Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180732 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 332 AM EDT THU SEP 18 2014 .SYNOPSIS...
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HIGH PRESSURE WILL CONTINUE ACROSS THE MID-ATLANTIC TODAY WHILE AN UPPER TROUGH AXIS PASSES OVERHEAD. THE HIGH WILL DRIFT ACROSS THE MID ATLANTIC REGION TO CLOSE OUT THE WEEK...WITH A COLD FRONT EXPECTED TO CROSS THE AREA LATE SUNDAY INTO MONDAY.
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&& .NEAR TERM /THROUGH FRIDAY/...
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HIGH PRESSURE IS CENTERED ACROSS THE MID-WEST THIS MORNING. A FLAT UPPER LEVEL TROUGH WILL CONTINUE ACROSS THE EASTERN HALF OF THE CONUS TODAY. A SHORTWAVE TROUGH CURRENTLY OVER THE OHIO VALLEY WILL APPROACH THE MID-ATLANTIC THIS MORNING. FOG HAS FORMED IN LOW LYING AREAS AND VALLEYS ACROSS THE PIEDMONT AND SHENANDOAH VALLEY THIS MORNING. A DEWPT GRADIENT EXISTS ACROSS THE CWA WITH PLACES NEAR THE MD/PA BORDER DRIER THAN THOSE IN CENTRAL VA DUE TO NRLY WINDS BRINGING DOWN LOWER DEWPTS. WINDS WILL VEER THROUGHOUT THE MORNING AND BECOME EASTERLY BY MIDDAY. AS THE SHORTWAVE TROUGH MOVES ACROSS THE MID- ATLANTIC TODAY AND E-SE WINDS DRAW MOISTURE INTO THE REGION AND UP AGAINST THE RIDGES ISO- SCT SHOWERS ARE POSSIBLE. THE BEST CHANCE WILL BE EAST OF THE BLUE RIDGE THIS AFTERNOON AS SFC HEATING AND MOISTURE ADVECTION INCREASES INSTABILITY. COVERAGE WILL BE ISO-SCT AT BEST AND ONLY LIGHT AMTS EXPECTED WITHIN SHOWERS. FCST MAX TEMPS TODAY WILL BE IN THE LOW TO MID 70S AND UPPER 70S IN THE CITIES/PIEDMONT/SOUTHERN MD. HIGH PRESSURE STRENGTHENS ACROSS THE MID-ATLANTIC TONIGHT AND WILL WEDGE DOWN THE EASTERN SEABOARD. WINDS WILL CONTINUE TO HAVE AN ONSHORE COMPONENT INTO FRIDAY MORNING. THIS WILL ALLOW MOISTURE TO POOL INTO THE REGION AND LOW STRATUS ARE EXPECTED ESPECIALLY NEAR THE BLUE RIDGE MTNS. THE WEDGE WILL HOLD FRIDAY AND EASTERLY FLOW THROUGH THE LOWEST 0-4 KM WILL LEAD TO MOSTLY CLOUDY CONDITIONS FOR MUCH OF THE LOOKOUT AREA. THE EXCEPTION BEING NEAR AND EAST OF THE I-95 CORRIDOR AND ALONG THE ALLEGHENY FRONT WHERE DRIER AIR WILL BE PRESENT. FCST MAX TEMPS WILL BE BELOW NORMAL DUE TO CLOUD COVER FRIDAY AND RANGE FROM THE UPPER 60S LOW 70S NEAR AND WEST OF THE BLUE RIDGE TO THE LOW TO MID 70S ALONG I-95 AND EAST.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/...
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HIGH PRESSURE WEDGE AXIS REMAINS IN PLACE ACROSS THE MID-ATLANTIC FRIDAY NIGHT UNDER WEAK FLOW ALOFT. LOW LEVEL MOISTURE PRESENT WITH WEAK ONSHORE FLOW COULD RESULT IN PATCHY GROUND/RIVER FOG DEVELOPING OVERNIGHT...AND INTRODUCED MENTION FOR FAVORED AREAS WEST OF THE METROS. SURFACE HIGH PRESSURE AXIS SHIFTS SOUTH SATURDAY AS WINDS VEER SOUTHEAST...AND SOUTHWEST ABOVE THE BOUNDARY LAYER. DECENT WARM AIR ADVECTION ENSUES AS A RESULT AND TEMPERATURES REBOUND BACK TO NEAR NORMAL.
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&& .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
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SURFACE WINDS CONTINUE TO VEER SOUTHWEST SATURDAY NIGHT AND SUNDAY. WARMING TREND ALSO CONTINUES SUNDAY AHEAD OF APPROACHING COLD FRONT. THIS COLD FRONT TRAILING FROM GREAT LAKES/CANADIAN LOW LOOKS TO PUSH THROUGH LATE SUNDAY NIGHT INTO MONDAY AS SECONDARY SHORT WAVE ROUNDS THE BASE OF UPPER LONG WAVE TROUGH. WILL SEE ISOLATED TO SCATTERED SHOWERS AHEAD AND ALONG THE FRONT...THUNDER CHANCES LOOK VERY MINIMAL AT THIS TIME WITH VERY LIMITED INSTABILITY PRESENT. GOOD COLD AIR ADVECTION WILL BEGIN MONDAY AS THE SHORT WAVE DIVES SOUTHEAST OVERHEAD. H85 TEMPS FALL INTO THE SINGLE DIGITS ABOVE ZERO CELSIUS AND REMAIN THERE THROUGH THE FIRST FULL DAY OF ASTRONOMICAL AUTUMN - TUESDAY. HIGH PRESSURE WITH CONTINUED COOL CONDITIONS ARE EXPECTED FOR WEDNESDAY.
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&& .AVIATION /07Z THURSDAY THROUGH MONDAY/...
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FOG WILL CONTINUE TO FORM AT CHO THIS MORNING AND MVFR/IFR CIGS ARE POSSIBLE THROUGH 12Z TODAY. HIGH PRESSURE WILL CONTINUE ACROSS THE AREA TODAY AND VFR CONDITIONS ARE EXPECTED. -SHRA ARE POSSIBLE MAINLY THIS AFTERNOON AT IAD-DCA-CHO BUT COVERAGE IS ISOLATED TO ADD TO TAFS AT THIS TIME. CLOUD COVERAGE WILL INCREASE THIS AFTERNOON AND THROUGH FRIDAY. MVFR CIGS ARE POSSIBLE LATE TONIGHT AND INTO FRIDAY MAINLY FOR CHO-MRB-IAD. A HIGH PRESSURE WEDGE WILL BE IN PLACE FOR FRIDAY NIGHT AND WINDS WILL VEER SOUTHERLY FOR THE WEEKEND AHEAD OF AN APPROACHING COLD FRONT. THIS FRONT WILL BRING THE CHANCE OF SHOWERS WITH AREAS OF LOWER CIGS SUNDAY NIGHT INTO MONDAY ACROSS THE REGION ALONG WITH A WIND SHIFT. COOL HIGH PRESSURE WILL RETURN FOR TUESDAY AND WEDNESDAY.
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&& .MARINE...
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HIGH PRESSURE WILL REMAIN ACROSS THE WATERS TODAY THROUGH FRIDAY. ISO-SCT SHOWERS ARE POSSIBLE LATE THIS MORNING AND AFTERNOON. SHOWERS WILL BE LIGHT AND SHOULDNT CAUSE VSBY ISSUES. WINDS WILL BE EASTERLY TODAY BEFORE BECOMING NELY LATE TONIGHT AND THROUGH FRIDAY. THIS WILL ALLOW CHANNELING ACROSS THE WATERS. A SCA IS IN EFFECT DURING THIS TIME. HIGH PRESSURE WILL SHIFT SOUTH OF THE REGION FRIDAY NIGHT INTO SATURDAY AS WINDS VEER SOUTHEAST. A COLD FRONT WILL PUSH THROUGH THE REGION SUNDAY NIGHT AND MONDAY...BRINGING THE CHANCE OF SHOWERS WITH GUSTY WINDS. HIGH PRESSURE WILL RETURN TO THE REGION FOR TUESDAY AND WEDNESDAY.
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&& .TIDES/COASTAL FLOODING...
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ANOMOLIES ARE RUNNING AROUND A FOOT ABOVE NORMAL THIS MORNING ON THE WESTERN SHORE OF THE BAY. THIS HAS LED TO MINOR FLOODING WHERE ANNAPOLIS IS IN MINOR FLOOD AT THIS TIME. THESE PAST HIGH TIDES WERE THE HIGHER OF THE TWO AND THERFORE NOT EXPECTED FLOODING FOR THE NEXT ONE TODAY. ANOMALIES AT THE SW WATERFRONT INCREASED TO 1.3 BEFORE TAPERING OFF AS THEY REACH THEIR HIGH TIDE THIS MORNING. BELIEVE SE FLOW AT THE MOUTH OF THE POTOMAC LED TO WATER LEVELS QUICKLY INCREASING IN THIS AREA. COASTAL FLOODING IS NOT EXPECTED THIS MORNING OR THE NEXT HIGH TIDE TODAY. AN EASTERLY COMPONENT TO THE WIND IS EXPECTED TODAY AND IT WILL LIKELY LAST THROUGH THE WEEKEND. THEREFORE...MINOR TIDAL FLOODING IS POSSIBLE NEAR TIMES OF HIGH TIDE THROUGH THE WEEKEND. THE BEST CHANCE FOR MINOR TIDAL FLOODING WILL BE DURING THE LATE EVENING AND MORNING HIGH TIDE CYCLE WHICH IS THE HIGHER OF THE TWO. WE WOULD NEED 2 FT DEPARTURES FOR MDT FLOODING TO BE REALIZED. DO NOT FORSEE THAT HAPPENING. IF IT DID...ANNAPOLIS AND ST GEORGE ISLAND WOULD BE THE MOST SUSCEPTIBLE.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...COASTAL FLOOD ADVISORY UNTIL 4 AM EDT EARLY THIS MORNING FOR MDZ014. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 2 AM TO NOON EDT FRIDAY FOR ANZ530>534-537-539>541-543.
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&& $$ SYNOPSIS...HAS NEAR TERM...HAS SHORT TERM...AEB LONG TERM...AEB AVIATION...HAS/AEB MARINE...HAS/AEB TIDES/COASTAL FLOODING...HAS

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