Area Forecast Discussion
Issued by NWS Sterling, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KLWX 041400
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1000 AM EDT FRI SEP 4 2015

.SYNOPSIS...
A BACKDOOR COLD FRONT WILL SINK SOUTH ACROSS THE
WATERS LATE TODAY INTO TONIGHT. HIGH PRESSURE WILL BUILD OVERHEAD
DURING THE LABOR DAY WEEKEND BEFORE MOVING OFF THE COAST DURING
THE MIDDLE PORTION OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
UPPER-LEVEL LOW PRESSURE WILL WEAKEN OVER THE GREAT LAKES THIS
AFTERNOON INTO TONIGHT WHILE HIGH PRESSURE BUILDS OVER NEW
ENGLAND. A BACKDOOR COLD FRONT WILL APPROACH THE AREA FROM THE
NORTH AND EAST THIS AFTERNOON BEFORE STALLING OUT OVER THE AREA
TONIGHT.

A NORTHERLY FLOW LATE THIS MORNING WILL TURN TO THE EAST THIS
AFTERNOON AS THE BACKDOOR BOUNDARY APPROACHES THE AREA.
HOWEVER...THE TEMPERATURE AND DEWPOINT GRADIENT SHOULD REMAIN WELL
OFF TO OUR NORTH AND EAST. THEREFORE...MORE HOT AND HUMID
CONDITIONS ARE EXPECTED WITH MAX TEMPS IN THE UPPER 80S AND LOWER
90S ACROSS MOST LOCATIONS. THE HEAT AND HUMIDITY WILL LEAD TO MORE
INSTABILITY. MODIFIED 12Z SOUNDING FROM KLWX SHOWS OVER 2KJ/KG OF
MLCAPE THIS AFTERNOON. FORCING MECHANISMS WILL BE WEAK...WITH
LITTLE CONVERGENCE ALONG THE BACKDOOR BOUNDARY AND TERRAIN
CIRCULATION OVER THE MOUNTAINS. STILL FEEL THAT IT WILL BE ENOUGH
FOR SCATTERED THUNDERSTORMS THIS AFTERNOON AND EVENING. DRIER AIR
SHOULD BUILD IN BEHIND THE FRONT...CAUSING ANY THUNDERSTORMS TO
QUICKLY DISSIPATE EARLY THIS EVENING NEAR WASHINGTON AND
BALTIMORE. HOWEVER...A FEW SHOWERS AND THUNDERSTORMS MAY CONTINUE
THROUGH MOST OF THE EVENING NEAR AND WEST OF THE BLUE RIDGE
MOUNTAINS.

THE BACKDOOR BOUNDARY WILL STALL OUT NEAR THE POTOMAC HIGHLANDS
INTO CENTRAL VIRGINIA AND SOUTHERN LATE TONIGHT. A FEW SHOWERS
ARE POSSIBLE ACROSS THESE AREAS...BUT PRECIPITATION AMOUNTS WILL
BE LIGHT DUE TO LIMITED INSTABILITY. ELSEWHERE...DRY CONDITIONS
WILL PREVAIL OVERNIGHT BUT LOW CLOUDS ARE EXPECTED AS MOISTURE
GETS TRAPPED UNDERNEATH THE SUBSIDENCE INVERSION.

&&

.SHORT TERM /SATURDAY/...
HIGH PRESSURE CONTINUES TO MOVE SOUTHWARD SATURDAY
AND COOLER DRIER AIR WILL MAKE ITS WAY INTO THE REGION. CLEARING
WILL INCREASE FROM N- S AS WELL WITH THE EXCEPTION OF THE SW WHERE
THE FRONT MAY STILL BE LOCATED. TEMPS IN THE 70S TO LOW 80S ARE
EXPECTED SATURDAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
SFC HIGH PRES OVER THE NORTHEAST WILL KEEP A DRY ENE FLOW AND
COMFORTABLE TEMPS THROUGH MON. SFC HIGH WEAKENS MORE RAPIDLY MON
THROUGH THE END OF NEXT WEEK WHILE MID-UPPER LEVEL HEIGHTS RISE
OVER THE MID ATLC RESULTING IN A WARMING TREND. IS NOT REALLY
UNTIL WED WHEN SFC HIGH WEAKENS ENOUGH TO ALLOW MOISTURE RETURN
INTO THE AREA. WILL KEEP FCST DRY THROUGH TUE NIGHT THEN BRING
CHANCES OF SHOWERS AND T-STORMS WED AFTERNOON WEST OF THE BLUE
RIDGE INTO THU FOR THE ENTIRE AREA. GLOBAL MODELS SHOW A SLOW
MOVING CDFNT CROSSING THE AREA THU OR THU NIGHT BUT SHOW SIG
DIFFERENCES WITH RESPECT TO TIMING AND WHETHER FRONT CLEARS THE
ENTIRE AREA OR NOT.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
NORTHERLY WINDS LATE THIS MORNING WILL TURN EASTERLY THIS
AFTERNOON. SCATTERED THUNDERSTORMS ARE EXPECTED AND BRIEF PERIODS
OF IFR CONDITIONS AND GUSTY WINDS ARE POSSIBLE IN ANY
THUNDERSTORMS. THE BEST CHANCE WILL BE DURING THE MID TO LATE
AFTERNOON HOURS ACROSS THE EASTERN TERMINALS...BUT THE
THUNDERSTORM CHANCES MAY CONTINUE WELL INTO THIS EVENING ACROSS
THE WESTERN TERMINALS.

MVFR/IFR CIGS ARE LIKELY LATER THIS EVENING AND OVERNIGHT DUE TO
THE EASTERLY FLOW. LOW CLOUDS SHOULD BURN OFF SATURDAY MORNING FOR
MOST AREAS...BUT THEY MAY HOLD ON INTO THE AFTERNOON ACROSS KCHO.
MORE LOW CLOUDS ARE POSSIBLE OVERNIGHT SATURDAY INTO SUNDAY.

NO AVIATION CONCERNS EARLY NEXT WEEK.

&&

.MARINE...
N WINDS BECOME EASTERLY TODAY. WINDS WILL INCREASE THIS EVENING
BEHIND A BACKDOOR COLD FRONT AND SCA CONDITIONS ARE EXPECTED
TONIGHT AND INTO SATURDAY. THE PRESSURE GRADIENT WILL BE FAVORABLE
FOR GUSTY WINDS ON THE BAY THROUGH SATURDAY. CONFIDENCE IS LOWER
ACROSS THE UPPER TIDAL POTOMAC AS IT IS CLOSER TO THE CENTER OF
THE HIGH.

SCA MAY LINGER OVER THE MIDDLE AND LOWER BAY INTO THE FIRS PART OF SUN.

&&

.TIDES/COASTAL FLOODING...
ANOMALIES REMAIN ABOUT HALF FOOT ABOVE NORMAL AS LIGHT
NORTHEASTERLY FLOW OCCURS ON THE WATERS. THE FLOW WILL TURN TO
THE EAST THIS AFTERNOON BUT IT SHOULD BE LIGHT ENOUGH TO KEEP
WATER LEVELS BELOW FLOODING THRESHOLDS.

THE EASTERLY FLOW WILL STRENGTHEN TONIGHT INTO SATURDAY. MINOR TIDAL
FLOODING IS POSSIBLE NEAR TIME OF HIGH TIDE.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 2 PM EDT
     SATURDAY FOR ANZ530>534-537>543.
     SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 2 PM EDT
     SATURDAY FOR ANZ535-536.

&&

$$
SYNOPSIS...LFR
NEAR TERM...BJL/HAS
SHORT TERM...HAS
LONG TERM...LFR
AVIATION...BJL/HAS/LFR
MARINE...BJL/HAS/LFR
TIDES/COASTAL FLOODING...BJL/HAS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.