Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 300143 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 943 PM EDT SUN MAR 29 2015 .SYNOPSIS... HIGH PRESSURE PUSHES OFFSHORE TONIGHT WITH A COLD FRONT CROSSING THROUGH THE REGION ON MONDAY. A REINFORCING CLIPPER LOW WILL PASS OVER THE REGION ON TUESDAY. THE HIGH PRESSURE THAT FOLLOWS WILL SLIDE TO OUR SOUTHEAST THURSDAY AND FRIDAY ALLOWING FOR WARM TEMPERATURES. ANOTHER COLD FRONT IS EXPECTED AT THE END OF THE WEEK. && .NEAR TERM /THROUGH MONDAY/... 01Z OBS HAS SFC HIGH TO THE SOUTH OFF THE CAROLINA COAST...WITH APPROACHING FRONTAL SYSTEM BACK OVER OHIO. WITH THE HIGH POSITIONED TO THE SOUTH...SOUTHERLY FLOW NOW OVER THE AREA...WORKING TO INJECT IN MORE MOISTURE RICH AIR. A VERY DRY AIRMASS NEEDS TO BE OVERCOME THOUGH...AS EVIDENT WITH DEW PTS STILL HOVERING IN THE SINGLE DIGITS ACROSS MUCH OF THE AREA. THINKING THE STRONGER SURGE OF MORE MOIST AIR...AS WELL AS WAA...WILL COME WITH THE LLJ INCREASING AFTER MIDNIGHT TONIGHT...WITH SW WINDS BETWEEN 40-50 KTS. LOOKING UPSTREAM...THERE ARE A FEW SPOTS REPORTING LIGHT RAIN WITH DEW PT DEPRESSIONS OF ALMOST 20. AS SUCH...HAVE VERY LIGHT RAIN MENTIONED THRU 07Z FOR ONLY EXTREME WESTERN AREAS...THEN THINKING WITH MORE MOISTURE ADVECTION SHOULD SEE THE AIRMASS SATURATE ENOUGH FOR LIGHT RAIN TO OCCUR. TRICKY SITUATION WHEN RELATING TO TEMPS...AS FORECASTED TEMPS HAVE DROPPED THIS EVENING...BUT ARE EXPECTED TO REMAIN NEAR STEADY AROUND MIDNIGHT THEN INCREASE TOWARD DAWN WITH THE WAA. DESPITE THE LOW DEW PTS...THE PCPN IS EXPECTED TO REMAIN LIGHT ENOUGH SO NOT ANTICIPATING WET BULBING. SO HAVE MAINLY LIGHT RAIN MENTIONED...WITH ISOLATED SPOTS THAT COULD DROP TO THE LOWER 30S POTENTIALLY SEEING SOME SNOWFLAKES MIX IN WITH THE RAIN. AFTER HAVING A DAY WITH HIGHS IN THE 40S AND LOWER 50S...NOT ANTICIPATING SFCS TO DROP TO OR BELOW FREEZING FOR LONG ENOUGH TO BE CONCERNED WITH ICE...ESP WITH ROAD TEMPS CURRENTLY SHOWING IN THE 40S AND 50S (AS OF 01Z). THE EXCEPTION TO THIS FORECAST WILL BE THE WESTERN SLOPES OF THE ALLEGHENIES WHICH SHOULD SEE A PERIOD OF SNOW SHOWERS...AND PSBL UP TO A COUPLE TENTHS OF AN INCH ACCUM. THE FNT ITSELF WL BE RATHER MSTR STARVED. THEREFORE XPCT MOST OF THE PCPN AHD OF THE FNT...AND THUS HAVE PCPN ENDING BY MIDDAY AS CFP WL OCCUR BY NOON AREAWIDE. CAA MAY RESULT IN A QUICK CHGOVER TO SHSN ON THE WRN SLOPES OF THE MTNS PRIOR TO A RAPID PCPN /AND CLDCVR/ DECREASE. AT THE SAME TIME...WINDS WL BE INCREASING...AND THE COMPRESSIONAL WARMING MAY YIELD MAXT WARMER THAN TDA. IT APPEARS AS THO THE CORE OF HIER WINDS WL BE AT THE TOP /OR JUST ABV/ THE MIXED LYR...W/ CLDS PRESENT TO INTERFERE W/ DP LYR MIXING. THEREFORE AM KEEPING GUSTS 20-25 KT. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... IN A RELATIVELY SHORT AMOUNT OF TIME AFTER THE EXIT OF THE GUSTY MONDAY SYSTEM...THE NEXT UPPER LEVEL DISTURBANCE WILL BE RIGHT ON THE DOORSTEP TO OUR NW. THIS FEATURE WILL BE MUCH MORE COMPACT AND THEREFORE AFFECTING MUCH LESS AREA...ALSO BEING DRIVEN BY A MORE COMPACT ADVECTION PATTERN - TIGHTLY WOUND AROUND THE SYSTEM. AHEAD OF AND BEHIND THIS NEXT UPPER WAVE SOME WIND...MAINLY AROUND 5-10KT BUT GENERALLY THE SYSTEM WILL PASS W/O THE DAY-LONG PERIOD OF STRONG WINDS BEHIND IT. THE NEXT QUESTION IS ABOUT PRECIP AND PTYPE. THE PAST FEW RUNS OF ALL MAIN GUIDANCE SUITES HAVE BEEN WAVERING BACK/FORTH ABOUT THE SFC LOW TREKKING DIRECTLY OVER THE CWA...A HUNDRED MILES TO THE NORTH...OR SOMEWHERE IN BETWEEN. THE 12Z NAM IS GOING W/ THE MASON- DIXON LINE SOLN...BUT IN TERMS OF PRECIP - THAT MEANS VERY LITTLE FOR AREAS S OF THE SFC LOW. MUCH OF THE PRECIP IS CARRIED ALONG NORTH OF THE LOW...AS IT IS FOR THE EURO AND GFS BUT THEIR DETERMINISTIC 12Z RUNS HAVE THE LOW FURTHER SOUTH - BETWEEN THE I-70 AND I-66 CORRIDOR OF THE CWA. AHEAD OF THE FEATURE...SWLY LOW LEVEL WINDS WILL INCREASE AND SO WILL SFC TEMPS - INTO 40S/50S FROM S TO N. ALTHOUGH A RAIN/SNOW MIX IS POSSIBLE EARLY TUE MRNG OVER THE EXTREME NW QUAD OF THE CWA AS PRECIP ARRIVES...PRECIP EXPECTED TO BE ALL RAIN FOR THE DAYTIME HRS AND MUCH OF IT WILL SPREAD ACROSS THE NRN HALF OF THE CWA. KEPT A HIGH CHANCE AND SOME LIKLIES IN FOR THESE AREAS. ON THE IMMEDIATE BACK END OF THE LOW`S PASSAGE IS STILL SOMEWHAT IN QUESTION. THE COLD AIR W/ THE FEATURE WILL AGAIN BE COMPACT AND CLOSE INTO THE BACK END OF THE SYSTEM. THERE MAY BE ENOUGH OVER NERN MD FOR A BRIEF PERIOD AND THE COLD FRONT SWINGS THRU TO MIX IN SOME SNOW BUT ALSO THE PRECIP MAY BE WELL E OF THE AREA BY THAT TIME. AS W/ A TYPICAL UPPER WAVE PASSAGE...THE DAY AFTER WILL BE A MODERATED VERSION OF THE PREV DAY IN TERMS OF TEMPS AND DRY. SFC WINDS WILL BE A STEADY NW AND DRIER BREEZE BUT NOT ALL THAT STRONG AND HIGHS WILL BE ALLOWED TO REACH THE 50S ACROSS MUCH OF THE AREA...NEAR 60 ACROSS THE SOUTH. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... HIGH PRESSURE...MOVING OFFSHORE THE EAST COAST...WILL SPONSOR DRY CONDITIONS AND NEAR NORMAL TEMPERATURES WEDNESDAY NIGHT. AN INCREASED SOUTHERLY FLOW WILL DEVELOP WEDNESDAY NIGHT AND THURSDAY AHEAD OF AN APPROACHING COLD FRONT. HIGHS ARE EXPECTED TO APPROACH 70 DEGREES ACROSS MUCH OF THE REGION THURSDAY WITH A CHANCE OF RAIN SHOWERS ACROSS THE WESTERN HALF OF THE REGION. THE COLD FRONT SHOULD PUSH ACROSS THE REGION THURSDAY NIGHT INTO FRIDAY BEFORE STALLING TO THE SOUTH FRIDAY NIGHT. ADDITIONAL RAIN SHOWERS AND PERHAPS A THUNDERSTORM OR TWO COULD DEVELOP IN LIEU OF THE PASSING FRONT. TEMPERATURES SHOULD REMAIN MILD THURSDAY NIGHT AND FRIDAY WITH HIGHS REACHING THE UPPER 60S TO NEAR 70 FRIDAY. THE STALLED FRONT SHOULD MEANDER NORTH AND SOUTH FRIDAY NIGHT AND SATURDAY...ONLY TO REMAIN THE FOCAL ZONE FOR ADDITIONAL RAIN SHOWERS OR RUMBLES OF THUNDER AND COOLER TEMPERATURES. A LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP ALONG THIS FRONT BEFORE PUSHING TO THE EAST COAST LATER SATURDAY INTO SATURDAY NIGHT. HIGH PRESSURE WILL BRING DRIER CONDITIONS AND REINFORCING COOLER AIR INTO THE MID ATLANTIC FOR SUNDAY. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... MAINLY VFR CONDITIONS THRU MON. PSBL MVFR CIGS WITH LIGHT RAIN TONIGHT...MAINLY BETWEEN 08-12Z. HAVE INCLUDED -RA AT THE METRO TERMINALS FOR 3 HR BLOCKS...THE PCPN COULD VERY WELL END UP MORE OCNL IN NATURE. LIGHT S FLOW TONIGHT...THOGUH WITH INCRSNG SW FLOW ALOFT...HAVE INCLUDED LLWS MENTION THRU 08/09Z. NO PCPN CONCERNS MONDAY...BUT INCRSNG WNW FLOW DURING THE DAY...WITH GUSTS 25-30 KTS. WINDS WILL DIMINISH MONDAY NIGHT. YET ANOTHER QUICK-MOVING UPPER LEVEL LOW WILL SWING BY THE AREA ON TUE...MAINLY DURING THE DAYTIME HRS. ANY PCPN IS EXPECTED TO BE RAIN...W/ WARMER TEMPS WORKING INTO THE SRN END OF THE SYSTEM AS IT PASSES BY. BRIEF MVFR CIGS COULD RESULT FROM THIS SYSTEM DURING THE DAYTIME HRS...BUT QUICKLY IMPROVING TUE NIGHT INTO WED AS SKIES CLEAR OUT. VFR CONDITIONS WEDNESDAY NIGHT. LIGHT SOUTHEAST WINDS WILL BECOME SOUTHERLY. VFR CONDITIONS AT ALL TERMINALS THU NGT INTO FRI...EXCEPT FOR MRB AND PERHAPS IAD WHERE MVFR COULD EVOLVE DUE TO SPOTTY RAIN SHOWERS IN THE AREA. SOUTH WINDS BECOMING SOUTHWEST AND GUSTING AROUND 15 KNOTS. && .MARINE... WITH WINDS AROUND 17 KTS OVER THE NORTHERN CHESAPEAKE BAY...HAVE GONE AHEAD AND BEGUN THE SCA THERE. REMAINING WATERS HAVE THE SCA STARTING AT MIDNIGHT...THEN ALL WATERS GO THRU THE DAY MONDAY AS WINDS INCREASE BEHIND A PASSING COLD FRONT. EXPECTING SOLID SCA CONDITIONS...WITH PSBL HIGHER GUSTS WITH STRONG WINDS ALOFT. HOWEVER...BUFKIT SOUNDINGS LOOK TO RESTRICT MIXING TO THESE STRONGEST WINDS AND THINK THE SCA WILL BE SUFFICIENT. SUB-SCA CONDITIONS THEN EXPECTED MON NIGHT. A COLD FRONT WILL CROSS THE REGION LATE TUE...W/ A PERIOD OF LOW-END SCA GUSTS POSSIBLE FROM SW WINDS AHEAD OF THE FRONT. HIGH PRES WILL CLEAR OUT THE CLOUDS/PRECIP TUE NIGHT. LOW-END SCA WINDS BEHIND THIS FEATURE WILL PICK UP AGAIN OVER THE WATERS DURING THE DAYTIME HRS WED. NO MARINE HAZARDS EXPECTED WEDNESDAY NIGHT AND THURSDAY. WINDS GENERALLY AROUND 5 KNOTS WEDNESDAY NIGHT...BECOMING SOUTH TO SOUTHWEST AT 10 KNOTS WITH OCCASIONAL GUSTS AROUND 15 KNOTS. && .TIDES/COASTAL FLOODING... WATER LEVELS RUNNING A FOOT TO A FOOT AND A HALF BELOW ASTRO PREDICTIONS DUE TO RECENT BLOWOUT WINDS. LEVELS SHOULD NORMALIZE SOMEWHAT TONIGHT IN SLY FLOW. BLOWOUT TIDES WILL RETURN MON AFTN AS NW WINDS RESUME. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR ANZ530-531-538- 539. SMALL CRAFT ADVISORY UNTIL 8 PM EDT MONDAY FOR ANZ532>534-537- 540>543. SMALL CRAFT ADVISORY FROM 9 AM TO 8 PM EDT MONDAY FOR ANZ535- 536. && $$ SYNOPSIS...HTS NEAR TERM...SEARS/HTS SHORT TERM...GMS LONG TERM...KLW AVIATION...SEARS/GMS/HTS/KLW MARINE...SEARS/GMS/HTS/KLW TIDES/COASTAL FLOODING...

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