Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 290731 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 331 AM EDT SAT AUG 29 2015 .SYNOPSIS...
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HIGH PRESSURE REMAINS OVER THE REGION THROUGH SUNDAY AND THEN SLIDES OFFSHORE THROUGH THE END OF THE NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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SFC HIPRES ATOP THE MID ATLC ATTM. IN SPITE OF THIS...A THIN MOIST LYR AT 5K FT SENDING SOME BKN CLDS ACRS THE CWFA. AS A RESULT... TEMPS RUNNING A LTL WARMER THAN PROGGED...AND FOG IS FAR LESS. SUSPECT WE/LL SEE SOME CLRG PRIOR TO DAWN...AND HV KEPT THE PSBLTY OF A PINCH OF FOG IN THE VLYS OF THE PIEDMONT...BUT DONT BELIEVE IT/LL BE ALL THAT MUCH. THE DAYLIGHT HRS TDA WL BE VERY SIMLR TO THE PRVS SVRL DAYS...ASIDE FM SUBTLE WAA/DEWPT ADVCTN. WHILE NOT UNSTBL...AMS MAY BE ABLE TO SUPPORT A CPL SHRA /TSRA?/ WITH THE SUPPORT OF TRRN CIRCULATIONS IN THE APLCNS. WL BE FOCUSING ON THE HIER PEAKS /HIGHLAND-PENDLTN CNTYS/ TIL SUNSET. DIURNAL CU SHUD BE DSPTG DURING THE EVNG HRS...AND STILL BELIEVE THAT THE OVNGT HRS WL BE MAINLY CLR. SINCE DEWPTS WL BUMP UP INTO THE LWR 60S AND WINDS WL ONCE AGN DCPL...STAGE SHUD BE SLGTLY BETTER FOR PATCHY FOG. AM STICKING W/ CLIMO...FAVORING THE PIEDMONT/SHEN VLY/PTMC HIGHLANDS. PTTN THUS FAR HAS FAVORED A MAV/EURO MAXT OUTPUT...AND WL EMPLOY THAT SOLN WHILE MAINTAINING A FRACTION OF CONTINUITY FM PREV FCST. MIN-T FCST WL BE A BLEND OF A MORE DIVERSE GDNC MEMBERSHIP.
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&& .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
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H5 HGTS LESS ACRS THE GRTLKS/OHVLY/MID MS VLY AS A CUTOFF LOW MEADERS NORTH. THIS WEAKNESS WL SUPPORT GREATER LAPSE RATES AND THUS A BIT MORE INSTBY THAN PRVS DAYS. HARD TO TELL IF THERE WL BE A CDFNT W/IN THIS ZONE OR NOT. EVEN IF THERE IS...IT WONT MAKE IT TO THE CWFA. INSTEAD...GRDLY XPCT MORE WARMTH AND HUMIDITY TO INFILTRATE AREA. THERMAL CHGS SUBTLE...AND THAT IS REFLECTED IN FCST GRIDS. MANY SITES ALONG I-95 CRRDR MAY REACH 90F SUN AFTN...IN SPITE OF MORE CLDCVR. THE LARGER CHG WL BE TO THE POPS. SINCE THERE WL BE MORE SUPPORT FOR RANDOM DIURNAL CNVCTN...HV HIER POPS FCSTD...SPCLY ACRS THE RDGS. HV GNLY KEPT THIS THREAT W OF THE BLURDG /CHC POPS/...ALTHO SKIES WL BE PTSUN AT BEST ACRS ENTIRE ARE DURING A PORTION OF THE AFTN HRS. RDGG PARKED SE OF CWFA SHUD PREVENT STORMS FM ADVCG OUT OF THE MTNS.
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&& .LONG TERM /MONDAY THROUGH FRIDAY/...
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SFC HIGH PRESSURE TO OUR EAST WILL TEND TO DOMINATE THE WEATHER PATTERN DURING THE LONG TERM...WITH DAY-TO-DAY WEATHER INFLUENCED BY ITS POSITIONING AND MID/UPPER LEVEL DISTURBANCES MOVING THROUGH/NEAR THE REGION. OVERALL...TEMPERATURES WILL REMAIN A FEW DEGREES AOA CLIMO NORMS...HUMIDITY WONT BE BE TOO HIGH...AND BENEFICIAL RAIN CHANCES APPEAR LOW. MON...MID/UPPER VORT MAX OVER GULF STATES WILL RIDE ALONG THE PERIPHERY OF RIDGE OVER ATLANTIC AND IMPACT MID-ATLANTIC EARLY IN THE DAY. IT GETS SHEARED APART AND WEAKENS AS IT IS ABSORBED INTO NORTHERN STREAM. TIMING OF FEATURE AND POOR LAPSE RATES...RESULTING FROM NEARLY MOIST ADIABATIC PROFILES ABOVE THE LCL...WILL LIKELY LIMIT ACTIVITY TO MAINLY SHOWERS EAST OF THE BLUE RIDGE...WITH PERHAPS A FEW ISOLATED THUNDERSTORMS OVER THE HIGHER TERRAIN. TUE/WED...POOR LAPSE RATES CONTINUE...WHICH WILL KEEP ISOLATED DIURNAL CONVECTION CONFINED MAINLY TO HIGHER TERRAIN AND OUR SOUTHWEST...WHERE TERRAIN CIRCULATIONS PROVIDE ADDED LIFT AND SLIGHTLY BETTER MOISTURE RESIDES. THU/FRI...WEAK HEIGHT FALLS AND STEEPENING LAPSE RATES WILL LEAD TO BETTER...THOUGH STILL LOW...CHANCES FOR DIURNAL CONVECTION ACROSS ENTIRE CWA.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
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VFR CONDS WL PREVAIL OVER THE VAST MAJORITY OF THE TAF PD. FOG PSBL CHO BEFORE DAWN...AND HV A CPL HRS OF MVFR TO ACCT FOR IT. CANT COMPLETE RULE OUT MRB TOO...BUT CONFIDENCE IN DETAILS RATHER LOW. NEED TO GET RID OF CURRENT CLDCVR. BELIEVE THAT CAN HAPPEN. LGT SLY FLOW TAFTN-EVE W/ DIURNAL CU BASED NEAR 050. CIGS SHUD HOLD ACRS THE MTNS. THERE MAY BE A STRAY STORM...BUT THAT SHUD STAY CLR OF THE TERMINALS. ANTHR ROUND OF POTL FOG PREDAWN SUN. AGAIN...CONFIDENCE IN DETAILS LACKING. WUD KEEP IT AWAY FM THE HUBS THO. DIURNAL CU WL DVLP ONCE AGN SUN AFTN-EVE...W/ SLGTLY GREATER CVRG OF SHRA/TSRA IN THE MTNS. MRB MAY BE CLIPPED BY ONE OF THESE. NO IMPACT XPCTD FOR BALT-WASH HUBS. OUTSIDE OF PATCHY PREDAWN FOG...VFR CONDITIONS EXPECTED MONDAY AND TUESDAY...WITH ISOLATED CONVECTIVE ACTIVITY MAINLY CONFINED TO APPALACHIANS AND AWAY FROM MOST TERMINALS...EXCEPT CHO. WHILE LOW...CHANCE FOR BRIEF SUB-VFR AT ALL TERMINALS OCCURS WEDNESDAY WITH AFTERNOON THUNDERSTORMS.
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&& .MARINE...
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SLY FLOW ON THE WATERS ELY THIS MRNG...MOSTLY AOB 10 KT. SLY FLOW WL CONT THRU THE WKND...ALTHO AN ONSHORE COMPONENT LKLY WL DVLP EACH AFTN. SIMILARLY...SLY CHANNELING WL LKLY INCR OVNGT. AT THIS POINT...WL KEEP WINDS UNDER SCA THRESHOLDS. WINDS EXPECTED TO REMAIN BELOW SCA THROUGH THE REMAINDER OF THE PERIOD. THUNDERSTORM CHANCES BEGIN TO INCREASE BY MIDWEEK OVER THE WATERS.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...MSE NEAR TERM...HTS SHORT TERM...HTS LONG TERM...MSE AVIATION...MSE/HTS MARINE...MSE/HTS

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