Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 170759 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 359 AM EDT FRI APR 17 2015 .SYNOPSIS...
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HIGH PRESSURE WILL CONTINUE TO MOVE OFF THE COAST THIS MORNING. A SURFACE TROUGH WILL PASS THROUGH THE REGION TODAY AND HIGH PRESSURE WILL RETURN FOR SATURDAY. THE HIGH WILL MOVE OFF THE COAST SUNDAY AND A WARM FRONT WILL MOVE INTO THE AREA SUNDAY NIGHT INTO MONDAY. A COLD FRONT WILL PASS THROUGH LATE MONDAY INTO MONDAY NIGHT BEFORE HIGH PRESSURE RETURNS FOR THE MIDDLE PORTION OF NEXT WEEK.
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&& .NEAR TERM /THROUGH SATURDAY/...
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HIGH PRESSURE WILL CONTINUE TO MOVE OFF THE EAST COAST THIS MORNING. AN UPPER LEVEL TROUGH WILL MOVE ACROSS THE MID- ATLANTIC THIS MORNING. WARM AIR ADVECTION COUPLED WITH AN UPPER LEVEL DISTURBANCE HAS ALLOWED SHOWERS TO MOVE ACROSS THE I-95 CORRIDOR THIS MORNING. LESS THAN A QUARTER INCH HAS BEEN REPORTED OVERNIGHT. AN UPPER LEVEL TROUGH WILL SWING THROUGH THE MID- ATLANTIC THIS MORNING AND MOISTURE AND LIFT WILL PUSH OFF THE EAST COAST GIVING WAY TO DRIER CONDITIONS. SHOWERS WILL DIMINISH BY MID- MORNING BUT A SFC TROUGH CURRENTLY ACROSS THE OHIO VALLEY WILL MOVE THROUGH THE REGION TODAY AND INCREASE POTENTIAL FOR MORE SHOWERS. A PERIOD OF DRY CONDITIONS ARE EXPECTED THIS MORNING BETWEEN THE EXITING UPPER LEVEL DISTURBANCE AND INCOMING SFC TROUGH. TEMPS SHOULD RISE INTO THE L-M 70S BY AFTERNOON. NW FLOW WILL DRAW IN COLD DRY AIR ALOFT TODAY. THIS WILL CAUSE LAPSE RATES TO INCREASE AND SHOWERS ARE EXPECTED TO FORM ALONG THE SFC TROUGH BY EARLY AFTERNOON. LATEST HRRR GUIDANCE SHOWS A BKN LINE OF CONVECTIVE SHOWERS TO MOVE E-SE THROUGH THE AFTERNOON. AS THE SHOWERS MOVE PAST I-66...WARMER SFC TEMPS AND DECENT BOUNDARY LAYER MIXING WILL ALLOW A FEW HUNDRED J/KG OF CAPE. A FEW THUNDERSTORMS ARE POSSIBLE SOUTH OF I-66/MD RT50 LATE THIS AFTERNOON AND EARLY EVENING. CLEARING IS EXPECTED BEHIND THE SFC TROUGH INTO THE EVENING. HIGH PRESSURE WILL MOVE INTO THE REGION TONIGHT AND PERSIST SATURDAY. FCST MIN TEMPS INT HE 50S EXPECTED TONIGHT. FULL SUNSHINE WILL ALLOW TEMPS TO RISE INTO THE UPPER 70S TO NEAR 80 IN THE METROS SATURDAY.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
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REGION REMAINS ON THE SOUTHERN PERIPHERY OF HIGH PRESSURE CENTERED JUST NORTH OF THE GREAT LAKES. RIDGING BUILDS IN ALOFT...WITH THE RIDGE AXIS SHIFTING ACROSS THE MID ATLANTIC BY SUN MORNING. OVERALL PATTERN WILL KEEP THE AREA DRY. CLOUDS WILL BEGIN TO INCREASE FROM THE SOUTHWEST AHEAD OF THE NEXT FRONTAL SYSTEM. WINDS WILL LIGHTEN AND BECOME NE OVERNIGHT AS THE HIGH BUILDS SOUTH.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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00Z MODEL SUITE CONTINUING WITH A SLOWER PROGRESSION OF THE NEXT FRONTAL SYSTEM...AND THE ARRIVAL TIMING OF THE PCPN. RIDGE AXIS SHIFTS EAST DURING THE DAY SUNDAY AS A DEEPENING CLOSED LOW OVER THE NORTHERN PLAINS BUILDS EAST. BROAD LOW PRESSURE AT THE SFC OVER THE CENTRAL PLAINS BECOMES ORGANIZED DURING HE DAY AS WELL AS IT MOVES INTO THE WESTERN GREAT LAKES...GRADUALLY LIFTING THE ASSOCIATED WARM FRONT TO THE NORTH AND INTO THE MID ATLANTIC. GENERAL CONSENSUS AMONGST THE MODELS KEEPS THE WARM FRONT AT OR JUST SOUTH OF THE VA/NC BORDER THRU SUN NIGHT...WITH PCPN OCCURRING SUN-SUN NIGHT AS A RESULT OF DYNAMIC FORCING ALOFT WITH MULTIPLE MID LVL SHORTWAVES AND STRENGTHENING LLJ AND 250MB JET. PWATS INCRSG TO BETWEEN 1.2-1.4 IN...WHICH COULD RESULT IN PERIODS OF MODERATE TO HEAVY RAIN. SOME UNCERTAINTY STILL EXISTS WITH PCPN TIMING AND TSTM DEVELOPMENT ON MONDAY. WARM FRONT LOOKS TO BE NEAR THE VA/NC BORDER EARLY MONDAY...THEN GRADUALLY LIFTING NORTH DURING THE DAY. HOW QUICKLY IT CAN CLEAR THE CWA AND WARM SECTOR THE AREA WILL AFFECT THE EXTENT OF TSTM DEVELOPMENT...AND AS SUCH WILL CONTINUE TO MENTION SLIGHT CHC T FOR MOST OF THE AREA NOW...AND CHC OVER CENTRAL VA WHERE THE BEST DAYTIME HEATING SHOULD OCCUR. KEPT NORTHEASTERN MD OUT OF THE THUNDER MENTION FOR NOW WITH COOLER TEMPS EXPECTED. IN ADDITION...THINKING THERE SHOULD BE TWO ROUNDS OF PCPN...THE INITIAL SUN NIGHT...WITH A BREAK AT SOME POINT MONDAY WITH THE NEXT ROUND MOVING IN AHEAD OF THE APPROACHING COLD FRONT. THE COLD FRONT PUSHES THROUGH MONDAY NIGHT...WITH PCPN CLEARING TO THE EAST BY EARLY TUES MORNING. SFC HIGH PRESSURE BUILDS IN FROM THE SOUTH IN THE WAKE OF THE FRONT THRU WED...QUICKLY PROGRESSING OFFSHORE BY THURS...AND RESULTING IN BRIEF PERIOD OF DRY WX. THE REGION REMAINS POSITIONED AT THE BASE OF A BROAD UPPER LVL CLOSED LOW...WHICH WILL SEND THROUGH THE NEXT COLD FRONT MIDWEEK...BRINGING THE NEXT CHC FOR PCPN. NEAR NORMAL TEMPS EXPECTED THROUGH THE PERIOD ON WLY FLOW.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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MVFR CONDITIONS POSSIBLE THIS MORNING AS CIGS LOWER BEHIND EXITING SHOWERS. CIGS SHOULD BECOME VFR SHORTLY AFTER SUNRISE AND A PERIOD OF DRY CONDTIONS EXPECTED THROUGH NOON. A SFC TROUGH ACROSS THE OHIO VALLEY WILL MOVE FROM WEST TO EAST ACROSS THE TERMINALS THIS AFTERNOON. SHOWERS WILL REDEVELOP. AN ISOLATED TS IS POSSIBLE MAINLY CHO-DCA. A WIND SHIFT FROM S-SW TO W-NW EXPECTED TODAY. VFR CONDITIONS EXPECTED TONIGHT AND SATURDAY. VFR CONDITIONS SAT NIGHT-SUN. SUB-VFR CONDITIONS BCMG LIKELY BY SUN NIGHT WITH WIDESPREAD RAIN. PERIODS OF HEAVIER RAIN COULD DROP CONDITIONS TO SUB-IFR SUN NIGHT. LLWS CONCERNS PSBL MON MORNING WITH SE WINDS 40-50 KTS AT 2KFT...SHIFTING TO THE SOUTH DURING THE MORNING. SUB-VFR CONDITIONS REMAIN PSBL DURING THE DAY MON AS A COLD FRONT BRINGS ANOTHER ROUND OF PCPN. SLIGHT CHC OF THUNDER CURRENTLY FOR THE TAF SITES...MAINLY MON AFTN/EVENING. WIND SHIFT EXPECTED MON EVENING WITH FRONTAL PASSAGE. VFR CONDITIONS MON NIGHT AS THE PCPN TAPERS OFF...LASTING THRU WED.
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&& .MARINE...
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SHOWERS WILL MOVE EAST OF THE WATERS BY MID-MORNING. SOUTHERLY CHANNELING IS EXPECTED THIS MORNING AS A PRESSURE GRADIENT TIGHTENS ACROSS THE WATERS. A SCA IS IN EFFECT FOR THE LOWER TIDAL POTOMAC AND MD CHESAPEAKE BAY FOR GUSTS 18-20KTS. A SFC TROUGH WILL CROSS THE WATERS THIS AFTERNOON. SHOWERS ARE EXPECTED AND AN ISOLATED THUNDERSTORM IS POSSIBLE MAINLY ACROSS THE SOUTHERN WATERS. S WINDS BECOME W-NW THIS EVENING. HIGH PRESSURE BUILDS IN TONIGHT AND SATURDAY. GENERALLY SUB-SCA CONDITIONS SAT NIGHT-SUN. SCA CONDITIONS PSBL BY SUN NIGHT WITH INCRSG ELY FLOW. SCA CONDITIONS LAST DURING THE DAY MON AHEAD OF THE COLD FRONT...BCMG SUB-SCA MON EVENING. GUSTS TO 20 KTS PSBL AGAIN TUES AFTN IN THE WAKE OF THE FRONT.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ530>534- 537>543.
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&& $$ SYNOPSIS...SEARS/HAS NEAR TERM...HAS SHORT TERM...HAS LONG TERM...SEARS AVIATION...SEARS/HAS MARINE...SEARS/HAS

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