Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 020734 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 334 AM EDT SAT MAY 2 2015 .SYNOPSIS... HIGH PRESSURE WILL BUILD TOWARD THE REGION TODAY BEFORE SETTLING OVERHEAD TONIGHT. THE HIGH WILL PUSH TO OUR SOUTH SUNDAY AND MONDAY. A COLD FRONT WILL APPROACH THE AREA TUESDAY AND IT WILL STALL OUT OVERHEAD DURING THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... A DENSE FOG ADVISORY IS IN EFFECT FOR THE CENTRAL SHENANDOAH VALLEY UNTIL 10 AM THIS MORNING. THERE HAVE BEEN ENOUGH BREAKS IN THE MID-LEVEL CLOUDS FOR RADIATIONAL COOLING TO SETUP. SOIL REMAINS MOIST FROM RAINFALL OVER THE PAST COUPLE DAYS AND THIS WILL ALLOW FOR AREAS OF DENSE FOG. WILL HAVE TO KEEP AN EYE ON THE NORTHERN SHENANDOAH VALLEY...EASTERN PANHANDLE OF WEST VIRGINIA...PORTIONS OF WESTERN MARYLAND AS WELL AS CENTRAL VIRGINIA INTO THE VIRGINIA PIEDMONT. TEMP/DEWPOINT DEPRESSIONS ARE ONLY A FEW DEGREES BUT THE MID-LEVEL CLOUDS HAVE PREVENTED FOG FROM DEVELOPING SO FAR. HOWEVER...THE MID-LEVEL CLOUDS SHOULD BREAK TOWARD SUNRISE AND THAT WILL BE ENOUGH FOR PATCHY DENSE FOG TO DEVELOP. NOT CONFIDENT ENOUGH AT THIS TIME FOR A DENSE FOG ADVISORY BUT THIS WILL HAVE TO BE MONITORED OVER THE NEXT FEW HOURS. LOW PRESSURE IS LOCATED WELL OFF THE NORTH CAROLINA COAST EARLY THIS MORNING. THE LOW WILL CONTINUE TO MOVE OUT TO SEA WHILE HIGH PRESSURE APPROACHES FROM THE TENNESSEE VALLEY. AN UPPER-LEVEL DISTURBANCE MOVING THROUGH THE AREA EARLY THIS MORNING HAS CAUSED MID-LEVEL CLOUDS...BUT THESE WILL DISSIPATE LATER THIS MORNING AS DRIER AIR AND UPPER-LEVEL RIDGING BUILD IN BEHIND THE DEPARTING DISTURBANCE. INCREASED SUNSHINE AND BUILDING 500MB HEIGHTS FROM RIDGING ALOFT WILL ALLOW FOR WARMER CONDITIONS COMPARED TO FRIDAY. MAX TEMPS WILL RANGE FROM THE 60S IN THE MOUNTAINS TO THE LOWER AND MIDDLE 70S ACROSS MOST OTHER LOCATIONS. DID LEAN TOWARD THE WARMER GUIDANCE DUE TO MORE SUNSHINE AND A DEEP MIXING LAYER EXPECTED. THE SUNSHINE AND WARMER CONDITIONS WILL LEAD TO LIMITED INSTABILITY UNDERNEATH THE SUBSIDENCE INVERSION. THIS WILL CAUSE A SCT TO BKN CU DECK TO DEVELOP LATE THIS MORNING AND AFTERNOON. AN ISOLATED SHOWER OR TWO CANNOT BE RULED OUT...MAINLY NEAR AND EAST OF INTERSTATE 95 WHERE INSTABILITY MAY BE A TAD HIGHER DUE TO COLDER AIR ALOFT. HOWEVER...MOISTURE WILL BE LIMITED AND THERE IS NO NOTICEABLE LIFTING MECHANISM SO MUCH OF THE TIME WILL BE DRY AND ANY PRECIPITATION AMOUNTS WILL BE LIGHT. HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT...BRINGING DRY AND SEASONABLY COOL CONDITIONS. DID LEAN TOWARD THE COLDER GUIDANCE IN RURAL AREAS AND VALLEYS DUE TO RADIATIONAL COOLING. MIN TEMPS WILL RANGE FROM THE UPPER 30S IN SOME OF THE COLDER SPOTS OF THE POTOMAC HIGHLANDS TO THE MID AND UPPER 50S IN DOWNTOWN WASHINGTON AND BALTIMORE. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... HIGH PRESSURE WILL SLIDE TO OUR SOUTH SUNDAY AND IT WILL REMAIN OVER THE CAROLINAS INTO THE WESTERN ATLANTIC SUNDAY NIGHT THROUGH MONDAY NIGHT. A SOUTHWEST FLOW AROUND THE HIGH WILL USHER IN NOTICEABLY WARMER CONDITIONS. PLENTY OF SUNSHINE IS EXPECTED BOTH SUNDAY AND MONDAY. MAX TEMPS SUNDAY WILL RANGE FROM THE 60S IN THE MOUNTAINS TO THE UPPER 70S/NEAR 80 IN THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS. A LIGHT SOUTHWEST WIND WILL KEEP MILD CONDITIONS IN PLACE SUNDAY NIGHT. FOR MONDAY...MORE UPPER-LEVEL RIDGING IS EXPECTED AND SUBSIDENCE FROM THIS COMBINED WITH PLENTY OF SUNSHINE WILL RESULT IN EVEN WARMER CONDITIONS. MAX TEMPS WILL REACH THE 80S ACROSS MOST LOCATIONS. MILD AND DRY CONDITIONS WILL CONTINUE MONDAY NIGHT. && .LONG TERM /TUESDAY THROUGH FRIDAY/... SFC HIGH SETTLES OFFSHORE TUESDAY AS LOW PRESSURE TRACKS THROUGH SOUTHEASTERN CANADA. THE ASSOCIATED COLD FRONT WILL SINK SOUTH THRU THE GREAT LAKES REGION...BCMG STATIONARY AS IT REACHES THE MASON DIXON LINE BY WED MORNING WITH NEAR ZONAL FLOW SETTING UP ALOFT. INITIALLY DRY CONDITIONS TUES MORNING...WITH INCRSG CHC OF PCPN AS THE FRONT NEARS THEN STALLS OVER THE AREA. HAVE KEPT HIGHER POPS OVER THE NORTHERN PORTION OF THE CWA...CLOSER TO THE FRONT FOR TUES AFTN/OVERNIGHT. SOUTHERN PORTIONS OF THE CWA COULD VERY WELL END UP DRY DURING THIS TIME. CHC FOR PCPN CONTINUES THRU WED NIGHT WITH A DEEPENING UPPER LVL TROUGH ALONG THE EASTERN SEABOARD ALLOWING FOR THE STATIONARY FRONT TO SINK TO THE SOUTH...THOUGH STILL REMAINING IN CLOSE PROXIMITY TO THE CWA WITH AN OFFSHORE AREA OF LOW PRESSURE NUDGING TO THE NORTH LIMITING ANY FURTHER SOUTHERN MOVEMENT. THIS LOW WILL BECOME THE FOCUS FOR PCPN CHCS THEN FOR THE LATTER HALF OF THE WEEKEND...THOUGH CONFIDENCE IS STILL LOW FOR TIMING OF PCPN AS THE 00Z MODEL GUIDANCE SUITE HAS A WIDE RANGE OF SOLUTIONS WITH THE PLACEMENT OF THE LOWS TRACK AS WELL AS THE STRENGTH. HAVE SLIGHT CHC POPS TO ACCOUNT FOR THE UNCERTAINTY. 850MB TEMPS REMAIN ANYWHERE BETWEEN 10 AND 15 DEGREES CELSIUS THRU THE EXTENDED...KEEPING TEMPS WELL ABV NORMAL THRU THE PERIOD. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... UNCERTAINTY FOR FOG EARLY THIS MORNING IS HIGH. TEMP/DEWPOINT DEPRESSIONS ARE ONLY A FEW DEGREES BUT A MID-LEVEL CLOUD DECK HAS PREVENTED FOG FROM DEVELOPING SO FAR. HOWEVER...THE MID-LEVEL CLOUD DECK SHOULD THIN OUT TOWARD SUNRISE...ESPECIALLY ACROSS THE WESTERN TERMINALS KMRB AND KCHO. IFR CONDITIONS ARE POSSIBLE AND THERE MAY EVEN BE DENSE FOG CAUSING VLIFR CONDITIONS. FARTHER EAST...THE MID-LEVEL CLOUDS MAY HANG ON...BUT MVFR VSBYS CANNOT BE RULED OUT NEAR SUNRISE. ANY FOG WILL BURN OFF BY MID-MORNING AND VFR CONDITIONS ARE EXPECTED WITH A SCT TO BKN CU DECK NEAR 5KFT LATE THIS MORNING AND AFTERNOON. THE BEST CHANCE FOR A BKN CU DECK WILL ACROSS THE EASTERN TERMINALS...FROM KIAD EASTWARD. NORTHERLY WINDS AROUND 5 TO 10 KNOTS ARE EXPECTED DURING THIS TIME. HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT. LIGHT WINDS AND VFR CONDITIONS ARE EXPECTED FOR MOST OF THE TIME. HOWEVER...PATCHY BR MAY RESULT IN MVFR VSBYS ACROSS THE WESTERN TERMINALS EARLY SUNDAY MORNING. HIGH PRESSURE WILL BUILD TO THE SOUTH LATER SUNDAY THROUGH MONDAY NIGHT. SOUTHWEST WINDS AND VFR CONDITIONS ARE EXPECTED. GENERALLY EXPECTING VFR CONDITIONS TUES-FRI...WITH PSBL SUB-VFR CONDITIONS WITH SHOWERS/TSTMS TUES-WED. && .MARINE... WINDS WILL TURN TO THE NORTH LATER THIS MORNING AS HIGH PRESSURE APPROACHES FROM THE WEST. HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT AND THEN SHIFT TO THE SOUTH SUNDAY THROUGH MONDAY NIGHT. WINDS WILL TURN TOWARD THE SOUTH OR SOUTHWEST DURING THIS TIME. HOWEVER...WINDS SHOULD REMAIN BELOW SCA CRITERIA TODAY THROUGH MONDAY. WINDS MAY APPROACH SCA CRITERIA ACROSS PORTIONS OF THE WATERS MONDAY NIGHT AS THE PRESSURE GRADIENT STRENGTHENS A BIT. SUB-SCA CONDITIONS EXPECTED TUES-WED WITH HIGH PRESSURE OVER THE WATERS. PSBL SCA GUSTS THURS-FRI...DEPENDING ON THE TRACK OF THE LOW. && .TIDES/COASTAL FLOODING... A LIGHT ONSHORE FLOW HAS CAUSED TIDAL ANOMALIES TO INCREASE TO AROUND ONE-HALF TO ONE FOOT ABOVE NORMAL ACROSS THE CHESAPEAKE BAY AND TIDAL POTOMAC RIVER. THE ONSHORE FLOW WILL CONTINUE EARLY THIS MORNING BEFORE TURNING MORE TOWARD THE NORTH AFTER SUNRISE. ELEVATED WATER LEVELS ARE EXPECTED THROUGH THE HIGH TIDE CYCLE EARLY THIS MORNING THE ANOMALIES SHOULD HOLD OR PERHAPS EVEN INCREASE A BIT THROUGH DURING THIS TIME. THIS WILL CAUSE WATER LEVELS TO COME CLOSE TO MINOR FLOODING THRESHOLDS...ESPECIALLY NEAR ANNAPOLIS WITH THE HIGH TIDE CYCLE THIS MORNING. DID NOT ISSUE AND ADVISORY SINCE CURRENT ANOMALIES SUGGEST THAT IT WILL FALL JUST SHORT...BUT IT WILL BE CLOSE. THE HIGH TIDE CYCLE LATE TONIGHT INTO SUNDAY MORNING WILL LIKELY CONTAIN ELEVATED WATER LEVELS. HOWEVER...WITH THE WINDS SHIFTING TOWARD THE NORTH TODAY...CURRENT FEELING IS THAT WATER LEVELS SHOULD BE BELOW MINOR FLOODING THRESHOLDS. WILL HAVE TO MONITOR BECAUSE CONFIDENCE IS LOW. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR VAZ025>027- 029-030. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL LONG TERM...BJL/SEARS AVIATION...BJL/SEARS MARINE...BJL/SEARS TIDES/COASTAL FLOODING...BJL

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