Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 171443 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 943 AM EST MON NOV 17 2014 .SYNOPSIS... A STRONG COLD FRONT WILL PASS THROUGH THE AREA THIS AFTERNOON AND EVENING. ARCTIC HIGH PRESSURE WILL BUILD TOWARD THE REGION BEHIND THIS SYSTEM TUESDAY THROUGH TUESDAY NIGHT. A REINFORCING COLD FRONT WILL APPROACH THE AREA WEDNESDAY AND WEDNESDAY NIGHT BEFORE PASSING THROUGH THURSDAY. AN UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE AREA FRIDAY AND HIGH PRESSURE WILL RETURN FOR SATURDAY. && .NEAR TERM /THROUGH TONIGHT/...
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14Z RADAR REFLECTIVITY SHOWING THE NEXT BATCH OF PCPN MOVING ACROSS THE AREA FROM THE SOUTH AND WEST OUT AHEAD OF AN APPROACHING STRONG COLD FRONT. THIS AREA OF RAINFALL WILL DEPOSIT A SOLID ONE HALF TO ONE INCH AREA WIDE. THE RAIN WILL END SHARPLY FROM WEST TO EAST BEHIND THE PASSAGE OF THE STRONG COLD FRONT. BEHIND THE COLD FRONT...WINDS WILL SHIFT INTO THE WEST TO NORTHWEST AND BECOME BREEZY LATE THIS AFTERNOON INTO TONIGHT. WIND GUSTS AT HIGHER ELEVATIONS COULD REACH 40 MPH. TEMPERATURES WILL ALSO FALL RAPIDLY AS AN ARCTIC AIRMASS BUILDS INTO THE MIDDLE ATLANTIC REGION. COLD AIR ADVECTION WILL CAUSE AN UPTICK IN SNOW SHOWER ACTIVITY OVER THE POTOMAC HIGHLANDS WITH AN INCH...POSSIBLY UP TO TWO EXPECTED. OVERNIGHT LOWS WILL DIP BACK INTO THE TEENS ACROSS THE HIGHLANDS WITH 20S MOST ELSEWHERE. TEMPERATURES WILL BE SLIGHTLY WARMER IN THE DC/BALTIMORE METRO AREAS WITH LOWS AROUND FREEZING. GUSTY NORTHWEST WINDS WILL CREATE COLD WIND CHILLS WITH VALUES NEAR ZERO OR SLIGHTLY BELOW OVER THE HIGHLANDS...SINGLE DIGITS TO TEENS ACROSS THE I-81 CORRIDOR...LOWER TO MID 20S ELSEWHERE.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... VERY COLD TEMPERATURES ARE EXPECTED ON TUESDAY WITH CONTINUED COLD AIR ADVECTION. AFTERNOON HIGH TEMPERATURES WILL ONLY REACH THE 20S TO LOWER 30S...WELL BELOW NORMAL FOR MID NOVEMBER. SCATTERED UPSLOPE SNOW SHOWERS WILL GRADUALLY TAPER OFF OVER THE POTOMAC HIGHLANDS DURING THE DAY. GUSTY NORTHWEST WINDS OF 15 TO 25 MPH WITH GUSTS TO 30 MPH CAN BE EXPECTED...EXCEPT HIGHER GUSTS ACROSS RIDGE TOPS. ARCTIC HIGH PRESSURE WILL BUILD TOWARD THE REGION TUESDAY NIGHT...CAUSING BITTERLY COLD CONDITIONS FOR THIS TIME OF YEAR. IN FACT...RECORD LOW TEMPERATURES ARE POSSIBLE BY EARLY WEDNESDAY MORNING. SEE THE CLIMATE SECTION FOR DETAILS. THE CENTER OF THE HIGH WILL ACTUALLY SETTLE TO OUR SOUTH LATE TUESDAY NIGHT...BUT THE PRESSURE GRADIENT SHOULD STILL WEAKEN ENOUGH FOR WINDS TO BECOME LIGHT. THEREFORE...THE FORECAST FOR MIN TEMPS HAS BEEN TWEAKED TOWARD THE COLDER GUIDANCE FOR RADIATIONAL COOLING. MIN TEMPS ARE FORECAST TO RANGE FROM THE SINGLE DIGITS IN THE MOUNTAINS...TO THE TEENS IN SUBURBS OF WASHINGTON AND BALTIMORE...TO THE LOWER AND MIDDLE 20S IN DOWNTOWN WASHINGTON AND BALTIMORE. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... HIGH PRESSURE WILL SLOWLY BUILD OVER THE SOUTHEASTERN CONUS WEDNESDAY WHILE A REINFORCING COLD FRONT APPROACHES FROM THE WEST. A SOUTHERLY FLOW WILL DEVELOP AHEAD OF THE APPROACHING BOUNDARY...AND THIS WILL ALLOW FOR TEMPS TO BE A FEW DEGREES WARMER THAN TUESDAY...BUT STILL BITTERLY COLD FOR THIS TIME OF YEAR. IN FACT...THE FORECASTED MAX TEMPS FOR WEDNESDAY WOULD STILL BE BELOW NORMAL FOR JANUARY. MAX TEMPS ARE FORECAST TO RANGE FROM THE 20S IN THE MOUNTAINS...TO THE MIDDLE 30S NEAR WASHINGTON AND BALTIMORE...TO THE UPPER 30S/NEAR 40 IN CENTRAL VIRGINIA. THE REINFORCING COLD FRONT WILL APPROACH THE AREA WEDNESDAY NIGHT FROM THE OHIO VALLEY BEFORE PASSING THROUGH THURSDAY. LITTLE MOISTURE WILL BE ASSOCIATED WITH THE BOUNDARY SO NO PRECIPITATION IS EXPECTED. MIN TEMPS WEDNESDAY NIGHT WILL NOT BE AS COLD AS RECENT NIGHTS DUE TO THE RETURN SOUTHERLY FLOW. MAX TEMPS THURSDAY WILL BE MILDER DUE TO SUNSHINE AND A DOWNSLOPING FLOW...BUT STILL CHILLY FOR THIS TIME OF YEAR. HIGH PRESSURE WILL BUILD OVERHEAD THURSDAY NIGHT BEFORE A WEAK UPPER-LEVEL DISTURBANCE SWINGS THROUGH FRIDAY. AS OF NOW...IT APPEARS THAT DRY CONDITIONS WILL PERSIST SINCE THERE WILL BE LITTLE MOISTURE WITH IT. HIGH PRESSURE WILL RETURN FOR SATURDAY BEFORE MOVING OFF THE COAST SUNDAY. UNUSUALLY COLD CONDITIONS ARE EXPECTED THROUGH SATURDAY NIGHT...BUT MILDER CONDITIONS MAY RETURN SUNDAY AS A SOUTHERLY FLOW DEVELOPS. && .AVIATION /15Z MONDAY THROUGH FRIDAY/...
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IFR CONDITIONS THROUGH THE AFTN WITH LIGHT TO MODERATE RAIN MOVING THROUGH THE AREA AHEAD OF AN APPROACHING COLD FRONT. LLWS PSBL FOR A PERIOD THROUGH MIDDAY MAINLY KBWI AND KMTN...LOW CHC OF OCCURRING AT KDCA. WIND SHIFT OCCURS QUICKLY THIS AFTN FROM S TO WNW...TIME OF SHIFT CAN BE +/- 1 HOUR. SLOW IMPROVING CONDITIONS IN THE WAKE OF THE FRONT WITH LINGERING MVFR CIGS PSBL THROUGH THE EVENING. VFR CONDITIONS BY THE SECOND HALF OF TONIGHT WITH GUSTY WNW FLOW...GUSTS 20-22 KTS. VFR CONDITIONS ARE EXPECTED TUESDAY NIGHT THROUGH FRIDAY.
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&& .MARINE... SOLID SMALL CRAFT CONDITIONS CAN BE EXPECTED MUCH OF TODAY AND CONTINUING INTO TUESDAY. SOUTHERLY WINDS WILL SHIFT TO WEST AND NORTHWEST BEHIND A STRONG COLD FRONT THIS AFTERNOON. SOLID GUSTS IN THE 25 TO 30 KT RANGE CAN BE EXPECTED. WINDS WILL BEGIN TO DIMINISH LATER TUESDAY. HIGH PRESSURE WILL BUILD TOWARD THE WATERS TUESDAY NIGHT AND THIS WILL ALLOW FOR WINDS TO SLOWLY DIMINISH. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER. A GALE WARNING MAY EVEN BE NEEDED FOR THESE AREAS TUESDAY EVENING. A REINFORCING COLD FRONT WILL APPROACH THE WATERS WEDNESDAY THROUGH WEDNESDAY NIGHT BEFORE PASSING THROUGH THURSDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS WEDNESDAY NIGHT AND THURSDAY. HIGH PRESSURE WILL BUILD TOWARD THE WATERS FRIDAY INTO SATURDAY. && .CLIMATE... BITTERLY COLD AIR FOR THIS TIME OF YEAR WILL MOVE OVERHEAD TUESDAY AND WEDNESDAY. TEMPERATURES WILL BE BETWEEN 10 AND 20 DEGREES BELOW NORMAL. IN FACT...TEMPERATURES TUESDAY AND WEDNESDAY WOULD BE SEVERAL DEGREES BELOW NORMAL IN JANUARY. BELOW IS A LIST OF RECORD DAILY MINIMUM AND RECORD DAILY LOW MAXIMUM TEMPERATURES FOR THE DATES OF NOVEMBER 18TH (TUESDAY) AND 19TH (WEDNESDAY). SITE 11/18 MIN 11/18 LOW MAX 11/19 MIN 11/19 LOW MAX DCA 21 (1959) 30 (1924) 18 (1891) 33 (1880) BWI 20 (1959) 31 (1959) 20 (1936) 35 (1880) IAD 20 (1991) 39 (2008) 20 (1990) 38 (2008) && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST TUESDAY FOR ANZ530>543. && $$ SYNOPSIS...BJL NEAR TERM...SEARS/KRW SHORT TERM...BJL/KRW LONG TERM...BJL AVIATION...BJL/SEARS/KRW MARINE...BJL/SEARS/KRW CLIMATE...

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