Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 220354 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1154 PM EDT TUE OCT 21 2014 .SYNOPSIS... AN UPPER LEVEL LOW WILL MOVE ACROSS THE MID-ATLANTIC TONIGHT. LOW PRESSURE WILL PERSIST ALONG THE COAST THROUGH THURSDAY. HIGH PRESSURE WILL RETURN FOR THE END OF THE WORKWEEK AND INTO THE WEEKEND. && .NEAR TERM /THROUGH WEDNESDAY/...
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POPS IN THE NERN PART OF THE FCST AREA WERE INCRSD DUE TO ONGOING RA. NO FLD THREAT. PRVS DSCN... LOW PRESSURE IS LOCATED ALONG THE MID-ATLANTIC COAST THIS EVENING. NORTHWEST WINDS HAVE MOVED INTO THE REGION AS PRESSURE CONTINUES TO RISE BEHIND THE LOW. AN UPPER LEVEL LOW WILL MOVE OVER THE MID- ATLANTIC TONIGHT. THE DYNAMICS WITH THIS FEATURE...COOLER AIR ALOFT AND VORTICITY ADVECTION HAS MADE FOR AN ACTIVE AFTERNOON AND EVENING TODAY. SHOWERS AND SCATTERED THUNDERSTORMS MOVED WEST TO EAST ACROSS THE REGION TODAY. ACTIVITY WAS CAPABLE OF HEAVY RAIN AND SMALL HAIL. OUTFLOW BOUNDARIES LED TO INCREASED COVERAGE OF SHOWERS AS WELL. AS OF 00Z...THE PRESSURE SURGE WAS AT THE WATERS AND GUSTS UP TO 25KTS HAVE BEEN OBSERVED. WINDS BEHIND THE SURGE ARE EXPECTED TO LESSEN TONIGHT BUT THE PRESSURE GRADIENT WILL CONTINUE AS THE SFC LOW MOVES TO THE EAST. NW WINDS AROUND 10-15 MPH ARE EXPECTED TONIGHT. WINDS WILL CONTINUE TONIGHT AND LIMIT THE FORMATION OF FOG DEVELOPMENT. SHOWERS WILL CONTINUE TO MOVE EASTWARD TONIGHT. AS THE UPPER LOW SPINS OVER THE REGION...MORE SHOWERS WILL ENTER THE REGION BUT THE COVERAGE WILL BE LESS THAN EARLIER. ADDITIONAL RAINFALL AMTS OF A QUARTER INCH OR LESS ARE EXPECTED TONIGHT. SHOWERS ARE EXPECTED ACROSS THE UPSLOPE REGION AS AN UPSLOPE COMPONENT WILL LEAD TO CONSTANT LIFT. LOWS TONIGHT RANGE FROM THE LOW 40S IN THE HIGHLANDS TO THE LOW 50S ALONG AND EAST OF I-95.
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&& .SHORT TERM /WEDNESDAY NIGHT/... SURFACE LOW PRESSURE MOVES OFFSHORE AND BEGINS TO STRENGTHEN AS IT REACHES THE GULF STREAM. WINDS STRENGTHEN TO AROUND 15-20 MPH WITH HIGHER GUSTS AS THE PRESSURE GRADIENT BETWEEN THE STRENGTHENING LOW AND HIGH PRESSURE OVER THE OHIO VALLEY. WRAPAROUND RAINFALL LIKELY AT TIMES OVER EASTERN MD AND PORTIONS OF VA. UPSLOPE RAIN WILL DEVELOP OVER THE POTOMAC HIGHLANDS AND CONTINUE WEDNESDAY NIGHT. LOOKS LIKE OVERNIGHT TEMPS WILL FAVOR LIQUID RAIN OVER MOST OF THE HIGHLANDS...BUT THE HIGHEST ELEVATIONS IN GRANT...PENDLETON AND HIGHLAND MAY SEE SNOW MIXED IN. LOW TEMPS IN THE 40S ACROSS MOST OF THE FORECAST AREA. && .LONG TERM /THURSDAY THROUGH TUESDAY/...
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TIME OF PARTIAL ECLIPSE FOR DC THU - 5:52 PM TO 6:17 PM. BALT IS 5:51 TO 6:15. QUSTN WL BE WHETHER IT WL BE VSBL DUE TO CLDS... WHICH SHOULD BE ON THE WANE DURG THIS TIME PD. PRVS DSCN... BLUSTERY CONDITIONS WILL CONTINUE INTO THE DAY THURSDAY AS SURFACE LOW PRESSURE SLOWLY SLIDES UP THE NEW ENGLAND COAST. DOWNSLOPING OF NORTHEASTERLY WINDS WILL ELIMINATE POPS LOCALLY DURING THE DAY THURSDAY EVERYWHERE EXCEPT THE POTOMAC HIGHLANDS...WHERE UPSLOPE RAIN IS POSSIBLE...AND THE FAR NORTHEASTERN PORTION OF THE CWA ALONG THE CHESAPEAKE BAY. HIGH PRESSURE WILL BEGIN TO FILL IN THURSDAY NIGHT AND WINDS WILL BE WEAKER FRIDAY. THE REST OF THE LONG TERM PERIOD WILL SEE QUIET/DRY WEATHER AS BROAD SURFACE HIGH PRESSURE MOVES OVERHEAD AND UPPER LEVEL RIDGING KEEPS PLENTY OF SUNSHINE ACROSS THE AREA. EXPECT TEMPS THIS WEEKEND TO BE RIGHT AROUND NORMAL...WITH HIGHS MOSTLY IN THE MID-60S...AND TEMPS EARLY NEXT WEEK TO BE JUST A FEW DEGREES ABOVE NORMAL.
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&& .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... LOW PRESSURE WILL MOVE EAST OF THE TERMINALS TONIGHT AND NW WINDS 5-10KTS ARE EXPECTED. DCA/MTN WILL LIKELY SEE GUSTS UP TO 20KTS OVERNIGHT. SHRA WILL MOVE EASTWARD TONIGHT IMPACTING DCA/BWI/MTN. SOME SHOWERS ARE HEAVY RESULTING IN REDUCED VSBYS. THEY WILL LIKELY STAY ABOVE IFR CONDITIONS. AS THE RAIN MOVES AWY FROM THE TERMINALS...MVFR CIGS WILL MOVE IN. THE WIND FIELD ALOFT WILL INCREASE OVERNIGHT AND ONLY ISOLATED IFR CONDITIONS ARE EXPECTED. NW WINDS 10-15KTS WITH GUSTS AROUND 20KTS ARE EXPECTED EARLY WED MORNING. THIS TREND WILL CONTINUE INTO WEDNESDAY. GUSTY NW WINDS WITH GUSTS UP TO 30KTS POSSIBLE ESPECIALLY AT IAD/DCA/BWI/MTN BY WED AFTERNOON. THU...VFR. NW WINDS GUSTING TO 20-25KT. FRI...VFR. NW WINDS AROUND 1OKT. CONFIDENCE IS LOW IN THE OCCURRENCE OF AVIATION HAZARDS OVER THE WEEKEND AS HIGH PRESSURE BUILDS IN. CLDY WED NGT BUT CIGS XPCTD TO BE VFR. BRZY NW WINDS XPCTD WED NGT AND THU. VFR/NO PROBS FRI AND SAT. && .MARINE... PRESSURE SURGE MOVED ACROSS THE WATERS THIS EVENING AND GUSTY NW WINDS WILL CONTINUE THIS EVENING. A TIGHT PRESSURE GRADIENT WILL MOVE ACROSS THE WATERS TONIGHT. A SCA IS NOW IN EFFECT FOR THE WATERS. PREVIOUS DISCUSSION... POTENTIAL CONTINUES FOR GALES WEDNESDAY NIGHT AS LOW PRESSURE STRENGTHENS OFF THE NJ/DELMARVA SHORE. MODEL FORECASTS ARE MARGINAL FOR GALES...SO FOR NOW OPTED TO EXTEND SCA THROUGH WEDNESDAY NIGHT WITH GUSTS LIKELY TO REACH 30KT IN SOME PARTS OF CHES BAY AT LEAST. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED THURSDAY THROUGH FRIDAY AND POSSIBLY INTO FRIDAY NIGHT IN GUSTY NORTHEASTERLY WINDS AS LOW PRESSURE MOVES UP THE NORTHEAST COAST. WINDS MAY APPROACH GALE FORCE THURSDAY AFTERNOON OVER THE WATERS...THOUGH CURRENTLY THINK THEY WILL STAY MOSTLY IN THE MID TO UPPER 20 KNOT RANGE. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ530>543.
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&& $$ UPDATE...WOODY! PRVS...KS/HAS/CEB

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