Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 150112 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 812 PM EST SUN DEC 14 2014 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD OVERHEAD THROUGH TONIGHT BEFORE SLOWLY MOVING TO OUR EAST MONDAY AND MONDAY NIGHT. A COLD FRONT WILL PASS THROUGH THE AREA LATER TUESDAY INTO TUESDAY NIGHT AND HIGH PRESSURE WILL RETURN FOR THE WEDNESDAY THROUGH FRIDAY. LOW PRESSURE MAY IMPACT THE AREA NEXT WEEKEND.
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&& .NEAR TERM /THROUGH MONDAY/...
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RIDGE OF HIGH PRESSURE CONTINUES TO EXTEND FROM THE APPALACHIANS DOWN TOWARD THE GULF COAST. STILL HAVE A STRATUS DECK IN THE SAME PLACES ITS BEEN ALL DAY...NAMELY THE WESTERN SLOPES OF THE POTOMAC HIGHLANDS AND THE NORTHERN HALF OF THE CWA GENERALLY NORTH OF I-66. SOUTH OF HERE IT/S BEEN CLEAR. DON/T THINK STRATUS WILL BE ABLE TO DO MUCH RETREATING OVERNIGHT. IN FACT...ITS POSSIBLE STRATUS SINKS A LITTLE FURTHER SOUTH INTO SOUTHERN MD AND THE VIRGINIA PIEDMONT. THUS WILL CONTINUE WITH A TIGHT GRADIENT OF SKY OVERNIGHT...FOCUSING ON MOSTLY CLOUDY WESTERN SLOPES AND NORTHERN HALF OF THE CWA TO MOSTLY CLEAR TO THE SOUTH. OVER THE WESTERN SLOPES...SIMILAR TO LAST NIGHT THERE MAY ALSO BE VIS RESTRICTIONS IN FOG AND CAN/T RULE OUT PATCHY DRIZZLE EITHER. CONFIDENCE IS LOW REGARDING DRIZZLE...BUT EVEN IF IT DOES OCCUR LATEST GUIDANCE FAVORS MINIMA ABOVE FREEZING THUS LIMITING CONCERNS FOR FREEZING DRIZZLE/ICING. RIDGE BUILDS OVER THE MID-ATLANTIC ON MONDAY. STRATUS SHOULD RETREAT TO A DEGREE IN THE MORNING...BUT CLOUDS MAY INCREASE AGAIN LATER IN THE DAY.
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&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... HIGH PRESSURE WILL WEAKEN AND MOVE OFF OF THE COAST MONDAY NIGHT AS LOW PRESSURE CROSSES THE SOUTHERN GREAT LAKES REGION. THE SURFACE LOW WILL BEGIN TO GRADUALLY FILL MONDAY NIGHT AND CONTINUE THROUGH THE DAY TUESDAY AS THE UPPER LEVEL LOW WEAKENS FROM A CUT-OFF LOW TO A SHORTWAVE TROUGH AND LIFTS NORTHEASTWARD THROUGH THE PERIOD. THE COLD FRONT ASSOCIATED WITH THIS SURFACE LOW WILL FOLLOW SUIT IN WEAKENING AS IT APPROACHES THE WESTERN PART OF THE CWA BEGINNING EARLY TUESDAY MORNING. WEAK WAA IN THE LOWER LEVELS AND A BLANKET OF CLOUDS WILL ENSURE THAT LOWS MONDAY NIGHT REMAIN ABOVE FREEZING AND ALL PRECIP SHOULD FALL AS RAIN. THE HIGHEST RAIN AMOUNTS SHOULD OCCUR ACROSS THE NORTHWESTERN PORTION OF THE CWA DUE TO THE PROXIMITY OF THE LOW AND THE STRUGGLE OF THE RAIN TO SURVIVE ACROSS THE APPALACHIAN CREST. THE METRO AREAS WILL SEE THEIR HIGHEST PRECIP CHANCES AROUND MIDDAY...THOUGH THE SHOWERS WILL MAINLY BE OF THE LIGHT/NUISANCE VARIETY. OUR ENTIRE AREA IS HIGHLIGHTED IN THE GENERAL THUNDER PORTION OF THE SPC DAY THREE OUTLOOK...WITH AROUND A 10 PERCENT CHANCE OF THUNDER. WHILE IT IS NOT TOTALLY IMPOSSIBLE FOR SOME THUNDER IN THE STRONGEST SHOWERS...DUE TO VERY SMALL AMOUNTS OF INSTABILITY IDEALLY LOCATED IN THE MIXED PHASE LAYER...THE OVERALL THREAT IS TOO SMALL TO INCLUDE IN THE FORECAST AT THIS TIME. GUSTY...SUB SEVERE WINDS COULD ALSO REACH THE SURFACE IN SHOWERS TUESDAY THANKS TO A MODERATELY STRONG MID/UPPER-LEVEL PREFRONTAL JET. RAIN SHOWERS SHOULD WRAP UP FROM WEST TO EAST AS THE FROPA OCCURS THROUGH THE EVENING TUESDAY...WITH RAIN CHANCES ONLY REMAINING OVER THE BAY BY MIDNIGHT. THE ARRIVAL OF A REINVIGORATING UPPER LEVEL SHORTWAVE TO THE LOW PRESSURE OVER NEW ENGLAND WILL ZONALLY ELONGATE THE SURFACE LOW TUESDAY NIGHT. WHILE THIS WILL HAVE LITTLE EFFECT ON OUR AREA IN TERMS OF PRECIP...IT WILL RESULT IN MORE WESTERLY POSTFRONTAL WINDS...WHICH WILL LIMIT THE POSTFRONTAL CAA. HOWEVER...UPSLOPING ALONG THE ALLEGHENY FRONT WILL KEEP POPS IN THE FORECAST THROUGH THE NIGHT TUESDAY FOR THE POTOMAC HIGHLANDS AND DOWNSLOPING ACROSS THE REST OF THE AREA WILL RESULT IN BREEZY WINDS AND DRY AIR. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AN UPPER LEVEL DISTURBANCE OVER THE GREAT LAKES WILL SHIFT TO THE EAST WEDNESDAY AND WEDNESDAY NIGHT BEFORE PIVOTING ACROSS THE MID ATLANTIC THURSDAY. MUCH OF THE REGION SHOULD BE DRY WITH EXCEPTION TO A CHANCE FOR SNOW SHOWERS IN THE HIGHER ELEVATIONS OF THE POTOMAC HIGHLANDS WEDNESDAY AND WEDNESDAY NIGHT. HIGH PRESSURE WILL BUILD LATE THURSDAY THROUGH FRIDAY. AS HIGH PRESSURE SLIDES TO THE DELMARVA PENINSULA AND EAST COAST LATE FRIDAY AND FRIDAY NIGHT...AN UPPER LEVEL DISTURBANCE WILL MOVE EAST ACROSS THE LOWER GREAT LAKES AND OHIO VALLEY. ENERGY AHEAD OF THE MAIN UPPER LEVEL LOW WILL COMBINE WITH SOME INCREASING MID LEVEL MOISTURE FRIDAY NIGHT INTO SATURDAY TO BRING A CHANCE OF A MIX OF LIGHT RAIN OR LIGHT SNOW. THERE ARE STILL SOME UNCERTAINTIES IN THE TRACK...INTENSITY...AND TIMING OF THE MAIN UPPER LEVEL STORM. COMPUTER MODELS ARE INDICATING THAT A SURFACE LOW COULD FORM NEAR THE COAST OF NORTH CAROLINA IN AFFILIATION WITH THIS UPPER LEVEL DISTURBANCE SOMETIME SATURDAY. SHOULD THIS COASTAL LOW DEVELOP...WE LEFT A CHANCE FOR SOME LIGHT SNOW ACROSS THE CWA FOR SATURDAY NIGHT. BY SUNDAY...THE MAIN DISTURBANCE WILL BE ACROSS NEW ENGLAND WITH A SURFACE LOW MOVING GRADUALLY OUT TO SEA. HIGH PRESSURE WILL WORK ITS WAY INTO THE REGION...RESULTING IN DRIER CONDITIONS. SOME UPSLOPE RAIN OR SNOW SHOWERS ARE POSSIBLE IN THE POTOMAC HIGHLANDS WITH A CHANCE OF SOME LINGERING RAIN OR SNOW SHOWERS IN THE NORTH AND EAST WITH RESPECT TO THE DEPARTING LOW PRESSURE. && .AVIATION /01Z MONDAY THROUGH FRIDAY/...
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STRATUS DECK IS STILL FIRMLY IN PLACE ALL TERMINALS EXCEPT CHO...AND NOW AM THINKING IT WILL HANG AROUND FOR MOST IF NOT ALL OF THE NIGHT. KEPT CIGS IN VFR AT THE HUBS...BUT CAN/T RULE OUT IAD LOWERING INTO MVFR /2500-3000 FT/ OVERNIGHT AS WE ARE SEEING AT MRB. STRATUS SHOULD BECOME LESS PRONOUNCED MONDAY MORNING. HIGH PRESSURE BUILDS OVERHEAD MONDAY FOR WINDS LGT/VRB BECOMING SW. MVFR AND IFR CONDITIONS CAN BE EXPECTED TUESDAY WITH SHOWERS AND POSSIBLY LOW CLOUD DECKS AS A COLD FRONT APPROACHES THE AREA. SOUTHERLY WINDS 10K OR LESS. VFR CONDITIONS WEDNESDAY AND WEDNESDAY NIGHT. WINDS WEST TO NORTHWEST 10 TO 20 KNOTS WITH HIGHER GUSTS BUT DIMINISHING WEDNESDAY NIGHT. VFR CONDITIONS THURSDAY. WINDS NORTHWEST AROUND 10 KNOTS.
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&& .MARINE...
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REMOVED A FEW ZONES FROM THE SCA BUT STILL HAD COVM2 G19 LAST HOUR AND THUS KEPT THE BAY SOUTH OF SANDY POINT IN ADVISORY FOR THE REST OF THE NIGHT. LIGHT WINDS EXPECTED MONDAY AND MONDAY NIGHT WITH HIGH PRESSURE OVERHEAD. GUSTY PREFRONTAL SOUTHERLY WINDS WILL LIKELY REQUIRE A SMALL CRAFT ADVISORY BEGINNING LATE MORNING TUESDAY...ESPECIALLY FOR AREAS PRONE TO SOUTHERLY CHANNELING. BREEZY DOWNSLOPING WINDS BEHIND THE FRONT MAY REQUIRE A SMALL CRAFT ADVISORY CONTINUING THROUGH TUESDAY NIGHT. SMALL CRAFT ADVISORIES MAY BE NEEDED WEDNESDAY WITH GUSTS TO 20 KNOTS. NO MARINE HAZARDS WEDNESDAY NIGHT AND THURSDAY.
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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 AM EST MONDAY FOR ANZ532>534-541- 543.
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&& $$ SYNOPSIS...KS NEAR TERM...BPP/KS SHORT TERM...CEB LONG TERM...KLW AVIATION...BPP/KS/CEB/KLW MARINE...BPP/KS/CEB/KLW

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