Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 221858 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 258 PM EDT TUE JUL 22 2014 .SYNOPSIS...
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HIGH PRESSURE WILL NEAR THE EASTERN SEABOARD TODAY AND TONIGHT. A COLD FRONT WILL APPROACH FROM THE WEST WEDNESDAY...AND MOVE THROUGH THE REGION WEDNESDAY NIGHT INTO EARLY THURSDAY. HIGH PRESSURE IS EXPECTED TO RETURN TO THE REGION TO END THE WORK WEEK.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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HIGH PRESSURE PERSISTS ALONG THE MID-ATLANTIC COAST LATE THIS AFTERNOON. S-SE WINDS HAVE SET UP OVER THE FORECAST AREA...WITH MOIST AIR ADVECTING INTO THE REGION. ISOLATED TO SCATTERED SHOWERS HAVE POPPED UP...AND WILL CONTINUE TO AFFECT PORTIONS OF THE AREA THIS AFTERNOON. 12Z SOUNDINGS INDICATED A WARM NOSE AROUND 600MB...AND THIS APPEARS TO BE HOLDING IN PLACE AS SHOWERS HAVE HAD LITTLE VERTICAL EXTENT WITH TOPS REACHING NOT FAR ABOVE THE FREEZING LEVEL. THIS WILL MINIMIZE THE POTENTIAL FOR THUNDERSTORM ACTIVITY...ALTHOUGH ISOLATED TSTMS WILL REMAIN POSSIBLE OVER SOME OF THE MOUNTAINS TODAY. OTHERWISE EXPECT SOME ISOLATED TO SCATTERED SHOWER ACTIVITY TO CONTINUE...MAINLY ALONG AND WEST OF THE BLUE RIDGE/CATOCTINS...WITH A FEW SPOTS RECEIVING BRIEF HEAVY RAINFALL. HIGH TEMPS GENERALLY IN THE M80S ACROSS THE FORECAST AREA. SHOWER ACTIVITY DECREASES THIS EVENING...WITH DRY CONDITIONS EXPECTED IN THE OVERNIGHT HOURS. WITH MOIST AIR IN PLACE...SOME FOG IS POSSIBLE...MOST LIKELY IN THE SHELTERED VALLEYS. MET/MAV GUIDANCE ARE IN GOOD AGREEMENT TONIGHT. LOWS IN THE 60S FOR MOST...WITH LOW 70S IN URBAN AREAS AND NEAR MARINE ZONES. WEDNESDAY STARTS WITH HIGH PRESSURE EXTENDING FROM THE OFFSHORE WATERS AND INTO THE CAROLINAS...WITH A COLD FRONT EXTENDING ACROSS THE LOWER GREAT LAKES AND OHIO VALLEY. THE COLD FRONT WILL APPROACH DURING THE DAY...WHILE A 500MB TROUGH STRENGTHENS OVER THE THE SAME REGION. COMBINATION OF INSTABILITY...LIFT AND MOISTURE IS EXPECTED TO SUPPORT SHOWERS AND THUNDERSTORMS...WITH ACTIVITY MORE LIKELY OVER NORTHERN AND WESTERN PORTIONS OF THE FORECAST AREA THAT WILL BE CLOSER TO THE APPROACHING FRONT. ISOLATED SEVERE STORMS WILL ALSO BE POSSIBLE ACROSS WESTERN MD AND THE EASTERN WV PANHANDLE...WHICH SHOULD BE IN THE RIGHT ENTRANCE REGION OF THE JET STREAM BY LATE IN THE DAY. DAMAGING WINDS IS LIKELY TO BE THE MAIN THREAT. WEDNESDAY WILL BE THE WARMEST DAY OF THE WEEK...WITH HIGHS IN THE LOW 90S AT MOST LOCATIONS.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
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THE COLD FRONT IS EXPECTED TO MOVE THROUGH MOST OF THE FORECAST AREA WEDNESDAY NIGHT...AND SHOULD BE EAST OF THE I-95 CORRIDOR BY THURSDAY MORNING. SHOWER/TSTM ACTIVITY SHOULD SHIFT EWD ACCORDINGLY. SEVERE THREAT IS UNCERTAIN...AS BETTER DYNAMICS WILL BE OFFSET BY LOWER NIGHTTIME INSTABILITY. LOWS RANGE FROM THE MID 60S OVER EASTERN WV...BEHIND THE FRONT...TO THE MID 70S ALONG AND EAST OF I-95. COLD FRONT MOVES EAST OF THE REGION ON THURSDAY...WHILE AN UPPER TROUGH APPROACHES FROM THE WEST. SHOWER/TSTM CHANCES CONTINUE WITH COOLER AIR ALOFT...BUT WITH A N-NW FLOW CHANCE OF SEVERE WX IS UNLIKELY AT THIS TIME. TEMPS WILL BE COOLER WITH HIGHS RANGING FROM THE UPPER 70S OVER HIGHER ELEVATIONS TO THE MID 80S ELSEWHERE. UPPER TROUGH MOVES THROUGH THURSDAY NIGHT...WITH DRY CONDITIONS EXPECTED EXCEPT POSSIBLY OVER SRN MD AND PORTIONS OF THE PIEDMONT. LOWS DROP INTO THE 50S AND 60S.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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A RIDGE OF HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST FRIDAY AND FRIDAY NIGHT TO ALLOW COOLER AND DRIER AIR TO PUSH INTO THE REGION THROUGH SATURDAY. WITH THE HIGH MOVING TO THE COAST AND OFFSHORE DURING THE DAY SATURDAY...SOUTHEAST TO SOUTHERLY WINDS WILL EVOLVE...THUS PERHAPS SPAWNING A SHOWER IN THE POTOMAC HIGHLANDS WITH THE UPSLOPE COMPONENT. DISTURBANCES IN THE UPPER LEVELS WILL ROTATE IN FROM THE OHIO VALLEY AND LOWER GREAT LAKES SATURDAY NIGHT AND SUNDAY...THUS...BRINGING THE CHANCE FOR SHOWERS AND THUNDERSTORMS. AS FOR SUNDAY NIGHT THROUGH TUESDAY...A POTENT UPPER LEVEL STORM SYSTEM WILL LINGER ACROSS THE GREAT LAKES REGION. SEVERAL WAVES OF ENERGY WILL ROTATE AROUND IT AND ACROSS THE MID ATLANTIC REGION. THE CHANCE OF SHOWERS AND THUNDERSTORMS...ONCE AGAIN...WILL BECOME A NUISANCE TO THE REGION.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/...
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ISOLATED SHOWER OR MAYBE A BRIEF TSTM PSBL THIS AFTERNOON. WINDS FROM THE S-SE...LESS THAN 10KT. VFR MOST OF THE NIGHT...BUT MVFR VSBYS WITH FOG IS POSSIBLE LATE TONIGHT INTO THE EARLY MORNING HOURS WITH MOIST AIR OVER THE REGION. SCATTERED SHOWERS AND TSTMS POSSIBLE WED AFTN INTO EARLY THU. AN OFFSHORE HIGH WILL PUSH UP THE HEAT/HUMIDITY BEFORE TSTMS ARRIVE/DEVELOP...WHILE A COLD FRONT APPROACHES FROM THE NW. THE FRONT WILL LIKELY MOVE ACROSS THE AREA LATE WED INTO EARLY THU...SWEEPING THIS ACTIVITY OFF THE COAST BY LATE THU AFTN. VFR CONDITIONS WITH LIGHT AND VARIABLE WINDS EXPECTED FRIDAY THROUGH SATURDAY AT ALL TERMINALS.
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&& .MARINE...
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WINDS BLO SCA VALUES TDA/TGNT WITH SOUTHERLY WINDS AROUND 10KT. LIGHT S-SW FLOW WILL CONTINUE WEDNESDAY AND MAXIMIZE JUST BEFORE THE PASSAGE OF A COLD FRONT EARLY THU. SHOWERS AND TSTMS POSSIBLE WED EVE INTO THE OVERNIGHT. NO MARINE HAZARDS EXPECTED FRIDAY THROUGH SATURDAY.
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&& .TIDES/COASTAL FLOODING... THE DAYTIME HIGH TIDE CYCLE IS THE LOWER OF THE TWO ASTRONOMICALLY...HENCE THERE WL BE NO NEED FOR AN ADVISORY DURG THE DAY. WILL CONTINUE TO MONITOR FOR POTENTIAL MINOR FLOODING AT HIGH TIDE EARLY WEDNESDAY MORNING. && .CLIMATE... YDA WAS ONE MONTH SINCE THE SUMMER SOLSTICE. WE`RE A LTL OVR HALFWAY THRU WHAT IS CONSIDERED MET SUMMER. HOW DOES THIS SUMMER SHAPE UP SO FAR TEMP-WISE? LOOKING AT THE PAST 30 YRS... 6/1-7/21...1984-2014... STATION AVG MAX RANK AVG MIN RANK AVG DAILY RANK DCA 87 12TH 70 6TH 78.5 9TH BWI 84.3 23RD 64.3 15TH 74.5 19TH IAD 83.6 23RD 63.6 12TH 73.6 20TH AN INTERESTING STAT - DCA...AVG LOW TEMPS FOR THE PAST 30 YRS... FIVE OF THE TOP SIX WARMEST HV BEEN 2010 THRU 2014. RANKINGS: 1 2010 72.1 2 2013 71.6 3 2011 71.0 4 1994 70.9 5 2012 70.2 6 2014 70.0 7 2008 68.9 EVEN IF YOU XTND TO THE ENTIRE DC RECORD - SINCE 1871...2014 RANKS #7 FOR WARMEST AVG LOW TEMPS FOR THE PD 6/1-7/21. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...KCS NEAR TERM...KCS SHORT TERM...KCS LONG TERM...KLW AVIATION...KCS/KLW MARINE...KCS/KLW TIDES/COASTAL FLOODING...WOODY!/KCS CLIMATE...WOODY!

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