Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 181313 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 913 AM EDT THU SEP 18 2014 .SYNOPSIS... 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. && .NEAR TERM /THROUGH FRIDAY/...
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A BROAD UPPER-LEVEL TROUGH WILL REMAIN OVER THE REGION THROUGH THIS AFTERNOON WHILE A WEAK UPPER-LEVEL DISTURBANCE PASSES THROUGH IN THE FLOW ALOFT. A WEAK COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL ALSO MOVE THROUGH THIS AFTERNOON INTO THIS EVENING. MOISTURE WILL BE LIMITED WITH THIS SYSTEM AND FORCING WILL BE WEAK...BUT A COUPLE SHOWERS ARE POSSIBLE...ESPECIALLY THIS AFTERNOON AND EVENING ACROSS CENTRAL VIRGINIA. HOWEVER...MOST PLACES WILL BE DRY AND EVEN FOR LOCATIONS THAT DO GET SHOWERS PRECIPITATION WILL BE LIGHT. MAX TEMPS WILL BE CLOSE TO CLIMO THIS AFTERNOON...RANGING FROM THE 60S IN THE MOUNTAINS TO THE MID AND UPPER 70S IN DOWNTOWN WASHINGTON AND BALTIMORE. A BKN CU DECK IS EXPECTED TO DEVELOP LATE THIS MORNING AND AFTERNOON. 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/... 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. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... 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. && .AVIATION /13Z THURSDAY THROUGH MONDAY/...
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VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING. A BRIEF SHOWER IS POSSIBLE...BUT MOST PLACES WILL BE DRY. WINDS WILL TURN ONSHORE BEHIND THE FRONT LATE TONIGHT INTO FRIDAY...SO MVFR CIGS ARE POSSIBLE DURING THIS TIME...ESPECIALLY 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 THIS AFTERNOON AND EARLY EVENING. THE FLOW WILL TURN ONSHORE TODAY BEFORE VEERING TOWARD THE NORTH- NORTHEAST BEHIND A COLD FRONT TONIGHT. A PRESSURE SURGE IS EXPECTED LATE TONIGHT INTO FRIDAY...CAUSING WINDS TO INCREASE. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER 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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TIDAL ANOMALIES HAVE INCREASED TO ABOUT 1 TO 1.5 FEET ABOVE NORMAL FROM THE SOUTHERLY FLOW WEDNESDAY. THE FLOW WILL BE LIGHT THROUGH THIS EVENING...BEFORE INCREASING AND TURNING TOWARD THE NORTHEAST LATE TONIGHT. WITH NO OFFSHORE FLOW TO PUSH THE WATER OUT OF THE BAY...THESE TIDAL ANOMALIES ARE LIKELY TO CONTINUE THROUGH TONIGHT. A COASTAL FLOOD ADVISORY IS IN EFFECT FOR THE HIGH TIDE CYCLE THIS AFTERNOON AND AGAIN LATE TONIGHT INTO EARLY FRIDAY FOR ANNE ARUNDEL COUNTY. HOWEVER...CONFIDENCE IN MINOR FLOODING IS HIGHEST WITH THE LATER OF THE TWO HIGH TIDE CYCLES. ELSEWHERE...MINOR TIDAL FLOODING IS POSSIBLE NEAR HIGH TIDE LATE TONIGHT INTO EARLY FRIDAY. HOWEVER...CONFIDENCE IS NOT HIGH ENOUGH FOR A COASTAL FLOOD ADVISORY AT THIS POINT. AN ONSHORE FLOW IS EXPECTED TO CONTINUE THROUGH SUNDAY...CAUSING ELEVATED WATER LEVELS AND THE POSSIBILITY OF MINOR TIDAL FLOODING.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...COASTAL FLOOD ADVISORY UNTIL 5 AM EDT FRIDAY 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...BJL

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