Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 161410 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1010 AM EDT THU APR 16 2015 .SYNOPSIS...
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HIGH PRESSURE OVER MAINE IS NOSING DOWN THE EAST COAST. A DISTURBANCE WILL MOVE INTO THE AREA TONIGHT AND FRIDAY. HIGH PRESSURE WILL RETURN FOR SATURDAY. LOW PRESSURE PUSHING INTO THE GREAT LAKES WILL LIFT A WARM FRONT THROUGH MONDAY...WITH THE ASSOCIATED COLD FRONTAL PASSAGE TUESDAY MORNING. HIGH PRESSURE RETURNS IN THE WAKE.
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&& .NEAR TERM /THROUGH FRIDAY/...
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HIGH PRESSURE CENTERED OVER ME IS WEDGING DOWN THE ERN SEABOARD INTO THE MID-ATLANTIC. MOISTURE IS FLOWING ARND THE BOTTOM OF THE HIGH INTO NC AND INTO THE APLCHNS...CREATING RW ALONG THE SRN AND WRN FRINGES OF THE FCST AREA. IT IS INTERESTING TO LOOK AT THE DIFFERENCE BTWN THE IAD AND RNK SNDGS - OURS IS VERY DRY IN THE LO LVLS WHILE RNK`S IS MOIST. HIGH PRESSURE WILL BREAK DOWN LATE TONIGHT. WAA ALONG W/ THE UPPER LEVEL TROUGH ACROSS THE TN AND OHIO VALLEY WILL SPREAD INTO THE MID-ATLANTIC THROUGH FRIDAY MORNING. RAIN SHOULD MOVE INTO THE POTOMAC HIGHLANDS AND NORTH-CENTRAL MARYLAND BEFORE THE TROUGH PULLS TO THE NORTH FRIDAY MORNING. UNCERTAINTY EXISTS FURTHER SOUTH AND EAST INCLUDING THE I-95 CORRIDOR AS RAIN MAY PULL NORTH BEFORE REACHING THESE AREAS. FCST MIN T IN THE MID TO UPPER 40S WEST OF THE BLUE RIDGE TO THE LOW TO MID 50S ACROSS I-95. THE TROUGH AXIS SWINGS THROUGH THE REGION FRIDAY MORNING AND DRY...COLD AIR WILL FILTER IN ALOFT. A TROUGH AXIS WILL MOVE THROUGH THE REGION FRIDAY AFTERNOON...AND CLOUDS WILL BEGIN TO DISSIPATE ACROSS THE SHENANDOAH VALLEY. MIXING IN THE LOW LEVELS AND STEEPENING LAPSE RATES WILL PRODUCE A FEW HUNDRED J/KG OF CAPE FRIDAY AFTERNOON. A LINE OF CONVECTIVE SHOWERS MAY FORM EARLY FRIDAY AFTERNOON AND MOVE SOUTHWARD BY EVENING. CAN`T RULE OUT A ROGUE TSTM ACROSS THE PIEDMONT OR SOUTHERN MD. TEMPS WILL CLIMB INTO THE UPPER 60S LOW 70S FRIDAY.
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&& .SHORT TERM /FRIDAY NIGHT/...
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LINGERING RAIN SHOWERS OVER EASTERN AREAS AND UPSLOPE REGION AS TROUGH SWINGS THROUGH THE REGION. POPS IN FOR THE FIRST HALF OF THE NIGHT...DRYING OUT FOR THE LATTER HALF THOUGH POPS MAY BE IN FOR EVEN TOO LONG. MINIMAL INSTABILITY AND SHEAR BY THE EVENING SO NO MENTION OF THUNDER NEEDED. SHORTWAVE ENERGY DIPPING SOUTH ALONG THE UPPER LVL TROUGH WILL KEEP PARTLY CLOUDY CONDITIONS IN PLACE...AND WITH LITTLE CHANGE IN 850MB TEMPS...EXPECTING LOW TEMPS A FEW DEGREES ABV NORMAL...GENERALLY IN THE 50S.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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CONDITIONS DRYING OUT SAT AS HIGH PRESSURE CENTERED OVER WESTERN GREAT LAKES DIPS SOUTH ACROSS THE EASTERN SEABOARD AND RIDGE AXIS SHIFTS EAST. INITIAL WIND FLOW SAT COULD RESULT IN DOWNSLOPING AFFECTS...WITH TEMPS REACHING WELL INTO THE 70S...ESP AS SKIES BEGIN TO CLEAR OUT UNDER SUBSIDENCE BUILDING ALONG RIDGING ALOFT. WEAK PRESSURE GRADIENT AND SCATTERING OUT SKIES WILL LEAD TO TEMPS DROPPING INTO THE 40S FOR MANY PLACES SAT NIGHT. DEVELOPING DYNAMIC LOW PRESSURE SYSTEM OVER THE CENTRAL PLAINS SUNDAY WILL BRING THE NEXT CHC FOR PCPN...MAINLY LATER SUN THROUGH MON NIGHT. 00Z MODEL SUITE IN DECENT CONSENSUS OF TRACKING THE SFC LOW INTO THE WESTERN GREAT LAKES SUN NIGHT. WITH THE ASSOCIATED WARM FRONT EXTENDING TO THE SOUTH AND WEST OF THE CWA...COULD SEE INCREASING PCPN COVERAGE SUN WITH OVERRIDING PCPN AS MULTIPLE SHORTWAVES MOVE THRU. HAVE POPS ACROSS THE BOARD DURING THE DAY SUN...BUT COULD VERY WELL END UP SEEING EASTERN AREAS MAINLY DRY FOR MOST OF THE DAY. HELD OFF WITH THE LIKELY POPS UNTIL SUN NIGHT TO ACCOUNT FOR THE UNCERTAINTY OF THE PCPN TIMING SUN. FAIRLY CONFIDENT THEN OF RAIN SUN NIGHT AS WARM FRONT NUDGES CLOSER FROM THE SOUTHWEST. THE MODEL SUITE SUGGESTS THE WARM FRONT LIFTING NORTH MON MORNING AS THE LLJ STRENGTHENS ACROSS THE AREA. HOWEVER...NOTING THAT THIS PASSAGE HAS BEEN SLOWER THAN MODELS HAVE BEEN SHOWING RECENTLY...AM HOLDING OFF PUSHING THE FRONT THRU TILL LATER DURING THE DAY. THIS TIMING WILL PLAY AN IMPORTANT PART ON WHETHER TSTMS DEVELOP MON...SO HAVE INCLUDED SLIGHT CHC FOR NOW TO ACCOUNT FOR BEST CHC OF WARM SECTORING...MAINLY CENTRAL VA AND SOUTHERN MD...WHICH CURRENTLY IS SHOWING AS HAVING DECENT SHEAR AND INSTABILITY OF A FEW HUNDRED J/KG. GFS SUGGESTING PWATS OF AROUND 1.4 IN WITH STRONG MOISTURE ADVECTION ON THE SLY FLOW SO COULD SEE PERIODS OF HEAVIER RAIN. COLD FRONT SWINGS THROUGH MON NIGHT...WITH PCPN CLEARING IN THE WAKE TUES AS HIGH PRESSURE THEN BUILDS IN. BRIEF DRY PERIOD AS THE REGION REMAINS UNDER A BROAD UPPER LVL TROUGH...WHICH WILL SEND THROUGH THE NEXT COLD FRONT BY THURSDAY. TEMPS RIGHT ABV NORMAL MON...THEN SETTLING NEAR NORMAL THRU MIDWEEK.
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&& .AVIATION /14Z THURSDAY THROUGH MONDAY/...
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HIGH PRESSURE/VFR CONDITIONS WILL PERSIST ACROSS THE REGION THROUGH TONIGHT. -SHRA WILL BEGIN TO MOVE INTO MRB-CHO THIS EVENING AND MOVE E-NE THROUGH FRIDAY MORNING. -SHRA MAY REACH DCA- BWI-MTN BUT CONFIDENCE IS LOW AT THIS TIME. CIGS/VSBYS SHOULD LOWER BY SUNRISE FRIDAY MORNING. MVFR IS EXPECTED AND IFR POSSIBLE AT MRB BY FRIDAY MORNING. A WEAK COLD FRONT CROSSES THE REGION FRIDAY. SHOWERS ARE POSSIBLE FRIDAY AFTERNOON. ANY LINGERING MVFR CIGS FRI EVENING WILL QUICKLY BECOME VFR. VFR CONDITIONS THEN THROUGH AT LEAST SAT NIGHT...IF NOT SUN AFTN. SUB-VFR CONDITIONS LIKELY BY SUN NIGHT AS PCPN OVERSPREADS THE REGION. SLIGHT CHC TSTM MON AFTN...WITH ALL TAF SITES EXPECTING RAIN INTO MON NIGHT. PERIOD OF LLWS CONCERNS MON WITH WINDS 40-50 KTS AROUND 2KFT. CONDITIONS IMPROVE TO VFR BEHIND THE COLD FRONT MON NIGHT...WITH VFR CONDITIONS THEN LASTING INTO MID WEEK. W WINDS INCREASE TUES...WITH GUSTS UP TO 20 KTS PSBL.
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&& .MARINE...
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HIGH PRESSURE IS DRIFTING OFF NEW ENGLAND THIS MORNING. A SURGE OF NORTH WINDS WARRANTED AN SCA EXTENTION TO COVER THE MORNING. AS THE HIGH MOVES OFFSHORE THERE WILL BE GUSTY SLY FLOW THIS AFTERNOON ACROSS THE WATERS. GUSTS UP TO 20 KT...LOW END SCA. WINDS WILL BECOME SW TONIGHT AS HIGH PRESSURE SHIFTS FURTHER OFFSHORE. A COLD FRONT CROSSES THE WATERS FRIDAY EVENING. GENERALLY EXPECTING SUB-SCA CONDITIONS SAT THRU SUN MORNING WITH HIGH PRESSURE TRAVERSING THE WATERS. INCRSG ELY FLOW SUN COULD RESULT IN OCNL GUSTS TO 20 KTS DURING THE DAY...WITH SCA GUSTS BCMG MORE LIKELY OVERNIGHT SUN INTO MON. SCA GUSTS ARE PSBL THRU TUES BEHIND THE COLD FRONT...WITH SUB-SCA GUSTS RETURNING BY TUES NIGHT-WED.
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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 6 PM EDT THIS EVENING FOR ANZ530>532-538>540. SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ533>537-541>543.
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&& $$ UPDATE...WOODY!/BAJ PRVS...HAS/APS

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