Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 201449 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 949 AM EST THU NOV 20 2014 .SYNOPSIS... HIGH PRESSURE MOVES OFFSHORE EARLY TODAY...FOLLOWED BY A COLD FRONT PASSING THROUGH THE CWA THIS AFTERNOON. BROAD HIGH PRESSURE PUSHES EAST TONIGHT THROUGH SATURDAY. A DEEPENING LOW PRESSURE SYSTEM WILL LIFT A WARM FRONT SUNDAY INTO MONDAY WITH THE ASSOCIATED COLD FRONT APPROACHING AND STALLING THROUGH MID WEEK BEFORE FINALLY PUSHING EAST. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A COLD FRONT WILL CONTINUE TO MOVE EASTWARD ACROSS THE POTOMAC HIGHLANDS AND SHENANDOAH VALLEY THIS MORNING. WESTERLY WINDS BEHIND THE FRONT HAVE LED TO MTN WAVES ACROSS THIS REGION. MIXING AS ALLOWED 25-35 KTS TO MIX DOWN BEHIND THE FRONT. AHEAD OF THE FRONT...CONVERGENCE IN THE MID LEVELS ALOFT HAS LED TO MID-HIGH LEVELS TO FORM ACROSS THE I-95 CORRIDOR. CLOUDS WILL MOVE EASTWARD BY THIS AFTERNOON. WESTERLY FLOW AGAINST THE WESTERN SLOPES WILL LEAD TO LIGHT SNOWFALL FOR THE ALLEGHENY FRONT. A STRONG JET WILL MOVE OVERHEAD THIS AFTERNOON WHICH SHOULD LEAD TO THE DEVELOPMENT OF CIRRUS. THE FRONT WILL MOVE EASTWARD TODAY AND SHOULD BE THROUGH THE I-95 CORRIDOR BY LATE AFTERNOON. TEMPS AHEAD OF THE FRONT WILL RISE INTO THE LOW TO MID 40S BY THIS AFTERNOON. WESTERLY WINDS WILL MOVE INTO THE REGION BEHIND THE FRONT AND ANOTHER SURGE OF COLD AIR WILL MOVE INTO THE REST OF THE MID-ATLANTIC TONIGHT. PREVIOUS ... AN INTERESTING FEATURE TODAY WILL BE THE DEVELOPMENT OF A STRONG UPPER LEVEL JET THIS AFTERNOON INTO THE EVENING...WHICH SHOULD CAUSE DEVELOPMENT OF CIRRUS AFTER NOON. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... OUR AREA WILL BE IN THE LOWER RIGHT QUAD OF A 140KT JET TONIGHT...SO THIS SHOULD PRODUCE DECENT CIRRUS CLOUDS TONIGHT. ANOTHER COLDER THAN NORMAL NIGHT WITH LOWS RANGING FROM THE UPPER TEENS POTOMAC HIGHLANDS TO UPPER 20S METRO AREAS. EXPECTING THE WIND TO STAY UP AND PROVIDE MIXING SO TEMPS NOT BOTTOM OUT TO NEAR THE MID-TO-LOWER TEEEN DEWPOINTS. USED ADJMET FOR MIN TEMPS TONIGHT. FRIDAY HIGH PRESSURE BUILDS OVERHEAD WITH NO REMARKABLE WEATHER. WENT WITH ADJMAV FOR FRI HIGH TEMPS. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... BROAD HIGH PRESSURE BUILDS EAST FRIDAY NIGHT...WITH THE CENTER OF THE HIGH SETTLING OVER THE MID ATLANTIC ON SATURDAY. ALOFT...ZONAL FLOW WILL TRANSITION INTO RIDGING OUT AHEAD OF THE NEXT APPROACHING DEEPENING TROUGH. OVERALL SYNOPTIC FEATURES THUS LEADING TO A QUIET AND DRY PERIOD. THE RETURN TO SOUTHERLY FLOW WILL BEGIN THE WARMING TREND UNDER RISING HEIGHTS ALOFT AND DECENT WAA WHICH WILL PUSH 850MB TEMPS FROM AROUND 15 BELOW ZERO 12Z FRIDAY TO AROUND 2 DEGREES ABOVE ZERO 12Z SAT. AFTER THE QUIET START TO THE WEEKEND...ATTENTION TURNS TO A DEVELOPING LOW PRESSURE SYSTEM WHICH IS EXPECTED TO LIFT A WARM FRONT THROUGH THE AREA SLOWLY SUNDAY INTO MONDAY. GENERAL CONSENSUS AMONGST THE 00Z MODEL SOLUTIONS IS DRY WX THRU SAT NIGHT WITH LIGHT RAIN MOVING IN SOMETIME AFTR 12Z SUN...WITH THE MUCH HIGHER CONFIDENCE OF PCPN THEN SUN AFTN-MONDAY. GFS MUCH MORE PRONOUNCED WITH THE UPPER LEVEL ENERGY ASSOCIATED WITH MULTIPLE SHORTWAVES ROUNDING THE BASE OF THE TROUGH AS WELL AS BEING A BIT QUICKER IN THE PROGRESSION WHILE THE ECMWF IS TRENDING MORE TO THE BULK OF THE PCPN SUNDAY NIGHT. AS SUCH...INTRODUCED POPS SUNDAY MORNING THEN QUICKLY TRANSITIONED TO LIKELY-CATEGORICAL SUNDAY AFTN AND MAINTAINED THESE POPS THRU THE FIRST HALF OF SUN NIGHT. PCPN BECOMES MORE SHOWER-LIKE AND PERIODIC IN NATURE MONDAY AS THE COLD FRONT NEARS THE REGION. WITH THE UPPER LEVEL TROUGH STAYING IN PLACE THROUGH WED...THE COLD FRONT STALLS NEAR THE AREA...EVENTUALLY PUSHING TO THE NORTH AND EAST BY WED AS A MUCH DEEPER...STRONGER TROUGH ALOFT NUDGES IT ALONG. AS FOR THE PCPN TYPE WITH THIS SYSTEM...STRONG WAA WILL REBOUND TEMPS BACK TO NEAR NORMAL SUNDAY AND A GOOD 5-10 DEGREES ABOVE NORMAL FOR MONDAY.AT THE MOMENT...EVERYWHERE LOOKS TO REMAIN RAIN AND RAIN SHOWERS SUNDAY-TUESDAY. FOR NOW HAVE DRY WX IN PLACE WED...BUT IF ANY PCPN DOES OCCUR...THIS WOULD BE THE NEXT CHC FOR SEEING SNOW SHOWERS IN THE HIGHEST ELEVATIONS. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... VFR AT ALL TERMINALS DURING TAF PERIOD. GUSTY WEST WIND WITH MAX DAYTIME BOTH TODAY AND FRIDAY...SLACKENING TONIGHT. VFR CONDITIONS FRI NIGHT THROUGH AT LEAST SUNDAY MORNING. SUB-VFR CONDITIONS ARE LIKELY BY SUNDAY AFTN AND LASTING THROUGH MONDAY...WITH IFR PSBL WITH THE HEAVIEST PCPN SUN EVENING-NIGHT. LLWS MAY BRIEFLY BE A CONCERN SUNDAY NIGHT AS A STRONG LLJ SETS UP OVER THE TERMINALS. AT THE SFC...SLY FLOW INCREASES AHEAD OF THE COLD FRONT...WITH GUSTS UP TO 20-25 KTS PSBL MONDAY. VFR CONDITIONS AND WINDS LESS THAN 10 KTS RETURN BY TUESDAY. && .MARINE... CONTINUING SCA FOR GUSTY W WINDS THROUGH FRIDAY AFTERNOON. TODAY WILL SEE HIGH END SCA WITH FROPA. THERE MAY BE A FEW HOURS BELOW THRESHOLD TONIGHT...BUT QUICKLY RETURN TO SOLID SCA ON FRIDAY. SUB-SCA CONDITIONS FRIDAY NIGHT THROUGH SATURDAY NIGHT. GUSTS TO 20 KTS POSSIBLE BY SUNDAY MORNING...WITH HIGHER CONFIDENCE OF OCCURRENCE BY SUNDAY AFTN. SOLID SCA CONDITIONS WITH GUSTS TO 25 KTS SUNDAY NIGHT-MONDAY. WINDS WILL DIMINISH AND DROP BELOW SCA CRITERIA ONCE AGAIN FOR TUES-WED. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR ANZ530>543. && $$ SYNOPSIS...LEE NEAR TERM...LEE/HAS SHORT TERM...SEARS LONG TERM...SEARS AVIATION...SEARS/LEE MARINE...SEARS/LEE

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