AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 233 PM EDT FRI JUL 8 2011 .SYNOPSIS... A COLD FRONT WILL PUSH INTO THE MID ALTANTIC THIS AFTERNOON AND EVENING...AND OFF THE DELMARVA COAST EARLY SATURDAY. HIGH PRESSURE WILL BUILD IN FROM THE NORTH SATURDAY AND REMAIN IN PLACE THROUGH THE WEEKEND. A SECOND FRONT WILL PUSH SOUTH ACROSS THE MID ATLANTIC LATE MONDAY INTO TUESDAY...WITH HIGH PRESSURE RETURNING FOR THE SECOND HALF OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... CDFNT HAS ENTERED CWFA...AND CAN BE FOUND FM BKW-MRB-MSV. NMRS- WIDESPREAD SHRA/EMBEDDED TSRA CAN BE FOUND ALNG/BHD CDFNT AND S/WV TROF AXIS. AHD OF FNT...ALTHO INSOLATION HASNT BEEN ALL THAT GREAT...WE/VE MANAGED TO ATTAIN 2000-3000 J/KG MUCAPE AND EFFECTIVE BULK SHEAR OF 40 KT. HENCE...SVR TSTM WATCH HAS BEEN POSTED THRU 01Z E OF BLURDG. DMGG WND/LRG HAIL BOTH CONCERNS. MODIFIED 12Z LWX RAOB YIELDS PWAT 1.75 IN. 12Z NAM/GFS BOTH PAINT A SWATH OF PWAT AOA 2 INCHES...MAINLY ALONG/E OF I-95.THUS...HVY RAIN ALSO A CONCERN...AND OVERALL MODE SHUD TRANSITION FM SVR TO FF BY ELY THIS EVNG. CDFNT WL SLOW DOWN...AND SLOWLY TREK ACRS REST OF CWFA TNGT. HV CAT POPS AHD OF AXIS THIS EVNG...AND BACKED OFF A LTL TO LKLY OVNGT. RGNL RDR SUGGESTS THAT ACTIVITY MAY COME IN WAVES PROPAGATING ALNG THE BNDRY. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... SATURDAY...COLD FRONT PUSHES INTO THE SOUTHERN MID ATLANTIC BY THE LATE MORNING. JUST LOW CHANCES FOR LINGERING SHOWERS SOUTH OF AN E-W LINE THROUGH DC FOR THE MID MORNING HOURS. OTHERWISE...LIGHT NLY FLOW BEHIND THE TROUGH WITH SKIES CLEARING BEFORE MIDDAY. ABUNDANT INSOLATION ALLOWS FOR SLIGHTLY ABOVE NORMAL MAX TEMPERATURES... AROUND 90F PER GRIDDED GFS MOS GUIDANCE. SATURDAY NIGHT THROUGH SUNDAY...SFC HIGH PRESSURE BUILDS SOUTH INTO THE CENTRAL MID ATLANTIC. DRY WITH A LIGHT ONSHORE FLOW WITH HIGH PRESSURE CENTER TO THE NORTH. MIN TEMPS LOW TO MID 60S INLAND...LOW 70S NEAR SHORE. MAX TEMPS AROUND 90F...THOUGH NO HEAT INDEX WITH DEW POINTS IN THE LOW TO MID 60S. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... SFC HIGH PRESSURE MOVES OFFSHORE WHILE A RIDGE OVER THE S-CNTRL CONUS DRIFTS EAST. SWLY LOW LEVEL FLOW BRINGS PLUME OF ABOVE NORMAL TEMPERATURE AIR FOR EARLY NEXT WEEK. MAX TEMPS SHOULD REACH INTO THE MID 90S WITH DEWPOINTS APPROACHING 70F. EXPECT HEAT INDICES IN THE UPR 90S. AN APPROACHING TROUGH MAY TRIGGER THUNDERSTORMS WEST OF THE BLUE RIDGE LATE MONDAY AFTERNOON. A COLD FRONT CROSSES TUESDAY...THE SLOWER 12Z GFS ALLOWS HEATING TO TAKE PLACE...WITH MAX TEMPS IN THE MID 90S AGAIN...WHILE THE 00Z ECMWF BRINGS THE TROUGH AXIS THROUGH BY DAYBREAK. CHANCE POPS MONDAY NIGHT INCREASE TO HIGH CHANCE TUESDAY. WITH THE LIFTED INDEX AROUND -5 AND DECENT SHEAR ALONG THE TROUGH...EXPECT THUNDERSTORMS. THE MAIN ACTIVITY WILL BE ASSOCIATED WITH THE FRONT...SO SPECIFICS ON PRECIP TIMING AND INTENSITY WILL BECOME MORE CLEAR IN THE COMING DAYS. HIGH PRESSURE FOLLOWS THE FRONT AGAIN...WITH TUESDAY NIGHT INTO THURSDAY LOOKING DRY. INCLUDED LOW CHANCES FOR THUNDERSTORMS ALONG THE ALLEGHENY FRONT AS RETURN FLOW COMBINED WITH TERRAIN CIRCULATIONS AIDING DEVELOPMENT. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... UNSETTLED FLGT CONDS THIS EVNG. MTRS SUGGEST IFR CONDS W/IN COMPLEX OF SHRA/TSTMS IN PTMC HIGHLANDS. EXTRAPOLATION SLIDES THAT AREA NEWD...JUST TOUCHING IAD/BWI. HV INTRODUCED MVFR/TEMPO IFR COINCIDENT W/ THIS AREA. THERE/S ANTHR COMPLEX IN MID OHVLY. ALSO...WDLY SCT TSRA DVLPG AHD OF THE ASSOCD CDFNT. THAT SUGGESTS THAT ONCE TROF AXIS NEARBY...MVFR WL BE PREDOMINANT. EXTENT OF IFR STILL TBD...AND LKLY WL NEED ONGOING ADJUSTMENT. VFR RETURNS BY MIDDAY SATURDAY MORNING WITH LIGHT NLY FLOW BEHIND THE COLD FRONT. VFR PREVAILS AS HIGH PRESSURE BUILDS FROM THE NORTH INTO SUNDAY OUTSIDE OF FOG POTENTIAL LATE SATURDAY NIGHT. COLD FRONT APPROACHES LATE MONDAY...CROSSING ON TUESDAY. HIGH CHANCES FOR THUNDERSTORMS ACCOMPANYING FRONT...LATE MONDAY NIGHT INTO TUESDAY. MORE HIGH PRESSURE THEN TUESDAY NIGHT INTO THURSDAY. && .MARINE... S/SWLY FLOW NEAR 15 KT ATTM. DONT ENVISION MUCH OF A CHG TO THAT THRU THE AFTN. SHRA/TSRA WL DVLP AHD OF A CDFNT/TROF AXIS TAFTN. ACTIVITY WL BECOME MORE WIDESPREAD INVOF THE FNT. SMW/S WL BE LKLY AHD OF THE STRONGEST STORMS. THREAT WL TRANSITION FM GUSTY WNDS TO HVY RAIN THRU THE NGT AS FWD PROGRESS OF FNT STALLS. IT MAY BE LINGERING ACRS MID BAY-LWR PTMC MUCH OF THE NGT. NLY FLOW 10 TO 15 KT SATURDAY BEHIND THE COLD FRONT. GUSTS MAY REACH INTO THE 18KT RANGE...SO A SMALL CRAFT ADVISORY MAY BE NEEDED. HIGH PRESSURE THEN BUILDS FROM THE NORTH THROUGH SUNDAY...ALLOWING A LIGHT ELY FLOW/BAY BREEZE SUNDAY. RETURN FLOW LATE SUNDAY THROUGH MONDAY NIGHT MAY CHANNEL AND GUST INTO THE MARGINAL SMALL CRAFT ADVISORY ZONE. A COLD FRONT CROSSES THE BAY IN THE TUESDAY TIMEFRAME...WITH HIGH CHANCES FOR THUNDERSTORMS. HIGH PRESSURE THEN BUILDS FROM THE NORTH WITH NLY FLOW THROUGH MIDDLE NEXT WEEK && .HYDROLOGY... POTENTIAL FOR HEAVY RAINS CONTINUES AS TROPICAL MOISTURE FROM THE GULF OF MEXICO INTERACTS WITH A SLOW MOVING FRONTAL BOUNDARY. MODELS PROG THE PWATS THIS EVENING AROUND 2-2.25 INCHES...WHICH IS ARND 2SD ABOVE NORMAL. SFC DEWPTS 70-75F THRU THE AFTN-EVE. IN ADDITION...QUASI- STATIONARY/SLOW MOVING FRONT WILL PROVIDE A FOCUS FOR TRAINING STORMS. FLASH FLOOD WATCH REMAINS IN EFFECT. && .EQUIPMENT... PIKESVILLE NWR WENT DOWN LAST NGT DUE TO A LIGHTNING STRIKE ON A COMMERCIAL POWER TRANSFORMER. TECHS ARE WORKING THE ISSUE...AND WILL DO THEIR BEST TO RETURN SERVICE TODAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...FLASH FLOOD WATCH UNTIL 2 AM EDT SATURDAY FOR DCZ001. MD...FLASH FLOOD WATCH UNTIL 2 AM EDT SATURDAY FOR MDZ004>007- 009>011-013-014-016>018. VA...FLASH FLOOD WATCH UNTIL 2 AM EDT SATURDAY FOR VAZ025>027- 029>031-036>040-042-050>057-501>504. WV...FLASH FLOOD WATCH UNTIL 2 AM EDT SATURDAY FOR WVZ505-506. MARINE...NONE. && $$ SYNOPSIS...HTS/BAJ