AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 916 PM EDT WED MAY 11 2011 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OVER THE EASTERN SEABOARD THROUGH THURSDAY BEFORE SLOWLY MOVING OUT INTO THE ATLANTIC FRIDAY. LOW PRESSURE WILL SLOWLY MOVE THROUGH THE OHIO VALLEY FRIDAY AND SATURDAY BEFORE APPROACHING THE MID-ATLANTIC EARLY NEXT WEEK. UNSETTLED CONDITIONS ARE EXPECTED DURING THIS TIME. && .NEAR TERM /THROUGH THURSDAY/... EXPECT MOSTLY CLEAR TO PARTLY CLOUDY SKIES TROUGH TONIGHT. MOST CLOUD COVER WILL BE LOCATED ACROSS SOUTHWEST PORTIONS OF THE CWA. THE DIVIDING LINE BETWEEN MOSTLY CLEAR AND PARTLY CLOUDY RUNS LOOSELY SOUTHEAST FROM PETERSBURG WV TO LURAY AND ORANGE VA. FOR OVERNIGHT LOWS WENT WITH CLOSER TO THE NAM GUIDANCE AS THE GFS DID VERY POORLY LAST NIGHT. WINDS WILL BE LIGHT. DO NOT EXPECT ANY SIGNIFICANT PRECIP OVERNIGHT WITH A SLIGHT POSSIBILITY OF A FEW SPRINKLES SOUTH AND WEST OF CHARLOTTESVILLE. EXPECT CONDITIONS OVERNIGHT TO CONTINUE INTO TOMORROW MORNING. CLOUD COVER AND SHOWERS WILL INCREASE NORTHWARD FROM SOUTHWEST PORTIONS OF THE CWA THROUGH THE DAY. BEST CHANCE OF ANY THUNDERSTORMS WILL BE IN THE POTOMAC HIGHLANDS OVER WESTERN PORTIONS OF THE CWA...AND DOWN TOWARDS STAUNTON AND WAYNESBORO IN OUR SW AREA. MOSTLY CLOUDY GENERALLY CENTRAL VA AND SHEN VALLEY AND EASTERN WV. MOSTLY SUNNY CENTRAL AND NE MARYLAND. WENT CLOSER TO GFS GUIDANCE FOR HIGH TEMPS WHICH DID BETTER WITH THE HIGH TEMP FORECASTS RECENTLY. && .SHORT TERM /THURSDAY NIGHT THROUGH 6 PM THURSDAY/... MUCH THE SAME AS OVERNIGHT TONIGHT. BEST CHANCE OF ANY THUNDERSTORMS WILL BE IN THE POTOMAC HIGHLANDS IN OUR WEST...AND DOWN TOWARDS STAUNTON AND WAYNESBORO IN OUR SW AREA. MOSTLY CLOUDY GENERALLY CENTRAL VA AND SHEN VALLEY AND EASTERN WV. MOSTLY SUNNY CENTRAL AND NE MARYLAND. WENT CLOSER TO GFS GUIDANCE FOR HIGH TEMPS WHICH DID BETTER WITH THE HIGH TEMP FORECASTS RECENTLY. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... SURFACE HIGH PRESSURE WILL MOVE OFF THE EAST COAST THURSDAY NIGHT THROUGH FRIDAY NIGHT WHILE LOW PRESSURE TRACKS THROUGH THE CENTRAL PLAINS INTO THE MIDWEST. AN ONSHORE FLOW IN BETWEEN THESE TWO SYSTEMS WILL USHER IN MOISTURE FROM THE ATLANTIC OCEAN. A WARM FRONT WELL AHEAD OF THE LOW WILL STALL OUT AS A STATIONARY BOUNDARY NEAR THE POTOMAC HIGHLANDS INTO CENTRAL VIRGINIA DURING THIS TIME. SHOWERS AND THUNDERSTORMS ARE POSSIBLE NEAR THE BOUNDARY...ESPECIALLY THURSDAY EVENING AND AGAIN FRIDAY AFTERNOON AND EVENING. FURTHER NORTH AND EAST ACROSS THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS...ISOLATED SHOWERS ARE POSSIBLE DUE TO THE ONSHORE FLOW BUT ANY PRECIPITATION AMOUNTS WILL BE LIGHT. THE STATIONARY BOUNDARY WILL SLOWLY LIFT NORTH AND EAST AS A WARM FRONT DURING THE WEEKEND WHILE THE UPPER-LEVEL LOW ASSOCIATED WITH THIS SYSTEM TRACKS OVERHEAD. INCREASED INSTABILITY AND MOISTURE WILL LEAD TO MORE WIDESPREAD SHOWERS AND THUNDERSTORMS DURING THIS TIME. SOME THUNDERSTORMS SOUTH AND WEST OF THE BOUNDARY MAY BECOME SEVERE. DEEP MOISTURE WILL LEAD TO LOCALLY HEAVY RAIN IN ANY THUNDERSTORMS THAT DO DEVELOP WHICH MAY CAUSE ISOLATED AREAS OF FLASH FLOODING. WILL CONTINUE TO MONITOR OVER THE NEXT COUPLE DAYS. LOW PRESSURE WILL LIKELY CONTINUE TO IMPACT THE REGION EARLY NEXT WEEK...BRINGING UNSETTLED CONDITIONS. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... VFR CONDITIONS AND WINDS LESS THAN 10KTS EXPECTED FOR TONIGHT AND TOMORROW. THE LAMP GUIDANCE WANTED TO BRING IN IFR FOG TO CHO AND MRB BY MORNING...BUT GIVEN NO RAIN EXPECTED AND CONDITIONS NOT TOO DISSIMILAR FROM LAST NIGHT WHICH FEATURED 10 MILE PLUS VSBYS...WILL DISREGARD THAT AND KEEP VFR OVERNIGHT. CEILINGS WILL LARGELY REMAIN ABOVE 7000 FEET THROUGHOUT THE TAF VALID PERIOD. CLOUD COVER WILL GRADUALLY INCREASE THROUGH THE DAY TOMORROW WITH SKIES BECOMING OVERCAST AFTER MIDNIGHT TOMORROW NIGHT. AN ONSHORE FLOW WILL CAUSE MOISTURE TO INCREASE OVER THE TERMINALS THURSDAY NIGHT THROUGH FRIDAY. SUBVFR CIGS AND VSBYS ARE EXPECTED DURING THIS TIME. LOW PRESSURE WILL BRING INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS DURING THE WEEKEND AND POSSIBLY INTO EARLY NEXT WEEK. SOME THUNDERSTORMS WILL HAVE THE POTENTIAL TO PRODUCE GUSTY WINDS AND HAIL. && .MARINE... CHANNELING GOING ON THE POTOMAC SE OF MATHIAS PT NECK ON SERLY FLOW. WL ISSUE AN SCA FOR THE RMDR OF THE EVE AND LET THE MIDSHIFT REVIEW THE NEED FOR ONE FURTHER. ONSHORE FLOW WILL PERSIST THURSDAY NIGHT THROUGH FRIDAY. THE ONSHORE FLOW MAY STRENGTHEN A BIT FOR THE WEEKEND INTO EARLY NEXT WEEK. HAVE CAPPED WIND GUSTS AROUND 15 KNOTS AT THIS TIME. LOW PRESSURE WILL BRING AN INCREASING CHANCE FOR SHOWERS AND THUNDERSTORMS THIS WEEKEND. SOME THUNDERSTORMS SUNDAY WILL HAVE THE POTENTIAL TO PRODUCE GUSTY WINDS AND HAIL. && .TIDES/COASTAL FLOODING... TODAYS HIGH TIDE BROUGHT MINOR TIDAL FLOODING TO MOST TIDAL GAUGED POINTS IN OUR FORECAST AREA AND VERIFIED THE COASTAL FLOOD ADVISORY. WEAK EAST TO SOUTHEAST WINDS AROUND HERE AND E TO NE WINDS AT THE MOUTH OF THE BAY WILL KEEP US WITH MINOR TIDAL FLOODING AT TIMES OF HIGH TIDE AT LEAST THRU THU. THEREFORE THE END OF THE COASTAL FLOOD ADVISORY HAS BEEN EXTENDED TO THU EVENING. AN ONSHORE FLOW WILL PERSIST THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. MINOR COASTAL FLOODING IS LIKELY TO CONTINUE DURING THIS TIME. A STRENGTHENING ONSHORE FLOW MAY LEAD TO MODERATE COASTAL FLOODING NEAR TIMES OF HIGH TIDE THIS WEEKEND. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...COASTAL FLOOD ADVISORY UNTIL 6 PM EDT THURSDAY FOR DCZ001. MD...COASTAL FLOOD ADVISORY UNTIL 6 PM EDT THURSDAY FOR MDZ007-011- 013-014-016>018. VA...COASTAL FLOOD ADVISORY UNTIL 6 PM EDT THURSDAY FOR VAZ052>055- 057. WV...NONE. MARINE...NONE. && $$ UPDATE...CJL/WOODY!