Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 170129 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 929 PM EDT WED APR 16 2014 .SYNOPSIS...
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HIGH PRESSURE OVER NEW ENGLAND WILL RIDGE SOUTHWARD TOWARD THE MID-ATLANTIC COAST THROUGH THE REMAINDER OF THE WEEK. AN AREA OF LOW PRESSURE AND COLD FRONT MAY AFFECT THE AREA SATURDAY.
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&& .NEAR TERM /THROUGH THURSDAY/...
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A 1036 MB SFC HIGH THAT IS CENTERED OVER NRN NEW ENGLAND AT 00Z RIDGES SWD INTO OUR REGION. WINDS HAD ALREADY DECOUPLED AT THE SFC IN MOST LOCATIONS AFTER SUNSET AND MAINLY CLEAR SKIES ARE PRESENT...SETTING THE STAGE FOR TEMPS TO DROP QUICKLY TNGT UNDER A GOOD RADIATIONAL COOLING SETUP. EXCEPT FOR SOME LOCATIONS ALONG THE WATERS AND IN THE CITIES...TEMPS WILL FALL AOB FREEZING OVNGT. FOR THE SECOND STRAIGHT NIGHT...FREEZE WARNINGS ARE IN EFFECT FOR ALL COUNTIES EAST OF THE BLUE RIDGE WHERE THE GROWING SEASON IS ACTIVE. A HARD FREEZE IS POSSIBLE IN THE MORE RURAL AREAS WEST OF I-95. N-NELY WINDS AROUND THE HIGH WILL GRADUALLY VEER OUT OF THE EAST LATE TNGT AND THU AS THE RIDGE AXIS SHIFTS TOWARD THE MID-ATLANTIC COAST. MARINE LAYER IS EXPECTED TO ADVECT INLAND UNDER ONSHORE FLOW IN THE LLVLS. MODELS SHOW MOISTURE TRAPPED BELOW SUBSIDENCE INVERSION TO THE EAST OF THE BLUE RIDGE. HAVE INCREASED CLOUD COVER ACCORDINGLY ACROSS THE ERN CWA DURING THE LATE MRNG AND AFTN. MAX TEMPS WILL BE BELOW NORMAL AND IN THE 50S. SOME SPOTS IN THE CENTRAL SHENANDOAH VLY AND VLYS OF THE POTOMAC HIGHLANDS MAY REACH 60F WITH MORE SUNSHINE.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... A WEDGE OF HIGH PRESSURE FROM NEW ENGLAND TO THE CAROLINAS WILL INTERACT WITH AN INVERTED TROUGH OF LOW PRESSURE BETWEEN THE EAST COAST AND BERMUDA TO PRODUCE A MODERATE NORTHEAST TO EAST FLOW. WINDS WILL BE GUSTY THURSDAY EVENING BUT THEN DIMINISH OVERNIGHT. LOW TEMPERATURES WILL BE ABOUT 5 TO 10 DEGREES BELOW NORMAL. AS THE HIGH PRESSURE PULLS AWAY TO THE NORTHEAST...THE PRESSURE GRADIENT WILL RELAX. AN UPPER LEVEL SYSTEM WILL PIVOT ACROSS EAST-CENTRAL CANADA FRIDAY AND FRIDAY NIGHT. A SURFACE COLD FRONT WILL PUSH ACROSS THE REGION LATE FRIDAY NIGHT BUT SHOULD BE A DRY FRONT AS THERE WILL BE VERY LITTLE LOW LEVEL MOISTURE. HIGH AND LOW TEMPERATURES WILL BE ABOUT 5 TO 10 DEGREES BELOW NORMAL ONCE AGAIN. AS THE SURFACE FRONT MOVES SOUTH AND EAST SATURDAY MORNING...HIGH PRESSURE WILL BUILD ACROSS THE EASTERN GREAT LAKES INTO THE MID ATLANTIC REGION. WINDS WILL BECOME GUSTY OUT OF THE NORTHWEST SATURDAY BUT SHOULD DIMINISH SATURDAY NIGHT WHEN HIGH PRESSURE RIDGES SOUTHWARD ALONG THE EASTERN SLOPES OF THE MOUNTAINS. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... HIGH PRESSURE WILL BRING DRY WEATHER WITH NEAR NORMAL TEMPERATURES TO THE AREA FOR THE SECOND HALF OF THE WEEKEND INTO EARLY NEXT WEEK. RIDGING ERODES BY MONDAY NIGHT WITH LOW PRESSURE APPROACHING FROM THE MISSISSIPPI VALLEY BY TUESDAY. THIS LOW WILL BRING A CHANCE OF SHOWERS TO THE AREA LATE MONDAY NIGHT THROUGH TUESDAY. RIDGING THEN RE-ESTABLISHES ITSELF ACROSS THE AREA DURING THE MIDDLE OF NEXT WEEK LEADING TO A RETURN TO DRY WEATHER. && .AVIATION /01Z THURSDAY THROUGH MONDAY/...
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HIGH PRESSURE BUILDS DOWN THROUGH THE MID-ATLANTIC THROUGH THURSDAY. VFR CONDITIONS EXPECTED DURING THE VALID TAF PERIOD...WITH WINDS VEERING FROM NORTHEAST TO EAST LATE TNGT AND THU. STRATOCU DECK ASSOCIATED WITH MARINE LAYER MAY BECOME BKN AFTER 15Z THU OVER ERN TERMINALS. CIGS WOULD LIKELY BE AROUND 4 KFT. MARINE STRATOCU HOVERING NEAR VFR-MVFR LVLS THU NIGHT. VFR FRI THROUGH SATURDAY. NORTHEAST WINDS MAY GUST 15 TO 20 KNOTS THURSDAY NIGHT NEAR MTN...BWI AND DCA WITH A PRESSURE GRADIENT ALONG THE COASTAL AREAS. LIGHT AND VARIABLE WINDS FRIDAY AND FRIDAY NIGHT. WITH THE PASSAGE OF A COLD FRONT SATURDAY...WINDS WILL BECOME NORTHWEST AND GUST 20 TO 30 KNOTS. VFR CONDITIONS ARE EXPECTED SUNDAY WITH EASTERLY WINDS 5 TO 10 KNOTS.
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&& .MARINE...
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WINDS HAVE SHIFTED OUT OF THE E-NE THIS EVE AND SUBSIDED TO 10-15 KT. WINDS MAY INCREASE A BIT LATER TONIGHT AS WINDS VEER TO THE EAST AS THE PRESSURE GRADIENT STRENGTHENS EVER SO SLIGHTLY. SCA IS EXPECTED TO EXPAND ACROSS THE WATERS ON THURSDAY. NO MARINE HAZARDS EXPECTED THURSDAY NIGHT THROUGH SATURDAY MORNING. SMALL CRAFT ADVISORY CONDITIONS MAY BE POSSIBLE SATURDAY AFTERNOON WITH NORTHWEST WINDS EXPECTED TO GUST 20 TO 30 KNOTS. SUB-SMALL CRAFT ADVISORY CONDITIONS ARE FORECAST SUNDAY INTO EARLY NEXT WEEK.
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&& .TIDES/COASTAL FLOODING...
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WATER LEVELS REMAIN 1 TO 2 FEET ABOVE NORMAL BUT AS WINDS HAVE DIMINISHED AND THEN VEER TO THE EAST NEGATIVE DEPARTURES WILL DECREASE THRU THU.
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&& .CLIMATE...
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NEAR RECORD COLD TEMPERATURES THIS MORNING... TWO OF THE THREE MAJOR METRO AREA AIRPORTS...BWI AND IAD...GOT CLOSE TO THEIR DAILY RECORD LOW TEMPERATURES THIS MORNING. AT REAGAN NATIONAL AIRPORT...DCA...A MORNING LOW OF 34F WAS WELL ABOVE THE RECORD OF 29F SET ON THIS DATE IN 1928. AT BALTIMORE-WASHINGTON INTERNATIONAL...BWI...A MORNING LOW TODAY OF 31F WAS JUST ONE DEGREE OFF THE RECORD LOW FOR THE DATE SET IN 1962. AT DULLES...IAD...THE MIN OF 30F THIS MORNING WAS TWO DEGREES SHY OF THE DAILY RECORD LOW OF 28F SET ON THIS DATE IN 1981. REGARDING RECORD LOW DAILY MAX TEMPERATURES FOR APRIL 16...AS OF 3PM TODAY...DULLES IS STILL TIED WITH ITS DAILY RECORD LOW-MAX OF 46F BUT WITH SEVERAL HOURS LEFT OF SUN WILL LIKELY RISE ABOVE 46F. BOTH BWI AND DCA HAVE RISEN ABOVE THEIR RESPECTIVE DAILY RECORD LOW-MAX TEMPERATURES FOR APRIL 16. RECORD LOWS FOR APRIL 17... BWI...26F IN 1962 DCA...26F IN 1875 IAD...27F IN 1983
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...FREEZE WARNING FROM 2 AM TO 9 AM EDT THURSDAY FOR DCZ001. MD...FREEZE WARNING FROM 2 AM TO 9 AM EDT THURSDAY FOR MDZ004>007- 009>011-013-014-016>018. VA...FREEZE WARNING FROM 2 AM TO 9 AM EDT THURSDAY FOR VAZ036>040- 042-050>057-501-502. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 3 AM TO 6 PM EDT THURSDAY FOR ANZ530>533-538>541. SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EDT THURSDAY FOR ANZ536- 542. SMALL CRAFT ADVISORY UNTIL 6 PM EDT THURSDAY FOR ANZ534-537- 543.
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&& $$ SYNOPSIS...JRK/BPP NEAR TERM...JRK SHORT TERM...KLW LONG TERM...DFH AVIATION...JRK/KLW/DFH MARINE...JRK/BPP/KLW/DFH TIDES/COASTAL FLOODING...BPP/JRK CLIMATE...SMZ

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