AT BWI. TERMINALS FARTHER WEST WILL NOT
BE IMPACTED BY ERY MRNG STRATUS. VFR TDA AND THIS EVE ACROSS ALL
TERMINALS. SLY WINDS WILL GUST AROUND 20 KT THIS AFTN.

STRATUS MAY DEVELOP ERY MON MRNG AGAIN NEAR THE BAY. VFR ON MON WITH
SLY WINDS 15-25 KT.

MON NIGHT VFR CONDITIONS INITIALLY...WITH LOWERING CIGS TO MVFR
DURING THE OVERNIGHT. ON TUE...IFR CIGS AND VSBYS IN AREAS OF RAIN
ALONG AND AHEAD OF THE FRONT...WITH BRIEF PDS OF TSTMS POSSIBLE.
FRONT MOVES THROUGH TUE AFTERNOON...WITH CONDITIONS VFR EXPECTED
LATE TUE THROUGH THE END OF THE WEEK. NW WINDS 15 TO 20 KT WITH
GUSTS TO 25 KT LATE TUE NIGHT AND WED MORNING.

&&

.MARINE...
SLY WINDS HAD DIMINISHED OVNGT TO UNDER 15 KT. WINDS WILL INCREASE
THIS AFTN AS MIXING DEEPENS. SCA IN EFFECT FOR ALL OF THE WATERS
THIS AFTN...TNGT AND NOW MON WITH SLY WINDS 20-25 KT. HOWEVER...
WINDS MAY RELAX BRIEFLY LATE TNGT OUTSIDE OF THOSE MARINE LOCATIONS
EXPOSED TO SLY CHANNELING.

SCA LEVEL WINDS ARE EXPECTED MON NIGHT THROUGH WED. NEAR GALE FORCE
WIND GUSTS POSSIBLE LATE TUE EVENING AND EARLY WED MORNING ON THE
LOWER BAY AND LOWER TIDAL POTOMAC. WINDS DIMINISH BELOW SCA LEVELS
BY LATE WED. THEN SMALL CRAFT ADVISORY LEVEL CONDITIONS ARE NOT
LIKELY AGAIN THROUGH THE END OF THE WEEK.


&&

.TIDES/COASTAL FLOODING...
NEGATIVE TIDAL ANOMALIES DECREASED LAST NGT AND ARE NOW NEAR
ASTRONOMICAL NORM AS A RESULT OF SLY FLOW. EXPECT THIS TREND TO
CONTINUE...LEADING TO POSITIVE ANOMALIES BETWEEN ONE-HALF AND ONE
FOOT BY TNGT AND MON. CBOFS KEEPS ALL WRN SHORE FCST POINTS BELOW
MINOR COASTAL FLOOD THRESHOLD THRU TNGT. WITH THE SOUTHERLY FLOW
EXPECTED TO PERSIST THRU MONDAY NIGHT AND A FULL MOON UPCOMING...
WATER LEVELS COULD APPROACH MINOR FLOOD CRITERIA AT THE MORE
SENSITIVE LOCATIONS MONDAY AND MONDAY NGT. WILL ADD MENTION TO THE
HWO.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 PM EDT MONDAY FOR
     ANZ530>543.

&&

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










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