Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 171923 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 323 PM EDT FRI OCT 17 2014 .SYNOPSIS... 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. && .NEAR TERM /THROUGH SATURDAY NIGHT/... AN UPPER LEVEL TROUGH IS LOCATED ACROSS THE GREAT LAKES TODAY. WESTERLY FLOW ALOFT WILL BECOME SOUTHWESTERLY AS A SHORTWAVE TROUGH MOVES ACROSS THE LOWER GREAT LAKES TONIGHT. THIS WILL INCREASE MOISTURE ACROSS THE MID-ATLANTIC BUT DUE TO OVERALL DRY CONDITIONS THE REGION SHOULD STAY MOSTLY CLEAR WITH THE EXCEPTION OF CLOUDS ALONG THE ALLEGHENY SLOPE/UPSLOPE REGION. FCST MIN TEMPS WILL RANGE FROM THE 40S IN THE HIGHLANDS TO UPPER 50S IN THE CITY CENTERS. FLOW ALOFT BECOMES MORE ZONAL AS A COLD FRONT MOVES ACROSS THE REGION SATURDAY MORNING. A STRATO-CU FIELD IS EXPECTED AND WILL LIKELY BE MORE WIDESPREAD THAN TODAY...FRIDAY. AN ISOLATED RAIN SHOWER IS POSSIBLE ACROSS THE POTOMAC HIGHLANDS AND NORTHERN VA SATURDAY AFTERNOON. W-NW WINDS ARE ALSO EXPECTED SATURDAY AND GUSTS UP TO 30 MPH ARE POSSIBLE SAT AFTERNOON. HIGH PRESSURE WILL MOVE INTO THE REGION SATURDAY NIGHT AS ANOTHER SHORTWAVE TROUGH MOVES OVERHEAD. AT THIS TIME...MODELS ARE SHOWING LITTLE TO NO RAIN WITH THIS FEATURE AS COLD AIR ADVECTION OCCURS THROUGHOUT THE COLUMN. SHOWERS ARE LIKELY IN THE UPSLOPE REGION AS NW FLOW MOVES UP AGAINST THE ALLEGHENY FRONT SAT NIGHT. TEMPS WILL LIKELY DROP INTO THE 30S IN THIS REGION BY SUN MORNING. SHOWERS ARE EXPECTED TO TAPER OFF BUT BEFORE THEY DO SOME SNOWFLAKES MAY MIX IN BEFORE SUNRISE SUNDAY MORNING. && .SHORT TERM /SUNDAY THROUGH MONDAY/... HIGH PRESSURE MOVES OVERHEAD SUNDAY AS A UPPER LEVEL RIDGE APPROACHES FROM THE WEST. SUNDAY WILL FEEL COOL WITH MAX TEMPS ONLY REACHING THE UPPER 40S IN THE HIGHLANDS AND UPPER 50S NEAR 60 ACROSS THE PIEDMONT AND SOUTHERN MD. HIGH PRESSURE WILL MOVE OFF THE COAST MONDAY AND SOUTHERLY FLOW WILL HELP TEMPS WARM BY A FEW MORE DEGREES THAN SUNDAY. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... ECMWF 500MB TROUGH MOVING EAST ACROSS THE MIDWEST THROUGH EARLY HALF OF THE WEEK. SHORTWAVES DIGGING DOWN TROUGH ALSO CAUSING IT TO DEEPEN DURING THE PERIOD. CUT-OFF LOW FORMING OVER UPPER OHIO VALLEY AT MID WEEK WILL CROSS MID ATLANTIC REGION DURING THE LATTER HALF OF THE WEEK. TRACK OF SURFACE LOW IS LIKELY TO PERMIT GREATEST OF OPPORTUNITY OF PRECIPITATION TO OCCUR OVER CWA TUESDAY NIGHT THROUGH WEDNESDAY AND AGAIN THURSDAY. INCREASING WINDS EXPECTED WEDNESDAY THROUGH FRIDAY AS PRESSURE GRADIENT TIGHTENING UP WHEN LOW PUSHES OFFSHORE AND SLOWLY MOVES NORTHEASTWARD. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... S WINDS 10-15KTS WILL CONTINUE THIS AFTERNOON. ISO-SCT CU FIELD WILL DIMINISH AROUND SUNRISE AND TERMINALS ARE EXPECTED TO BE VFR TONIGHT AND SATURDAY. WINDS BECOME W-NW SATURDAY AT 10-15KTS WITH GUSTS UP TO 25 KTS BY AFTERNOON. W-NW BREEZY WINDS WILL CONTINUE INTO SUNDAY WITH GUSTS UP TO 25 KTS POSSIBLE SUN AFTERNOON. 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... WINDS HAVE BECOME SOUTHERLY ACROSS THE WATERS THIS AFTERNOON RESULTING IN 10-15KTS WITH OCCATIONAL GUSTS AROUND 17-19 KTS. THESE GUSTS WILL BE ISOLATED AND THEREFORE SCA IS NOT IN EFFECT THIS AFTERNOON. SW FLOW WILL INCREASE THIS EVENING ACROSS THE LOWER TIDAL POTOMAC AND BAY SOUTH OF DRUM PT AND THE TANGIER SOUND. A SCA IS IN EFFECT OVERNIGHT FOR THIS AREA. A DRY COLD FRONT WILL CROSS THE WATERS SATURDAY MORNING AND W-NW WILL INCREASE BEHIND IT. GUSTS UP TO 25 KTS ARE EXPECTED ON THE WATERS SATURDAY. THESE WINDS MAY CONTINUE ON THE WATERS THROUGH SUNDAY AND A SCA WILL LIKELY NEED TO BE EXPANDED IN TIME SAT NIGHT 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... 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. && .LWX WATCHES/WARNINGS/ADVISORIES... 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. && $$ SYNOPSIS...HAS NEAR TERM...HAS SHORT TERM...HAS LONG TERM...CEM AVIATION...HAS MARINE...HAS TIDES/COASTAL FLOODING...HTS

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