Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 201857 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 257 PM EDT SUN APR 20 2014 .SYNOPSIS...
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HIGH PRESSURE OVER QUEBEC WILL BUILD INTO THE AREA TONIGHT AND MONDAY. A COLD FRONT WILL MOVE THROUGH THE AREA TUESDAY AND TUESDAY EVENING. HIGH PRESSURE BUILDS BACK IN FOR THE SECOND HALF OF THE WORK WEEK.
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&& .NEAR TERM /THROUGH MONDAY NIGHT/...
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SURFACE HI HAS MOVED SOUTH OF LONG ISLAND AND WILL WEAKEN AND PUSH INTO THE MID ATLANTIC OVERNIGHT. ABUNDANT SUNSHINE IN PLACE WITH TEMPERATURES IN THE 50/S HIGHLANDS TO THE 60/S METRO AREAS. EAST TO NORTHEAST PRESSURE GRADIENT WINDS AND DEW POINTS IN THE 30/S MAKE FOR A CHILLY BREEZE ESPECIALLY ONCE THE SUN SETS. WINDS WILL DECOUPLE OVERNIGHT AND GOOD RADIATIONAL COOLING IS EXPECTED. GIVEN WHERE CURRENT DEW POINTS AND GOOD MIXING UNTIL LATER TONIGHT...WE DO NOT EXPECT A WIDESPREAD FROST TONIGHT AS MANY AREAS WILL REMAIN IN THE LOWER TO MID 30/S. SHELTERED AREAS COULD HAVE SOME FROST OVERNIGHT. BY MONDAY AFTERNOON AND NIGHT SURFACE LOW PRESSURE MOVES INTO THE GREAT LAKE STATES AND A COLD FRONT BEGINS TO APPROACH THE AREA. MODELS KEEP SUNSHINE IN PLACE FOR MOST OF TOMORROW BEFORE HI CLOUDS INCREASE LATE IN THE DAY AND NIGHT. LIGHT SOUTHERLY WINDS DEVELOP BUT DRY AIR REMAINS IN PLACE FOR MUCH OF THE DAY. WOULD EXPECT TEMPERATURES TO BE A BIT WARMER WITH HIGHS IN THE UPPER 50/S TO UPPER 60/S...AND IT WILL FEEL MILDER WITH LESS WIND. MIN TEMPS MON NGT IN THE MID 40S TO LOWER 50S.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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SUB-1000 MB SFC LOW TRACKS EWD ACROSS UPSTATE NY AND NRN NEW ENGLAND ON TUE. ATTENDANT COLD FRONT OVER THE OH VLY IS EXPECTED TO CROSS THE APPALACHIANS BY ABOUT 18Z TUE BEFORE MOVING EWD THRU THE CWA BETWEEN APPROX 18Z TUE AND 00Z WED. THE BEST FORCING LOOKS TO STAY NORTH OF CWA AND CLOSER TO TO SFC LOW AND UPPER SHORTWAVE TROUGH. PREVIOUS FCST HAD LIKELY POPS WITH FROPA. DID NOT WANT TO INCREASE POPS FURTHER DUE TO THE LIMITED FORCING AND PROGRESSIVE NATURE WITH THIS SYSTEM. THUNDER A POSSIBILITY WITH TIMING OF FROPA COINCIDENT WITH PEAK HEATING. WEAK MID-LVL LAPSE RATES AND INCREASING CLOUD COVER AHEAD OF THE FRONT DURING THE MRNG SHOULD LIMIT DEGREE OF DESTABILIZATION. FCST MEAN MLCAPE VALUES FROM THE 09Z SREF ARE UNDER 500 J/KG FOR THE ENTIRE CWA AND MLCAPE PROBABILITIES AOA 500 J/KG ARE LOW...JUST TWO INDICATIONS OF A VERY LIMITED TSTM POTENTIAL. EVEN WITH CLOUD COVER...MAX TEMPS IN THE 70S AHEAD OF THE FRONT. THE COLD FRONT MOVES OFF THE DELMARVA COAST TUE NGT WHILE HIPRES BUILDS IN FROM CENTRAL CANADA. A STRONG PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS WILL PRODUCE BREEZY NW WINDS TUE NGT AND CONTINUING INTO WED. 12Z NAM/GFS BUFKIT PROFILES SHOW A POTENTIAL FOR WIND GUSTS OF 30-35 MPH TO MIX DOWN THE SFC ON WED. MAX TEMPS A FEW DEGREES BELOW NORMAL ON WED OWING TO THE CAA IN WAKE OF FROPA.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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SURFACE HIGH BUILDING ACROSS AREA WEDNESDAY NIGHT. TEMPERATURES MAY DROP 5 DEGREES BELOW NORMAL BEFORE REBOUNDING THROUGH THURSDAY NIGHT. HIGH PRESSURE MOVING OFFSHORE FRIDAY EVENING AND NIGHT AS COLD FRONT FROM CENTRAL PLAINS TRACK EAST ACROSS GREAT LAKES/OHIO VALLEY. MARGINALLY SUPPORT FOR PRECIPITATION WITH THE FRONT AS MAIN AREA PVA IS NORTH OF AREA. INCREASED CHANCES OF PRECIPITATION SATURDAY MORNING WHEN A SECOND FRONT SUPPORTED BY STRONG PVA ENTERS THE AREA FROM THE NORTH.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/...
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VFR SKC-SCT/BKN250 THRU MONDAY AFTERNOON AT THE TERMINALS. EAST SURFACE WINDS 10-15KT WILL SUBSIDE AT SUNSET THIS EVENING THEN SHIFT TO THE SOUTH BUT LESS THAN 10KT MONDAY. INCREASING HI CLOUDS LATE MONDAY. A COLD FRONT IS ANTICIPATED TO MOVE THRU THE TERMINALS FROM WEST TO EAST BETWEEN 18Z TUE AND 00Z WED. SHRA LIKELY AND ISO TSRA DURING THE AFTN WITH FROPA. BRIEF/LOCAL RESTRICTIONS POSSIBLE WITH HEAVIER SHRA OR TSRA. SLY WINDS AROUND 10 KT AHEAD OF THE FRONT WILL BECOME NWLY 10-15 KT FOLLOWING FROPA. WIND GUSTS UP TO 30 KT POSSIBLE ON WED AS HIPRES BUILDS IN FROM THE NW. VFR WITH HIPRES OVERHEAD WED NGT THRU FRI.
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&& .MARINE...
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SCA CONDITIONS IN PLACE FROM MIDDLE AND LOWER TIDAL POTOMAC TO PORTIONS OF THE BAY AS HIGH PRESSURE BUILDS OVER THE WATERS. WINDS WILL DECREASE TONIGHT THOUGH NE GUSTS TO 15 KT POSSIBLE SOUTHERN WATERS UNTIL MIDNIGHT OR SO. WINDS WILL BE LIGHTER FROM THE SOUTH DURING THE DAY MONDAY. SLY FLOW AHEAD OF A COLD FRONT GENERALLY 10 KT ON TUE. THERE IS A LIMITED POTENTIAL HOWEVER FOR WINDS TO REACH SCA CRITERIA IN THE MAIN STEM OF THE CHSPK BAY DUE TO SLY CHANNELING. CAPPED WINDS AT 15 KT IN THESE ZONES FOR NOW WITH SUCH A MARGINAL WIND FIELD. SHRA AND POSSIBLY AN ISO TSTMS WITH THE FROPA LATE TUE AFTN AND EVE. NW WINDS BEHIND THE FRONT WILL BECOME GUSTY AS HIPRES BUILDS IN FROM THE NW. SCA LIKELY TUE NGT AND WED. WINDS BELOW SCA LVLS BY WED NGT AS HIPRES BUILDS OVERHEAD.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ531>534-536-537-541>543.
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&& $$ SYNOPSIS...JRK/SDG NEAR TERM...SDG SHORT TERM...JRK LONG TERM...CEM AVIATION...SDG/JRK/CEM MARINE...SDG/JRK/CEM

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