Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 300759 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 359 AM EDT THU JUL 30 2015 .SYNOPSIS...
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A COLD FRONT WILL CROSS THE AREA THIS AFTERNOON WITH SHOWERS AND THUNDERSTORMS EXPECTED. HIGH PRESSURE BUILDS INTO THE AREA TONIGHT AND PERSISTS INTO EARLY NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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AS OF 07Z...SFC HIGH PRESSURE IS OFFSHORE WITH A LIGHT SLY FLOW OVER THE AREA. THIS FLOW...ALONG WITH MID/HIGH CLOUDS HAS LIMITED FOG POTENTIAL. THE APPROACHING COLD FRONT IS OVER SERN OH WITH A SCATTERED LINE OF PREFRONTAL SHOWERS AND THUNDERSTORMS OVER CENTRAL WV. DEWPOINTS ARE IN THE LOW TO MID 70S WITH MUCAPE AROUND 500 J/KG. THIS ACTIVITY WILL SHIFT EAST ACROSS THE AREA TODAY...PUSHING EAST OF THE BAY THIS EVENING. DUE TO WLY FLOW WITH THE ACTIVITY...EXPECT A TYPICAL PATTERN OF GREATER COVERAGE NORTH IN THE CWA DUE TO INCREASING DOWNSLOPING EFFECTS FROM NORTH TO SOUTH FROM THE ALLEGHENY FRONT. THEREFORE...LIKELY POPS PROGRESS EAST ACROSS THE NRN 2/3 OF THE CWA WITH CHANCE POPS FOR THE SRN THIRD. EXCEPTIONAL SFC MOISTURE OVER THE AREA MAKES THE GREATEST RISK TODAY FLASH FLOODING FROM EXCESSIVE RAINFALL. ACTIVITY EXPECTED TO BE PROGRESSIVE...SO THIS THREAT IS ISOLATED AT BEST. THERE IS A MARGINAL SEVERE RISK EAST OF THE BLUE RIDGE WHERE DIURNAL TIMING OF ACTIVITY IS BEST (AFTERNOON). HOWEVER...DEEP MOISTURE JUST LIKE YESTERDAY WILL LIMIT MID LEVEL LAPSE RATES AND THE SEVERE THREAT. JUST A LOW WET MICROBURST THREAT WITH THE STRONGEST ACTIVITY. WILL NEED TO WATCH FOR TWO LINES DEVELOPING THIS AFTERNOON...THE BROKEN PREFRONTAL LINE WITH A SECOND BROKEN LINE ON THE FRONT ITSELF THRIVING ON ANY REMAINING UNTAPPED INSTABILITY. BOTH LINES LOOK TO BE GENERAL-YET-HEAVY THUNDERSTORMS. HOT TODAY WITH MAX TEMPS LOW 90S EAST OF THE BLUE RIDGE WHERE THICK CLOUDS SHOULD HOLD OUT THE LONGEST. DEWPOINTS IN THE LOW TO MID 70S WILL RESULT IN MAX HEAT INDICES AGAIN AROUND 100F (JUST LIKE PREVIOUS TWO DAYS). NO HEAT ADVISORY...BUT IT WILL BE UNCOMFORTABLE UNTIL THE STORMS HIT/FRONT CROSSES.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
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COLD FRONT CLEARS THE SERN ZONES THURSDAY EVENING WITH DRIER AIR TRAILING. DEWPOINTS DROP INTO THE UPR 50S/LOW 60S TONIGHT. MIN TEMPS 60S WEST OF I-95...LOW 70S EAST. FRIDAY...H85 TEMPS 16-18 WITH MAX TEMPS AROUND 90F. DEWPOINTS WILL BE DOWN AROUND 60F...SO NO HEAT INDEX IS EXPECTED. DRY.
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&& .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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WEAK HIGH PRESSURE BUILDS FRI NIGHT. A PRESSURE TROUGH ESTABLISHES SAT WITH SOME MOISTURE RETURN AND A SLIGHT CHANCE OF SHOWERS AND T-STORMS. SFC RIDGE BUILDS AGAIN SUN GIVING WAY TO A HOT SUNNY DAY. WINDS TURN SWRLY AGAIN ON MON AS PRESSURE TROUGH ESTABLISHES WITH SOME MOISTURE RETURN AND A RISK OF T-STORMS. A CDFNT PUSHES THROUGH THE AREA TUE WITH DRY NWRLY WINDS AND A COOLING TREND MID TO LATE NEXT WEEK AS HIGH PRES BUILDS OVER THE REGION. IN SUMMARY...HOT WX DURING THE WEEKEND AND EARLY NEXT WEEK THEN TURNING COOLER MID WEEK ON. PRECIP LOOKS TO BE BELOW NORMAL NEXT 7 DAYS.
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&& .AVIATION /08Z THURSDAY THROUGH MONDAY/...
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VFR PREVAILS THIS MORNING WITH HIGH PRESSURE OFFSHORE AND SLY FLOW 5- 10KT. WEAK COLD FRONT CURRENTLY ENTERING WV CROSSES TERMINALS LATE THIS MORNING THROUGH THE AFTERNOON WITH LIKELY THUNDERSTORMS FOR ALL TAFS EXCEPT KCHO MIDDAY INTO THIS EVENING. THUNDERSTORMS END THIS EVENING WITH NWLY FLOW AROUND 10 KT AFTER THE FRONT. DRIER AND VFR TONIGHT AND FRIDAY. A SLIGHT RISK OF T-STORMS SAT AND MON. REST OF THE TIME LOOKS FINE WITH VFR CONDITIONS.
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&& .MARINE...
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SCA FOR SLY CHANNELING FOR MOST BAY WATERS UNTIL SUNRISE. SCA FOR ALL WATERS STARTING AT 3PM AND CONTINUING UNTIL LATE EVENING AS A WEAK COLD FRONT WITH HEAVY AND GUSTY THUNDERSTORMS CROSS. SCA CONTINUES FOR MAIN BAY WATERS FOR NWLY FLOW 15 TO 20 KT LATE TONIGHT. FLOW DECREASES TO 10 TO 15 KT FRIDAY. POSSIBLE SCA SATURDAY AFTERNOON. OTHERWISE...WINDS SHOULD REMAIN BELOW SCA MOST OF THE 5-DAY FCST PERIOD. A SLIGHT RISK OF T-STORMS SAT AND MON.
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&& .TIDES/COASTAL FLOODING...
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WATER LEVELS AROUND 0.65FT ABOVE NORMAL AT ANNAPOLIS IS MAKING FOR A MINOR COASTAL FLOOD (THRESHOLD 2.4FT). COLD FRONT CROSSES THIS EVENING...SO NO FURTHER FLOODING EXPECTED.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...COASTAL FLOOD ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MDZ014. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR ANZ530>534-537-539>541-543. SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM EDT FRIDAY FOR ANZ530>533-538>541. SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 10 PM EDT THIS EVENING FOR ANZ535-536-542. SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 8 AM EDT FRIDAY FOR ANZ534-537-543.
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&& $$ SYNOPSIS...LFR NEAR TERM...BAJ SHORT TERM...BAJ LONG TERM...LFR AVIATION...BAJ/LFR MARINE...BAJ/LFR TIDES/COASTAL FLOODING...BAJ

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