Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 291852 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 252 PM EDT MON SEP 29 2014 .SYNOPSIS... AN UPPER LEVEL DISTURBANCE WILL SLIDE ACROSS THE REGION LATER THIS AFTERNOON...BRINGING A FEW RAIN SHOWERS TO THE EASTERN PORTIONS. WEAK HIGH PRESSURE WILL BUILD BRIEFLY OVERNIGHT BEFORE A COLD FRONT SAGS FROM THE NORTHWEST AND BRINGS A CHANCE OF RAIN SHOWERS OR PERHAPS AN AFTERNOON THUNDERSTORM TUESDAY. HIGH PRESSURE WILL RETURN LATER IN THE WEEK. ANOTHER COLD FRONT COULD PUSH THROUGH THE AREA LATE FRIDAY INTO SATURDAY. && .NEAR TERM /THROUGH TONIGHT/... AT 2PM...RADAR INDICATED A WIDE SWATH OF LIGHT RAIN SHOWERS FROM SOUTH CENTRAL VIRGINIA TO NORTHEAST MARYLAND AND THE CHESAPEAKE BAY. RAIN AMOUNTS AVERAGE A FEW HUNDREDTHS OF AN INCH TO ONE TENTH OF AN INCH. WINDS ARE LIGHT AND VARIABLE. TEMPERATURES ARE IN THE MIDDLE 70S ACROSS THE NORTH AND WEST WHERE RAIN SHOWERS DO NOT EXIST AND THERE ARE A FEW BRIEF BREAKS IN THE CLOUD COVER. TEMPERATURES ARE IN THE UPPER 60S TO NEAR 70 WHERE RAIN SHOWERS HAVE BEEN MORE PERSISTENT SINCE THIS MORNING. AS THE RAIN SHOWERS MOVE EAST AND PIVOT ACROSS THE MAIN STEM CHESAPEAKE BAY...DRIER AIR WILL ENSUE BRIEFLY WITH HIGH PRESSURE NOSING IN FROM THE SOUTHWEST THROUGH THE OVERNIGHT. WINDS WILL REMAIN LIGHT AND VARIABLE. TEMPERATURES WILL GRADUALLY FALL INTO THE MIDDLE TO UPPER 50S. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS HIGH PRESSURE PUSHES OFFSHORE TUESDAY...A SURFACE FRONT AND ITS UPPER LEVEL SUPPORT WILL NUDGE INTO THE REGION FROM THE NORTHWEST. THIS FRONT COULD SPAWN A COUPLE OF RAIN SHOWERS AND PERHAPS A RUMBLE OF THUNDER OR TWO...GIVEN ANY AMPLE SUNSHINE. WE SHOULD ENCOUNTER MORE SUNSHINE TUESDAY THAN THIS AFTERNOON BEFORE THE CLOUDS AND SHOWERS ROLL INTO THE REGION. TEMPERATURES SHOULD BE GENERALLY IN THE UPPER 70S. MODELS ARE IN AGREEMENT WITH A 500 MB SHORTWAVE PIVOTING NORTH OF THE AREA TUESDAY NIGHT. ANY SHOWERS OR THUNDERSTORMS SHOULD ABATE WITH THE LOSS OF HEATING DURING THE EVENING WITH JUST A FEW STRAY SHOWERS LEFTOVER ALONG THE MASON-DIXON LINE OVERNIGHT. HIGH PRESSURE WILL NOSE IN FROM THE NORTH DURING THE DAY WEDNESDAY RESULTING IN A LOW-LEVEL NORTHEASTERLY FETCH...HOLDING IN LOW-LEVEL MOISTURE AND KEEPING CLOUDS AROUND. A FEW SHOWERS WILL BE POSSIBLE PARTICULARLY OVER THE HIGHER TERRAIN WHERE UPSLOPE FORCING COULD PROVIDE ENOUGH LIFT TO SQUEEZE OUT SOME RAIN DURING THE DAY. TEMPERATURES WILL BE RIGHT AROUND NORMAL THROUGH THE PERIOD...LOWS IN THE MID-UPPER 50S AND HIGHS 70-75. SCATTERED SHOWERS WILL DWINDLE QUICKLY AROUND SUNSET WEDNESDAY EVENING. && .LONG TERM /THURSDAY THROUGH MONDAY/... HIGH PRESSURE WILL REMAIN NORTH OF THE AREA THURSDAY BUT SHIFT A BIT FURTHER EAST. THIS WILL ALLOW WINDS TO BECOME MORE SOUTHEASTERLY WITH NOT QUITE AS MANY CLOUDS EXPECTED AND PERHAPS A COUPLE DEGREES WARMER OVER THE WESTERN AREAS AS COMPARED TO WEDNESDAY...BUT STILL RIGHT AROUND CLIMO NORMS. CLOUDS INCREASE THURSDAY NIGHT INTO FRIDAY AS A LARGE AND DEEP TROUGH DIGS INTO THE UPPER MIDWEST...THEN PIVOTS TOWARD THE MID-ATLANTIC LATE FRIDAY INTO FRIDAY NIGHT. THE UPPER TROUGH WILL DRIVE SURFACE LOW DEVELOPMENT OVER THE GREAT LAKES WITH A SUBSEQUENT TRACK INTO SOUTHEASTERN CANADA. THIS SETUP WILL DRAG A SEASONABLY STRONG COLD FRONT THROUGH THE AREA FRIDAY NIGHT. STRONG FORCING ASSOCIATED WITH THE TROUGH AS WELL AS A BIT OF A LOW-LEVEL JET AHEAD OF THE FRONT WILL LIKELY DRIVE A BAND OF SHOWERS...PERHAPS A FEW EMBEDDED THUNDERSTORMS GIVEN STRONG FORCING IN SPITE OF A LACK OF APPRECIABLE CAPE. THE 12Z GFS IS QUITE AMPLIFIED /AS IT WAS YESTERDAY/ SHOWING THE TROUGH TAKING ON A NEGATIVE TILT IN THE UPPER LEVELS AND A STRONGER LOW-LEVEL JET RESULTING IN STRONGER FORCING AND MORE WIDESPREAD HEAVIER RAIN PERHAPS ACCOMPANIED BY GUSTY WINDS. THE 00Z ECMWF IS NOT QUITE AS STRONG SUGGESTING A BIT LESS WIDESPREAD SHOWERS WITH WEAKER LOW-LEVEL WINDS. THE FRONT MOVES EAST OF THE AREA SATURDAY USHERING IN A COOLER AND DRIER AIRMASS FOR THE WEEKEND. ANOTHER STORM SYSTEM MAY APPROACH BY EARLY NEXT WEEK BUT FORECAST MODELS/ENSEMBLES DISAGREE ON TIMING. && .AVIATION /19Z MONDAY THROUGH SATURDAY/... CIGS AND VSBY CONDITIONS SHOULD REMAIN AT VFR CONDITIONS AT ALL TERMINALS THE REMAINDER OF THIS AFTERNOON INTO THIS EVENING. IF ANY REDUCTION IN CIGS AND VSBY OCCURS...IT WOULD BE LATER TONIGHT AT THE CHO OR PERHAPS THE MTN TERMINALS DUE TO RESIDUAL MOISTURE FROM LIGHT RAIN SHOWERS OR A LIGHT SOUTHEAST FLOW OFF OF THE CHESAPEAKE BAY, RESPECTIVELY. VFR CONDITIONS DURING THE DAY TUESDAY UNTIL SHOWERS PUSH IN FROM THE NORTHWEST DURING THE AFTERNOON HOURS. CIG/VSBY RESTRICTIONS PSBL WRN MOST TERMINALS TUE EVE W/ ISO SHWRS/TSTMS. MOD CONFIDENCE MAINLY VFR WED-THU. WINDS LIGHT E TO NE TUE NIGHT...AND GENERALLY LESS THAN 10 KTS THROUGH THU. MORE CIG/VSBY RESTRICTIONS PSBL FRI-FRI NIGHT AS STRONG FRONT APPROACHES. && .MARINE... NO MARINE HAZARDS EXPECTED THE REMAINDER OF THIS AFTERNOON...TONIGHT AND INTO TUESDAY. LOOKING LESS LIKELY FOR SCA CONDITIONS LATE TUESDAY NIGHT INTO WEDNESDAY AS GUIDANCE HAS TRENDED WEAKER AND FURTHER OFFSHORE WITH LOW PRESSURE. SCA CONDITIONS BECOMING INCREASINGLY LIKELY AHEAD OF A STRONG COLD FRONT FRIDAY...THEN BEHIND THE FRONT SATURDAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...KLW NEAR TERM...KLW SHORT TERM...KLW/DFH LONG TERM...DFH AVIATION...KLW/DFH MARINE...KLW/DFH

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