Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 121830
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
230 PM EDT SAT APR 12 2014

.SYNOPSIS...
A WARM FRONT WILL LIFT NORTHWARD ACROSS THE AREA TONIGHT. 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 SUNDAY/...
DRY AIR ALOFT HAS MIXED DOWN TO THE SFC THIS AFTERNOON...HELPING
TEMPERATURES OVERACHIEVE A BIT AS DEWPOINTS HAVE DROPPED INTO THE
20S AND 30S. CONVECTIVE CU HAS DEVELOPED IN THE SW PORTIONS OF THE
CWA WHERE SFC MOISTURE STILL EXISTS. THERE ARE NOT YET RADAR ECHOES
IN THIS REGION...BUT HI-RES MODELS STILL INDICATE THE POTENTIAL FOR
-SHRA DEVELOPMENT BETWEEN 22Z AND 02Z...AND THIS CONTINUES TO BE
REFLECTED IN THE GRIDS.

TONIGHT...SFC MOISTURE WILL BE ON THE INCREASE AS A WARM FRONT MOVES
NORTHWARD AND LOW-LEVEL MOISTURE SURGES. MODELS HAVE BACKED OFF THE
DEEP LOW-LEVEL MOISTURE SOMEWHAT...BUT STILL APPEARS THERE WILL BE
SOME POTENTIAL FOR STRATUS DEVELOPMENT...PATCHY FOG...OR BOTH. HAVE
REFLECTED THESE IN THE GRIDS AND TAFS OVERNIGHT. GIVEN THE POTENTIAL
FOR CLOUD COVER AND WINDS STAYING UP...HAVE GONE A BIT ABOVE
GUIDANCE...BUT NOT AS HIGH AS I MIGHT HAVE GIVEN THE CURRENTLY LOW
DEWPOINTS.

SUNDAY APPEARS TO BE A FANTASTIC...IF NOT SOMEWHAT HUMID...DAY.
EARLY STRATUS WILL GIVE WAY TO SCATTERED DIURNAL CUMULUS CLOUDS. THE
DEEP SOUTHERLY FLOW WILL YIELD HIGHS AROUND 80...BUT WITH
DEWPOINTS IN THE MIDDLE IF NOT UPPER 50S. WINDS WILL BE GUSTY IN
THE AFTERNOON...WITH WIND GUSTS NEAR 30 MPH POSSIBLE.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
SOUTHERLY FLOW PERSISTS SUNDAY NIGHT. SOME LOW CLOUD DEVELOPMENT IS
POSSIBLE BUT DECOUPLING WILL NOT OCCUR. GIVEN PERSISTENT LOW-LEVEL
MOISTURE AND THE WIND...LOWS MAY HAVE A DIFFICULT TIME DROPPING MUCH
BELOW 60 EAST OF THE BLUE RIDGE. DEEPER MOISTURE APPROACHES BY LATE
MONDAY AS A COLD FRONT ORGANIZES SLOWLY PUSHES ACROSS THE EASTERN
GREAT LAKES AND OHIO VALLEY. WHILE I AM NOT PARTICULARLY CONVINCED
ABOUT CONVECTIVE POTENTIAL WELL AHEAD OF THE FRONT ON MONDAY...AS
THE DEEPER MOISTURE ARRIVES LATE IN THE DAY...COMBINED WITH SOME
TERRAIN LIFT...MOUNTAIN -SHRA WILL BE POSSIBLE...MAYBE EVEN A TSTM.
CLOUDS SPREADING NORTHWARD AHEAD OF THE SYSTEM WILL HOLD HIGHS DOWN
JUST A BIT COMPARED TO SUNDAY...BUT STILL WELL ABOVE NORMAL.

PRECIPITATION SPREADS FURTHER EAST MONDAY NIGHT AS THE FRONT
APPROACHES. STILL SOME UNCERTAINTY WHETHER THERE WILL EVEN BE MUCH
PRE-FRONTAL PRECIP...SO POPS WERE KEPT BELOW CATEGORICAL ON MONDAY
NIGHT IN ALMOST ALL AREAS. A TSTM CANNOT BE RULED OUT AT ANY TIME
DURING THE NIGHT. THE BEST CHANCE OF RAIN APPEARS TO BE TUESDAY
MORNING /THOUGH THAT TIMING IS NOT YET A LOCK/ AS THE FRONT PUSHES
THROUGH. RAIN COULD BE HEAVY TUESDAY MORNING WITH PWATS AROUND 1.5
INCHES...BUT THE SYSTEM IS PROGRESSIVE OVERALL...WHICH WILL LIMIT A
FLOOD THREAT. AVERAGE RAINFALL LOOKS TO BE AROUND AN INCH.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A STRONG PUSH OF COLD AIR...WITH 850 MB TEMPERATURES AT OR BELOW 0 C
WILL MOVE INTO THE REGION BEHIND A DEPARTING COLD FRONT TUESDAY
EVENING. SNOW SHOWERS COULD MIX WITH ANY LINGERING PRECIPITATION
GENERALLY AT ELEVATIONS AT OR ABOVE 1500 FEET. LOW TEMPERATURES WILL
BE WELL BELOW NORMAL...GENERALLY IN THE 30S AREA-WIDE.

A WAVE OF LOW PRESSURE WILL DEVELOP ALONG THE FRONT AND MOVE NORTH
ALONG THE EASTERN SEABOARD DURING THE DAY WEDNESDAY.
MODELS/ENSEMBLES DIFFER ON HOW FAR EAST THE FRONT GETS BY THE TIME
LOW PRESSURE APPROACHES FROM THE SOUTH. THE 00Z DETERMINISTIC ECMWF
IS SLOWEST AND FURTHEST WEST WITH THE FRONT AND WAVE OF LOW
PRESSURE...WITH THE 12Z GFS FURTHER EAST. FOR NOW HAVE CHANCE POPS
ACROSS THE VA PIEDMONT AND I-95 CORRIDOR ON EAST WHERE HIGHEST
CHANCE OF RAIN WOULD BE.

HIGH PRESSURE WILL MOVE ACROSS THE AREA WEDNESDAY NIGHT THROUGH
THURSDAY WITH DRY WEATHER AND BELOW NORMAL TEMPERATURES EXPECTED.
ANOTHER STORM SYSTEM MAY APPROACH THE AREA TOWARDS THE END OF NEXT
WEEK...BUT TRACK AND TIMING DETAILS ARE FAR FROM CERTAIN AT THIS
JUNCTURE.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
THERE IS SOME POTENTIAL FOR LOW STRATUS AND/OR PATCHY FOG TONIGHT.
BOTH ARE HINTED AT IN THE TAFS WITH MVFR CIGS/VSBY BUT DID NOT GO
LOWER THAN THAT FOR EITHER AT THIS TIME. OTHERWISE...VFR EXPECTED
THROUGH SUNDAY. WINDS WILL BECOME GUSTY BY SUNDAY AFTERNOON...AND
REMAIN FAIRLY BREEZY/GUSTY THROUGH TUESDAY. LOWER CIGS/VSBY
POSSIBLE IN -SHRA MONDAY NIGHT AND TUESDAY. TSRA ARE POSSIBLE AS
WELL.

SUB-VFR STILL POSSIBLE IN SHOWERS TUESDAY NIGHT...POSSIBLY
PERSISTING INTO WEDNESDAY ESPECIALLY FOR SOUTHERN AND EASTERN
TERMINALS /I.E. BWI-DCA-CHO SOUTH AND EAST/. NORTHERLY FLOW AROUND
10 KNOTS.

&&

.MARINE...
GENERALLY LIGHT WINDS OVERNIGHT. SOUTHERLY FLOW INCREASES ON
SUNDAY...AND A SMALL CRAFT ADVISORY IS IN EFFECT. THAT ADVISORY HAS
BEEN EXTENDED THROUGH SUNDAY NIGHT...AND LIKELY WILL HAVE TO BE
EXTENDED BEYOND THAT THROUGH THE FIRST PART OF NEXT WEEK AS THE
SOUTHERLY FLOW PERSISTS.

GUSTY NORTHERLY FLOW BEHIND DEPARTING COLD FRONT/WAVE OF LOW
PRESSURE COULD RESULT IN SCA LEVEL GUSTS ON PARTS OF THE WATERS
WEDNESDAY. HIGH PRESSURE NEAR THE AREA SHOULD THEN PRECLUDE SCA
CONDITIONS THROUGH THURSDAY.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES ARE CURRENTLY BETWEEN 0.5 AND 1.0 FOOT BELOW
NORMAL...BUT AS SOUTHERLY FLOW COMMENCES...THE ANOMALIES WILL
GRADUALLY TURN POSITIVE. WITH THE SOUTHERLY FLOW EXPECTED TO
PERSIST THROUGH MONDAY NIGHT...WATER LEVELS COULD APPROACH MINOR
FLOOD CRITERIA AT THE MORE SENSITIVE LOCATIONS BY MONDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON SUNDAY TO 6 AM EDT MONDAY 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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