Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 171407 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1007 AM EDT FRI OCT 17 2014 .SYNOPSIS...
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AN UPPER LEVEL TROUGH WILL SWING EAST THROUGH THE WESTERN GREAT LAKES TODAY AND ACROSS THE MID-ATLANTIC THROUGH SATURDAY NIGHT. AN UPPER CUT OFF LOW WILL LIKELY AFFECT THE REGION FOR MUCH OF THE COMING WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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UPR LOW WL CONT SPINNING ACRS THE GRTLKS TDA. CWFA WL BE IN WLY FLOW. CLDS WL BE FEW BASED ON DOWNSLOPING AND SPARCE MSTR PER LWX RAOB. GOING FCST ON TRACK. TONIGHT...SECONDARY UPR TROUGH SWINGS EAST ACROSS THE GREAT LAKES WITH HEIGHT FALLS AND UPSLOPE FLOW BRINGING RAIN SHOWERS WEST FROM THE ALLEGHENY FRONT. INCREASING CLOUDS OVER THE AREA W/ MIN TEMPS LOWER TO MID 50S.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY/... A WINDY WEEKEND...OR AT LEAST BREEZIER THAN WE HAVE EXPERIENCED IN THE RECENT PAST. A COUPLE OF UPPER TROUGHS PARALLEL TO EACH OTHER AND EMBEDDED IN THE SAME TROUGH AXIS WILL MOVE ACROSS THE AREA. EACH WILL MIX-DOWN HIGHER WINDS FROM THE TOP OF THE BOUNDARY LAYER...WHICH ALSO SPELLS THE END OF THE MOIST AIRMASS FROM THE PAST FEW DAYS. HIGH HUMIDITY VALUES FROM THE PAST WEEK WILL BE REPLACED W/ COOL-DRY AIR FROM THE NW. COOLER THAN AVG TEMPS WILL ALSO RESULT...W/ THE MTNS REMAINING UNDER CLOUDY SKIES FROM THE NEAR CONSTANT INFLUX OF BOUNDARY LAYER MOISTURE FROM THE NW THAT DRIES OUT AFTER CLEARING THE HIGHER TERRAIN - GIVING THE PIEDMONT/LOWLANDS ONLY A FRACTION OF SKY COVER. A LOW CHANCE OF SNOW MIXED W/ RAIN LATE SAT NIGHT ACROSS THE HIGHER TERRAIN - THE SPINE OF THE CNTRL APLCNS - WHERE SCATTERED SHOWERS WILL MEET UP W/ SUB-FREEZING 850MB TEMPS FOR A BRIEF PERIOD OF THE OVERNIGHT. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... ANOTHER RESIDENT UPPER LOW FOR THE COMING WEEK...THAT IS WHAT APPEARS TO BE SHAPING-UP W/ EACH NEW LONG-RANGE MODEL RUN. ALL OF THESE GUIDANCE VOICES - THOUGH NOT QUITE IN-SYNC W/ TIMING AND POSITION OF A CHALLENGING CUT-OFF LOW - GIVING THE SAME GENERAL DESCRIPTION. AFTER THE WEEKEND UPPER TROUGH PAVES THE WAY W/ STILL FAIRLY LOW HEIGHTS SPREADING FROM THE GREAT LAKES TO THE MID-ATLC COAST...A CLIPPER FEATURE WILL TAKE THIS PATH STRAIGHT DOWN TOWARD THE CNTRL APLCNS. AFTER A ONE-DAY HIGH PRESSURE APPEARANCE ON MON IN BETWEEN EACH UPPER WAVE...THE CLIPPER WILL DIVE DOWN INTO THE UPPER MIDWEST/TENN VLY BY LATE MON NIGHT. BACK FURTHER WEST...TRENDS IN THE UPPER PATTERN WILL ALSO NEED TO BE MONITORED SINCE THE TRACK/POSITION OF OUR EVENTUAL CUT-OFF LOW WILL DEPEND ON HOW AMPLIFIED THE RIDGE AXIS BECOMES OVER THE PLAINS/MS VLY. STILL WARM GULF STREAM WATERS APPEAR TO BE PICKED-UP BY GUIDANCE AS THE WARM-SECTOR OF THE UPPER WAVE INTENSIFIES THE SYSTEM...TAPS INTO SRN ATLC MOISTURE AND ESSENTIALLY POWERS THE SYSTEM FOR MUCH OF THE WEEK. CAUGHT IN BETWEEN THE HIGH-AMPLITUDE RIDGE TO THE WEST AND ANOTHER STRONG WAVE OVER THE OPEN NRN ATLC WATERS...THE UPPER LOW LOOKS LIKE IT WILL HAVE SEVERAL REVOLUTIONS ABOUT THE I-95 CORRIDOR/ERN SEABOARD FROM TUE THROUGH THU...POSSIBLY INTO FRI. WHAT WILL FINALLY PUSH THIS SYSTEM OFF THE COAST AND AWAY FROM THE REGION IS A KICKER-WAVE IN THE POLAR JET OVER CNTRL CANADA LATE IN THE WEEK. UNTIL THEN...A BETTER PART OF NEXT WEEK WILL LIKELY BE AN ALTERNATING DAILY ENVIRONMENT OF MORE COOL/MOIST CONDITIONS/MOSTLY CLOUDY SKIES/PERIODIC SHOWERS. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... LIGHT SWLY FLOW THIS MORNING INCREASES THROUGH THE DAY WITH 10 TO 15 KT FLOW THIS AFTERNOON. VFR PREVAILS THROUGH TONIGHT WITH THE MIXING. BREEZY W-NWLY WINDS WILL AFFECT THE REGION BOTH SAT INTO SUN. MAINLY DRY INTO EARLY NEXT WEEK...THOUGH ANOTHER SLOW-MOVING LOW PRESSURE SYSTEM MAY AFFECT THE REGION DURING THE MIDDLE PART OF NEXT WEEK. NOT NEARLY AS MUCH PRECIP TO CONTEND W/ AS THE EXITING FEATURE BUT MAY SEE PERIODICALLY LOWER CIGS AND SOME SCATTERED SHOWERS. && .MARINE... WLY FLOW 10 TO 15 KT BECOMES SWLY TODAY IN THE WAKE OF AN UPPER LEVEL TROUGH THAT MOVED THROUGH THE AREA LAST EVENING. FLOW BACKS SOUTHERLY THIS EVENING WITH CHANNELING POSSIBLE IN SRN MD WATERS...CAPPED 17 KT GUSTS FOR NOW...MAY SEE LOW END SCA GUSTS THROUGH TONIGHT. A SECONDARY WAVE OF DRY BUT BREEZY LOW PRESSURE WILL LIKELY INDUCE SCA WINDS OVER THE WATERS BOTH SAT AND SUN AFTNS. SCA IN EFFECT FOR THE DAYTIME HRS ON SAT. WILL LIKELY NEED TO BE EXTENDED FOR THE MIDDLE/LOWER PORTIONS OF THE BAY OVERNIGHT AND THEN AGAIN FOR ALL THE WATERS ON SUN AFTN W/ ANOTHER UPPER WAVE MIXING DOWN GUSTY WINDS. HIGH PRESSURE EXPECTED TO BUILD IN BEHIND THIS WAVE TO START THE WORK WEEK. && .TIDES/COASTAL FLOODING...
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WATER LEVELS LESS THAN A HALF-FOOT ABV ASTRO NORMS. WINDS WILL TURN SLY AND INCREASE THIS AFTERNOON. CBOFS PICKING UP ON THIS AND BRINGING TIDES WELL INTO CAUTION STAGE /ALMOST TO MINOR FLOOD STAGE AT ANNAPOLIS/ FOR TONIGHTS TIDE CYCLE. WHILE INCREASED DEPARTURES PLAUSIBLE...THE MAGNITUDE OF THE CBOFS FORECAST DOES NOT. DO NOT ANTICIPATE ADVYS AT THIS TIME.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT SATURDAY FOR ANZ530>533-535-536-538>542. SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM EDT SATURDAY FOR ANZ534-537-543.
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&& $$ SYNOPSIS...HTS NEAR TERM...HTS/BAJ SHORT TERM...GMS LONG TERM...GMS AVIATION...BAJ/GMS MARINE...BAJ/GMS TIDES/COASTAL FLOODING...HTS

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