Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 222022 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 322 PM EST THU JAN 22 2015 .SYNOPSIS...
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HIGH PRESSURE BUILDS IN TONIGHT. A LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP ALONG THE CAROLINA COAST FRIDAY NIGHT AND TRACK OFF THE DELMARVA SATURDAY. ANOTHER LOW IS EXPECTED TO CROSS THE AREA SUNDAY NIGHT INTO MONDAY.
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&& .NEAR TERM /THROUGH FRIDAY/...
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NORTHWEST FLOW IS IN PLACE BEHIND A TROUGH OF LOW PRESSURE. WINDS HAVE BECOME GUSTY EAST OF THE BLUE RIDGE...GUSTING 20 TO 25 MPH AT TIMES. DOWNSLOPING FLOW AND SOME SUNSHINE HAVE ALSO ALLOWED TEMPERATURES TO RISE WELL INTO THE 40S AND EVEN AROUND 50 INTO THE FOOTHILLS. HIGH PRESSURE WILL BUILD IN FROM THE WEST TONIGHT. THIS HIGH WILL THEN MOVE OFFSHORE ON FRIDAY. THERE ARE A LOT OF CLOUDS UPSTREAM BUT MOST OF THESE WILL LIKELY REMAIN WEST OF THE BLUE RIDGE OVERNIGHT...WITH PARTLY CLOUDY SKIES FURTHER EAST. WITH THE HIGH MOVING OFFSHORE AND OVERRUNNING BEGINNING TO DEVELOP...CLOUDS WILL THICKEN/LOWER ACROSS THE CWA BY FRIDAY AFTERNOON AND SOME LIGHT RAIN WILL START TO BREAK OUT ACROSS THE SOUTHERN PORTION OF THE CWA...POSSIBLY MIXING WITH SNOW OVER THE HIGHER ELEVATIONS. USED MAV/SREFS BLEND FOR MAXIMA FRIDAY.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/...
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FOCUS OF FRI NIGHT-SAT WILL BE A DEVELOPING COASTAL LOW AS IT PASSES JUST TO THE EAST SAT...THEN HEADS TO THE NORTHEAST INTO SAT NIGHT. LATEST FORECAST BRINGS ADVISORY LVL SNOW TO AREAS WEST OF THE I-95 CORRIDOR FRI NIGHT-SAT. DO HAVE MENTION OF A CHC OF FZRA WHICH AS WE GET CLOSER IF THE CONFIDENCE CONTINUES OF OCCURRING...WOULD ALSO WARRANT THE ISSUANCE OF AN ADVISORY. WILL HOLD ON ANY ISSUANCE AT THIS TIME WITH MANY UNCERTAINTIES STILL IN PLACE. SHORTWAVE OVER THE MOUNTAIN WEST TODAY WILL SWING THROUGH THE SOUTHERN US...WITH THE NORTHERN STREAM SWEEPING THE ENERGY UP ALONG THE EASTERN SEABOARD LATER SAT. AT THE SFC...ASSOCIATED DEVELOPING LOW OVER THE SOUTHEASTERN US NUDGES JUST OFF THE COAST OF THE CAROLINAS BY 12Z SAT...EVENTUALLY DEEPENING GREATLY WELL TO THE NORTH AND EAST OF THE REGION. THE EXACT PATH OF THIS LOW WILL BE A MAJOR PLAYER IN THE EVENT AS WE HAVE HIGH CONFIDENCE OF THE PCPN MOVING IN LATE FRI AFTN/EARLY EVENING...THEN OVERSPREADING THE ENTIRE MID ATLANTIC AREA BY 06Z SAT. P-TYPE HOWEVER IS STILL IN DEBATE WITH THE 12Z EURO NOW TRENDING THE LOW CLOSER TO SHORE...AND BRINGING IN WARMER TEMPS MUCH FURTHER WEST. 12Z NAM REMAINS THE COLDER SOLUTION...BUT IS TRENDING WARMER AS WELL. IF THE LOW TRACKS FURTHER EAST...WE WOULD SEE COLDER TEMPS...BUT IT WOULD ALSO TAKE THE AXIS OF HEAVIER PCPN TO THE EAST WHERE IT WOULD MORE LIKELY FALL AS RAIN. IF THE LOW TRACKS TO THE WEST...WE GET A WETTER SOLUTION...BUT AGAIN MORE IN THE FORM OF RAIN. SO FOR THE P-TYPE...SIDING WITH THE TREND OF THE WARMER SOLUTION...HAVE PREDOMINATELY A RAIN EVENT FOR SOUTHERN MD. FOR THE I-95 CORRIDOR...STARTING OFF WITH RAIN...WITH PSBL SLEET MIXING. HEADING NORTH AND WEST...BETTER CHC OF STARTING OFF SNOW/SLEET MIX. DECREASING CONFIDENCE FOR THE SECOND HALF OF THE NIGHT WITH UNCERTAINTY ON WHERE EXACTLY THE RAIN/SNOW LINE SETS UP. HOWEVER...WITH BOTH THE NAM AND GFS BUFKIT SOUNDINGS BECOMING ISOTHERMAL...HAVE REMOVED THE SLEET POTENTIAL. SFC TEMPS HOVERING IN THE UPPER 20S/LOWER 30S EXTENDING FROM NORTH OF BALTIMORE DOWN THROUGH NORTHERN VA INTO THE SHENANDOAH VALLEY COULD LEAD TO PERIODS OF FREEZING RAIN. HOWEVER...TEMPS COULD BE TOO LOW...ESPECIALLY IF THE TREND CONTINUES WITH WARMING TEMPS AND WITH NO BLOCKING HIGH TO THE NORTH USHERING IN THE COLDER TEMPS...THIS COULD VERY WELL END UP BEING ONLY A RAIN/SNOW MIX. BY DAYBREAK...WILL SEE MOSTLY RAIN EVENT EAST OF BLUE RIDGE...WITH SOME SNOWFLAKES MIXING IN...THEN LIGHT SNOW TO THE WEST. BEST FRONTOGENETIC FORCING FROM THE 12Z MODELS LINING UP BASICALLY ALONG THE BLUE RIDGE AND EAST AND AS SUCH HAVE THE HIGHEST SNOW TOTALS MAINLY SPREAD BETWEEN THE BLUE RIDGE AND THE I-95 CORRIDOR. AS THE LOW DEEPENS AND PUSHES NORTHEAST...PCPN WILL TAPER OFF FROM WEST TO EAST DURING THE DAY SAT. MOST 12Z SOLUTIONS ARE MOVING THE LOW THROUGH QUICKER NOW...AND AS SUCH...THE PCPN COULD VERY WELL TAPER OFF SOONER THAN CURRENTLY IN THE FORECAST. BY SAT NIGHT...DRY WX TO THE EAST...WITH UPSLOPING SNOWS TO THE ALLEGHENY FRONT.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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AN ALBERTA CLIPPER LOW PRESSURE SYSTEM WILL MOVE ACROSS THE LOWER GREAT LAKES SUNDAY...SLIDE ACROSS OHIO AND PENNSYLVANIA SUNDAY NIGHT...BEFORE PUSHING OFFSHORE NEW JERSEY MONDAY. WITH THE STORM TRACK OF THIS SYSTEM TO THE NORTH OF OUR FORECAST REGION SUNDAY NIGHT AND MONDAY...A SOUTH TO SOUTHWESTERLY WIND WILL HAVE MORE OF AN INFLUENCE ON PRECIPITATION TYPE DUE TO SLIGHTLY MILDER AIR IN THE LOWER 5000 FEET OF THE ATMOSPHERE. CURRENT THINKING IS A CHANCE FOR OCCASIONAL LIGHT SNOW AT THE START AND MAINLY IN THE WEST SUNDAY. THEN AS THE SURFACE LOW AND SOME UPPER LEVEL FORCING PENETRATES THE REGION FROM THE WEST...A WINTRY MIX OF SNOW...SLEET AND RAIN COULD EVOLVE SUNDAY NIGHT. EXPECTED AMOUNTS APPEAR TO BE LIGHT. AS THE SURFACE LOW EXITS EAST AND THE UPPER LEVEL TROUGH OF LOW PRESSURE PIVOTS TO THE CHESAPEAKE BAY MONDAY...A WEST-NORTHWEST TO NORTHWEST FLOW WILL DEVELOP AND ANY LEFTOVER RAIN AND SNOW SHOWERS WILL BE ISOLATED AND MAYBE CONFINED TO THE HIGHER ELEVATIONS OF THE POTOMAC HIGHLANDS AND BLUE RIDGE DUE TO THE SQUASH OF THE DOWNSLOPING FLOW ON ANY PRECIPITATION. THESE SAME NORTHWEST WINDS COULD GUST 30 TO 40 MPH. ASIDE FROM SOME UPSLOPE SNOW IN THE HIGHER TERRAIN OF THE POTOMAC HIGHLANDS TUESDAY AND TUESDAY NIGHT...THEN AGAIN WEDNESDAY NIGHT AND THURSDAY...DRY AND COLD CONDITIONS WILL PREVAIL ACROSS THE REGION TUESDAY THROUGH THURSDAY. TEMPERATURES COULD BE ABOUT 10 DEGREES BELOW NORMAL.
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&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/...
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WINDS MAY GUST UP TO 20 KT THROUGH SUNSET...OTHERWISE AS HIGH PRESSURE BUILDS IN VFR CONDITIONS ARE EXPECTED DURING THE TAF VALID PERIOD. SUB-VFR CONDITIONS LIKELY FRI NIGHT-SAT WITH PCPN OVERSPREADING THE REGION. INCREASING CHC OF IFR OR LOWER 06-15Z SAT. LOW CONFIDENCE ON P-TYPE...WITH I-95 CORRIDOR SITES MORE LIKELY ALL RAIN OR BRIEF SNOW/RAIN MIX SAT MORNING...WHILE HEADING WEST HAS INCREASING CHC OF WINTRY MIX. SNOW TOTALS AT THIS TIME 1 INCH OR LESS I-95 CORRIDOR...2-4 INCHES FURTHER WEST. A CHANCE OF A WINTRY MIX OF SNOW...SLEET AND RAIN COULD LEAD TO IFR CONDITIONS...MAINLY SUNDAY NIGHT INTO EARLY MONDAY. OTHERWISE...VFR CONDITIONS SUNDAY AND MIDDAY TO LATE MONDAY. WINDS SOUTH TO SOUTHWEST AND LESS THAN 5 KNOTS SUNDAY...BECOMING MAINLY SOUTHWEST AT 10 KNOTS SUNDAY NIGHT. WINDS WILL VEER WEST TO NORTHWEST AND BECOME GUSTY BY MONDAY AFTERNOON. WINDS MAY GUST 25 TO 30 KNOTS MONDAY AFTERNOON.
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&& .MARINE...
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SCA IN EFFECT FOR MOST OF THE WATERS TIL 5 PM FOR GUSTY NW WINDS. THERE IS A CHANCE SCA WINDS MAY CONTINUE LONGER THAN THIS BUT CONFIDENCE IS LOW. HIGH PRESSURE BUILDS IN TONIGHT FOR LESS WIND. SUB-SCA CONDITIONS FRIDAY NIGHT WILL QUICKLY INCREASE SAT MORNING...WITH SCA MOST LIKELY DURING THE DAY. LINGERING GUSTS TO 20 KTS IN THE EVENING...THEN DECREASING OVERNIGHT. PCPN LIKELY FRI NIGHT-SAT...WITH PERIODS OF HEAVY RAIN. LOW CHC OF FROZEN PCPN OVER THE WATERS. NO MARINE HAZARDS SUNDAY THROUGH MONDAY MORNING. SMALL CRAFT ADVISORIES MAY BE NEEDED MONDAY AFTERNOON FOR WIND GUSTS OF 25 TO 30 KNOTS.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR ANZ530>533-535-536-538>541. && $$ SYNOPSIS...BPP/SEARS NEAR TERM...BPP SHORT TERM...SEARS LONG TERM...KLW AVIATION...BPP/SEARS/KLW MARINE...BPP/SEARS/KLW

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