Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 070228 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 928 PM EST SAT FEB 6 2016 .SYNOPSIS...
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HIGH PRESSURE WILL WEAKEN THROUGH MONDAY. COASTAL LOW PRESSURE WILL PASS BY WELL TO THE SOUTH AND EAST SUNDAY NIGHT. ANOTHER LOW PRESSURE SYSTEM WILL DIVE SOUTH INTO THE OHIO VALLEY MONDAY BEFORE PASSING THROUGH OUR AREA MONDAY NIGHT INTO TUESDAY. HIGH PRESSURE WILL SLOWLY BUILD TOWARD OUR AREA DURING THE MIDDLE PORTION OF NEXT WEEK.
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&& .NEAR TERM /THROUGH SUNDAY/...
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HIGH CLOUDS OVER THE AREA WILL TEND TO THIN OUT OVERNIGHT LEADING TO MOSTLY CLEAR SKIES TOWARD MORNING. HOWEVER..HIGH CLOUDS ASSOCIATED WITH JET STREAK ON EAST SIDE OF UPPER LOW OVER THE GULF STATES WILL SPREAD NORTHWARD ACROSS THE AREA SUN MORNING WITH MOSTLY CLOUDY/CLOUDY SKIES EXPECTED SUN ESPECIALLY EAST OF THE BLUE RIDGE. NO PRECIP IS EXPECTED WITH THIS SYSTEM ANYWHERE IN OUR FCST AREA BUT DID INCREASE THE SKY COVER SIGNIFICANTLY FOR SUN.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
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UPDATE ON WINTRY WX MON AND TUE...P-TYPE ISSUES EARLY AND LACK OF A WELL DEFINED LOW-MID LEVEL CIRCULATION AND INFLOW OF GULF OR ATLC MOISTURE STRONGLY SUGGEST THIS WILL BE A MINOR SNOW EVENT. LOW-LEVEL TEMPS EAST OF THE BLUE ARE VERY MARGINAL FOR AN ALL SNOW EVENT MON AND MON NIGHT SO A MIXTURE OF RAIN AND/OR WET SNOW LIKELY. COLUMN DOES NOT GET SUFFICIENTLY COLD ENOUGH FOR ALL SNOW UNTIL TUE AND BY THAT TIME THE MOISTURE WILL BE DEPARTING AS WINDS BECOME WESTERLY. ONE NOTEWORTHY ASPECT OF THIS SYSTEM IS VERY COLD AIR ALOFT AND STEEP LAPSE RATE ENVIRONMENT WHICH COULD SUPPORT CONVECTION. SEVERAL STABILITY INDICES SUCH AS K...LIFTED AND SHOWALTER INDICES SUGGEST THUNDERSTORMS POSSIBLE WHICH MAY ENHANCE PRECIP RATES. AT THIS TIME...EVERYTHING POINTS OUT TO ADVISORY LEVEL EVENT WITH MINOR SNOW ACCUMULATIONS. PREVIOUS DISCUSSION... BY SUNDAY NIGHT...THE COASTAL LOW WILL BE MOVING OUT TO SEA WHILE A BROAD UPPER LEVEL LOW MOVES INTO THE GREAT LAKES. THIS VERTICALLY STACKED SYSTEM WILL MOVE INTO THE OHIO VALLEY BY MONDAY AFTERNOON. AN ASSOCIATED COLD FRONT WILL PROGRESS EASTWARD MONDAY AND RAIN AND SNOW SHOWERS WILL MOVE ACROSS THE APPALACHIANS BY MONDAY AFTERNOON. SFC TEMPS ARE EXPECTED TO RISE INTO THE U30S/L40S AND L30S IN THE MTNS MONDAY. AS PRECIPITATION MOVES EASTWARD MOST OF IT WILL BE RAIN WITH THE EXCEPTION OF THE HIGHER ELEVATIONS. THE BROAD UPPER LEVEL LOW WILL MOVE OVERHEAD MONDAY NIGHT INTO TUESDAY AND SFC LOW PRESSURE TRANSFERS TO THE MID-ATLANTIC COAST. THERE IS A LARGE SPREAD IN MODEL GUIDANCE FOR MOISTURE AND QPF FIELDS AND THEREFORE UNCERNTAINITY EXISTS IN SNOWFALL ACCUMULATIONS. TEMPS WILL DROP INTO THE 20S AND L30S NEAR I-95 BY TUESDAY MORNING AND FOR THAT REASON PRECIPITATION WILL TRANSITION TO ALL SNOW INTO TUESDAY. ACCUMULATION IS EXPECTED WITH 3-6 INCHES NORTH AND WEST OF I-95 AND 1-3 INCHES ACROSS THE WASHINGTON DC AND BALTIMORE METROS. AT THIS TIME...THE SNOWFALL ACCUMULATION CONFIDENCE LEVEL IS LOW TO MEDIUM AS POTENTIAL EXISTS FOR HEAVY BANDS OF SNOW TO FORM ACROSS THE MID-ATLANTIC PRODUCING MORE ACCUMULATION. AT THIS TIME...LOCATION OF THESE BANDS COULD EXIST ANYWHERE ACROSS THE MID-ATLANTIC REGION.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... A NEWLY-DEVELOPED LOW PRESSURE SYSTEM OFF OF THE COAST OF THE DELMARVA PENINSULA WILL MOVE FARTHER OUT TO SEA TUESDAY AND TUESDAY NIGHT...BUT NOT BEFORE LEAVING BEHIND A LITTLE MORE SNOW ACCUMULATION IN EASTERN AREAS ALONG THE CHESAPEAKE BAY. ADDITIONAL UPPER LEVEL ENERGY IN THE WESTERN ZONES WILL BRING ADDITIONAL SNOW ACCUMULATION TO THE POTOMAC HIGHLANDS AS WELL. THE MAIN UPPER LEVEL TROUGH OF LOW PRESSURE WILL PIVOT ACROSS THE REGION LATER IN THE DAY WEDNESDAY INTO WEDNESDAY NIGHT. ADDITIONAL UPSLOPE SNOW EXPECTED IN THE POTOMAC HIGHLANDS...WHILE GRADUAL CLEARING SKIES ARE EXPECTED TO THE EAST. AN OCCASIONAL DAYTIME SNOW SHOWER OR TWO ARE POSSIBLE IN THE EASTERN ZONES DUE TO DIURNAL DIFFERENCES. FOR NOW...IT IS A SLIGHT CHANCE OF SNOW SHOWERS. MUCH COLDER AIR WILL BE ON THE HEELS OF THIS UPPER TROUGH WEDNESDAY NIGHT AS A COLD DOME OF HIGH PRESSURE BUILDS IN FROM THE WEST. HIGH PRESSURE WILL DOMINATE THURSDAY AND THURSDAY NIGHT WITH VERY COLD AND DRY AIR ACROSS THE REGION. TEMPERATURES WILL BE 10 TO 15 DEGREES BELOW NORMAL. AS THE HIGH FLATTENS OUT LATE THURSDAY NIGHT INTO FRIDAY...AN AREA OF LOW PRESSURE SHOULD SCOOT ACROSS THE TENNESSEE VALLEY. THIS LOW SHOULD JUST SPREAD ADDITIONAL CLOUD COVER ACROSS THE SOUTHERN HALF OF OUR REGION. A BRIEF PERIOD OF LIGHT SNOW CANNOT BE RULED OUT. VERY COLD TEMPERATURES WILL CONTINUE FRIDAY INTO FRIDAY NIGHT WITH TEMPERATURES ABOUT 10 TO 15 DEGREES BELOW NORMAL. BEHIND THE AREA OF LOW PRESSURE...THE MAIN UPPER LEVEL TROUGH OF SUPPORT WILL PIVOT EAST WITH A FIRM RIDGE OF HIGH PRESSURE QUICKLY TO FOLLOW IT. ASIDE FROM DIURNAL CLOUD COVER SATURDAY...THIS TROUGH WILL MAINLY SUPPORT ARCTIC AIR SURGING INTO THE MID ATLANTIC SATURDAY. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... VFR CONDITIONS EXPECTED THROUGH MONDAY. WINDS WILL BECOME NE BY SUNDAY AFTERNOON AS A COASTAL LOW MOVES SOUTH OF THE REGION. A COLD FRONT WILL APPROACH THE REGION MONDAY AND RAIN OR SNOW IS EXPECTED MONDAY BECOMING ALL SNOW BY TUESDAY MORNING. VSBY AND CIGS RESTRICTIONS EXPECTED BY MONDAY NIGHT. && MVFR TO BRIEFLY IFR CONDITIONS TUESDAY WITH A CHANCE OF LIGHT SNOW...POSSIBLY MIXING WITH RAIN. WINDS NORTHWEST 5 TO 10 KNOTS. MVFR CONDITIONS TUESDAY NIGHT WITH AN OCCASIONAL SNOW SHOWER IN PARTS OF THE REGION. WINDS NORTHWEST BECOMING WEST 10 TO 15 KNOTS WITH HIGHER GUSTS. .MARINE... HIGH PRESSURE ACROSS THE REGION WILL KEEP WINDS BELOW SCA CONDITIONS. WINDS WILL BECOME NE BY SUNDAY AFTERNOON. WINDS ARE EXPECTED TO INCREASE AND GUSTY WINDS WILL BEGIN SUNDAY NIGHT INTO MONDAY AS A COASTAL LOW MOVES TO THE SOUTH AND EAST. A SCA MAY BE NEEDED. NO MARINE HAZARDS TUESDAY. WINDS NORTHWEST 5 TO 10 KNOTS. SMALL CRAFT ADVISORY CONDITIONS POSSIBLE TUESDAY NIGHT. WINDS NORTHWEST BECOMING WEST 10 TO 15 KNOTS GUSTS 20 KNOTS. && .MARINE... && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 PM SUNDAY TO 6 AM EST MONDAY FOR ANZ533-534-537-543.
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&& $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...KLW AVIATION...HAS/KLW MARINE...HAS/KLW

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