Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 030713 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 313 AM EDT MON AUG 3 2015 .SYNOPSIS...
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A COLD FRONT WILL APPROACH THE AREA TODAY BEFORE STALLING OUT OVERHEAD TONIGHT THROUGH FRIDAY. LOW PRESSURE WILL RIDE A STALLED FRONT...PASSING THROUGH THE MID ATLANTIC THURSDAY AND FRIDAY BEFORE PUSHING OFFSHORE BY SATURDAY. HIGH PRESSURE BUILDS SOUTH THEN FOR THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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CURRENT ANALYSIS SHOWS A COLD FRONT OVER THE EASTERN GREAT LAKES THIS MORNING. POTENT UPPER-LEVEL LOW PRESSURE CONTINUES TO SPIN OVER THE HUDSON BAY AND THE UPPER-LEVEL TROUGH AXIS ASSOCIATED WITH THIS SYSTEM EXTENDS SOUTH INTO THE MID-ATLANTIC. A SQUALL LINE CONTINUES TO DIVE SOUTH AHEAD OF THE COLD FRONT INTO THE OHIO VALLEY EARLY THIS MORNING. CURRENT FEELING IS THAT THIS WILL WEAKEN AS THE MORNING PROGRESSES...SO IT SHOULD NOT IMPACT OUR AREA. THE COLD FRONT WILL SLOWLY DROP SOUTH AND EAST APPROACHING OUR AREA TODAY. SOUTHWEST WINDS AHEAD OF THE FRONT ALONG WITH A DEEP MIXING LAYER AND PLENTY OF SUNSHINE WILL ALLOW FOR UNSEASONABLY HOT CONDITIONS. MAX TEMPS WILL REACH THE LOWER TO MIDDLE 90S ACROSS MOST LOCATIONS. DEEP TROPICAL MOISTURE WILL REMAIN SUPPRESSED TO OUR SOUTH TODAY...SO DEWPOINTS SHOULD MIX DOWN INTO THE 50S AND 60S TODAY...KEEPING HEAT INDICES CLOSER TO AIR TEMPERATURES. THE COLD FRONT WILL MOVE INTO THE REGION THIS EVENING. A THETA-E RIDGE AHEAD OF THE BOUNDARY MAY INCREASE INSTABILITY SOME...AND THIS WILL BRING THE CHANCE FOR SHOWERS AND THUNDERSTORMS. THE BEST CHANCE FOR CONVECTION WILL BE ACROSS NORTHERN MARYLAND INTO THE POTOMAC HIGHLANDS WHERE FORCING ON THE BOUNDARY WILL BE STRONGER. THE BOUNDARY WILL STALL OVERHEAD LATE TONIGHT...AND A COUPLE SHOWERS OR THUNDERSTORMS MAY IMPACT THE AREA DURING THIS TIME...BUT MOST OF THE TIME SHOULD BE DRY SINCE FORCING ON THE FRONT WILL BE WEAK. THERE WILL BE LITTLE TEMPERATURE GRADIENT ALONG THE FRONT...BUT IT WILL BE WARMER AND MORE HUMID NEAR AND EAST OF THE I-95 CORRIDOR. MIN TEMPS WILL RANGE FROM THE 60S ACROSS MOST AREAS WEST OF THE BLUE RIDGE MOUNTAINS TO THE MID AND UPPER 70S NEAR DOWNTOWN WASHINGTON/BALTIMORE AND ALSO EAST OF INTERSTATE 95.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
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THE BOUNDARY WILL REMAIN STALLED OVERHEAD...MOST LIKELY NEAR INTESTATE 95 SOUTH AND WEST ACROSS CENTRAL VIRGINIA INTO THE POTOMAC HIGHLANDS. AGAIN...LITTLE TEMPERATURE GRADIENT IS EXPECTED ALONG THE BOUNDARY SO MOST AREAS WILL TURN OUT QUITE WARM WITH MAX TEMPS IN THE UPPER 80S TO LOWER 90S FOR MANY LOCATIONS. A COUPLE SHOWERS AND THUNDERSTORMS MAY POP UP...MAINLY DURING THE AFTERNOON AND EVENING HOURS ALONG AND AHEAD OF THE BOUNDARY. THE BOUNDARY WILL REMAIN NEARLY STATIONARY TUESDAY NIGHT...BUT ANY CONVECTION SHOULD DISSIPATE DUE TO THE LOSS OF DAYTIME HEATING. THE BOUNDARY MAY SHIFT A BIT FARTHER SOUTH FOR WEDNESDAY AND WEDNESDAY NIGHT...BUT WITH A ZONAL FLOW ALOFT IT SHOULD NOT MOVE TOO FAR. A WESTERLY FLOW WILL ALLOW FOR MORE WARM CONDITIONS ACROSS ALL AREAS...BUT HUMIDITY MAY BE A BIT HIGHER ACROSS SOUTHERN MARYLAND AND CENTRAL VIRGINIA CLOSER TO THE BOUNDARY. THEREFORE...A COUPLE SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS THESE AREAS WEDNESDAY AFTERNOON AND EVENING. HOWEVER...MOST AREAS SHOULD REMAIN DRY SINCE THE BOUNDARY WILL BE WEAK. A POTENT AREA OF LOW PRESSURE WILL STRENGTHEN OVER THE MIDWEST OVERNIGHT WEDNESDAY. LATEST GUIDANCE SHOWS THIS SYSTEM BEING A BIT SLOWER THAN PREVIOUSLY FORECASTED. THEREFORE...POPS HAVE BEEN TWEAKED DOWN A BIT WITH THE LATEST FORECAST UPDATE. WILL CONTINUE WITH A SLIGHT CHANCE/CHANCE FOR SHOWERS OVERNIGHT BUT IF THE LATEST TRENDS CONTINUE IT ACTUALLY END UP DRY DURING THIS TIME.
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&& .LONG TERM /THURSDAY THROUGH SUNDAY/...
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00Z MODEL SUITE HAS A WEAKENING STATIONARY FRONT POSITIONED OVER SOUTHERN VA BY 12Z THURS. SOME INCONSISTENCIES ON SFC LOW PRESSURE ORGANIZING OVER THE MIDWEST...WITH ALL BUT THE GFS DEVELOPING A CLOSED LOW THAT THEN PROCEEDS TO DEEPEN AS IT RIDES THE FRONTAL BOUNDARY. WILL GO WITH MORE OF THE CONSISTENT SOLUTION AND BRING THE CLOSED SFC LOW INTO THE MID ATLANTIC THURS NIGHT. CONCERNING PCPN...USING THIS SOLUTION WOULD HAVE SHOWERS AND EMBEDDED TSTMS OVERSPREADING THE REGION DURING THE DAY THURS AND THRU THE NIGHT INTO FRI...CORRESPONDING WITH THE PASSAGE WITH MID LVL SHORTWAVE ENERGY. THE EXACT PATH OF THE LOW WILL DICTATE THE EXTEND OF ANY TSTM ACTIVITY...WITH THE BETTER CHC IN THE LATEST RUNS INDICATING CENTRAL VA AND SOUTH. THE LOW PUSHES OFFSHORE FRI NIGHT WITH HIGH PRESSURE OVER CANADA THEN ATTEMPTING TO BUILD SOUTH. AM KEEPING SLIGHT CHC POPS IN DURING THE WEEKEND TO ACCOUNT FOR MULTIPLE SHORTWAVES MVG THRU THE REGION WHICH COMBINED WITH DIURNAL HEATING COULD TRIGGER SHOWERS AND PSBL EVEN TSTMS. TEMPS NEAR OR SLIGHTLY BELOW NORMAL THRU THE EXTENDED.
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&& .AVIATION /07Z MONDAY THROUGH FRIDAY/...
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VFR CONDITIONS ARE EXPECTED MOST OF THE TIME TODAY THROUGH WEDNESDAY NIGHT. SOUTHWEST WINDS WILL GUST AROUND 15 TO 20 KNOTS THIS AFTERNOON. PATCHY BR MAY REDUCE VSBYS BRIEFLY TO MVFR LEVELS LATE TONIGHT INTO TUESDAY MORNING. A SHOWER OR THUNDERSTORM IS POSSIBLE THIS EVENING...ESPECIALLY ACROSS KMRB BUT CONVECTION SHOULD REMAIN ISOLATED/SCATTERED. A COUPLE SHOWERS AND THUNDERSTORMS MAY POP UP NEAR THE EASTERN TERMINALS TUESDAY AFTERNOON AND EVENING AS WELL. SUB-VFR CONDITIONS LIKELY THURS INTO FRI WITH DEVELOPING SHOWERS AND TSTMS. PCPN WILL BE MORE OCNL IN NATURE DURING THE DAY THURS...BCMG MORE WIDESPREAD THURS NIGHT AND FRI BEFORE TAPERING OFF BY FRI NIGHT. VFR CONDITIONS RETURN FOR THE WEEKEND.
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&& .MARINE...
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A COLD FRONT WILL APPROACH THE WATERS TODAY. A SOUTH TO SOUTHWEST FLOW AHEAD OF THE BOUNDARY WILL STRENGTHEN DUE TO AN INCREASING PRESSURE GRADIENT. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE WATERS THIS AFTERNOON AND EVENING. SOUTH TO SOUTHWEST WINDS MAY CHANNEL UP THE BAY AND LOWER TIDAL POTOMAC RIVER OVERNIGHT INTO TUESDAY. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER TONIGHT...AND FOR THE MIDDLE PORTION OF THE BAY AND LOWER TIDAL POTOMAC RIVER TUESDAY MORNING. A BOUNDARY WILL REMAIN NEAR THE WATERS FOR TUESDAY AND WEDNESDAY. A COUPLE SHOWERS AND THUNDERSTORMS ARE POSSIBLE TUESDAY AFTERNOON AND EVENING. CONVECTION MAY BE SUPPRESSED FURTHER SOUTH WEDNESDAY AFTERNOON AND EVENING. SUB-SCA CONDITIONS CURRENTLY EXPECTED THURS AND FRI. DEPENDING ON THE STRENGTH OF THE LOW...COULD SEE SCA CONDITIONS THURS NIGHT INTO FRI. SUB-SCA CONDITIONS THEN FOR THE WEEKEND.
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&& .TIDES/COASTAL FLOODING...
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TIDAL ANOMALIES REMAIN BELOW A HALF FOOT EARLY THIS MORNING. SOUTHERLY FLOW AHEAD OF AN APPROACHING COLD FRONT WILL ELEVATE TIDAL ANOMALIES THIS AFTERNOON THROUGH TONIGHT. WATER LEVELS MAY COME CLOSE TO MINOR FLOODING THRESHOLDS FOR SENSITIVE AREAS AROUND HIGH TIDE TONIGHT...AND AGAIN TUESDAY MORNING. HOWEVER...LATEST GUIDANCE CONTINUES TO KEEP WATER LEVELS BELOW THOSE MINOR THRESHOLDS...WHICH MAKES SENSE SINCE THIS WINDS ARE EXPECTED TO SHIFT WEST OF SOUTH LATER TONIGHT INTO TUESDAY. WATER LEVELS WILL HAVE TO BE MONITORED...SINCE IT WILL BE CLOSE.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM EDT TUESDAY FOR ANZ530-531-538-539. SMALL CRAFT ADVISORY FROM NOON TODAY TO NOON EDT TUESDAY FOR ANZ532>534-537-540>543. SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR ANZ535-536.
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&& $$ 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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