Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 240019 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 819 PM EDT SAT AUG 23 2014 .SYNOPSIS... A WEAK COLD FRONT WILL PUSH SOUTH AND WEST THROUGH THE APPALACHIANS THIS EVENING. HIGH PRESSURE WILL BUILD FROM THE CANADIAN MARITIMES DOWN THE COAST...REACHING THE DELMARVA BY SUNDAY...AND REMAINING THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH SUNDAY/... LATEST ANALYSIS SHOWS HIGH PRESSURE EXTENDING THROUGH NEW ENGLAND. A WEAK COLD FRONT IS LOCATED OVER THE APPALACHIAN MOUNTAINS AND AN EASTERLY FLOW BEHIND THE BOUNDARY HAS CAUSED MOISTURE TO MOVE IN FROM THE ATLANTIC. THE EASTERLY FLOW WILL CONTINUE ACROSS MOST OF THE AREA THIS EVENING AS THE COLD FRONT SLOWLY MOVES SOUTH AND WEST THROUGH THE APPALACHIAN MOUNTAINS. SHOWER ACTIVITY HAS BEEN MOVING SOUTHWARD THIS EVENING...WITH MOST AREAS DRYING OUT FOR AT LEAST A BRIEF TIME. THE HIGH WILL REMAIN TO OUR NORTH TONIGHT...WITH LIGHT NORTHEASTERLY FLOW ACROSS THE REGION. LOW CLOUDS AND AREAS OF FOG ARE EXPECTED AS LOW-LEVEL MOISTURE GETS TRAPPED UNDERNEATH THE NOCTURNAL INVERSION. SCATTERED LIGHT RAIN/SHOWERS ARE EXPECTED TO REDEVELOP...MAINLY ALONG AND WEST OF THE BLUE RIDGE. MIN TEMPS WILL RANGE FROM THE UPPER 50S AND LOWER 60S IN THE MOUNTAINS TO THE MIDDLE 60S IN DOWNTOWN WASHINGTON AND BALTIMORE. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA SUNDAY...ALLOWING FOR DRIER AIR TO MOVE IN FROM THE NORTH AND EAST. A FEW MORNING SHOWERS ARE POSSIBLE ACROSS CENTRAL VIRGINIA INTO THE POTOMAC HIGHLANDS...BUT EVEN ACROSS THESE AREAS SUNDAY AFTERNOON SHOULD TURN OUT DRY. MAX TEMPS WILL RANGE FROM THE UPPER 60S AND LOWER 70S IN THE MOUNTAINS TO NEAR 80 IN WASHINGTON AND BALTIMORE. NICE STRETCH OF WEATHER COMING UP SUNDAY NIGHT THROUGH WEDNESDAY AS POSITIVELY TILTED UPPER RIDGE DOMINATES THE UPPER PATTERN OVERHEAD. SURFACE HIGH PRESSURE BUILDING IN BEHIND BACKDOOR COLD FRONT...AND PWATS UNDER ONE INCH WILL RESULT IN LOW HUMIDITY WITH LIGHT WINDS AND BELOW NORMAL TEMPERATURES THROUGH EARLY WEEK. TEMPS AND HUMIDITY BEGIN TO MODERATE BY WEDNESDAY AS UPPER RIDGE NUDGES EASTWARD. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... NICE STRETCH OF WEATHER COMING UP SUNDAY NIGHT THROUGH WEDNESDAY AS POSITIVELY TILTED UPPER RIDGE DOMINATES THE UPPER PATTERN OVERHEAD. SURFACE HIGH PRESSURE BUILDING IN BEHIND BACKDOOR COLD FRONT...AND PWATS UNDER ONE INCH WILL RESULT IN LOW HUMIDITY WITH LIGHT WINDS AND BELOW NORMAL TEMPERATURES THROUGH EARLY WEEK. TEMPS AND HUMIDITY BEGIN TO MODERATE BY WEDNESDAY AS UPPER RIDGE NUDGES EASTWARD. TROUGH PROGRESSING ACROSS THE NORTHERN CONUS LATE IN THE WEEK IS NOW SLOWER THAN PREVIOUS RUNS WHICH BRINGS THE TRACK OF TROPICAL SYSTEM FARTHER WEST ON BACKSIDE OF MID-LEVEL UPPER RIDGE FLOW. CURRENT TRACK IS STILL WELL OFFSHORE TO THE SOUTHEAST OF THE MID-ATLANTIC LATE IN THE WEEK BUT UNCERTAINTY EXISTS ATTM. AFOREMENTIONED UPPER TROUGH WILL THEN DRAG A SURFACE COLD FRONT EASTWARD ACROSS THE REGION NEXT WEEKEND WITH DEEP LAYER SHEAR AND INSTABILITY PROFILES LOOKING FAVORABLE FOR SOME ORGANIZED CONVECTION. FROPA TIMING DIFFERENCE STILL PRESENT BETWEEN EXTENDED MODELS HOWEVER...WITH THE EURO MUCH LESS PROGRESSIVE. TEMPERATURES WILL CLIMB BACK TO NEAR NORMAL AHEAD OF THE THIS FRONT AS RETURN FLOW SETS IN THURSDAY AND FRIDAY. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... HIGH PRESSURE REMAINS TO OUR NORTH TONIGHT. LIGHT EASTERLY FLOW IS EXPECTED TO KEEP LOW LEVEL MOISTURE IN PLACE. AS A RESULT...MVFR CIGS EXPECTED ACROSS THE TERMINALS. CIGS MAY DROP TO IFR TONIGHT AND FOG MAY DEVELOP...MORE LIKELY OVER KCHO AND KMRB...BUT POTENTIAL EXISTS FOR BALTIMORE/DC TERMINALS AS WELL. SOME OCCASIONAL LIGHT RAIN IS POSSIBLE AS WELL...ALTHOUGH CONFIDENCE IN TIMING/LOCATION IS NOT STRONG ENOUGH TO PUT IN TAFS AT THE MOMENT. ANY LOW CLOUDS AND FOG WILL BURN OFF SUNDAY MORNING...WITH VFR CONDITIONS RETURNING. E-NE WINDS EXPECTED...LESS THAN 10KT. HIGH PRESSURE WILL PREVAIL THROUGH MID WEEK BEFORE A COLD FRONT APPROACHES FRIDAY. && .MARINE... A PRESSURE SURGE IS EXPECTED BEHIND A COLD FRONT TONIGHT. THIS WILL CAUSE WIND GUSTS AROUND SCA CRITERIA FOR THE MARYLAND CHESAPEAKE BAY SOUTH OF POOLES ISLAND AND THE LOWER TIDAL POTOMAC RIVER. A SMALL CRAFT ADVISORY IS IN EFFECT UNTIL 10 AM SUNDAY MORNING FOR THESE AREAS. ELSEWHERE...WIND GUSTS HAVE BEEN CAPPED AT 10 TO 15 KNOTS. HIGH PRESSURE WILL THEN BUILD ACROSS THE AREA THROUGH MID WEEK BEFORE A COLD FRONT APPROACHES FRIDAY. WINDS LOOK TO STAY BELOW SCA LEVELS. && .TIDES/COASTAL FLOODING... A COASTAL FLOOD ADVISORY IS IN EFFECT FOR THE WESTERN SHORE OF THE CHESAPEAKE BAY AND THE UPPER TIDAL POTOMAC FOR HIGH TIDE LATE TONIGHT INTO SUNDAY MORNING. THIS IS THE HIGHER OF THE TWO DAILY HIGH TIDE CYCLES...AND ANOMALIES SHOULD BE AROUND ONE FOOT OR SLIGHTLY HIGHER. THE EASTERLY FLOW WILL CONTINUE INTO MONDAY. THE HIGH TIDE CYCLE LATE SUNDAY NIGHT INTO MONDAY MORNING MAY CAUSE MORE MINOR TIDAL FLOODING FOR SENSITIVE LOCATIONS. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EDT SUNDAY FOR DCZ001. MD...COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EDT SUNDAY FOR MDZ011-014-017-018. VA...COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EDT SUNDAY FOR VAZ054. COASTAL FLOOD ADVISORY UNTIL 9 PM EDT THIS EVENING FOR VAZ054. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EDT SUNDAY FOR ANZ531>534-537- 539>541-543. && $$ SYNOPSIS...BJL NEAR TERM...BJL/KCS SHORT TERM...AEB LONG TERM...AEB AVIATION...BJL/KCS/AEB MARINE...BJL/KCS/AEB TIDES/COASTAL FLOODING...KCS

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