Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190230 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 930 PM EST TUE NOV 18 2014 .SYNOPSIS... SURFACE HIGH PRESSURE CENTERED OVER EASTERN TEXAS WILL BUILD SHIFT EAST ACROSS THE DEEP SOUTH THROUGH WEDNESDAY. A WARM FRONT WILL LIFT NORTH OVER THE AREA LATE WEDNESDAY...WITH A DRY COLD FRONT PASSING FROM THE WEST LATE THURSDAY. HIGH PRESSURE WILL CROSS THE AREA FRIDAY NIGHT. THE HIGH WILL MOVE OFF THE COAST SATURDAY AND A WARM FRONT WILL CROSS THE AREA SUNDAY. && .NEAR TERM /THROUGH WEDNESDAY/...
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AS OF 02Z...SURFACE HIGH PRESSURE WILL CONTINUE TO NOSE NORTHEASTWARD FROM THE CENTRAL GULF COAST TONIGHT WHILE A DEEP LOW PRESSURE SYSTEM MOVES AWAY FROM LABRADOR. THE PRESSURE GRADIENT IS EXPECTED TO SIGNIFICANTLY RELAX AFTER 06Z...ALTHOUGH A LOT OF THE GUSTS HAVE ALREADY DIMINISHED AT THIS HOUR. MEANWHILE A WEAK WAVE OF LOW PRESSURE IS APPROACHING FROM THE OHIO VALLEY...MOST NOTED BY THE INCREASING CLOUDS APPROACHING THE CENTRAL APPALACHIANS. SNOW SHOWER/FLURRY ACTIVITY HAS BEEN OBSERVED UPSTREAM WITH THIS WAVE AND IT IS REASONABLE TO EXPECT SOME OF THIS MOISTURE TO BE REALIZED ON THE WESTERN FACING SLOPES. THINK THE CHANCE OF MEASURABLE SNOW IS IFFY...BUT SOME LOCATIONS MAY SQUEEZE OUT SEVERAL TENTHS. AFTER THE MAIN WAVE PASSES AROUND 07-08Z...CARRIED A MENTION OF FLURRIES THROUGH 12Z. THE MAIN STORY CONTINUES TO BE THE COLD THOUGH WITH THE DEEP UPPER TROUGH OVERHEAD...AND THERMAL PROFILES HAVE BOTTOMED OUT FOR THIS EVENT. FROM THE 00Z SOUNDING DATA...850 MB TEMPERATURE OF -15.9C TIES FOR THE 5TH LOWEST TEMPERATURE AT THAT LEVEL FROM DCA/IAD SOUNDINGS DATING TO 1948. HOWEVER...THIS IS THE EARLIEST DATE FOR A READING THAT LOW...AS ALL OF THE TOP 5 OCCURRED ON 11/25 OR LATER. SO EXPECTING A VERY COLD NIGHT WITH RECORD LOWS THREATENED (SEE CLIMATE SECTION BELOW). TEMPERATURES HAVE ALREADY STARTED PLUMMETING THIS EVENING OWING TO A RELATIVELY QUICK SLACKENING OF THE WINDS AND CLEAR SKIES. DEW POINTS ARE CURRENTLY IN THE LOWER SINGLE DIGITS. THE ONLY THINGS THAT WILL HOLD BACK A COMPLETE FREEFALL ARE A LITTLE BIT OF A BREEZE AND SOME ENCROACHING CLOUDS FROM THE AFOREMENTIONED WAVE. THE LOW TEMPERATURE FORECAST STILL NEEDED TO BE LOWERED BY SEVERAL DEGREES HOWEVER...AND WOULDNT BE SURPRISED IF SOME LOCATIONS DROPPED LOWER...PARTICULARLY ANY WIND SHELTERED AREAS TOWARD CENTRAL VA AND THE SOUTHERN SHENANDOAH VALLEY. LOCATIONS OUTSIDE OF URBAN AND COASTAL AREAS CAN EXPECT MID TEENS OR LOWER. WIND CHILLS (ASSUMING THE WIND DOESNT COMPLETELY DECOUPLE) WILL BE IN THE LOWER TEENS TO SINGLE DIGITS IN THE LOWLANDS...AND THE ADVISORY STILL LOOKS GOOD ABOVE 3000FT FOR READINGS OF -5 TO -15. WEDNESDAY...A SFC HIGH RIDGE WILL SHIFT OFF THE CAROLINA COAST DURING THE DAY WITH AFTERNOON SWLY FLOW. THIS CONTINENTAL AIR IS DRY AND WILL HAVE LITTLE SENSIBLE EFFECT OTHER THAN MID-LEVEL CLOUDS. TEMPS SLOWLY RISE IN THE MORNING DUE TO LACK OF MIXING AND POSSIBLE CLOUDS. MAX TEMPS GENERALLY MID 30S...UPR 20S FOR RIDGES AND AROUND 30 FOR NERN MD WHERE THE SWLY FLOW REACHES LAST.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... LOW PRESSURE IS EXPECTED TO BE ACROSS THE NRN GREAT LAKES WITH A COLD FRONT MOVING THROUGH THE OHIO VALLEY WEDNESDAY NIGHT. HIGH PRESSURE WILL BE MOVING OFF THE SE COAST DURING THIS TIME. WINDS WILL BE OUT OF THE SOUTH WED EVENING AHEAD OF THE ADVANCING COLD FRONT. CLOUDS WILL INCREASE FROM WEST TO EAST AS THE COLD FRONT NEARS. SNOW SHOWERS ARE POSSIBLE ALONG THE WESTERN SLOPES OF THE ALLEGHENY FRONT LATE WEDNESDAY NIGHT AND THURSDAY. FURTHER EAST...LITTLE MOISTURE WILL LEAD TO A DRY FRONTAL PASSAGE BY THURSDAY AFTERNOON. WINDS WILL BECOME WESTERLY THURSDAY. THIS WILL LEAD TO ANOTHER ROUND OF COLD AIR ADVECTION BY THURSDAY EVENING. MOSTLY SUNNY CONDITIONS EAST OF THE BLUE RIDGE WILL ALLOW TEMPS TO RISE INTO THE MID TO UPPER 40S. HIGH PRESSURE MOVES INTO THE REGION THURSDAY NIGHT. FCST MIN TEMPS WILL BE IN THE 20S. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A BUILDING RIDGE OF HIGH PRESSURE EXPECTED FRIDAY AND FRIDAY NIGHT. TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH FRIDAY NIGHT. THE HIGH WILL SHIFT TO THE COAST AND THEN OFFSHORE SATURDAY AND SATURDAY NIGHT. WINDS WILL SHIFT TO THE SOUTH AHEAD OF A STORM SYSTEM AND COLD FRONT MOVING ACROSS THE WESTERN OHIO VALLEY. TEMPERATURES WILL MODIFY SATURDAY NIGHT THROUGH MONDAY. DRY CONDITIONS SATURDAY WITH A SLIGHT CHANCE OF SOME WARM-FRONTAL PERIODS OF LIGHT SNOW...MIXING WITH RAIN SHOWERS...SATURDAY NIGHT FROM THE POTOMAC HIGHLANDS TOWARD THE WASHINGTON D.C. AREA. SOME LIGHT RAIN WILL MOVE IN AS TEMPERATURES MODIFY SUNDAY AND SUNDAY NIGHT. THERE IS A CHANCE OF A FEW LINGERING RAIN SHOWERS MONDAY INTO MONDAY NIGHT BUT THE HIGHER PROBABILITIES OF RAIN WOULD BE SUNDAY AND SUNDAY NIGHT. A TRAILING COLD FRONT WILL GRADUALLY MOVE EAST MONDAY NIGHT INTO TUESDAY. ALTHOUGH MOST RAIN ACTIVITY SHOULD BE OFFSHORE TUESDAY...WE CAN`T RULE OUT A FEW LINGER RAIN SHOWERS ALONG AND ON THE COLD SIDE OF THE TRAILING FRONT. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
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VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD AS HIGH PRESSURE BUILDS ALONG THE GULF COAST TONIGHT AND TOWARD THE SOUTHEASTERN STATES WEDNESDAY. WIND GUSTS WILL BEGIN TO RELAX THIS EVENING...BUT GRADIENT FROM STRONG LOW PRESSURE OVER LABRADOR WILL PREVENT WINDS FROM DIMINISHING COMPLETELY. THE WINDS WILL SHIFT TO SOUTHERLY BETWEEN 16-19Z WEDNESDAY AND BEGIN INCREASING TOWARD EVENING AS A LOW PRESSURE SYSTEM SWINGS INTO THE GREAT LAKES. MID LEVEL CLOUDS WILL ALSO INCREASE WEDNESDAY AFTERNOON. VFR CONDITIONS EXPECTED WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. A COLD FRONT WILL CROSS THE REGION CAUSING S WINDS TO BECOME WEST BY THURSDAY EVENING. LACK OF MOISTURE WILL ONLY ALLOW A MID-HIGH LEVEL CLOUD DECK TO MOVE ACROSS THE TERMINALS. VFR CONDITIONS FRIDAY AND FRIDAY NIGHT. WINDS COULD GUST OVER 20 KNOTS LATE FRIDAY MORNING INTO MIDDAY AS HIGH PRESSURE BUILDS IN FROM THE WEST. WINDS WILL BECOME LIGHT AND VARIABLE LATE FRIDAY AND FRIDAY NIGHT. VFR CONDITIONS SATURDAY INTO SATURDAY NIGHT. WINDS WILL BECOME SOUTHERLY AT 5 TO 10 KNOTS.
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&& .MARINE...
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NW TO W WINDS HAVE BEEN SLOWLY DIMINISHING THIS EVENING AND WILL CONTINUE TO DO SO TOWARD DAWN. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR OCCASIONAL GUSTS ABOVE 18 KT. THE NORTHERN TIDAL POTOMAC WILL DROP OFF AT 3AM...WITH ALL HEADLINES DOWN BY 9AM OVER THE WATERS WHILE HIGH PRESSURE GAINS GREATER CONTROL FROM THE SOUTH. AS THE HIGH MOVES OFF THE COAST WEDNESDAY AFTERNOON...RETURN SOUTHERLY FLOW WILL DEVELOP...LEADING TO CHANNELING BY THE EVENING. SOUTHERLY FLOW WILL INCREASE AHEAD OF A COLD FRONT WED NIGHT AND A SCA IS IN EFFECT THROUGH WED NIGHT. THE COLD FRONT WILL CROSS THE WATERS BY THURS AFTERNOON AND A WESTERLY PRESSURE SURGE WILL CAUSE WINDS TO INCREASE ACROSS THE WATERS THURSDAY NIGHT. SMALL CRAFT ADVISORIES ARE POSSIBLE FRIDAY. WINDS COULD GUST OVER 20 KNOTS FROM THE WEST TO NORTHWEST DUE TO BUILDING HIGH PRESSURE. SMALL CRAFT ADVISORIES ARE POSSIBLE AGAIN LATER SATURDAY AFTERNOON AS HIGH PRESSURE SHIFTS TO THE EAST COAST AND WINDS BECOME SOUTHERLY.
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&& .CLIMATE...
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A RARE FEAT MAY BE ACCOMPLISHED TONIGHT AT BOTH DULLES AIRPORT AND BWI. TWO RECORD DAILY MINIMUM TEMPERATURES COULD BE BROKEN IN ONE NIGHT. TEMPERATURES ARE FALLING QUICKLY THIS EVENING...AND ARE ALREADY VERY CLOSE TO THEIR RECORDS FOR THE 18TH. AFTER THE CLOCK HITS MIDNIGHT AND A NEW DAY IS BORN...TEMPERATURES WILL CONTINUE FALLING...BREAKING THEIR RECORDS FOR THE 19TH. BELOW IS A TABLE OF RECORD COLD TEMPERATURES FOR TONIGHT...TOMORROW AND TOMORROW NIGHT. SITE 11/18 LOW MAX 11/19 MIN 11/19 LOW MAX DCA 30 (1924) 18 (1891) 33 (1880) BWI 31 (1959) 20 (1936) 35 (1880) IAD 39 (2008) 20 (1990) 38 (2008)
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...WIND CHILL ADVISORY UNTIL 7 AM EST WEDNESDAY FOR VAZ503-504. WV...WIND CHILL ADVISORY UNTIL 7 AM EST WEDNESDAY FOR WVZ501-505- 506. MARINE...SMALL CRAFT ADVISORY UNTIL 9 AM EST WEDNESDAY FOR ANZ530>534- 537-539>541-543. SMALL CRAFT ADVISORY FROM 3 PM WEDNESDAY TO 6 AM EST THURSDAY FOR ANZ530>534-537>543. SMALL CRAFT ADVISORY UNTIL 6 AM EST WEDNESDAY FOR ANZ536-538- 542. SMALL CRAFT ADVISORY UNTIL 3 AM EST WEDNESDAY FOR ANZ535.
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&& $$ SYNOPSIS...BAJ NEAR TERM...BAJ/ADS SHORT TERM...HAS LONG TERM...KLW AVIATION...ADS/HAS/KLW MARINE...ADS/HAS/KLW CLIMATE...DFH

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