Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 040901 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 401 AM EST WED MAR 4 2015 .SYNOPSIS...
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A COLD FRONT WILL MOVE INTO THE REGION WEDNESDAY NIGHT AND SLOWLY CROSS THROUGH THURSDAY. HIGH PRESSURE BUILDS OVERHEAD FRIDAY...THEN PERSISTS THROUGH THE WEEKEND.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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WINTER STORM WATCH TO BE UPGRADED TO WARNING YET LATE TONIGHT FOR MOST OF THE CWA. A WATCH WILL BE LEFT FOR ANY AREAS (FAR SE) THAT CONFIDENCE IS NOT YET HIGH ENOUGH TO WARN FOR. REGIONAL RADAR THIS MORNING ALREADY SHOWS THE DYNAMICAL...HIGH MOISTURE CONTENT FRONTAL ZONE SAGGING OUR WAY FROM THE NORTHERN OHIO VALLEY. TEMPERATURES CONTINUE TO RISE THIS MORNING ON A SOUTHERLY FLOW AND WILL BE ABLE TO LET THE SHORT FUSE FZRA ADVISORY EXPIRE. IN SHORT...TODAY WILL FEATURE OCCASIONAL ROUNDS OF RAIN...MOST PREVALENT ACROSS THE NORTHERN HALF OF THE CWA. WILL KEEP AN EYE ON RAIN TOTALS...ESPECIALLY IN THE HIGHLANDS WHERE TEMPERATURES HAVE WARMED AND THE HEAVIEST RAIN WILL FALL. SOME SMALL STREAM RISES MAY OCCUR. SEE HYDRO SECTION BELOW. EXPECTING ALL RAIN THROUGH THE DAY. IN-SITU WEDGE WILL HOLD TEMPERATURES IN THE 40S ACROSS MUCH OF AREA...50S SOUTH AND IN HIGHER ELEVATIONS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
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ARCTIC HIGH PRESSURE WILL QUICKLY BUILD IN THURSDAY NIGHT. THERE MAY BE A PERIOD OF UPSLOPE SNOW SHOWERS IN THE EVENING. NAM INDICATES SNOW SHOWERS WILL BE POSSIBLE EAST OF THE MOUNTAINS AS WELL AS A VORT MAX PASSES...BUT HAVE NOT INCLUDED THIS IN THE FORECAST NOW. TEMPERATURES HAVE TRENDED COLDER...SINGLE DIGITS EXCEPT IN THE METROS/NEAR THE BAY AND BELOW ZERO IN THE HIGHLANDS. IF GRADIENT DOES NOT RELAX...WIND CHILL ADVISORIES MAY BE NEEDED IN THE HIGHLANDS. THE HIGH WILL SLIDE EAST ACROSS THE AREA THROUGH SATURDAY. FRIDAY WILL STILL BE QUITE COLD BUT TEMPERATURES BEGIN TO MODERATE SATURDAY. MOISTURE STARVED COLD FRONTS TRAILING LOW PRESSURE CENTERS WELL TO THE NORTH WILL MAKE RUNS AT THE AREA SATURDAY NIGHT AND AGAIN MONDAY. FOR NOW HAVE ONLY INCLUDED POPS IN THE UPSLOPE AREAS. THERE ALSO WILL BE LITTLE EFFECT ON TEMPERATURES...WITH READINGS SLIGHTLY BELOW NORMAL EXPECTED. TAIL END OF SNOW THURSDAY EVENING IS A FEW MORE TENTHS INCH FOR SRN MD BEFORE TAPERING OFF. SKIES CLEAR LATE IN THE NIGHT WITH HIGH PRESSURE QUICKLY BUILDING OVERHEAD. GUSTY NW FLOW (AROUND 20 MPH) FOLLOWS THE COLD FRONT. WIND CHILLS REACH ZERO ACROSS THE CWA WITH WIND CHILL ADVISORIES LIKELY OVER PORTIONS WEST OF INTERSTATE 95. AREAS WEST OF INTERSTATE 95 SHOULD DECOUPLE BEFORE SUNRISE WHICH WILL ALLOW FOR SINGLE DIGIT MIN TEMPS...TWEENS EAST. SUNNY FRIDAY UNDER HIGH PRESSURE WITH TRANQUIL CONDITIONS AND MAX TEMPS MID TO UPR 20S DUE TO LITTLE MIXING AND FRESH SNOW.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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ONE OF THE LONGEST CONSISTENT WARMING PATTERNS IN AWHILE SATURDAY THROUGH MIDDLE OF NEXT WEEK AS VERY BROAD EAST COAST TROUGH SLOWLY DEAMPLIFIES. WELCOME CALM WEATHER PATTERN AS THE SUBTROPICAL RIDGE BUILDS INTO THE SERN CONUS. A FEW DEGREES WARMER ON MAX TEMPS EACH DAY IN SWLY FLOW...LOW 40S FOR SATURDAY...50S BY MONDAY...60S...MAINLY SOUTH OF DC MONDAY THROUGH WEDNESDAY. UNCERTAINTY DUE TO CLOUD COVER IN THE MIDDLE OF NEXT WEEK PREVENTED A BOLDER FORECAST OF MID 60S SOUTH/MID 50S NORTH BY WEDNESDAY...AS OF NOW IT IS AROUND 60F SOUTH AND AROUND 50 NORTH.
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&& .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
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RAIN IS FORECAST TO CHANGE TO SNOW THURSDAY NIGHT. VSBY/CIG REDUCTIONS WILL CONTINUE AND MAY DROP TO LIFR IF MODERATE/HEAVY SNOW DEVELOPS. THE SNOW WILL END ON THURSDAY. NO AVIATION HAZARDS EXPECTED THEREAFTER. CONDS QUICKLY IMPROVE TO VFR THURSDAY EVENING FROM NW TO SE WITH NW GUSTS AROUND 20 KT. SINGLE DIGITS MIN TEMPS THAT NIGHT FOR MOST OF THE AREA. HIGH PRESSURE BUILDS OVERHEAD FRIDAY WITH VFR/TRANQUIL CONDS. SWLY FLOW AND MORE HIGH PRESSURE THEN THROUGH THE WEEKEND.
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&& .MARINE...
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A COLD FRONT WILL PASS THROUGH THE WATERS WEDNESDAY NIGHT. RAIN WILL CHANGE TO SNOW BY THURSDAY MORNING. SCA CONDITIONS ARE POSSIBLE FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY NIGHT BEHIND THE FRONT. WINDS WILL SUBSIDE THEREAFTER UNDER HIGH PRESSURE. SCA THROUGH THURSDAY NIGHT FOR NWLY GUSTS BEHIND COLD FRONT...LIKELY TO EXTEND INTO FRIDAY BEFORE HIGH PRESSURE BUILDS OVERHEAD. HIGH PRESSURE THEN THROUGH THE WEEKEND WITH SWLY FLOW DEVELOPING FRIDAY NIGHT.
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&& .HYDROLOGY...
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THROUGH THIS AFTERNOON...AROUND A HALF TO THREE QUARTERS OF AN INCH OF RAIN IS EXPECTED...EXCEPT FOR HEAVIER AMOUNTS THAT COULD APPROACH 1.0 - 1.5 INCHES ALONG THE ALLEGHENY FRONT. TEMPERATURES WILL RISE WELL INTO THE 40S EVERYWHERE /AND 50S IN THE RAPPAHANNOCK AND JAMES RIVER BASINS/...PROMOTING SNOWMELT. THE SNOWPACK IS CURRENTLY ESTIMATED TO BE HOLDING ANYWHERE FROM A HALF INCH OF WATER IN THE CACAPON/LOST RIVER BASIN TO AROUND AN INCH AND A HALF IN THE SOUTH BRANCH POTOMAC BASIN. MODELING INDICATES NOT ALL OF THIS SNOW WATER WILL BE RELEASED...ESPECIALLY GIVEN A TOTAL LACK OF SUNSHINE. GIVEN THIS...THE COMBINATION OF SNOWMELT AND RAIN WILL PROMOTE RISES ON AREA RIVERS...BUT AT THIS TIME STREAMS ARE LIKELY TO REMAIN WITHIN-BANK. SOME COMPLICATING FACTORS TO KEEP IN MIND...IF THE CHANGEOVER FROM RAIN TO WINTRY PRECIP ON WEDNESDAY EVENING OCCURS LATER THAN EXPECTED...CONCERNS MAY BECOME HEIGHTENED. ALSO MANY OF OUR AREA STREAMS ARE COVERED WITH ICE OR EVEN PARTIALLY FROZEN. THESE EFFECTS WILL HAVE TO BE MONITORED FOR A POTENTIAL ROLE IN AFFECTING RUNOFF. LASTLY...AS WE SAW WITH THE RECENT RAIN/ICE/MINOR SNOWMELT...ANY AMOUNT OF LIQUID PRECIPITATION STANDS A GOOD CHANCE OF CAUSING MINOR POOR DRAINAGE FLOODING...AS NORMAL DRAINAGE PATTERNS MAY BE BLOCKED BY PLOWED SNOW.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING FOR DCZ001. MD...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING FOR MDZ003>006-011-013-014-501>508. WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING FOR MDZ016>018. FREEZING RAIN ADVISORY UNTIL 5 AM EST EARLY THIS MORNING FOR MDZ006-507-508. VA...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING FOR VAZ026>031-040-052>054-501-503>507. WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING FOR VAZ025-036>039-050-051-055>057-502-508. WV...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING FOR WVZ050>053-055-501>506. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR ANZ530>543. SMALL CRAFT ADVISORY FROM 1 AM THURSDAY TO 6 AM EST FRIDAY FOR ANZ530>543. && $$ SYNOPSIS...BAJ/ADS NEAR TERM...ADS SHORT TERM...BAJ/ADS LONG TERM...BAJ AVIATION...BAJ/ADS MARINE...BAJ/ADS HYDROLOGY...LWX

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