Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 151947 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 247 PM EST SAT NOV 15 2014 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH TONIGHT...AS LOW PRESSURE WILL APPROACH FROM THE SOUTH SUNDAY...BRINGING THE CHANCE FOR MAINLY RAIN SUNDAY EVENING THROUGH MONDAY. COLD HIGH PRESSURE WILL RETURN FOR THE MIDDLE PART OF THE WEEK.
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&& .NEAR TERM /THROUGH SUNDAY/...
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STRONG HIGH PRESSURE TRAVERSES THE REGION TONIGHT...BEFORE SETTLING OFFSHORE DURING THE DAY SUNDAY. ALOFT...WEAK RIDGING WILL WEAKEN AHEAD OF AN APPROACHING...DEEPENING TROUGH. OVERALL SYNOPTIC FEATURES WILL RESULT IN A DRY AND COLD NIGHT FOR THE AREA. INCREASING CLOUD COVER DURING THE PERIOD AS MID AND HIGH LVL CLOUDS STREAM IN AHEAD OF A LOW PRESSURE SYSTEM CURRENTLY OVER THE MIDWEST. A RELAXED PRESSURE GRADIENT KEEPS WINDS LIGHT AND VRB TONIGHT...WITH A SHIFT TO THE SOUTH AND SLIGHT INCREASE AS THE HIGH SITS TO THE EAST. CONCERNING PCPN...GENERAL CONSENSUS ON THE 12Z MODEL RUN KEEPS MOST OF THE PCPN OUT OF THE CWA TILL AT LEAST 21Z SUNDAY...IF NOT 00Z MONDAY. THE ONLY AREA THAT COULD SEE SOME LIGHT AFTN RAIN IS EXTREME WESTERN AREAS AS A WEAK SHORTWAVE/ASSOCIATED VORT MAX CROSSES THE AREA. THE HIGHEST ELEVATIONS MAY SEE A BRIEF PERIOD OF RAIN/SNOW MIX. TEMPS TONIGHT A FEW DEGREES WARMER THAN PREVIOUS NIGHT DUE IN PART TO THE COMBO OF INCREASING CLOUDS AND WAA. HOWEVER...THE MAJORITY OF THE AREA STILL REMAINS BELOW FREEZING WITH ONLY SITES RIGHT ALONG THE WATER HOVERING NEAR 32 DEGREES. WITH LIGHT WINDS...NOT EXPECTING WIND CHILLS VALUES TO BE TOO DIFFERENT THAN ACTUAL TEMPS. STRONG SURGE OF WAA ON SUNDAY PUSHES TEMPS INTO THE MID TO UPPER 40S WITH ISOLATED AREAS REACHING 50.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
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EVEN W/ A FAIRLY SOLID MID-LEVEL CLOUD DECK DRIFTING ACROSS THE AREA ON SUN...PLENTY OF DRY AIR UNDERNEATH WILL PREVENT PRECIP UNTIL LATE EVE. FROM SW TO NE...ISENTROPIC LIFT WILL BE ON THE INCREASE...SATURATING THE LOW LEVELS AND BEGINNING W/ LIGHT MIX OF RAIN-SNOW OVER THE HIGHER APLCN RIDGELINES. THE VLYS AND PIEDMONT WILL SEE BATCHES OF LIGHT RAIN ARRIVING TOWARD THE LATE NIGHT HRS...W/ SFC TEMPS STILL IN THE U30S/L40S. A LIGHT SLY WIND WON`T HELP MUCH TO SUBSTANTIALLY DROP TEMPS INTO THE LATE NIGHT HRS AND VERY LITTLE RADIATIONAL COOLING...SO PRECIP WILL STAY RAIN THROUGHOUT THE OVERNIGHT HRS...OUTSIDE OF THE HIGHER TERRAIN ALONG THE SPINE OF THE APLCNS. MUCH OF THE EAST COAST WILL BE IN THE WARM SECTOR OF THE DEEPENING A LARGE-SCALE UPPER TROUGH DIGGING ALL THE WAY DOWN INTO THE GULF COAST REGION. SUCH A LARGE-SCALE FEATURE WILL UNDOUBTEDLY HAVE SEVERAL COMPLEX SMALLER-SCALE AREAS OF FORCING AND SUBSIDENCE... ALL ACTING ON EACH OTHER. THE PARENT SFC LOW WILL BE WELL TO OUR NW ACROSS THE GREAT LAKES...BUT HEADING INTO THE DAYTIME HRS MON... A SFC LOW WILL BE DEVELOPING AND STRENGTHENING WHILE SLIDING ACROSS THE MID-ATLC REGION. IMMEDIATELY WRAPPED-AROUND THIS FEATURE WILL NOT BE MUCH COLD AIR OR A LARGE SWING IN TEMPS/WINDS/PRECIP ETC. MAINLY A MIX OF LIGHT AND MODERATE RAIN WILL BE PUSHING ACROSS THE AREA AND TEMPS WILL REMAIN IN THE 40S FOR MUCH OF THE REGION THRU THE DAYTIME HRS. ON THE WARM-SIDE OF THE SFC LOW...SOME LOCALES MAY SEE TEMPS CLIMB INTO THE M-U50S. QPF AMOUNTS WILL BE A REASONABLE AUTUMN-TIME EVENT W/ A SOLID QUARTER-HALF INCH OF LIQUID - LOCALLY SLIGHTLY HIGHER. MOST SHORT-TERM MEMBERS IN THE LATEST MODEL GUIDANCE SUITE HAVE BEEN IN GOOD AGREEMENT ON THE PROGRESS OF THIS SYSTEM...ALSO TAPERING OFF PRECIP FAIRLY QUICKLY GOING INTO THE EVE HRS MON. BY LATE MON NIGHT...ONLY A FEW RESIDUAL SHOWERS EXPECTED TO BE MOVING ACROSS THE ERN MOST PORTION OF THE AREA AHEAD OF A COLD FRONT. A VERY BRIEF MIX OF RAIN/SNOW POSSIBLE ON THE WRN PERIPHERY OF THE PRECIP...W/ LITTLE IF ANY SNOW ACCUM EXPECTED/POSSIBLE. SFC TEMPS WILL STILL BE FAIRLY WARM AND THE WAVE OF COLDER AIR IS NOT EXPECTED TO BE THE IMMEDIATELY BEHIND THE FRONT...INSTEAD - THE ACCOMPANYING UPPER TROUGH AXIS WILL HELP MIX DOWN AND IMPRESSIVE REGION OF COLD AND DRY AIR ADVECTION. OF NOTE...THE EURO IS SLIGHTLY SLOWER AND MORE AGGRESSIVE W/ DEEPENING THE UPPER TROUGH...WHICH DECELERATES THE PROCESS AND MAKES A WIDER SWING AND THEREFORE A SLOWER EXIT OF THE PRECIP OVERNIGHT.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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VERY COLD AIRMASS ACCOMPANYING ARCTIC HIGH PRESSURE WILL BECOME WELL ENTRENCHED OVER THE AREA TUESDAY INTO WEDNESDAY...WITH 850 TEMPS DROPPING TO -14 TO -17 C. HIGH TEMPERATURES WILL STRUGGLE TO REACH THE FREEZING MARK OVER A GOOD PART OF THE AREA INCLUDING THE GREATER DC AND BALTIMORE METRO AREAS TUESDAY...AND GUSTY WEST WINDS WILL MAKE IT FEEL EVEN COLDER. LOWS TUESDAY NIGHT WILL BOTTOM OUT IN THE TEENS AND LOW 20S...WITH A FEW SINGLE DIGIT READINGS POSSIBLE OVER THE HIGHEST ELEVATIONS. THESE READINGS ARE 15 TO 20 DEGREES BELOW NORMAL...AND ALSO APPROACH RECORD VALUES. AIRMASS WILL GRADUALLY MODERATE THROUGH THE REMAINDER OF THE WEEK AS HIGH PRESSURE WEAKENS AND SHIFTS EAST...BUT TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH THE BEGINNING OF NEXT WEEKEND.
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&& .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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VFR CONDITIONS THROUGH SUNDAY. PERIODS OF SUB-VFR LIKELY SUNDAY NIGHT THROUGH MONDAY WITH LIGHT TO MODERATE PCPN - ENDING LATE MON NIGHT. VFR AGAIN FOR THE SECOND HALF OF THE WEEK. GUSTY W WINDS 10-20 KTS GUSTING TO 25 KTS TUE...DIMINISHING TO LESS THAN 10 KTS TUE NIGHT THEN BECOMING SW WED...THEN S WED NIGHT-THU VFR EXPECTED TUE-THU.
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&& .MARINE...
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SUB-SCA CONDITIONS ON ALL WATERS THROUGH THE WEEKEND. OCNL GUSTS MAY REACH 18 KTS SUNDAY AFTN ON THE OPEN WATERS OF THE CHESAPEAKE BAY...HOWEVER WILL NOT BE WIDESPREAD ENOUGH FOR ISSUANCE OF A SCA. SMALL CRAFT ADVISORIES LIKELY MONDAY NIGHT THROUGH TUESDAY AS LOW PRESSURE AND A COLD FRONT MOVE THROUGH. WINDS DECREASE MID-LATE WEEK. SOLID SCA WINDS LIKELY TUE IN BRISK WESTERLY FLOW...WITH GUSTS AS HIGH AS 30 KTS POSSIBLE. WINDS DIMINISH TUE NIGHT-WED...THEN INCREASE AGAIN POSSIBLY TO SCA LEVELS WED NIGHT-THU.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...GMS NEAR TERM...SEARS SHORT TERM...GMS LONG TERM...DFH AVIATION...SEARS/GMS/DFH MARINE...SEARS/GMS/DFH

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