Area forecast discussion National Weather Service Baltimore Maryland/Washington District of Columbia 929 PM EDT Wednesday may 22 2013 Synopsis... high pressure persisting over the Atlantic with warm and humid conditions until a cold front Thursday night. An upper trough will linger over the area Friday with high pressure building through Saturday. A frontal boundary stalls out across the middle- Atlantic Sunday night through early next week. && Near term /through Thursday/... convective activity on the decrease acrss County Warning Area at this time. Looking at line of rain showers/thunderstorms and rain roughly along I-81 that will slowly make its way across the County Warning Area late tonight. Expecting mainly showers with isolated elevated thunderstorm in this activity as the upper-level trough continues to slide closer to our area. Min temperatures tonight will range from the 50s in the mountains to the lower and middle 70s in downtown Washington/Baltimore. Areas that received rainfall today will be apt to fog-up overnight. && Short term /Thursday night through Friday/... heights continue to drop Thursday as cold front approaches. Although instability will be lower...shear will be greater. There may be two rounds of weather...first coming midday with the disturbance and ribbon of instability...and then second nearer the cold front and diurnal heating. Have raised probability of precipitation into the def range rather quickly...and holding it there throughout the day. Cold front passage Thursday night. Will scale back probability of precipitation and transition from thunderstorms and rain to rain showers in the evening. After frontal passage...only lingering rain showers will remain. Friday...upper trough drifts east over the area with back edge of clouds slow to come in the afternoon. Gusty northwesterly flow Friday continues as high pressure builds through Saturday. && Long term /Friday night through Wednesday/... shortwave from Tennessee Valley on Sunday now looks to expand east across the southern-central mid-Atlantic. Convergence along this boundary would set off showers. Pattern is stalled into middle next week...so a prolonged cloudy/rainy period is possible. This would result in below normal temperatures. && Aviation /02z Thursday through Monday/... VFR-MVFR conditions at all terminals overnight. Threat for storms continue until cold front passage Thursday night. Northwesterly flow with gusts 25 to possibly 30 knots with middle level ceilings Friday. Northwesterly flow continues through Saturday as high pressure builds. && Marine... high pressure will remain over the Atlantic Ocean overnight. A southerly flow will continue over the waters during this time. A Small Craft Advisory remains in effect for portions of the waters through tonight. Scattered showers and thunderstorms are possible later this afternoon and evening. Any thunderstorms that do develop will be capable of producing gusty winds and hail. Southerly flow ahead of a late Thursday night cold front. Small Craft Advisory expanded through Thursday. Expect an extension Thursday night for prefrontal southerly flow...then northwesterly flow around 25 knots Friday through Saturday as high pressure builds. && Lwx watches/warnings/advisories... District of Columbia...none. Maryland...none. Virginia...none. WV...none. Marine...Small Craft Advisory until 6 PM EDT Thursday for anz530>534- 536-537-539>543. Small Craft Advisory from 9 am to 6 PM EDT Thursday for anz535- 538. && $$