Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 230754 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 354 AM EDT TUE SEP 23 2014 .SYNOPSIS...
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CANADIAN HIGH PRESSURE HOLD OVER THE REGION THROUGH MIDWEEK. A CUT-OFF UPPER LEVEL LOW PRESSURE SYSTEM WILL DRIFT NORTH FROM THE SOUTHERN ATLANTIC COAST THROUGH THE MID-WEEK...POSSIBLY AFFECTING THE AREA WEDNESDAY NIGHT INTO FRIDAY. MORE HIGH PRESSURE IS ON TAP FOR THIS WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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WHILE A CUT-OFF UPPER LEVEL LOW GEARS UP OVER THE SRN ATLC...WAVES OF DEBRIS CIRRUS CONTINUE TO SLIDE UP THE ERN SEABOARD. FROM LAST EVE INTO THE EARLY MRNG HRS...CIRRUS BANDS COVER THE SRN PERIPHERY OF THE CWA BUT CLEAR SKIES ARE MAINTAINED OVER THE REMAINDER OF THE AREA. DEWPOINTS AT THEIR LOWEST LEVELS IN RECENT MEMORY ARE ALLOWING TEMPS TO RESPOND IN A SIMILAR FASHION. THE MICRO-SCALE CLIMATE DICTATING TEMPS ACROSS THE AREA FOR THE MOST PART...W/ SHELTERED VLYS IN THE PIEDMONT IN THE 40S AND HIGHER LATITUDE LOCALES IN HIGHER ELEVATIONS IN THE 50S. AREAS OF FROST STILL ANTICIPATED ACROSS THE HIGHER ELVN VLYS IN THE APLCNS HIGHLANDS IN THE NEXT FEW HRS. TEMPS ACROSS THESE AREAS SLOWLY DROPPING DOWN OUT OF THE 40S AND INTO THE M-U30S. THE POST-DAWN HRS WILL SEE A SLOW/STEADY WARM-UP BACK INTO THE 50S/60S BUT AFTER A COOL AND SOMEWHAT CHILLY MRNG BECAUSE OF THE LOW DEWPOINTS. SOME OF THE RIDGELINES WON`T REACH THE 70F DEG MARK THIS AFTN...W/ MOST OTHER PLACES BARELY SURPASSING IT. THE CLOUD SITUATION WILL REMAIN ABOUT THE SAME. THE SRN ATLC LOW WILL CONTINUE TO ROTATE GENERALLY IN PLACE OVER THE NEXT SEVERAL HRS OR MORE...SPREADING MORE WAVES OF CIRRUS UP THE COAST AND THE REST OF THE AREA WILL BE CLEAR. THE SFC CONDITIONS WILL SEE A TRANSITION HOWEVER...W/ THE CONTINENTAL SFC HIGH PRES AREA SLIDING OFF THE NEW ENGLAND COAST LATER TODAY AND SWINGING THE SFC WINDS FROM NW TO NE.
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&& .SHORT TERM /WEDNESDAY/...
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WEDNESDAY WILL BE THE SAME AS TUE...AT LEAST TO START THE DAY. HIGHS WILL END UP A COUPLE OF DEG HIGHER BUT THE MOST NOTABLE DIFFERENCE WILL BE HIGHER DEWPOINTS - AND MORE CLOUD COVER THE SECOND-HALF OF THE DAY - AS THE SRN ATLC LOW BEGINS TO JOG UP THE ATLC COAST.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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MODELS HAVE COME INTO BETTER AGREEMENT WITH RESPECT TO THE EVOLUTION OF LOW PRESSURE ALONG THE CAROLINAS WEDNESDAY NIGHT. IT APPEARS MORE LIKELY THAT HIGH PRESSURE WILL WEAKEN AND MOVE OFFSHORE WHILE UPPER LEVEL ENERGY GETS TRANSFERRED TO THE COAST. GFS AND ECMWF NOW SHOWING A SURFACE LOW TRACK NORTHWARD AND CLOSER TO THE COAST WITH MOISTURE INCREASING ON PERSISTENT EASTERLY FLOW ACROSS THE REGION. HAVE INTRODUCED LIKELY POPS MAINLY EAST OF THE BLUE RIDGE AND ACROSS THE I-95 CORRIDOR WHERE HIGHEST CONFIDENCE EXISTS FOR STEADIER RAINFALL. PUSHED TEMPERATURES BACK A COUPLE DEGREES WITH EXPECTED CLOUD COVER AND EASTERLY FLOW. BEST CHANCES FOR RAIN LOOK TO BE LATE WEDNESDAY NIGHT INTO THURSDAY NIGHT. RAIN CHANCES DIMINISH BY FRIDAY ALTHOUGH THE SYSTEM COULD SLOW DOWN LEAVING MORE CLOUD COVER DURING THE DAY. HIGH PRESSURE IS EXPECTED TO BUILD ACROSS THE MIDDLE ATLANTIC REGION BRINGING MORE PLEASANT CONDITIONS WITH MODERATING TEMPERATURES OVER THE WEEKEND AND INTO THE FIRST PART OF NEXT WEEK. AFTERNOON HIGH TEMPERATURES ARE EXPECTED TO CLIMB INTO THE MIDDLE 70S TO NEAR 80 DEGREES.
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&& .AVIATION /07Z TUESDAY THROUGH SATURDAY/...
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SOLID VFR CONDITIONS FOR THE AREA TODAY AND INTO TONIGHT. THE ONLY TOPIC OF NOTE BESIDES THE SEASONABLY COOL/DRY CONDITIONS IS THE WIND SHIFT LATER THIS AFTN FROM NW TO NE. ONLY CIRRUS DECKS TO THE SOUTH AND EAST OF DCA/BWI IN TERMS OF CLOUD COVER TODAY/TONIGHT. MUCH THE SAME TOWARD THE END OF THE CURRENT TAF PERIOD...INTO WED. AS THE SRN ATLC LOW PRES SYSTEM MOVES UP THE COAST LATER IN THE DAY...MORE CLOUDS AND LOWER CIG HEIGHTS WILL ARRIVE. SUB VFR CONDITIONS LIKELY TO DEVELOP EAST OF THE BLUE RIDGE LATE WEDNESDAY NIGHT CONTINUING INTO THURSDAY AS LOW PRESSURE TRACKS NORTH ALONG THE MIDDLE ATLANTIC COAST. VSBY RESTRICTIONS IN RAIN MOST LIKELY FROM KBWI SOUTH ACROSS KDCA. VFR CONDITIONS EXPECTED TO RETURN LATER FRIDAY THROUGH THE WEEKEND.
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&& .MARINE...
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OCCASIONAL GUSTS NEAR SCA RANGE APPEAR IN DIFFERENT SPOTS OVER THE WATERS DURING THE OVERNIGHT PERIOD AND WILL CONTINUE OVER THE NEXT FEW HRS. OVER LAND...WINDS ARE MUCH LIGHTER BUT SFC PRES AND TEMP DIFFERENCES OF THE WATERS ARE HELPING WINDS TO CHANNEL IN CERTAIN LOCATIONS OVER THE BAY. GRADUALLY LATER THIS AFTN...THE LIGHT AND STEADY NW WINDS WILL SWITCH TO NE AND WILL REMAIN SO INTO THE OVERNIGHT HRS. AN UPPER LOW HOVERING OVER THE SRN ATLC STATES WILL SLOWLY DRIFT TOWARD THE AREA OVER THE NEXT COUPLE OF DAYS AND BEGIN CREATING SCA GUSTS OVER THE BAY ON WED. A SCA IS NOW IN EFFECT FOR THE LOWER MD BAY/TP FROM THE LATE MRNG INTO THE AFTN HRS ON WED. SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED WEDNESDAY NIGHT INTO THURSDAY NIGHT AS LOW PRESSURE TRACKS SLOWLY NORTH ALONG THE MIDDLE ATLANTIC COAST. VISIBILITY RESTRICTIONS IN RAIN ALSO LIKELY DURING THIS TIME FRAME. WINDS ARE EXPECTED TO DIMINISH FRIDAY AS LOW PRESSURE PULLS AWAY. HIGH PRESSURE WILL RETURN TO THE WATERS OVER THE WEEKEND.
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&& .TIDES/COASTAL FLOODING...
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WATER LEVELS ARE LARGELY IN BLOW-OUT MODE OR BELOW NORMAL ATTM... MOSTLY HOVERING IN THE HALF-FOOT BELOW RANGE. THIS WILL CONTINUE OR SLOWLY CONTINUE TO DROP FOR MUCH OF THE DAY W/ THE SAME WIND FIELD THAT WILL GRADUALLY TURN NELY INTO THE OVERNIGHT HRS TONIGHT. A COASTAL LOW PRES SYSTEM WELL TO OUR SOUTH WILL SLOWLY APPROACH THE AREA BY MIDWEEK...EXPECTED TO EVENTUALLY BRING UP THE LEVELS CLOSER TO NORMAL. A PERSISTENT ONSHORE FLOW IS EXPECTED TO DEVELOP MIDWEEK. 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 THROUGH THURSDAY NIGHT.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR MDZ501. VA...FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR VAZ503-504. WV...FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR WVZ501>503-505- 506. MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT WEDNESDAY FOR ANZ532>534-537-540>543.
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&& $$ SYNOPSIS...GMS NEAR TERM...GMS SHORT TERM...GMS LONG TERM...KRW AVIATION...GMS/KRW MARINE...GMS/KRW TIDES/COASTAL FLOODING...GMS/KRW

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