Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 080738 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 338 AM EDT TUE JUL 8 2014 .SYNOPSIS... A COLD FRONT ACROSS THE GREAT LAKES AND MIDWEST WILL APPROACH THE REGION LATE TODAY AND TONIGHT...CROSS THE AREA EARLY WEDNESDAY...AND STALL OVER SOUTHERN VIRGINIA WEDNESDAY NIGHT INTO THURSDAY. HIGH PRESSURE THEN BUILDS OVER THE MID-ATLANTIC THURSDAY AND FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... A TROF AXIS RESIDES ALONG THE I-95 CRRDR ELY THIS MRNG. BUT WITH WARM MID-LVLS...NOTHING HAS COME OF IT. EVEN THE ASSOCD CLDCVR HAS THINNED OUT. LAST NGTS CNVCTN IN THE UPR OHVLY HAS DSPTD AS WELL... AND THE RESULTANT DEBRIS CLDS WL BE ADVECTING EWD THRU THE ELY MRNG HRS. A SFC CDFNT CAN BE ANALYZED ACRS WI-MO-NRN TX...IN A SIMLR POSN TO WHERE ONE WAS 24 HRS AGO. IT WL BE MIGRATING EWD DURING THE DAY. THEREFORE...THE CWFA WL EXPERIENCE SWLY FLOW THRUT THE DAY...WITH A RATHER SGFNT P-GRAD FOR THE HEART OF SUMMERTIME. THINK DEWPTS WL BE RISING INTO THE UPR 60S...WHICH WL CONTRIBUTE TO INSTBY LVLS /SOMETHING THAT WAS MISSING YDA/. HWVR...CAPE/LI NOT AS GREAT AS NEIGHBORING AREAS...LKLY A CONSEQUENCE OF WARM MID-LVLS AS EVIDENCE IN MDL SNDGS. SINCE KINEMATICS ON THE STRONGER SIDE...THERE/S A LTL SHEAR TO WORK WITH AS WELL...BETTER W OF APCLNS NWD INTO PA/NYS. OVERALL...INGREDIENTS FOR CNVCTN PRESENT...PROVIDED THE CAP CAN BE BROKEN. WHAT MAY BE THE MORE LKLY SITUATION WL BE FOR TSRA TO DVLP IN THE UPR OHVLY IN THE AFTN...AND THEN FOR THAT CNVCTN TO PROPAGATE EWD...SUSTAINING ITS OWN COLD POOL. WL START TSRA IN THE AFTN W/ THE ASSISTANCE OF TRRN CIRCULATIONS...AND THEN SPREAD PCPN EWD FM THERE. HV BEEN RATHER RESERVED W/ POPS...GNLY GOING NO HIER THAN SCT. THE ONLY EXCEPTION WL BE ERN WVA/NRN SHEN VLY/WRN-CENTRL MD BY LT DAY-ELY EVE. ITS A QSTN IF CVRG...NOT IF ITS GOING TO HPPN. LATER GDNC MAY PUSH ME TO BE MORE EMPHATIC. CAN SEE A SVR THREAT JUST ABOUT ANYWHERE W/IN CWFA...BUT THE MORE CONCENTRATED/ORGANIZED ACTIVITY WHERE LKLY POPS PAINTED. BY LT TNGT...NAM/GFS DEPICTION OF CDFNT START TO DIVERGE. NAM IS THE SLOW OUTLIER...AND IT WAS DROPPED FM THE BLEND. WITH THAT IN MIND... MAY HV SCT TSRA LINGERING WELL INTO THE NGT...SPCLY E OF I-95...BUT HV OFFERED A DECRSG TREND FOR THE OVNGT HRS. HV MAINLY SIDED W/ THE WARMER GDNC FOR BOTH MAXT AND MIN-T. HWVR... HV BACKED OFF FM FULL EXTENT OF MAV BASED ON H8. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... NAM/GFS DIFFS...WHILE SUBTLE...MANIFEST THEMSELVES BY WED. BASED ON GFS/CONSENSUS SOLN...THE CWFA WL BE DRAPED ACRS CWFA BY WED MRNG...PUSHING MOST OF THE INSTBY S/E OF THE AREA. /NAM...ON THE OTHER HAND...STILL HAS FNT W OF AREA. THAT MAKES THE NAM SOLN MUCH WETTER THAN ALL OTHER GDNC./ THIS FNT WL STALL DURING THE DAY AS IT GETS TRAPPED W/IN THE TROF AXIS...TIL AN UPR S/WV ACTS AS A KICKER WED NGT. KEPT PTMC HIGHLANDS/OKV-MRB- HGR/FDK-W54 ALL DRY AS LWR DEWPTS ADVECT SEWD. MEANWHILE...PCPN WL BUBBLE NEAR THE SFC BNDRY BY MID- LT MRNG. WHILE THERE WL BE MODEST INSTBY AND AVBL SHEAR... THE DEEPER VALUES OF EACH WL BE S/E OF AREA. THEREFORE...DAY WL FEATURE SCT SHRA/TSRA...WHICH BE PUSHED SE OF AREA DURING THE EVNG. LIMITING FACTOR FOR TEMPS WED WL BE CLDCVR...WHICH MAY BE XTNSV. /THE CLDS WL PREVENT GREATER INSTBY AS WELL./ VALUES NEAR CLIMO. MIN-T ALSO CLOSE TO AVG...W/ DEWPTS DROPPING THRU THE 60S. THE MID-UPR 50S SHUD RETURN W OF THE BLURDG. && .LONG TERM /THURSDAY THROUGH MONDAY/... HIGH PRESSURE WILL BE MOVING INTO THE MID-ATLANTIC THURSDAY WHILE A COLD FRONT WILL BE NEAR DELMARVA EXTENDING SOUTH TO CENTRAL VA. CLOUDS WILL ACCOMPANY THE FRONT AS IT MOVES EASTWARD AS WELL AS SHOWERS AND THUNDERSTORMS IN THE AFTERNOON. AT THIS TIME THE PIEDMONT AND SRN MD AND SURROUNDING WATERS HAVE THE BEST CHANCE FOR ISO-SCT SHOWERS AND THUNDERSTORMS THURS AFTERNOON BUT ACTIVITY MAY STAY TO THE EAST AND OUT OF THE LOOKOUT AREA. FCST MAX TEMPS WILL REACH THE MID TO UPPER 80S ON THURSDAY. AN UPPER LEVEL TROUGH WILL CROSS THE REGION FRIDAY WHILE HIGH PRESSURE PERSISTS AT THE SURFACE. RETURN FLOW WILL SET UP AT THE SFC FRIDAY AFTERNOON AND SCT SHOWERS WILL BE POSSIBLE ALONG THE HIGHER ELEVATIONS DUE TO TERRAIN CIRCULATIONS. ANOTHER TROUGH WILL EJECT DOWN FROM THE GREAT LAKES REGION SATURDAY. HIGH PRESSURE WILL MOVE OFF THE NEW ENGLAND COAST AND RETURN FLOW WILL INCREASE. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE MAINLY WEST OF THE BLUE RIDGE SATURDAY AS THE TROUGH PASSES OVER THE REGION. LITTLE INSTABILITY AND A WEAK WIND PROFILE WILL LEAD TO NON-SVR CONVECTION. HIGH PRESSURE WILL MOVE FURTHER OFF THE EAST COAST SAT NIGHT AND SUNDAY AND SRLY FLOW WILL ADVECT WARM AND HUMID CONDITIONS INTO THE REGION SUNDAY. MULTIPLE DISTURBANCES WILL ROTATE AROUND A DEEP LOW IN NRN CANADA TO START THE WORK WEEK. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE SUN AND MONDAY WHILE A COLD FRONT APPROACHES FROM THE OHIO VALLEY. HEAVY RAIN AND STRONG THUNDERSTORMS WILL BE POSSIBLE MONDAY. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... VFR CONDS WL PREVAIL THRU THE MRNG PUSH. SCT-BKN CLDS DUE TO A PASSING TROF AXIS AND DECAYED TSRA IN THE UPR OHVLY. HGTS MID-HIGH DECK. THE AMS ACRS THE AREA TUE WL BE WM AND UNSTBL...SUPPORTING DVLPG SCT-NRMS TSRA. THE BEST OPPORTUNITY FOR TSRA AT THIS PT INVOF MRB... AND A VCTS MNTN INCL IN ITS TAF. ELSW...CVRG SCT WHICH MAKES A SPECIFIC PT FCST PROBLEMATIC. FOR THAT REASON...VCTS MENTION HAS BEEN EXCLUDED FM TAF ATTM. IT MAY BE ADDED AS THE EVENT TIME NEARS. TIME FRAME REPRESENTED BY BKN050-060 CLDS. BRIEF AOB IFR FLGT RESTRICTIONS AND GUSTY NW WNDS PSBL W/IN ANY TSRA TAFTN-EVE. PCPN CVRG WL GRDLY DECR OVNGT...BUT CANNOT COMPLETELY RULE OUT LT NGT PCPN...EVEN LT NGT TSRA. BELIEVE VFR WL GNLY PREVAIL OUTSIDE OF ANY SHRA/TSRA...AND FLGT RESTRICTIONS W/IN MAINLY MVFR. CDFNT WL PUSH ACRS TERMINALS ELY WED AND THEN STALL. SCT TSRA SHUD DVLP ONCE AGN BY LT MRNG...BUT BEST CHCS E OF THE BLURDG. SCT CVRG AND INTENSITY NOT AS STRONG AS TUE. ANY SHRA/TSRA SHUD BE SE OF TERMINALS BY DARK. HIGH PRESSURE MOVES INTO THE MID-ATLANTIC THURSDAY AND FRIDAY. A UPPER LEVEL DISTURBANCE WILL CROSS SATURDAY AND TSRA WILL BE POSSIBLE MAINLY AT MRB. && .MARINE... HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC AND A SOUTHERLY FLOW WILL CONTINUE OVER THE WATERS. WITH NOCTURNAL DCPLG...WNDS HV DECREASED A LTL...PREVAILING SUSTAINED SPDS SW 10-15 KT W/ FEW IF ANY HIER GUSTS. HV DROPPED THE SCA FOR THE OVNGT AND MRNG HRS. AS THE GRADIENT FLOW RETURNS DURING THE DAY...XPCT WNDS TO INCREASE ONCE AGN. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ALL OF THE WATERS THIS AFTERNOON AND EARLY EVENING...AND IT CONTINUES THROUGH TNGT FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER. SCT TSRA WL THREATEN THE WATERS BY LT DAY INTO THE NGT. STRONG GUSTY WNDS AND LRG HAIL WL BNE PSBL W/IN ANY STORM...AND SPECIAL MARINE WRNGS WL BE PSBL. CDFNT WL BE NEAR THE WATERS BY WED...AND IT/LL STALL OUT FOR MUCH OF THE DAY. WITH THE FNT IN THE NEIGHBORHOOD...XPCT SCT SHRA/TSRA BUT THE GRADIENT OF TDA WL BE LACKING. SWLY WNDS AOB 10 KT WL VEER NWLY WED NGT. A COLD FRONT WILL STALL NEAR THE WATERS THURSDAY. HIGH PRESSURE MOVES INTO THE REGION THURSDAY NIGHT AND FRIDAY. SRLY WINDS INCREASE SATURDAY-MONDAY AND SCA WILL BE POSSIBLE ACROSS ALL THE WATERS. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EDT WEDNESDAY FOR ANZ530>534-537-539>541-543. SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 9 PM EDT THIS EVENING FOR ANZ535-536-538-542. && $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...HTS LONG TERM...HAS AVIATION...HTS/HAS MARINE...HTS/HAS

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