Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 290856 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 356 AM EST THU JAN 29 2015 .SYNOPSIS...
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HIGH PRESSURE WILL MOVE OFF THE COAST THIS MORNING. A COLD FRONT WILL SWING THROUGH THE REGION LATE TODAY INTO TONIGHT. A STRONG PRESSURE GRADIENT AHEAD OF HIGH PRESSURE WILL BRING WINDY AND COLD CONDITIONS FRIDAY INTO FRIDAY NIGHT. HIGH PRESSURE WILL BUILD OVER THE AREA SATURDAY...BUT LOW PRESSURE MAY IMPACT THE AREA LATER SUNDAY INTO MONDAY. COLD HIGH PRESSURE WILL RETURN FOR THE MIDDLE PORTION OF NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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SURFACE HIGH PRESSURE REMAINS OVER THE REGION EARLY THIS MORNING. THE COMBINATION OF LIGHT WINDS...DRY AIR AND ONLY A THIN DECK OF HIGH CLOUDS HAS ALLOWED FOR RADIATIONAL COOLING. THEREFORE...IT WILL BE QUITE COLD EARLY THIS MORNING WITH TEMPS IN THE TEENS FOR MOST AREAS...BUT MID TO UPPER 20S IN DOWNTOWN WASHINGTON AND BALTIMORE. THE HIGH WILL MOVE OFF THE COAST LATER THIS MORNING AND LOW PRESSURE WILL TRACK THROUGH THE GREAT LAKES THIS AFTERNOON AND THE COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL APPROACH OUR AREA FROM THE WEST. MOISTURE WILL BE LIMITED WITH THIS SYSTEM...DESPITE A SOUTHERLY FLOW AHEAD OF IT. HOWEVER...THERE SHOULD BE ENOUGH FORCING FROM A POTENT UPPER-LEVEL DISTURBANCE THAT WILL TRACK THROUGH THE REGION THIS AFTERNOON INTO THIS EVENING. THIS WILL CAUSE A PERIOD OF LIGHT PRECIPITATION. STRONG WARM ADVECTION ALOFT FROM THE SOUTHERLY FLOW COMBINED WITH COLD AND DRY AIR NEAR THE SURFACE POSES A THREAT FOR MIXED PRECIPITATION. PRECIPITATION AMOUNTS WILL BE LIGHT AND THE DURATION OF PRECIPITATION WILL BE ABOUT ONE TO TWO HOURS. HOWEVER...SOME OF THAT PRECIPITATION IS EXPECTED TO FALL IN THE FROM OF FREEZING RAIN ACROSS PORTIONS OF WESTERN AND NORTHERN MARYLAND...NORTHERN VIRGINIA AND THE EASTERN PANHANDLE OF WEST VIRGINIA. GIVEN THE RECENT COLD CONDITIONS...ANY FREEZING RAIN THAT DOES FALL WILL LIKELY FREEZE ON UNTREATED SURFACES EVEN IF THE SURFACE TEMPS ARE SLIGHTLY ABOVE FREEZING. THIS WILL IMPACT THE EVENING RUSH. THEREFORE...A WINTER WEATHER ADVISORY IS IN EFFECT FOR THESE AREAS. FARTHER SOUTH AND EAST ACROSS CENTRAL VIRGINIA...SOUTHERN MARYLAND...AND THE WASHINGTON METROPOLITAN AREAS SURFACE TEMPS WILL BE A BIT WARMER. SOME SLEET MAY MIX IN WITH RAIN...BUT CONFIDENCE IN FREEZING RAIN IS LOW AT THIS TIME. HOWEVER...WILL HAVE TO MONITOR PAVEMENT TEMPS TODAY BECAUSE RAIN MAY FREEZE ON SOME SURFACES EVEN WITH TEMPS A LITTLE ABOVE FREEZING. ACROSS THE BLUE RIDGE MOUNTAINS INTO THE POTOMAC HIGHLANDS...FREEZING RAIN IS POSSIBLE BUT CONFIDENCE IN PRECIPITATION IS TOO LOW AT THIS TIME TO WARRANT AN ADVISORY. PRECIPITATION WILL MOVE AWAY FROM MOST AREAS THIS EVENING AND THE COLD FRONT IS EXPECTED TO PASS THROUGH OVERNIGHT. GUSTY NORTHWEST WINDS ARE POSSIBLE LATE TONIGHT...ESPECIALLY ALONG THE RIDGES. UPSLOPE SNOW SHOWERS ARE EXPECTED TONIGHT ALONG AND WEST OF THE ALLEGHENY FRONT. A WINTER WEATHER ADVISORY IS IN EFFECT FOR THESE AREAS.
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&& .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
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LOW PRESSURE WILL INTENSIFY OVER NEW ENGLAND FRIDAY WHILE HIGH PRESSURE APPROACHES FROM THE MIDWEST. THE PRESSURE GRADIENT BETWEEN THESE SYSTEMS WILL BE QUITE STRONG...RESULTING IN GUSTY NORTHWEST WINDS. WIND GUSTS AROUND 45 TO 50 MPH ARE POSSIBLE AND A WIND ADVISORY MAY BE NEEDED FOR PORTIONS OF THE AREA. THE STRONG NORTHWEST WINDS WILL USHER IN COLD CONDITIONS. IN FACT...TEMPS MAY HOLD STEADY OR EVEN FALL THROUGHOUT THE DAY. TEMPS FRIDAY AFTERNOON WILL RANGE FROM THE SINGLE DIGITS IN ALLEGHENY HIGHLANDS TO THE LOWER AND MIDDLE 30S IN SOUTHERN MARYLAND. MORE UPSLOPE SNOW SHOWERS ARE EXPECTED ALONG AND WEST OF THE ALLEGHENY FRONT. THE WINTER WEATHER ADVISORY CONTINUES UNTIL NOON...BUT SNOW SHOWERS ARE POSSIBLE DURING THE AFTERNOON AS WELL. FOR LOCATIONS EAST OF THE ALLEGHENY FRONT...A FEW SNOW SHOWERS ARE POSSIBLE FRIDAY AS ANOTHER POTENT UPPER-LEVEL DISTURBANCE SWINGS THROUGH THE AREA. MOST AREAS WILL NOT SEE ACCUMULATING SNOW...BUT THERE WILL BE ENOUGH INSTABILITY TO COMBINE WITH STRONG COLD ADVECTION FOR THE POSSIBILITY OF A FEW BURSTS OF HEAVIER SNOW SHOWERS. THIS COULD LEAVE A QUICK COATING IN SPOTS AND WITH SUDDEN CHANGES IN VISIBILITY THAT COULD HAVE A SIGNIFICANT IMPACT ON TRAVEL...ALTHOUGH IT WOULD BE LOCALIZED. THE BEST CHANCE FOR THE HEAVIER SNOW SHOWERS WILL BE ACROSS NORTHERN MARYLAND...EASTERN WEST VIRGINIA AND NORTHERN VIRGINIA. COLD AND DRY CONDITIONS FRI NIGHT AS SFC HIGH PRESSURE BUILDS SOUTH AND EAST. LINGERING SNOW SHOWERS OVER THE ALLEGHENY FRONT FRI EVENING EXPECTED TO DIMINISH AS THE NW FLOW INJECTS MUCH DRIER AIR. MAIN CONCERN FOR FRIDAY NIGHT WILL BE THE WELL BELOW NORMAL TEMPS...ALMOST 10-15 DEGREES BELOW. COMBINING WITH NW WINDS WITH GUSTS 20-30 KTS...AND IN HIGHER ELEVATIONS 30-35 KTS...WIND CHILLS FORECASTED TO DROP TO AROUND -10 DEGREES CELSIUS POTOMAC HIGHLANDS...NEGATIVE SINGLE DIGITS ALONG THE MASON-DIXON LINE...AND POSITIVE SINGLE DIGITS THE REMAINDER OF THE AREA. WILL CONTINUE TO HIGHLIGHT THE WIND CHILL ADVISORY POTENTIAL IN THE HWO...MAINLY FOR THE FAR WESTERN AREAS. USED A BLEND OF ADJMETBC/MOSBC WHICH HAS BEEN TRENDING WELL FOR OVERNIGHT TEMPS.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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CENTER OF THE HIGH SLIPS SOUTHEAST INTO THE SE US SAT WHILE A NEAR ZONAL FLOW SETS UP DURING THE DAY...AND WEAK RIDGING BUILDS SAT NIGHT-SUN MORNING. THE PATTERN KEEPS THE AREA DRY THOUGH COLD THRU SAT WITH TEMPS STILL RUNNING BELOW NORMAL. WARMING TREND BY SAT NIGHT AS WINDS BACK TO SW FLOW...WITH 850MB TEMPS WARMING TO AROUND -5 DEGREES CELSIUS. NEXT CHC FOR PCPN SUN-MON WITH SFC LOW DEVELOPING OVER GOM AND RIDING A NEAR STATIONARY FRONT TO OUR SOUTH. SOME QUESTION REMAINS ON PCPN TIMING AND INTENSITY...AND AS SUCH THEN P-TYPE. GFS/CMC STRONGER SOLUTIONS WITH THE LOW DEVELOPMENT AS UPPER LVL TROUGH DIGS DEEPER SOUTH...AND PICKS UP SHORTWAVE ENERGY RIDING THE SOUTHERN STREAM...WHILE THE ECMWF KEEPS MORE OF A SEPARATION. WENT WITH LIKELY POPS BY SUN AFTN OVER WESTERN AREAS TO HIGHLIGHT THE HIGHER CONFIDENCE OF PCPN...THEN SPREADING THE LIKELY POPS TO THE EAST FOR SUN NIGHT-MON. CONCERNING PCPN TYPE...MAINTAINED MAINLY A SNOW EVENT...WITH PSBL TRANSITION TO RAIN DURING THE AFTN SUN OVER JUST THE FAR SOUTHERN AREAS OF THE CWA. HIGHER CONFIDENCE ANY PCPN ON MONDAY REMAINS ALL SNOW WITH 850MB TEMPS DROPPING -10 TO -15 DEGREES CELSIUS DURING THE DAY. AS THE LOW BECOMES CLEARER ON SUBSEQUENT SHIFTS...WILL BE ABLE TO HAVE A BETTER HANDLE ON P-TYPE AND AMTS AT THE ONSET. PCPN CLEARS THE AREA BY TUES MORNING...WITH SFC HIGH BRINGING ANOTHER PERIOD OF DRY AND COLD TEMPS. TRENDED COLDER WITH HIGHS TUES AND LOWS TUES NIGHT AS A RESULT. MODEL DIVERGENCE BY MID WEEK ON THE HANDLING OF THE NEXT LOW PRESSURE SYSTEM...WITH PCPN PSBL ONCE AGAIN LATE WED-THURS.
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&& .AVIATION /08Z THURSDAY THROUGH MONDAY/...
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SOUTHERLY WINDS ARE EXPECTED TODAY. A BRIEF PERIOD OF WINTRY PRECIPITATION IS POSSIBLE LATE THIS AFTERNOON INTO EARLY THIS EVENING. DRIER CONDITIONS WILL RETURN TONIGHT. STRONG NORTHWEST WINDS ARE EXPECTED FRIDAY WITH A COUPLE SNOW SHOWERS POSSIBLE. NORTHWEST WINDS WILL GUST AROUND 35 TO 40 KNOTS FRIDAY. FRIDAY NIGHT-SAT NIGHT...VFR LIKELY...PSBL SUB-VFR LATE SAT NIGHT. GUSTY NW WINDS 15-20 KTS WITH GUSTS TO 25 KTS FRI NIGHT...BCMG LESS THAN 10 KTS BY SAT AFTN. PSBL LLWS FRI NIGHT WITH 2KFT WINDS 40-50 KTS. SUN-MON...SUB-VFR LIKELY WITH PCPN...PSBL SUB-IFR SUN NIGHT/MON MORNING. WINTRY MIX PSBL. INCREASING NW WINDS MON...GUSTS TO 20 KTS. MON NIGHT-TUES NIGHT...VFR LIKELY. WED-WED NIGHT...SUB-VFR PSBL WITH PCPN.
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&& .MARINE...
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SOUTHERLY WINDS ARE EXPECTED AHEAD OF A COLD FRONT TODAY. THE COLD FRONT WILL PASS THROUGH TONIGHT AND GUSTY NORTHWEST WINDS ARE EXPECTED BEHIND THE FRONT FRIDAY. A SMALL CRAFT ADVISORY IS IN EFFECT FOR PORTIONS OF THE WATERS THROUGH TONIGHT. A GALE WARNING IS IN EFFECT FOR THE WATERS FRIDAY. GALES LIKELY AT LEAST FIRST HALF OF FRIDAY NIGHT ON CHESAPEAKE BAY...AND POSSIBLY ON THE UPPER POTOMAC. OCNL GALES MAY LINGER TILL DAYBREAK SAT ON THE BAY. WINDS SUBSIDE SAT BUT REMAINING 15-20 KTS DURING THE DAY. WINDS DIMINISH SAT NIGHT...AND REMAIN SUB-SCA THROUGH SUNDAY. DEPENDING ON THE TRACK OF THE LOW SUN NIGHT-MON...SCA CONDITIONS WILL BECOME POSSIBLE AGAIN. SUB-SCA CONDITIONS RETURN FOR MID WEEK.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO NOON EST FRIDAY FOR MDZ501. WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM EST THIS EVENING FOR MDZ003-502. WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM EST THIS EVENING FOR MDZ004-005-503-505. VA...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO NOON EST FRIDAY FOR VAZ503. WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM EST THIS EVENING FOR VAZ028-031. WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM EST THIS EVENING FOR VAZ505. WV...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO NOON EST FRIDAY FOR WVZ503. WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO NOON EST FRIDAY FOR WVZ501-505. WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM EST THIS EVENING FOR WVZ050>053-504. MARINE...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EST FRIDAY FOR ANZ530>534-537>543. GALE WARNING FROM 6 AM TO 6 PM EST FRIDAY FOR ANZ530>543. SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 PM EST THIS EVENING FOR ANZ535-536.
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&& $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL/SEARS LONG TERM...SEARS AVIATION...BJL/SEARS MARINE...BJL/SEARS

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