Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 240014 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 814 PM EDT TUE SEP 23 2014 .SYNOPSIS... HIGH PRESSURE WILL HOLD OVER THE REGION THROUGH EARLY WEDNESDAY. LOW PRESSURE WILL MOVE NORTH ALONG ATLANTIC COAST FROM LATE WEDNESDAY THROUGH THROUGH THURSDAY NIGHT. MORE HIGH PRESSURE IS ON TAP FOR THIS WEEKEND. && .NEAR TERM /TONIGHT/...
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LARGE AREA OF HIGH PRESSURE CENTERED OVER NEW YORK STATE. HIGH CLOUDS PRIMARILY COVER SRN VA...BUT SCT CI STRETCH INTO SRN PA. TONIGHT CLOUD COVER WILL BEGIN TO SPREAD INTO SOUTHERN AND EASTERN PARTS OF THE CWA...BUT DRY WX IS EXPECTED. LOWS RANGE FROM THE LOW 40S IN THE POTOMAC HIGHLANDS TO THE UPPER 50S NEAR CHESAPEAKE BAY.
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
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LOW PRESSURE BECOMES GRADUALLY MORE ORGANIZED AS IT MOVES UP THE COAST. FORECAST FOLLOWS ECMWF AND GFS MORE CLOSELY...AS NAM IS AN OUTLIER IN ORGANIZING THE LOW MORE FULLY AND A MORE EASTWARD TRACK. LIKELY POPS FOR RAIN INTO SRN MARYLAND...BUT PRECIP SHIELD MAY REACH FURTHER NORTHWARD TOWARDS WASHINGTON DC AND CHARLOTTESVILLE BY THE END OF THE DAY. HIGHS GENERALLY IN THE UPPER 60S AND LOW 70S. THE LOW CONTINUES TO PUSH NORTHWARD WEDNESDAY NIGHT...REACHING THE DELMARVA BY EARLY THURSDAY MORNING. SEE HYDRO SXN BLO ABT RAIN. BREEZY EASTERLY WINDS EXPECTED AS THE LOW INTERACTS WITH A HIGH ALONG THE NEW ENGLAND COAST. LIKELY POPS PRETTY MUCH EVERYWHERE EAST OF THE BLUE RIDGE. CLOUD COVER AND MARINE MOISTURE WILL KEEP TEMPS FROM DROPPING MUCH WEDNESDAY NIGHT...WITH LOWS OVER MOST OF THE AREA IN THE UPPER 50S AND LOW 60S.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/... AS AN AREA OF LOW PRESSURE MOVES NORTHEAST FROM THE DELMARVA PENINSULA OUT INTO THE OPEN ATLANTIC OCEAN THURSDAY...RAIN CHANCES WILL DECREASE FROM WEST TO EAST. HIGH PRESSURE WILL PROVIDE GOOD SUBSIDENCE IN THE WESTERN HALF OF THE REGION. THIS HIGH WILL DOMINATE THE REGION THURSDAY NIGHT THROUGH SUNDAY MORNING...PROVIDING PLENTY OF SUNSHINE WHICH WILL LEAD TO WARM AFTERNOONS AND COMFORTABLE NIGHTS. HIGHS SHOULD REACH 80 IF NOT A FEW DEGREES ABOVE DURING EACH AFTERNOON. A WEAK...YET MOISTURE-STARVED...COLD FRONT COULD DROP IN ACROSS THE REGION LATE SUNDAY INTO SUNDAY NIGHT. LEFT POPS AROUND 10 PERCENT OR LESS FOR NOW...CONSIDERING THE LIMITING MOISTURE FACTOR AHEAD OF THE FRONT. A REINFORCING AREA OF HIGH PRESSURE WILL BUILD BEHIND THE FRONT MONDAY THROUGH TUESDAY. THIS WILL LEAD TO HIGHS REACHING THE UPPER 70S TO NEAR 80 AND BEAUTIFUL AFTERNOONS. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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VFR CONDITIONS EXPECTED THROUGH WED MORNING. RAIN EXPECTED TO MOVE INTO THE BALTIMORE/WASHINGTON TERMINALS WEDNESDSAY EVENING AND WEDNESDAY NIGHT...WITH MVFR OR IFR CIGS/VSBYS. MVFR OR IFR CONDITIONS MORE PROBABLE AT THE IAD...DCA...BWI AND MTN TERMINALS THURSDAY AS RAIN SHOWERS AND A GUSTY BREEZE LINGER ON THE BACKSIDE OF A DEPARTING LOW PRESSURE SYSTEM. WINDS NNE 10 TO 20 KTS GUSTING 25 KTS THURSDAY. VFR CONDITIONS AT ALL TERMINALS THURSDAY NIGHT AND FRIDAY. WINDS NORTH TO NORTHWEST 5 TO 10 KNOTS GUSTS 15 KNOTS THURSDAY NIGHT AND FRIDAY.
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&& .MARINE... WINDS CONTINUE TO INCREASE WEDNESDAY AS LOW PRESSURE APPROACHES FROM THE SOUTH. SCA BEGINS 10 AM WEDNESDAY FOR THE SOUTHERN PORTION OF THE TIDAL POTOMAC AND CHESAPEAKE BAY SOUTH OF SANDY POINT. PERIODS OF RAIN LIKELY WEDNESDAY AFTERNOON THROUGH WEDNESDAY NIGHT. SCA HAS BEEN EXTENDED THROUGH WEDNESDAY NIGHT FOR THESE AREAS AS THE LOW APPROACHES THE TIDEWATER/DELMARVA REGION AND THE PRESSURE GRADIENT NEAR THE LOW INCREASES. THE SCA MAY NEED TO BE EXPANDED FURTHER NORTHWARD IN FUTURE UPDATES. SMALL CRAFT ADVISORIES MAY BE NEEDED THURSDAY INTO THURSDAY NIGHT. SMALL CRAFT ADVISORIES ARE POSSIBLE...ONCE AGAIN...FRIDAY AS A LOW PRESSURE SYSTEM NEAR THE EAST COAST INTERACTS WITH BUILDING HIGH PRESSURE. && .HYDROLOGY...
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TOOK A LOOK AT THE PTNL FOR FRESHWATER FLDG. AT THIS TIME BLV THREAT IS ON THE LOW END. ALTHO FOR THE YR TOTAL WE HV BEEN ABV AVG IN PCPN THIS MONTH HAS BEEN VERY DRY. SEPT TOTALS: DCA 0.43" IAD 0.22" BWI 0.95" CHO 0.26" MRB 1.83" THIS AVGS OVR 2" BLO NRML FOR THE MONTH. THERE WL BE LOW LVL ERLY FLOW WED INTO THU. RAFL WL LKLY BEGIN WED AFTN IN THE NRN NECK OF VA...WORKING INTO THE DC/BALT CORRIDOR WED EVE. HVIEST RAFL XPCTD WED NGT INTO THU MRNG. THE AREA OF HVIEST RAFL LOOKS AGN TO BE IN THE I-95 CORRIDOR. MDLS PROJECT THE LOW PRES AS BEING FAIRLY TRANSITORY...WHICH WORKS AGAINST THE PSBLTY OF FLDG FM RAIN. IN ADTN GIVEN THE LOW RAFL TOTALS OF THE PAST MONTH THE GRND IS QUITE DRY. IF THE RAFL INTENSITY WAS GOING TO BE AT THE R+ LVL THE HARDNESS OF THE GRND COULD WORK TO EXACERBATE THE RUNOFF/FLD THREAT. HOWEVER SUSPECT RA WOULD FALL AT MORE OF A MDT RATE WHICH WOULD LEAD TO GRTR ABSORPTION. HV ADDED MENTION OF PSBL FLDG OF STREAMS AND CRKS IN THE ERN PART OF THE FCST AREA. RIVER LVLS ARE MUCH TOO LOW TO BE OF CONCERN. BLV HVIEST RAFL WL BE MOVG INTO DE/NJ THU MRNG.
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&& .TIDES/COASTAL FLOODING... A COASTAL LOW PRES SYSTEM WELL TO OUR SOUTH WILL SLOWLY APPROACH THE AREA WEDNESDAY INTO WEDNESDAY NIGHT. THIS WILL LEAD TO HIGHER THAN NORMAL WATER LEVELS PARTICULARLY OVER THE WESTERN SHORE OF THE CHESAPEAKE BAY. MINOR TIDAL INUNDATION WILL BE POSSIBLE DURING THE TIMES OF HIGH TIDE. EFFECTS FOR THURSDAY WILL BE HIGHLY DEPENDENT ON THE TRACK OF THIS SYSTEM. WINDS WILL SHIFT TO THE NORTH OF THE LOW TRACKS EAST OF THE BAY...WHICH WOULD REDUCE OR ELIMINATE TIDAL ANOMALIES. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM WEDNESDAY TO 6 AM EDT THURSDAY FOR ANZ532>534-537-540>543. && $$ UPDATE...WOODY! PRVS...KCS/KLW

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