Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 181903 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 303 PM EDT SAT OCT 18 2014 .SYNOPSIS... AN UPPER TROUGH AXIS WILL CLEAR THE AREA LATER TONIGHT...WITH CANADIAN HIGH PRESSURE BUILDING TROUGH MONDAY. A SLOW MOVING CUT OFF UPPER LEVEL LOW PRESSURE SYSTEM WILL HOVER AROUND THE EAST COAST THROUGH MUCH OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... MUCH OF ERN OH AND WRN/CNTRL PA COVERED IN NUMEROUS LIGHT SHOWERS W/ THE LAKE EFFECT WINDS DRIVEN BY A SHARP UPPER TROUGH AXIS. ON THE OTHER SIDE OF THE APLCNS...JUST THE LEFTOVER CLOUD FIELD WHICH EARLIER HAD DISSIPATED E OF THE BLUE RIDGE BUT HAS NOW MADE IT TO I-95. THE EXTRA PUSH OF THE VORT MAX ASSOCIATED W/ THE UPPER TROUGH IS HELPING THE SOLID STRATUS DECK TO MAKE IT FURTHER EAST OF THE MTNS - W/ ONLY SOME SUN POKING THRU THE STRANDS OF LOW 5-7KFT. INCREASED THE HIGHS FOR THE AFTN W/ A PREV UPDATE...AS SOME MINOR DOWNSLOPING EFFECTS AND EARLIER LACK OF CLOUD COVER ALLOWED TEMPS ALONG I-95 FOR INCREASE INTO THE L70S. TEMPS HAVE NOW STEADIED AT THEIR NEAR-HIGHEST LEVELS FOR THE AFTN BEFORE AN EXPECTED COOL OVERNIGHT PERIOD. TONIGHT`S OVERNIGHT LOWS WILL END-UP A SOLID 5-10F DEG LOWER THAN LAST NIGHT`S...DROPPING WELL INTO THE 40S ACROSS THE REGION...30S ACROSS THE HIGHER ELEVATIONS. SOME SPOTS IN THE HIGHEST ELEVATIONS OF HIGHLAND AND PENDLETON COUNTIES DROPPING BELOW FREEZING. SHOWERS ARE EXPECTED TO TAPER OFF BUT BEFORE THEY DO SOME SNOWFLAKES MAY MIX IN BEFORE SUNRISE SUNDAY MORNING. IN TERMS OF FREEZE HEADLINE POTENTIAL...GEOGRAPHIC EXTENT SHOULD BE LESS THAN HALF OF THESE ZONES...SO A FREEZE WATCH HAS NOT BEEN ISSUED. EAST OF THE MOUNTAINS...OVERNIGHT LOWS WILL DROP INTO THE 40S. SOME AREAS IN METRO BALTIMORE/WASHINGTON AND ALONG CHES BAY MAY HANG ON TO LOWS AROUND 50. && .SHORT TERM /SUNDAY THROUGH MONDAY/... SFC HIGH PRESSURE CENTER ENTERS THE CWA FROM THE WEST SUNDAY AFTERNOON...MOVING OFFSHORE MONDAY MORNING. GUSTY NWLY FLOW THROUGH SUNDAY...EXPECT 30 MPH GUSTS THROUGH MUCH OF THE DAY. DOWNSLOPING FLOW WILL WARM AS IT DESCENDS WITH MORNING CLOUDS OVER THE MOUNTAIN QUICKLY DISSIPATING (ALONG WITH ANY LIGHT WINTRY MIX PRECIP WEST OF THE ALLEGHENY FRONT). MAX TEMPS GENERALLY MID TO UPR 50S AT LOWER ELEVATION. 60F POSSIBLE EAST OF THE BLUE RIDGE. SUNDAY NIGHT...HIGH PRESSURE CROSSES THE MOUNTAINS IN THE EVENING...TO THE CHESAPEAKE BAY BY SUNRISE. CLEAR...CALM...AND DRY WILL MAKE FOR AN IDEAL RADIATIONAL COOL NIGHT. MIN TEMPS AROUND FREEZING LIKELY PIEDMONT AND VALLEYS WEST OF THE BLUE RIDGE (INVERSION FOR RIDGES). COULD NEED A FROST OR FREEZE HEADLINE FOR NEARLY ALL OF THE CWA (GRIDDED GUIDANCE GENERALLY HAS A WARM BIAS FOR INTERIOR SOUTHERN MARYLAND ON CLEAR/CALM NIGHTS). LOW TO MID 40S FOR URBAN/NEAR SHORE. RETURN FLOW MONDAY AS HIGH PRESSURE MOVES OFFSHORE AND LOW PRESSURE APPROACHES FROM THE GREAT LAKES. MOISTURE RETURNS WITH RAIN CHANCES INCREASING FROM THE WEST MONDAY AFTERNOON AHEAD OF AN AMPLIFYING TROUGH. UPR TROUGH AXIS CROSSES THE CWA MONDAY NIGHT WITH LOW CHANCES FOR LIGHT RAIN ACROSS THE CWA. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... ECMWF HAS 500MB CUT-OFF LOW OVER WESTERN PA TUESDAY NIGHT WITH VORT MAX DROPPING DOWN WEST SIDE OF TROUGH. VORT MAX WILL ROUND THE BOTTOM OF THE TROUGH WEDNESDAY MORNING AND MOVE OFFSHORE BY WEDNESDAY EVENING. UPPER LEVEL LOW WILL CROSS CWA LATE TUESDAY INTO WEDNESDAY AND MOVE OFFSHORE WEDNESDAY EVENING. BROAD UPPER LEVEL LOW PRESSURE PATTERN WILL SET UP OVER CANADA AND NEW ENGLAND THROUGH THE REST OF THE PERIOD. CWA WILL BE ON THE SOUTHERN EDGE OF THE TROUGH WITH SHORTWAVE CROSSING AREA FRIDAY. ALTHOUGH ANTICIPATED PATH OF THE SURFACE LOW WILL KEEP THE STRONGEST OF ITS ASSOCIATED PRECIPITATION IN PA...OUR CWA LOOKS TO GET WET ALSO. GREATEST OPPORTUNITY FOR PRECIPITATION APPEARS TO BE TUESDAY NIGHT THROUGH THURSDAY. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... VFR CONDS THROUGH TONIGHT. OCCASIONAL GUSTS TO 25KT WILL BE POSSIBLE THRU THE LATE AFTN HRS...DROPPING OFF TO MORE OF A STIFF BREEZE IN THE 10-15KT RANGE. SOUNDINGS FOR SATURDAY NIGHT HINT AT POSSIBLE MVFR CIGS...BUT CONFIDENCE NOT HIGH ENOUGH TO INCLUDE IN TAFS AT THIS TIME. GUSTS WILL DIMINISH IN THE EVENING. GUSTY VFR SUNDAY WITH NWLY FLOW GUSTING 25 KT AS HIGH PRESSURE BUILDS FROM THE WEST. GUSTS EASE THROUGH THE EVENING AS THE HIGH CENTER CROSSES INTO THE AREA. VFR CONTINUES THROUGH MONDAY AS THE HIGH SHIFTS OFFSHORE. LOW PRESSURE APPROACHES TUESDAY WITH RAIN CHANCES INCREASING. LOW LINGERS INTO LATE IN THE WEEK. && .MARINE... THE SCA CONTINUES FOR ALL WATERS THRU THE REST OF THE DAY. GUSTS UP TO 25 KTS ARE EXPECTED ON THE WATERS THROUGH THE AFTERNOON. SCA LINGERS OVERNIGHT FOR CHES BAY SOUTH OF SANDY POINT AND THE LOWER TIDAL POTOMAC RIVER. SCA FOR SUNDAY AND SUNDAY EVENING AS HIGH PRESSURE BUILDS FROM THE WEST. NWLY FLOW GUSTS 25 TO 30 KT SUNDAY...EASING THROUGH THE NIGHT AS HIGH PRESSURE CENTER CROSSES THE BAY LATE IN THE NIGHT. RETURN FLOW MONDAY AS HIGH PRESSURE MOVES OFF SHORE. LOW PRESSURE DRIFTS OVER THE REGION THEN INTO THURSDAY. && .TIDES/COASTAL FLOODING... THE EARLIER POSITIVE TIDAL ANOMALIES THAT WERE 0.75-1.0 FT ABOVE NORMAL HAVE TAKEN A TUMBLE AS A SOLID WLY WIND HAS BEGUN TO PUSH WATER BACK DOWN THE BAY. THE DC PORTION OF THE TIDAL POTOMAC TAKING A BIT LONGER TO RESPOND. REGARDLESS...ALL COASTAL AREAS WILL BE WELL BELOW MINOR CF POTENTIAL HEADING INTO THE NEXT FEW H.T. CYCLES AT THE VERY LEAST W/ A COUPLE OF DAYS OF THIS STEADY WNW WIND. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530- 531-535-536-538-539. SMALL CRAFT ADVISORY FROM 6 AM SUNDAY TO MIDNIGHT EDT SUNDAY NIGHT FOR ANZ531-539. SMALL CRAFT ADVISORY FROM 6 AM TO 8 PM EDT SUNDAY FOR ANZ530- 535-536-538. SMALL CRAFT ADVISORY UNTIL 8 PM EDT SUNDAY FOR ANZ542. SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT SUNDAY NIGHT FOR ANZ532>534-537-540-541-543. && $$

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