Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 011847 AAA AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 244 PM EDT SAT AUG 1 2015 .SYNOPSIS... HIGH PRESSURE WILL DOMINATE THE AREA THROUGH SUNDAY NIGHT. A WARM FRONT WILL MOVE ACROSS THE AREA MONDAY. A COLD FRONT WILL MOVE INTO THE AREA AND STALL TUESDAY. A WAVE OF LOW PRESSURE WILL DEVELOP NEARBY ALONG THE FRONT WEDNESDAY AND THURSDAY BEFORE MOVING AWAY FRIDAY. && .NEAR TERM /THROUGH SUNDAY/... TROUGH ALOFT WITH SURFACE REFLECTION IS CURRENTLY CROSSING THE REGION. FORCING IS PRETTY WEAK...BUT SOME MOISTURE HAS RETURNED AS EVIDENCED BY DEW POINTS CLIMBING BACK INTO THE MID 60S IN MANY LOCALES. THE LATEST SPC MESOANALYSIS SHOWS A MAX OF CAPE SOUTH OF DC...AND MESOSCALE GUIDANCE HAS BEEN DEPICTING A FEW SHOWERS POPPING UP THIS AFTERNOON INTO EARLY EVENING IN THIS AREA AS WELL. LATEST RADAR TRENDS SHOW THAT THIS APPEARS TO BE STARTING TO HAPPEN...SO THEREFORE INCLUDED SOME ISOLATED SHOWERS IN THE FORECAST IN THIS AREA. AN ISOLATED LIGHTNING STRIKE CANNOT BE COMPLETELY RULED OUT EITHER. OTHERWISE...AND FOR THE MAJORITY OF LOCATIONS AND MAJORITY OF TIME IN THE REST OF THE AREA...IT SHOULD BE A DRY AND PLEASANT LATE AFTERNOON AND EVENING WITH TEMPS NEAR TO SLIGHTLY BELOW NORMAL AND HUMIDITY WHICH IS STILL LOWER THAN WHAT YOU WOULD EXPECT FOR EARLY AUGUST. SURFACE HIGH PRESSURE BUILDS IN FROM THE WEST BEHIND THE TROUGH TONIGHT AND PERSISTS THROUGH SUNDAY AS HEIGHTS RISE ALOFT AND THE FLOW ALOFT BECOMES MORE WEST TO SOUTHWEST. THIS SHOULD PROMOTE MOSTLY SUNNY SKIES AND A LACK OF PRECIPITATION. LIGHT WIND LATE TONIGHT INTO EARLY SUNDAY MAY RESULT IN PATCHY FOG ACROSS INLAND LOCALES AWAY FROM THE METRO...BUT THAT IS PRETTY MUCH ALL THERE IS TO TALK ABOUT. HIGHS WILL BE NEAR NORMAL AGAIN BUT DEW POINTS WILL DROP BACK INTO THE UPPER 50S SO OVERALL...SUNDAY SHOULD BE SLIGHTLY MORE COMFORTABLE THAN TODAY. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... HIGH PRESSURE WILL MAINTAIN CONTROL SUNDAY NIGHT WITH MOSTLY CLEAR SKIES...THOUGH DEW POINTS WILL BEGIN TO CREEP BACK UP. PATCHY FOG WILL AGAIN BE A CONCERN IN THE SHELTERED INLAND LOCALES AWAY FROM THE METRO WHERE RADIATIONAL COOLING SHOULD ALLOW TEMPS TO REACH THE DEW POINT. WITH THE RISING DEW POINTS...LOWS SHOULD END UP A BIT MILDER THAN TONIGHT. MONDAY LOOKS TO BE QUITE HOT WITH GRADUALLY INCREASING HUMIDITY AND 850 MB TEMPS INCREASING TO 19- 22 C. IT WILL BE THE FIRST DAY WITH APPRECIABLE SOUTHERLY RETURN FLOW SO EXPECT DEW POINTS TO REMAIN IN THE 60S...LEADING TO APPARENT TEMPERATURES IN THE MIDDLE TO UPPER 90S DURING THE AFTERNOON. A COLD FRONT WILL APPROACH FROM THE WEST LATE IN THE DAY...ALONG WITH AN UPPER JET MAX AROUND 250 MB. THINKING THIS WILL FIRE SHOWERS AND THUNDERSTORMS DURING THE AFTERNOON TO THE NORTHWEST OF THE CWA...PROPAGATING INTO THE POTOMAC HIGHLANDS DURING THE EVENING. MOST GUIDANCE IS IN AGREEMENT WITH MODERATE CAPE AND SHORTWAVE FORCING...AS WELL AS MODEST SHEAR OVER THESE AREAS. AS SUCH...SPC HAS THE NORTHWESTERN CORNER OF THE AREA IN A MARGINAL RISK FOR SEVERE THUNDERSTORMS ON DAY 3/MONDAY. CANNOT RULE OUT A STRONG STORM OR TWO ACCOMPANIED BY GUSTY WINDS. WENT WITH LIKELY POPS/CHANCE THUNDER OVER THE HIGHLANDS IN THE EVENING...GRADUALLY TAPERING OFF AS ACTIVITY MOVES EAST AND DIMINISHES OVERNIGHT WITH THE LOSS OF HEATING. A POP UP THUNDERSTORM IS ALSO POSSIBLE IN A ZONE OF ENHANCED CONVERGENCE AHEAD OF LEE SIDE PRESSURE TROUGH OVER CENTRAL MD/BALTIMORE METRO AREA MONDAY AFTERNOON...SO HAVE ISOLATED POPS FOR THESE AREAS AS WELL. TUESDAY WILL BE ANOTHER VERY WARM DAY AS THE FRONT STALLS NEAR/JUST SOUTH OF THE AREA. DEEP-LAYER WESTERLY FLOW /DOWNSLOPING/ TAKES OVER ON TUESDAY AND WITH NO REAL FORCING MECHANISM EXPECT RAIN CHANCES TO BE PRETTY MINIMAL...BUT THAT COULD CHANGE IF THE FRONT STALLS FURTHER NORTH /KEEPING LOW-LEVEL WINDS MORE SOUTHERLY AND MOIST/. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... MEAN TROUGHING ALOFT WILL LINGER OVER THE NORTHEASTERN CONUS DURING THE SECOND HALF OF THE WEEK. AT THE SURFACE...A FRONT WILL REMAIN STALLED NEAR THE AREA. UNSETTLED CONDITIONS ARE LIKELY AT TIMES...BUT PINPOINTING THE EXACT TIMING AT THIS TIME RANGE IS DIFFICULT AT BEST. GEFS/EC MEAN SEEMS TO WANT TO HIGHLIGHT WEDNESDAY NIGHT INTO THURSDAY WITH HIGHER POPS AS A WAVE OF LOW PRESSURE MOVES ALONG THE FRONT...BUT TIMING/PLACEMENT/STRENGTH OF SAID WAVE ARE ALL IN QUESTION. THE PATTERN PERSISTS BUT WITH EVEN LESSER CERTAINTY IN DETAILS THROUGH THE END OF THE WEEK. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... HIGH PRESSURE WILL KEEP VFR CIGS AND VIS WITH WINDS MAINLY BELOW 10 KNOTS THROUGH SUNDAY NIGHT. THE PROVERBIAL FLY IN THE OINTMENT IS THAT SOME INLAND TERMINALS AWAY FROM THE METRO...I.E. MRB AND CHO...MAY SEE SOME PATCHY FOG DEVELOP WITH IFR VIS/CIGS LATE TONIGHT...AND AGAIN LATE SUNDAY NIGHT. THIS SHOULD NOT AFFECT THE BUSIER TERMINALS IN THE METRO. GENERALLY REMAINING VFR MON-WED...BUT SUB-VFR POSSIBLE ESPECIALLY FOR MRB/CHO MON EVE...INITIALLY IN SHRA/SCTD TSRA...THEN LWR VSBYS PSBL OVERNIGHT IN PATCHY FOG AS WINDS LIGHTEN W/ FRONT OVERHEAD. SLY WINDS 10-15 KT MON BECOME WLY MON NIGHT-TUE AOB 10 KT. WIND FORECAST BECOMES UNCERTAIN BY WED AND DEPENDS ON POSITIONING OF FRONT/APPROACHING WAVE OF LOW PRESSURE. && .MARINE... WINDS HAVE STAYED BELOW SCA CRITERIA SO FAR TODAY AND AM NOT EXPECTING THEM TO INCREASE AS MUCH AS SOME GUIDANCE HAS SUGGESTED THEY MIGHT AS THE TROUGH PASSES. THEREFORE...KEPT WINDS BELOW SCA LEVELS THROUGH EVENING. HIGH PRESSURE WILL KEEP WINDS LIGHT TONIGHT THROUGH SUNDAY NIGHT. SCA GUSTS LOOK LIKELY MONDAY AFTERNOON INTO MONDAY NIGHT IN SOUTHERLY CHANNELING AHEAD OF AN APPROACHING COLD FRONT/LEE SIDE PRESSURE TROUGH. GRADIENT WEAKENS AS FRONT MOVES OVERHEAD AND WINDS TURN WESTERLY TUESDAY INTO WEDNESDAY. && .TIDES/COASTAL FLOODING... FULL MOON WILL CAUSE ASTRONOMICALLY HIGH TIDES TODAY. WHILE TIDES WILL BE SLIGHTLY ABOVE NORMAL...AM NOT EXPECTING ANY FLOODING. SOUTHERLY FLOW AHEAD OF THE NEXT FRONT WILL ALSO ELEVATE TIDES ON MONDAY...BUT AT THIS POINT NOT EXPECTING MINOR FLOODING. THIS POSSIBILITY WILL REQUIRE MONITORING HOWEVER. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM/DFH LONG TERM...DFH AVIATION...RCM/DFH MARINE...RCM/DFH TIDES/COASTAL FLOODING...KRW/RCM

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