Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 131849
AFDLWX

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

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OFF THE EAST COAST THROUGH MONDAY. A COLD
FRONT WILL MOVE THROUGH THE MID-ATLANTIC REGION LATE MONDAY NIGHT
AND TUESDAY. HIGH PRESSURE WILL BUILD INTO THE AREA FOR THE SECOND
HALF OF THE WEEK...WITH ANOTHER STORM SYSTEM APPROACHING BY NEXT
WEEKEND.

&&

.NEAR TERM /THROUGH MONDAY/...
FOR THE SECOND DAY IN A ROW...TEMPERATURES HAVE OVERACHIEVED
EXPECTATIONS. YESTERDAY IT WAS DUE TO DRY AIR MIXING DOWN. TODAY
WARM AIR ADVECTION IS HELPING YIELD THE WARMEST DAY SO FAR IN 2014
EVEN WITH MORE MOISTURE BEING ADVECTED IN ON SOUTHERLY FLOW. THIN
HIGH CLOUDS COVER THE SKY BUT THE CONVECTIVE CU WE HAD YESTERDAY
HAVE NOT BEEN ABLE TO DEVELOP YET TODAY.

THE SOUTHERLY FLOW PERSISTS TONIGHT...WITH DEWPOINTS THAT WILL STAY
STEADY OR PERHAPS EVEN RISE. WENT WITH LOWS AT OR SLIGHTLY ABOVE
GUIDANCE DUE TO EXPECTED WINDS. WE DID DECOUPLE LAST NIGHT BUT THE
INVERSION TONIGHT LOOKS LESS IMPRESSIVE AND DECOUPLING LESS LIKELY
EXCEPT PERHAPS IN THE ERN WV PANHANDLE VALLEYS AND THE I-81
CORRIDOR. COULD AGAIN SEE LOW STRATUS DEVELOP MAINLY NEAR THE BAY.

CLOUDS WILL INCREASE ON MONDAY AS THE UPPER RIDGE SHIFTS EAST AND AN
UPPER TROUGH AND RELATED ENERGY APPROACHES. WENT ABOVE GUIDANCE FOR
TEMPS YET AGAIN THOUGH CLOUD COVER WILL PLAY A HUGE ROLE. RAIN
CHANCES DO ENTER THE PICTURE MAINLY WEST OF THE BLUE RIDGE IN THE
AFTERNOON...WITH TERRAIN ENHANCING THE LIFT POTENTIAL AND THE
CONVECTIVE TEMP EASILY BEING REACHED. TEMPS WILL BE HELD DOWN AGAIN
ALONG THE BAY JUST AS THEY HAVE BEEN TODAY.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
SFC FRONT MOVES FROM THE OHIO VALLEY TO OUR DOORSTEP ON MONDAY
NIGHT. DEEP MOISTURE WILL ADVECT IN AHEAD OF THE FRONT WITH SHOWERS
AND PERHAPS TSTMS DEVELOPING. HEAVY RAIN IS POSSIBLE IN CONVECTION
THAT DEVELOPS AFTER MIDNIGHT. TEMPERATURES WILL LIKELY NOT FALL
BELOW 60 IN MOST AREAS...AND MAYBE NOT BELOW 65 IN THE METRO AREAS.

THE COLD FRONT ADVANCES THROUGH THE AREA DURING THE DAY ON TUESDAY.
THE POST-FRONTAL RAIN WILL LIKELY BE PUSHED NORTHWARD WITH TIME
GIVEN THAT IS WHERE THE UPPER SUPPORT IS HEADED. BUT THERE WILL
STILL BE PRECIP ALONG AND AHEAD OF THE FRONT LOCALLY...WITH AVERAGE
RAINFALL STILL LOOKING TO BE AROUND AN INCH WITH SOME LOCALLY HIGHER
AMOUNTS.

THE BIG STORY TUESDAY WILL BE THE CHANGE IN TEMPERATURES. IN THE
METRO AREAS...TEMPS WILL BE NEAR 70 IN THE MORNING...BUT ONLY IN THE
40S BY THE AFTERNOON RUSH. THERE WILL BE A BRIEF WINDOW FOR UPSLOPE
SNOW /THE WINTER THAT REFUSES TO END/ ALONG THE ALLEGHENY FRONT
TUESDAY AFTERNOON AND EARLY EVENING...AND I CANNOT EVEN RULE OUT A
FEW SNOWFLAKES ON THE TRAILING END OF THE PRECIP FURTHER EAST.

DRY CONDITIONS SHOULD PREVAIL BY MIDNIGHT TUESDAY NIGHT...WITH
DEWPOINTS DROPPING INTO THE TEENS. DESPITE A DECENT BREEZE...LOWS
NEAR FREEZING LOOK LIKELY NORTH AND WEST OF THE METRO AREAS WITH
WIND CHILLS IN THE LOWER 20S. COULD BE NEAR RECORD COLD. HIGH
PRESSURE QUICKLY BUILDS IN ON WEDNESDAY...LESSENING THE WINDS...BUT
HIGHS WILL ONLY BE AROUND 50.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
500 MB HEIGHT RISES ARE EXPECTED OVER THE MID-ATLANTIC REGION
WEDNESDAY NIGHT INTO THURSDAY DOWNSTREAM OF AN AMPLIFYING TROUGH
OVER THE GREAT PLAINS. AT THE SURFACE...STRONG SURFACE HIGH PRESSURE
/I.E. ABOUT 1040 MB/ WILL DRIFT EAST ACROSS THE CANADIAN MARITIME
PROVINCES. THIS SETUP WILL RESULT IN LOW-LEVEL EAST TO NORTHEAST
FLOW AND COOL AIR DAMMING AS HIGHER PRESSURES WEDGE DOWN THE EASTERN
SLOPES OF THE APPALACHIAN MOUNTAINS. GIVEN THIS PATTERN...ANOTHER
UNSEASONABLY COOL NIGHT IS EXPECTED WEDNESDAY NIGHT WITH LOW
TEMPERATURES DROPPING WELL INTO THE 30S...AND TO NEAR OR BELOW
FREEZING FOR THE WESTERN HALF OF THE FORECAST AREA.

WARM ADVECTION AT 850 MB ENSUES DURING THE DAY THURSDAY...BUT
STRUGGLES TO REACH THE SURFACE WITH PERSISTENT EASTERLY FLOW AT THE
SURFACE KEEPING HIGH TEMPERATURES IN CHECK /GENERALLY AROUND
60...SEVERAL DEGREES BELOW NORMAL/. CLOUDS WILL GRADUALLY INCREASE
THROUGH THE DAY FROM SOUTH TO NORTH AS THE TROUGH OVER THE CENTRAL
UNITED STATES SPAWNS SURFACE LOW DEVELOPMENT OVER THE LOWER
MISSISSIPPI RIVER VALLEY.

MODELS/ENSEMBLES DIVERGE ON THE HANDLING OF SHORTWAVE ENERGY
PIVOTING AROUND THE GREAT PLAINS TROUGH THURSDAY NIGHT INTO
FRIDAY...AND SUBSEQUENTLY DISAGREE WITH THE TRACK/STRENGTH OF THE
RESULTANT SURFACE LOW. STUCK WITH WPC/ENSEMBLE MEAN APPROACH...WHICH
DEPICTS A POTENTIAL FOR PRECIPITATION MOVING ACROSS THE AREA
SOMETIME BETWEEN FRIDAY NIGHT AND SUNDAY MORNING. DAYTIME HIGHS LOOK
TO STAY BELOW NORMAL LATE THIS WEEK INTO NEXT WEEKEND WITH
INCREASING CLOUDS AND POTENTIAL PRECIPITATION.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
VFR EXPECTED THROUGH MOST OF THE TAF PERIOD. CANNOT RULE OUT ANOTHER
PERIOD OF MVFR STRATUS TONIGHT. THOUGH IT IS IN THE 18Z TAF FORECAST
AT ALL TAF SITES EAST OF THE BLUE RIDGE...IT IS MOST LIKELY AT
BWI/MTN. THIS WILL BE REASSESSED WITH THE 21Z/00Z UPDATE CYCLES.
WILL CONTINUE TO BE WINDY OUT OF THE SOUTH...AROUND 15 KNOTS WITH
GUSTS OVER 20 KNOTS TODAY AND MONDAY...AROUND 10 KNOTS AT NIGHT.

LOW CIGS/VSBY EXPECTED BY LATE EVENING MONDAY AS SHRA/TSRA MOVE INTO
THE AREA. THESE LOW CIGS/VSBY WILL CONTINUE THROUGH TUESDAY WITH A
WIND SHIFT EXPECTED DURING THE DAY FROM SOUTHERLY TO NORTHERLY.
BREEZY CONDITIONS PERSIST THROUGH TUESDAY NIGHT BUT WINDS LESSEN BY
WEDNESDAY AS VFR CONDITIONS RETURN.

VFR CONDITIONS ARE EXPECTED WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
ACCOMPANIED BY EASTERLY WINDS OF 5 TO 10 KNOTS.

&&

.MARINE...
SMALL CRAFT ADVISORY NOW EXTENDED THROUGH MONDAY NIGHT. GUSTY WINDS
OVER 20 KNOTS CURRENTLY OBSERVED OVER MOST OF THE WATERS...AND THIS
WILL CONTINUE THROUGH MONDAY NIGHT. THERE WILL BE PERIODS BOTH
TONIGHT AND TOMORROW NIGHT WITH LIGHTER WINDS...ESPECIALLY ON THE
UPPER/MIDDLE TIDAL POTOMAC...BUT THE DURATION OF THE LIGHTER WINDS
APPEARS TO BE SMALL ENOUGH TO JUST BLANKET THE SMALL CRAFT ADVISORY
THROUGH THE PERIOD. THE ADVISORY WILL LIKELY HAVE TO BE EXTENDED
THROUGH TUESDAY AND TUESDAY NIGHT...AND PROBABLY EVEN WEDNESDAY.
THERE IS ALSO POTENTIAL FOR GALE FORCE GUSTS BEHIND THE FRONT
TUESDAY AFTERNOON AND NIGHT.

WINDS AND WAVES LIKELY DIMINISH TO BELOW SMALL CRAFT ADVISORY LEVELS
WEDNESDAY NIGHT AS HIGH PRESSURE MOVES OVERHEAD. MARGINAL SMALL
CRAFT ADVISORY GUSTS ARE POSSIBLE ON PARTS OF THE AREA WATERS
THURSDAY AFTERNOON AND EVENING...WITH LIGHT EASTERLY FLOW AND
SUB-SMALL CRAFT ADVISORY CONDITIONS FORECAST FOR THE END OF THE WEEK.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES HAVE NOW TURNED POSITIVE AS SOUTHERLY FLOW PERSISTS.
POSITIVE ANOMALIES WILL CONTINUE TO GRADUALLY INCREASE OVER THE NEXT
48 HOURS. ALTHOUGH CBOFS GUIDANCE KEEPS ALL WRN SHORE FCST POINTS
BELOW MINOR COASTAL FLOOD THRESHOLD...WITH THE SOUTHERLY FLOW
EXPECTED TO PERSIST THRU TUESDAY AND A FULL MOON UPCOMING...WE
BELIEVE WATER LEVELS COULD APPROACH MINOR FLOOD CRITERIA AT THE
MORE SENSITIVE LOCATIONS AROUND TIMES OF THE HIGHER HIGH TIDES
EARLY MONDAY AND EARLY TUESDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT TUESDAY FOR ANZ530>543.

&&

$$

SYNOPSIS...JE
NEAR TERM...JE
SHORT TERM...JE
LONG TERM...DFH
AVIATION...JE/DFH
MARINE...JE/DFH
TIDES/COASTAL FLOODING...JE





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