Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 122354 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 754 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/...
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SURFACE OBS AND MSAS ANALYSIS INDICATE HIGH PRESSURE HAS MOVED EAST OF THE CWA. CONTINUING WITH SLIGHT CHANCE POPS OVER WESTERN PORTIONS OF THE FORECAST AREA FOR A WHILE THIS EVENING FOR A FEW POSSIBLE SHOWERS...BUT POTENTIAL FOR THIS WILL DIMINISH AS INSTABILITY WANES THIS EVENING. TONIGHT...WEAK WARM FRONT WILL MOVE THROUGH THE CWA FROM THE SOUTH...WITH AN ASSOCIATED INCREASE IN LOW-LEVEL MOISTURE. STILL APPEARS THERE WILL BE SOME POTENTIAL FOR STRATUS DEVELOPMENT...PATCHY FOG...OR BOTH. CONFIDENCE IS NOT VERY HIGH...AS THIS WILL DEPEND ON HOW MUCH RADIATIONAL COOLING DEVELOPS WITH SOME MID-HIGH LEVEL CLOUDS. LOW TEMPS EXPECTED TO BE GENERALLY IN THE UPPER 40S TO LOW 50S OVER MOST OF THE REGION...AND THE MID 50S IN METRO BALTIMORE/WASHINGTON. 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.
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&& .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 /00Z SUNDAY THROUGH THURSDAY/...
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VFR CONDITIONS EXPECTED THIS EVENING AND MOST OF THE NIGHT. GUIDANCE CONTINUES TO INDICATE POTENTIAL FOR MVFR CIGS/VSBYS IN THE PREDAWN HOURS AS LOW LEVEL MOISTURE INCREASES. CONFIDENCE IS MODERATE...AS MOISTURE RETURN MAY NOT BE QUITE ENOUGH. LIGHT SOUTHERLY FLOW EXPECTED. VFR EXPECTED 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.
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&& .MARINE...
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SOUTHERLY FLOW HAS DEVELOPED OVER THE WATERS...WITH SOME GUSTS INTO THE TEENS. WINDS ARE EXPECTED TO DIMINISH THIS EVENING AS INVERSION OVER THE COOL WATER DEVELOPS. 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.
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&& .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...JCE NEAR TERM...JCE/KCS SHORT TERM...JCE LONG TERM...DFH AVIATION...KCS/DFH MARINE...JCE/KCS/DFH TIDES/COASTAL FLOODING...JE

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