Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 220800 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 400 AM EDT WED APR 22 2015 .SYNOPSIS...
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LOW PRESSURE WILL SLOWLY PIVOT FROM THE GREAT LAKES TOWARD THE SAINT LAWRENCE VALLEY THROUGH THE END OF THE WEEK. A COLD FRONT TRAILING THE LOW WILL CROSS THE MID-ATLANTIC TODAY. HIGH PRESSURE WILL BUILD IN FROM THE WEST FRIDAY...FOLLOWED BY ANOTHER LOW PRESSURE SYSTEM THIS WEEKEND.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE MAIN STORY OF THE DAY IS WIND POTENTIAL. A VERTICALLY STACKED LOW PRESSURE CONTINUES TO SPIN IN THE VICINITY OF THE GREAT LAKES. A COLD FRONT EXTENDS DOWN INTO THE OHIO VALLEY EARLY THIS MORNING. THIS FRONT WILL MAKE A PUSH TOWARD THE AREA TODAY WITH THE HELP OF A STRONGER VORT MAX. SCATTERED SHOWERS HAVE MAINLY BEEN CONFINED TO PA/WRN MD OVERNIGHT AS WEAK DISTURBANCES RIPPLE AROUND THE LOW. THIS ACTIVITY...ALONG WITH THE MORE WIDESPREAD SHOWERS OVER INDIANA WILL BEGIN TO PUSH IN THIS MORNING. OPERATIONAL MODELS HAVE SPED UP THE FRONT FROM PREVIOUS FORECAST...WITH IT BISECTING THE AREA AROUND MIDDAY AND PUSHING TO THE SOUTHEAST BY LATE AFTERNOON. SHOWERS WILL ACCOMPANY THE FRONT AND WHILE THEY MAY NOT PRODUCE A LOT OF RAIN...COVERAGE WILL BE FAIRLY WIDESPREAD...ESPECIALLY IN THE NORTHERN PART OF THE AREA. WEAK INSTBY WILL DEVELOP AHEAD OF THE FRONT DUE TO COLD TEMPERATURES ALOFT. IN ADDITION...DEEP INVERTED-V PROFILES ARE EXPECTED...AND A MID LEVEL SPEED MAX WILL BE ROTATING OVER THE AREA. SO EVEN THOUGH LIGHTNING MAY BE SOMEWHAT SPARSE...STRONG WIND GUSTS WILL BE POSSIBLE. SMALL HAIL MAY ALSO OCCUR WITH THE MORE ROBUST SHOWERS DUE TO LOW FREEZING LEVELS. THE AREA IS IN A MARGINAL RISK FOR SEVERE WX AS A RESULT. 850 MB LLJ WILL BE FOCUSED ACROSS THE SW PART OF THE CWA. THIS MAY RESULT IN SOME GUSTS EXCEEDING 40 KT...ESPECIALLY IN THE HIGHER ELEVATIONS. WILL BE RAISING A WIND ADVISORY FOR THE BLUE RIDGE WESTWARD TO THE SOUTHERN POTOMAC HIGHLANDS. ACROSS THE REST OF THE AREA...EXPECT GUSTS OF AROUND 30 KT OUTSIDE OF CONVECTION. HIGHS TODAY MAY RISE INTO THE 70S AHEAD OF THE FRONT (SE AREA) BUT MAY NOT TOP 60 IN THE WEST WHERE RAIN ARRIVES FIRST.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
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THE UPPER LEVEL LOW WILL MOVE TOWARD THE ST LAWRENCE VALLEY TONIGHT INTO THURSDAY. THE PERIOD IS EXPECTED TO BE DRY EXCEPT PERHAPS IN THE UPSLOPE AREAS WHERE SOME POST-FRONTAL RAIN AND SNOW SHOWERS MAY OCCUR EARLY TONIGHT...THEN AGAIN THURSDAY AS A VORT MAX SWINGS THROUGH. EAST OF THE MOUNTAINS...THERE WILL ONLY BE AN INCREASE IN CLOUDS THURSDAY. EXPECT BREEZY CONDITIONS ONCE AGAIN ON THURSDAY...BUT MORE IN THE 25 KT RANGE. LOWS MAY FALL BELOW FREEZING IN THE HIGHLANDS TONIGHT...WITH MID 30S-LOW 40S EAST. 850 MB TEMPS DROP BELOW 0C THURSDAY...RESULTING IN HIGHS ONLY IN THE 50S TO AROUND 60. HIGH PRESSURE WILL BUILD ACROSS THE REGION THURSDAY NIGHT THROUGH FRIDAY NIGHT. THERE IS A SLIGHT CHANCE FOR A BRIEF UPSLOPE SNOW SHOWER OR TWO IN THE POTOMAC HIGHLANDS THURSDAY NIGHT AS LOW TEMPERATURES BOTTOM OUT NEAR 30. TEMPERATURES ACROSS THE REGION WILL BE BELOW NORMAL. PATCHY FROST IS ALSO A POSSIBILITY THURSDAY NIGHT...THEN AGAIN FRIDAY NIGHT...AS TEMPERATURES FRIDAY NIGHT BOTTOM OUT IN THE LOWER 30S AS WELL.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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A CHANCE OF RAIN RETURNS SATURDAY AND SATURDAY NIGHT AS A STORM SYSTEM MOVES FROM THE TENNESSEE VALLEY TO THE CAROLINA COAST. TEMPERATURES WILL REMAIN BELOW NORMAL. HIGH PRESSURE WILL BUILD IN BEHIND AN ASSOCIATED COLD FRONT SUNDAY THROUGH MONDAY NIGHT...BRINGING DRY CONDITIONS AND KEEPING TEMPERATURES 5 TO 7 DEGREES BELOW NORMAL. BY TUESDAY...A WARM FRONT WILL TRY TO WORKS ITS WAY NORTHWARD. A CHANCE OF RAIN RETURNS TUESDAY INTO TUESDAY NIGHT AHEAD OF AND ALONG THE WARM FRONT AS THE RIDGE OF HIGH PRESSURE BREAKS DOWN.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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PREDOMINANT VFR CONDITIONS THROUGH THURSDAY. HOWEVER...SHOWERS COULD BRING A BRIEF VSBY REDUCTION AROUND MIDDAY INTO THE EARLY AFTERNOON TODAY. THE SHOWERS MAY ALSO CONTAIN THUNDER AND WILL LIKELY BRING HIGHER WIND GUSTS. OUTSIDE THE SHOWERS...WIND GUSTS AROUND 30 KT WILL BE COMMON. WINDS WILL SHIFT FROM SW TO W WITH FRONTAL PASSAGE. EXPECT ANOTHER BREEZY DAY ON THURSDAY BUT WNW WINDS WILL BE CLOSER TO 20-25 KT. VFR CONDITIONS THURSDAY NIGHT THROUGH FRIDAY NIGHT. MVFR OR IFR CONDITIONS POSSIBLE SATURDAY AND SATURDAY NIGHT DUE TO THE CHANCE OF LIGHT RAIN. VFR CONDITIONS SUNDAY.
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&& .MARINE...
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SW WINDS WILL RAPIDLY INCREASE THIS MORNING AND A GALE WARNING WILL GO INTO EFFECT AT 9 AM. GALE GUSTS MAY BE SPORADIC. SHOWERS/PERHAPS A THUNDERSTORM WILL MOVE THROUGH THIS AFTERNOON AND BE MUCH MORE LIKELY TO BRING DOWN GALE GUSTS. WINDS SHIFT TO THE WEST WITH THE COLD FRONTAL PASSAGE. CONTINUE A SCA OVERNIGHT EXCEPT FOR THE UPPER POTOMAC SINCE AM NOT SURE HOW WELL ATMOS WILL DECOUPLE. SCA CONTINUES FOR ALL WATERS THURSDAY AS W WINDS GUST UP TO 25 KT. NO MARINE HAZARDS THURSDAY NIGHT. SMALL CRAFT ADVISORIES POSSIBLE FRIDAY. NO MARINE HAZARDS FRIDAY NIGHT THROUGH SUNDAY.
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&& .TIDES/COASTAL FLOODING...
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TIDE LEVELS HAVE DROPPED ENOUGH THAT DO NOT THINK THERE WILL BE PROBLEMS WITH MORNING HIGH TIDE CYCLE BUT WILL MONITOR. WITH SW WINDS SHIFTING WEST TODAY...DO NOT EXPECT DRAMATIC DECREASES IN WATER LEVEL. WILL HAVE TO MONITOR THIS FOR THE NEXT COUPLE OF DAYS...AS WATER LEVELS WILL AT THE VERY LEAST REMAIN ELEVATED.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...WIND ADVISORY FROM 11 AM THIS MORNING TO 7 PM EDT THIS EVENING FOR VAZ025-026-503-504-507-508. WV...WIND ADVISORY FROM 11 AM THIS MORNING TO 7 PM EDT THIS EVENING FOR WVZ505-506. MARINE...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 8 PM EDT THURSDAY FOR ANZ530>534-537>543. GALE WARNING FROM 9 AM THIS MORNING TO 8 PM EDT THIS EVENING FOR ANZ530>543. SMALL CRAFT ADVISORY FROM 10 AM TO 8 PM EDT THURSDAY FOR ANZ535-536.
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&& $$ SYNOPSIS...ADS NEAR TERM...ADS SHORT TERM...ADS/KLW LONG TERM...KLW AVIATION...ADS/KLW MARINE...ADS/KLW TIDES/COASTAL FLOODING...ADS

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