Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 141042 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 642 AM EDT MON APR 14 2014 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN OFF THE EAST COAST TODAY. A COLD FRONT WILL CROSS THE APPALACHIANS LATE TONIGHT AND MOVE THROUGH THE AREA TUESDAY. HIGH PRESSURE WILL BUILD EAST INTO THE NORTHERN MID-ATLANTIC WEDNESDAY AND REMAIN OVER THE AREA THROUGH FRIDAY. LOW PRESSURE MAY IMPACT THE REGION ON SATURDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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SFC HIPRES AND UPPER RIDGE WILL CONTINUE TO MOVE FARTHER OFFSHORE TDA AS AN UPPER TROUGH AND COLD FRONT PROGRESS EWD ACROSS THE CENTRAL CONUS. MOISTURE IN BETWEEN THESE TWO SYSTEMS WILL STREAM NWD UP THE ERN SEABOARD TDA OWING TO S-SWLY FLOW THRUOUT THE TROPOSPHERE. HI CLOUDS HAVE BEEN CONTINUALLY STREAMING INTO THE AREA SINCE YDA. THE LATEST IR/WV SATELLITE AND EXTRAPOLATING UPSTREAM METAR OBS SHOWS THIS PATTERN CONTINUING TDA. GUIDANCE HAS CONSISTENTLY HAD A COLD BIAS DURING THIS CURRENT WARM SPELL. WENT ABOVE GUIDANCE FOR MAX TEMPS ACCORDINGLY BUT ONLY SLIGHTLY THOUGH WITH MORE CLOUD COVER TDA THAN OVER THE PAST THREE WARM DAYS. FCST MAX TEMPS GENERALLY IN THE MID 70S TO LOW 80S. LOCATIONS ALONG AND EAST OF I-95 AND AWAY FROM THE CHSPK BAY SHOULD HAVE THE BEST OPPORTUNITY TO REACH 80F WITH LESS CLOUD COVER. CONSENSUS OF HIRES GUIDANCE KEEPS ORGANIZED PRECIP WITH THE COLD FRONT TO THE WEST OF THE ALLEGHENY FRONT UNTIL LATE THIS AFTN AND SOME OF THE SLOWER MODELS HOLD IT OFF IN THE FAR WEST UNTIL SUNSET. POPS REFLECT MAINLY SCT COVERAGE OF SHOWERS WEST OF CHO-OKV-MRB THIS AFTN. CANNOT RULE OUT AN ISO SHOWER THIS AFTN FARTHER EAST EVEN TOWARD I-95 BUT KEPT IT OUT OF THE FCST FOR NOW WITHOUT DISCERNIBLE LIFT. THE COLD FRONT WILL APPROACH THE WRN SIDE OF THE APPALACHIANS THIS EVE BEFORE CROSSING THE MTS LATE TNGT. TNGT WILL BE MILD WITH SLY FLOW AND PRE-FRONTAL WARM SECTOR BECOMING INCREASINGLY ESTABLISHED IN THE MID-ATLANTIC REGION. POPS INCREASE FROM WEST TO EAST TNGT AS THE COLD FRONT APPROACHES FROM THE WEST. SHOWERS EXPECTED TO BECOME WIDESPREAD OVNGT INTO ERY TUE MRNG. INSTABILITY PROFILES RATHER MEAGER ACROSS THE CWA OWING TO WEAK MID-LVL LAPSE RATES. MENTION OF A SLIGHT CHANCE FOR THUNDER CONFINED TO THE SHENANDOAH VLY/POTOMAC HIGHLANDS FOR LATE THIS AFTN AND EVE. HIGHER INSTABILITY FROM THE 00Z NAM WOULD SUPPORT CHANCES FOR TSTMS EVERYWHERE...BUT A QUICK COMPARISON OF OBS TO THE 6-H NAM FCST INDICATES THE MODEL WAS ALREADY OVERDOING THE MOISTURE RETURN.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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TUESDAY...A RATHER AMPLIFIED TROUGH/COLD FRONT FROM A HUDSON BAY LOW SHIFTS EAST ACROSS THE ERN CONUS THROUGH THE DAY...PUSHING OFF THE COAST THAT NIGHT. THE LOW LEVEL JET INCREASES TO 50-60 KT AHEAD OF THE COLD FRONT WITH 60F DEWPOINTS SPREADING IN EAST OF THE BLUE RIDGE. STRONG DYNAMICS CONTINUE ACROSS THE FRONT WITH ARCTIC AIR SPILLING IN BEHIND. EXPECT SWATHS OF MODERATE TO LOCALLY HEAVY RAIN WITH GUSTY WINDS AHEAD OF THE FRONT WITH A THIN SQUALL ON THE LEADING EDGE OF THE FRONT. WENT WITH SCHC OF THUNDER...THOUGH LIGHTNING IS NOT OFTEN PRESENT WITH QLCS ACTIVITY. SPC DAY TWO HIGHLIGHTS SERN PORTION OF CWA FOR DAMAGING WIND THREAT. WILL NEED TO BE ON THE LOOKOUT FOR STRONG GUSTS ACROSS THE BALT-WASH METRO. THE COLD FRONT IS FAIRLY PROGRESSIVE...SO IN SPITE OF A MAX PWAT AROUND 1.5 INCHES (ABOVE 2 STDEV FOR KIAD) WIDESPREAD FLOODING IS NOT EXPECTED. QPF OF HALF TO ONE INCH CAN BE EXPECTED. TEMPERATURES WILL REACH INTO THE 70S IN THE AFTERNOON AHEAD OF THE FRONT...EAST OF I-95 (60S FARTHER WEST BUT TO EARLIER FROPA). RAPID COOL DOWN BEHIND THE COLD FRONT THAT CROSSES LATE AFTERNOON. THE GROWING SEASON STARTS APRIL 15 EAST OF THE BLUE RIDGE...SO EVEN THOUGH A FREEZE IS POSSIBLE ACROSS CWA A HEADLINE WOULD ONLY BE EAST OF THE BLUE RIDGE. MIN TEMPS 20S WEST OF THE BLUE RIDGE AND THE MD PIEDMONT. LOW 30S VA PIEDMONT AND INTERIOR CENTRAL MD. MAY BE TOO MUCH MIXING TO ALLOW FROST...SO A FROST ADVISORY MAY NOT BE NECESSARY FOR LOCATIONS 33-36F MIN TEMPS. SNOWFLAKES ARE POSSIBLE AT END OF PRECIP ACROSS MOST OF THE CWA...BUT ACCUM SHOULD BE LIMITED TO ABOVE 2000 FT...UP TO AN INCH OR SO. STRONG WINDS BEHIND THE COLD FRONT...WIND ADVISORY POSSIBLE FOR RIDGELINES TUESDAY NIGHT... GUSTING AT LEAST 40 MPH EAST ACROSS THE REST OF THE CWA. WEDNESDAY...HIGH PRESSURE BUILDS EAST ACROSS THE NRN MID- ATLANTIC...THEN NEW ENGLAND WEDNESDAY NIGHT. MAX TEMPS AROUND 50F IS 15 OR SO DEGREES BELOW NORMAL.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... SFC PRESSURE RIDGE/COLD AIR DAMMING PERSISTS WEDNESDAY NIGHT THROUGH FRIDAY NIGHT...UNTIL THE NEXT DISTURBANCE DISLODGES THE ONSHORE FLOW. EXPECT BELOW NORMAL TEMPS WITH THE ONSHORE FLOW...BECOMING SATURATED FRIDAY NIGHT. UNCERTAINTY ON WEEKEND SYSTEM ON WHETHER IT IS A COLD FRONT (LIKE 00Z GFS) OR LOW SYSTEM (LIKE 00Z ECMWF). && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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A 45 KT SWLY JET ABOVE THE SFC PRODUCING LLWS CONDITIONS ERY THIS MRNG ACROSS THE TERMINALS. A SURGE OF LLVL MOISTURE TO OUR SW WILL REACH THE TERMINALS AFTER SUNRISE. MAY BRIEFLY SEE A PERIOD OF LOWER CIGS THAT APPROACH MVFR CIGS BETWEEN 11Z-15Z AT CHO. OTHERWISE VFR AND BREEZY SLY WINDS GUSTING TO 25 KT TDA. A COLD FRONT APPROACHES FROM THE WEST TNGT. SHOWERS WILL INCREASE IN COVERAGE FROM WEST TO EAST TNGT...ESPECIALLY AFTER MIDNIGHT. MVFR CIGS/VSBYS LIKELY IN SHOWERS WITH THE POTENTIAL FOR IFR BY ERY TUE MRNG. STRONG COLD FRONT CROSSES THE TERMINALS TUESDAY WITH WIDESPREAD RAIN... STRONG SOUTH WIND (AND LLWS) AND LOW CHANCES FOR THUNDER AHEAD WITH STRONG NW FLOW TUESDAY NIGHT BEHIND. JUST SOME SNOWFLAKES...NO ACCUM POSSIBLE AT THE TERMINALS. HIGH PRESSURE WEDNESDAY...WITH COLD AIR DAMMING THEN THROUGH FRIDAY.
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&& .MARINE...
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SLY WINDS CONTINUE TO GUST TO SCA LEVELS OVNGT. FLOW STRENGTHENS A BIT TDA. COMBINED WITH DAYTIME MIXING...GUSTS NEAR 20-25 KT WILL BE COMMON TDA. SCA CONTINUES TNGT WITH BREEZY SLY WINDS AHEAD OF AN APPROACHING COLD FRONT. SCA EXTENDED INTO TUESDAY FOR ALL MARINE ZONES WITH GUSTY SLY FLOW AHEAD OF A COLD FRONT. TSTMS POSSIBLE TUE AHEAD OF THE COLD FRONT. STRONG NW WINDS BEHIND THE COLD FRONT LATE AFTERNOON/EARLY EVENING TUESDAY. GALES MAY BE NEEDED LATE TUESDAY AFTERNOON AND CERTAINLY TUESDAY NIGHT. SCA THEN FOR WEDNESDAY AS HIGH PRESSURE BUILDS NORTH. ONSHORE FLOW THEN THROUGH FRIDAY.
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&& .TIDES/COASTAL FLOODING...
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POSITIVE TIDAL ANOMALIES OVNGT HAVE BEEN STEADY AROUND ONE-HALF TO THREE-QUARTERS FOOT ALONG THE WRN SHORE OF THE MD CHSPK BAY. NO COASTAL FLOODING THIS MRNG AS ANOMALIES WOULD HAVE NEEDED TO REACH 1 FT AND ANNAPOLIS AND 1.5 FT AT BALTIMORE/HAVRE DE GRACE TO PRODUCE MINOR FLOODING. ON THE POTOMAC...POSITIVE ANOMALIES ARE NEGLIGIBLE AT WASHINGTON DC. POSITIVE ANOMALIES WILL CONTINUE TO GRADUALLY INCREASE TDA AND TNGT. WITH THE SOUTHERLY FLOW EXPECTED TO PERSIST THRU TUESDAY MRNG AND A FULL MOON UPCOMING...WE BELIEVE WATER LEVELS COULD APPROACH MINOR FLOOD CRITERIA AT THE MORE SENSITIVE LOCATIONS AROUND TIMES OF THE HIGHER HIGH TIDES EARLY TUESDAY MRNG. CBOFS GUIDANCE HOWEVER FCSTS TIDAL LVLS BELOW MINOR COASTAL FLOODING THRESHOLDS AT ALL SITES.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ530>543.
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&& $$ SYNOPSIS...BAJ/JRK NEAR TERM...JRK SHORT TERM...BAJ LONG TERM...BAJ AVIATION...BAJ/JRK MARINE...BAJ/JRK TIDES/COASTAL FLOODING...JRK

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