000 FXUS61 KLWX 161605 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1205 PM EDT MON MAR 16 2009 .SYNOPSIS... OVERCAST AND DAMP CONDITIONS WILL CONTINUE THROUGH TONIGHT AS MOISTURE OVERRIDES A COOL AIRMASS AT THE SURFACE. TUESDAY AND WEDNESDAY WILL BE DRIER WITH HIGH PRESSURE IN CONTROL. A BRIEF WARM UP IS ALSO EXPECTED ON WEDNESDAY BEFORE A COLD FRONT PUSHES THROUGH THURSDAY...BRINGING A CHANCE OF RAIN...FOLLOWED BY COOLER CONDITIONS FOR THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... AS OF 16Z...RADAR MOSAIC SHOWS ONLY LIGHT RETURNS OVER WESTERN MARYLAND AS LIGHT RAIN CONTINUES TO PUSH NE ACROSS THE POTOMAC HIGHLANDS. MORE SIGNIFICANT SCATTERED SHOWERS NOW ENTERING WESTERN WV TO CONTINUE PUSHING EAST...REACHING WESTERN SECTIONS OF THE CWA BY MID AFTERNOON. MEANWHILE...A LARGE SWATH OF RAIN ACROSS GA/SC TO CONTINUE MOVING ENE AND REMAIN SOUTH OF THE CWA. IN BETWEEN THESE TWO AREAS/ACROSS THE CWA...EXPECT LIGHT RAIN TO DEVELOP AND CROSS THE SOUTHERN MID ATLANTIC THIS AFTERNOON THROUGH THE EVENING HOURS. SOLID CLOUD COVER...THEN LIGHT RAIN THIS AFTERNOON...TO KEEP TEMPERATURES FROM RISING MUCH MORE THAN THEY ARE NOW WITH HIGHS STRUGGLING TO REACH 50. PREVIOUS DISCUSSION... EXPECT VSBYS TO IMPROVE BY MID MORNING. SKY COVER WILL REMAIN CLOUDY BUT CIG HEIGHTS WILL EXHIBIT SOME IMPROVEMENT. RAIN SHOULD HOLD OFF DURING THE MORNING...BUT WILL LIKELY DEVELOP DURING THE AFTERNOON ACROSS THE HIGHLANDS/SHENANDOAH VALLEY/CENTRAL VA PIEDMONT AHEAD OF LOW PRESSURE NEAR THE GULF COAST EARLY THIS MORNING. BALTIMORE/WASHINGTON METRO WILL GENERALLY WAIT UNTIL LATE IN THE DAY OR EVENING TO SEE THE RAIN. SREF WAS PREFERRED FOR THE COVERAGE AND TIMING OF RAIN. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... CONTINUE TO PREFER THE SREF FOR RAIN CHANCES AND TIMING TONIGHT...ALTHOUGH THE NAM WOULD SUGGEST SOMETHING SIMILAR. LOW PRESSURE SCOOTS OFF THE SOUTHEAST COAST THIS EVENING...BUT ISENTROPIC LIFT SHOULD BE ABLE TO EXTEND PRETTY FAR NORTH INTO OUR CWA. BELIEVE THIS WILL BE A VERY LIGHT QPF EVENT...BUT ONE THAT SHOULD AFFECT MOST OF THE CWA THEREFORE HAVE INCREASED POPS THAT ARE CLOSER TO WHAT THE SREF/NAM WOULD INDICATE. AFTER THE LIGHT MEASURABLE RAIN MOVES OUT...THEN THERE MAY BE SOME LINGERING DRIZZLE AND FOG AFTER MIDNIGHT AND HAVE TRENDED IN THIS WAY. WITH CLOVER COVER AND SUCH...FORECAST LOWS WILL BE A FEW DEGREES ABOVE MOS. && .LONG TERM /TUESDAY THROUGH SUNDAY/... HIGH PRESSURE BUILDING OVER THE SOUTHERN PLAINS FINALLY ACTS TO SHOVE THE COOL...DAMP...AND STAGNANT AIRMASS OFF THE ATLANTIC COAST ON TUESDAY...ALLOWING TEMPS TO WARM UP. LOW LEVEL STRATUS ASSOCIATED WITH REMNANT MOISTURE TRAPPED ALONG THE EAST SIDE OF THE APPALACHIANS WILL BE SLOW TO CLEAR...MAKING TUESDAY AN TRANSITIONAL DAY WITH SEASONAL TEMPS IN THE MID TO UPPER 50S. HIGH PRESSURE SLIDES TO OUR SOUTH WEDNESDAY...SETTING UP SOUTHWEST FLOW AT THE LOW LEVELS. RICH WAA IN ADVANCED OF DEVELOPING NORTHERN PLAINS STORM SYSTEM SUGGEST 850MB TEMPS NEAR 10 C ON WEDNESDAY...AND WITH AMPLE SUNSHINE AND MIXING...70 DEGREE MAX TEMPS NOT OUT OF THE QUESTION. WARMUP WILL BE SHORT LIVED...AS SHORTWAVE EJECTS FROM THE PLAINS INTO THE NE US BY THURSDAY AM...SENDING COLD FRONT THROUGH THE CWA DURING THE DAY THURSDAY. 0Z GUIDANCE SUITE HAS DELAYED FROPA 6-12 HRS FROM PREVIOUS RUNS...SO ONE OF THE FEW CHANGES TO EXTENDED FORECAST IS TO DELAY PRECIP ONSET UNTIL AFTER 12Z THURSDAY. FRONT SHOULD QUICKLY CLEAR THINGS OUT BY THURSDAY NIGHT...WITH COOL HIGH PRESSURE SETTLING IN. LARGE SURFACE RIDGE ANCHORS OVER THE DEEP SOUTH FRIDAY THROUGH THE WEEKEND...KEEPING US DRY BUT ALSO BLOCKING ANY SUBSTANTIAL SOUTHWEST FLOW OR WARMING TEMPS. KEPT TEMPS NEAR SEASONAL AVERAGE FOR THE LATTER PART OF THE EXTENDED. && .AVIATION /16Z MONDAY THROUGH FRIDAY/... AS OF 16Z...MVFR CIGS TO PERSIST THROUGH THE AFTERNOON AS LIGHT RAIN MOVES IN ACROSS THE AREA LATE THIS AFTERNOON. VSBYS HAVE IMPROVED TO MVFR AND WILL REACH VFR EARLY THIS AFTERNOON AND UNTIL IT BEGINS TO RAIN. RAIN WILL BREAK OUT LATE IN THE DAY AND EVENING...AND EXPECT A DETERIORATION TO IFR ALL TERMINALS BY THEN WHICH WILL LIKELY LAST THROUGH THE NIGHT. LOW...PSBL MVFR LEVEL STRATUS DECK WILL PERSIST EARLY TUESDAY AT MOST AIRPORTS...WITH CHO LIKELY LATEST TO LIFT. AS THE DAY WEARS ON...DRIER AIR FROM THE WEST AND DIURNAL MIXING SHOULD SEND CONDITIONS TO VFR AREAWIDE AS LOW CIGS SCATTER OUT. VFR CONDITIONS THEN PREVAIL UNDER SOUTH WINDS 5-10KT THROUGH WEDNESDAY NIGHT...WHEN SOUTHERLY WINDS INCREASE AND RAIN CHANCES INCREASE IN ADVANCE OF APPROACHING COLD FRONT. SUB-VFR CIGS/VIS PSBL THURSDAY WITH FRONTAL PASSAGE. && .MARINE... RAIN WILL MOVE IN THIS EVENING...LOWERING VSBYS ONCE AGAIN. LIGHT EAST WINDS THIS MORNING WILL BECOME NORTH OVERNIGHT AS A COASTAL LOW DEVELOPS OFF NC. WINDS WILL INCREASE TO 10 TO 15 KT...WITH POSSIBLE SCA GUSTS FOR THE CENTRAL BAY FROM MIDNIGHT THROUGH TOMORROW MORNING. THE POTENTIAL FOR THIS WILL BE REASSESSED AND ANY HEADLINES WILL BE ISSUED WITH THE AFTERNOON FORECAST PACKAGE. LIGHT WINDS AND DRY CONDITIONS WILL DOMINATE TUESDAY AND EARLY WEDNESDAY. BY WEDNESDAY AFTERNOON...SOUTH WIND CHANNELLING MAY APPROACH SMALL CRAFT CRITERIA...WHICH MAY CONTINUE WEDNESDAY NIGHT INTO THURSDAY. AS A COLD FRONT PASSES THROUGH THE WATERS THURSDAY...SHOWERS ARE POSSIBLE. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BPP NEAR TERM...BAJ/BPP SHORT TERM...BPP LONG TERM...SBK AVIATION...BAJ/SBK MARINE...BAJ/SBK