Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 191331 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 931 AM EDT SAT APR 19 2014 .SYNOPSIS...
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HIGH PRESSURE CENTERED OVER ONTARIO WILL BUILD INTO THE NORTHEAST U.S. THIS AFTERNOON AND TONIGHT. THE HIGH WILL REMAIN IN CONTROL OF THE REGION`S WEATHER THROUGH MONDAY. A COLD FRONT WILL BRING SHOWERS TO THE AREA TUESDAY. HIGH PRESSURE WILL RETURN FOR WEDNESDAY AND THURSDAY...BEFORE ANOTHER COLD FRONT APPROACHES THE AREA ON FRIDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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13Z VISIBLE SATELLITE IMAGERY SHOWS CIRRUS GRADIENT OVER REGION WITH SCT-TO-BKN-TO-OVC FROM NORTH-TO-SOUTH. KNHK HAS BKN MID DECK AND EXPECTING THAT TO SUSTAIN ITSELF IN THE SOUTHERN PART OF THE MD PORTION OF THE CHESAPEAKE THROUGH MID AFTERNOON. USING GFS LAYER H5-H3 RH AS A PROXY FOR THE HIGH CLOUDS...EXPECTING ERODING TREND FOR HIGH CLOUDS FOR THIS AFTERNOON ACROSS MUCH OF THE AREA EXCEPT EXTREME SOUTHERN MD AND LOWER BAY MARINE ZONE. NOT EXPECTING PRECIP SHIELD ASSOCIATED WITH RAIN ACROSS SE VA/NC TO MAKE IT MUCH FURTHER NORTH THAN IT CURRENTLY IS...AS STRONG ANTICYCLONIC SFC FLOW WILL PREVENT NORTHWARD PUSH. ENTIRE CWA WILL BE PRECIP FREE TODAY...WITH LIGHT N/NE WIND FLOW. ADJUSTED TEMPS ALONG THE IMMEDIATE WEST SHORE OF THE CHESAPEAKE INCLUDING CITY OF BALTIMORE AND ANNAPOLIS AS NE FLOW OVER THE 50F BAY TO INHIBIT HEATING ABOVE 60F. OTHERWISE...TEMPS ARE EXPECTED TO HIT MID60S THROUGHOUT CWA DESPITE THE CHILL START OF TODAY.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... THE SERN LOW WL MOVE OFFSHORE TNGT...BUT IS NOT XPCTD TO BE A PLAYER IN MID ATLC WX. AGN HIGH PRES TO THE N WL BE FILTERING IN TO THE RGN...BRINGING CLR SKIES AND GOOD RAD CONDS. ATTM MDLS ARE FCSTG A40 BUT FEEL W/ THIS SET UP TEMPS COULD DROP LOWER AWAY FM THE CITIES. W OF I-95 TEMPS WL FALL INTO THE U30S - IF DAYSHIFT FEELS TEMPS COULD GO A LTL LOWER A FROST ADVSRY MAY BE NEEDED BUT AM GOING TO ALLOW THE LATER SHIFT TO MAKE THAT DETERMINATION. && .LONG TERM /SUNDAY THROUGH FRIDAY/... `TIS THE SEASON FOR CUT-OFF UPPER LOWS. WITH THE JET STREAM RETREATING SLOWLY TO THE NORTH BUT STILL HANGING AROUND THE US/CANADA BORDER...ENOUGH ENERGY EXISTS IN THE INCOMING SHORTWAVES FOR SOME TO `BREAK OFF` AND HOVER FURTHER SOUTH OVER THE CONUS. THE FIRST ONE IN THE CURRENT FORECAST CYCLE IS THE UPPER LEVEL LOW SPINNING OFF THE SE ATLC COAST. THIS FEATURE WILL CONTINUE TO SPREAD RAIN ACROSS THE CAROLINAS INTO SUNDAY AS THE UPPER LOW SLOWLY DRIFTS OFF THE COAST AHEAD OF THE NEXT SHORTWAVE. HIGH PRESSURE WILL SQUEEZE IN BETWEEN THESE TWO SYSTEMS...CENTERED OVER NEW ENGLAND AND STRETCHING DOWN ACROSS THE DEEP SOUTH. THE POSITION OF THE HIGH WILL CONTINUE TO STREAM IN ONSHORE FLOW TO THE MID-ATLC...KEEPING THE TEMPS/HUMIDITY MODERATED W/ HIGHS ON SUN ONLY IN THE L/M60S. RELATIVELY DRY AIR FROM THE ELY FLOW WILL ALLOW TEMPS TO DROP DOWN INTO THE 40S FOR OVERNIGHT LOWS BUT STILL WELL ABOVE FREEZING. ON MONDAY...THE SHORTWAVE THAT WAS INITIALLY ASSOCIATED W/ AN UPPER LOW OVER THE CNTRL PLAINS WILL GET PULLED BACK INTO THE FASTER UPPER FLOW. BY LATE MON...THE BETTER ORGANIZED SHORTWAVE WILL BE STRETCHED OUT FROM THE GREAT LAKES TO THE SRN PLAINS WHILE THE MID ATLC RECEIVES ANOTHER DAY OF REPRIEVE FROM ACTIVE WX. THE ELY ONSHORE FLOW WILL DROP OFF AND WINDS WILL TURN MORE SLY...ALLOWING THE WRN HALF OF THE REGION TO WARM-UP INTO THE L70S WHILE THE ERN HALF ENDS UP A FEW DEGREES COOLER FOR DAYTIME HIGHS. MOST MED RANGE MEMBERS SHOWING THIS...ESPEC THE GFS. THE BIAS-CORRECTED VERSIONS OF BOTH THE GFS AND NAM ARE BOTH A FEW DEG WARMER OVERALL THAN THEIR DETERMINISTIC PARENT - SO MORE OF A BLEND WAS UTILIZED. A DECENT COLD AIR ADVECTION REGION WILL BE PUSHING THE SHORTWAVE FROM THE OHIO VLY TOWARD THE APLCNS EARLY TUE. THE SFC LOW WILL GAIN SOME STRENGTH ON TUE AS IT MOVES ACROSS THE ERN GREAT LAKES...BUT TAKE A GOOD PORTION OF THE DYNAMICS W/ IT TO THE NORTHEAST - AT LEAST INITIALLY. THOUGH THE NAM`S CURRENT CYCLE ENDS EARLY TUE...COMPARING THE APPROACH OF THE SHORTWAVE AND SFC FEATURES TO THE GFS AND EURO SHOWS A WEAKER FEATURE THAN EITHER LONG RANGE MEMBER BUT CLOSER TO THE EURO. THE 00Z GFS BRINGS A KICKER DOWN ACROSS THE REGION LATE TUE INTO EARLY WED...BUT JUST AFTER A BULK OF THE PRECIP HAS EXITED. THE 00Z EURO IS A BIT SLOWER W/ THE PROGRESSION AND EXIT OF THESE FEATURES...WHICH BRINGS INTO QUESTION THE POTENTIAL FOR CONVECTION ALONG W/ THE FRONTAL PASSAGE ON TUE AFTN/EVE. MODEL SOUNDINGS ONLY PAINTING A LOW/MODEST AMOUNT OF FAVORABLE CONVECTIVE PARAMETERS ACROSS THE SRN TIER OF THE CWA WHICH TAPERS OFF SUBSTANTIALLY TOWARD THE I-66 OF NRN VA. ENOUGH WARM AIR AND EXPECTED HIGHS IN THE L-M70S FOR THESE SRN TIER AREAS FOR AT LEAST A CHANCE FOR ELEVATED OR BRIEF CONVECTIVE INITIATION - SO A SLIGHT CHANCE OF THUNDER INTRODUCED FOR THE BRIEF FEW HRS OF TUE AFTN/EVE. A MODEST REGION OF SUBSIDENCE WILL THEN SPREAD ACROSS THE AREA ON WED...BRINGING GUSTY NW WINDS AND DRIER/COOLER AIR. NOT NEARLY AS POTENT AS THE STORM SYSTEM A WEEK AGO AT THE SAME TIME...BUT STILL ONLY ALLOWING TEMPS TO RISE BARELY INTO THE L60S ACROSS MUCH OF THE AREA W/ A BRISK 15-25MPH NW WIND. A POTENT CUT-OFF UPPER LOW OVER THE NRN ROCKIES WILL LOSE SOME OF ITS PUNCH AS IT SLIDES EAST OF THE MISS RVR LATE THIS WEEK...AS HIGH PRESSURE AGAIN GIVES THE MID ATLC A COUPLE MORE QUIET WX DAYS FOR THU AND FRI. && .AVIATION /13Z SATURDAY THROUGH WEDNESDAY/... VFR CONDS XPCTD TDA AND TNGT. ONSHORE WINDS WILL CONTINUE ON SUNDAY...W/ A STEADY 10-15KT BREEZE EXPECTED BUT THE NEXT CHANCE FOR PRECIP WILL HOLD OFF UNTIL TUE AFTN/EVE W/ A COLD FRONTAL PASSAGE. A CHANCE FOR A FEW TSTMS SOUTH OF THE DC METRO AREA TAF SITES W/ THE BOUNDARY...THEN THIS ACTIVITY WILL PUSH OFF THE COAST INTO THE LATE NIGHT HRS. HIGH PRESSURE AND SOME GUSTY NW WINDS ON WED...W/ MORE QUIET WX ON THU AND FRI. && .MARINE...
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HAVE INTRODUCED A SCA FOR THE LOWEST MARINE SEGMENTS FOR THE PERIOD OF PEAK SOLAR HEATING THIS AFTERNOON 2PM TO 6PM ...AS BOTH THE NAM AND GFS HAS MEAN 15-20KTS WIND IN THE LAYER 975 TO 925 MB. THERE WILL BE A LULL IN THE SCA UNTIL LATER TONIGHT...WHEN THE SAME AREA WILL SEE SCA CONDITIONS ONCE AGAIN AS THE SFC PRESSURE GRADIENT INCREASES AS HIGH MOVES OVER CAPE COD...COUPLED WITH THE SFC LOW OVER THE SE US COAST. HIGH PRESSURE WILL HANG TIGHT OVER NEW ENGLAND AND INTO THE MID ATLC REGION ON SUN...THOUGH THE INCREASING PRES GRADIENT OVER DELMARVA WILL ALLOW THE ELY FLOW TO RISE JUST INTO SCA RANGE FOR MUCH OF THE MD BAY FROM THE PREDAWN HRS SUN THRU LATE EVE. WINDS WILL THEN SLACK OFF FOR THE OVERNIGHT HRS AS THE HIGH MOVES OFF THE COAST AND WINDS TURN SLY. A COLD FRONT WILL PUSH THRU THE REGION LATE TUE...BRINGING SOME SCATTERED SHOWERS AND POSSIBLY SOME ISOLATED TSTMS JUST SOUTH OF THE METRO DC AREA. BREEZY NW WINDS OF WED AFTN...THOUGH HIGH PRESSURE WILL AGAIN OVERTAKE THE REGION FOR THE SECOND HALF OF THE WEEK.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT SUNDAY FOR ANZ531>533-538>542. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 6 PM EDT THIS EVENING FOR ANZ534-537-543. SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT SUNDAY FOR ANZ534- 537-543.
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&& $$ SYNOPSIS...LEE NEAR TERM...LEE SHORT TERM...GMS/ABW LONG TERM...GMS/ABW AVIATION...GMS/ABW MARINE...LEE/GMS/ABW

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