036  
FXUS61 KLWX 260801  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
401 AM EDT WED SEP 26 2018  
   
SYNOPSIS
 
 
A STRONG COLD FRONT WILL APPROACH THE REGION FROM THE OHIO  
VALLEY TODAY, CROSS THE AREA TONIGHT, AND STALL SOUTH OF THE  
REGION THURSDAY. A WAVE OF LOW PRESSURE WILL RIDE NORTHEAST  
ALONG THE FRONT THURSDAY NIGHT. HIGH PRESSURE WILL BUILD OVER  
THE AREA DURING THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH THURSDAY/
 
 
UNUSUALLY SUMMER-LIKE AIR MASS WITH WARM TEMPERATURES AND HIGH  
DEW POINTS HAS ENVELOPED THE REGION, BUT IT WILL NOT LAST.  
HOWEVER, IT WILL PROVIDE PATCHY DENSE FOG AND LOW CLOUDS ACROSS  
MUCH OF THE REGION THIS MORNING. WILL NEED TO MONITOR FOR ANY  
DENSE FOG ADVISORY NEEDS, BUT AT PRESENT THINK IT SHOULD STAY  
PATCHY ENOUGH THANKS TO MID AND HIGH CLOUDS LIMITING RADIATIONAL  
COOLING AND FOG DEVELOPMENT. THAT SAID, WE'VE SEEN VISIBILITIES  
AS LOW AS 1/8 MILE SO FAR IN SPOTS, INCLUDING THE URBAN CENTERS.  
 
AS THE MORNING PROGRESSES, INSOLATION AND INCREASED MIXING  
SHOULD ALLOW THE CLOUDS AND FOG TO BREAK FOR SOME SUN. WITH THE  
WARM AIR MASS IN PLACE, HIGHS SHOULD RISE INTO THE 80S ACROSS  
MOST OF THE REGION. THIS WILL BE THE FUEL, AND THE APPROACHING  
TRIGGER WILL BE THE COLD FRONT LURKING TO OUR WEST. THE FRONT  
WON'T CROSS THE AREA TIL EVENING, BUT EXPECT ADEQUATE JET  
FORCING AND SHEAR TO START CAUSING STORMS TO DEVELOP BY EARLY  
AFTERNOON. BEST COVERAGE ACROSS THE METRO AREA LOOKS LIKE LATE  
AFTERNOON/EARLY EVENING, IN THE GENERAL VICINITY OF THE EVENING  
RUSH, BUT STILL A LITTLE UNCERTAINTY HERE, SO WOULDN'T BE  
SURPRISED AT SOMETHING BEFORE OR AFTER THIS WINDOW. CAPE WHICH  
COULD MEASURE GREATER THAN 2,000 J/KG AND SHEAR IN EXCESS OF 30  
KNOTS SHOULD COMBINE TO RESULT IN A SEVERE THREAT, MAINLY GUSTY  
WINDS, THOUGH HAIL CAN'T BE RULED OUT COMPLETELY EITHER. A  
SLIGHT RISK OF SEVERE WEATHER FROM THE SPC REMAINS IN PLACE  
FROM ABOUT DC NORTHWARD, WITH A MARGINAL RISK FURTHER SOUTH  
WHERE SHEAR IS WEAKER.  
 
THE FRONT CLEARS THE AREA LATER TONIGHT, BUT WILL STALL NOT FAR  
TO OUR SOUTHEAST. JET DYNAMICS AND OVERRUNNING WARM MOIST AIR  
SHOULD CAUSE SPOTTY SHOWERS TO LINGER OVERNIGHT INTO THURSDAY  
MORNING. THEN, APPROACHING SHORT WAVE/VORT MAX AND JET STREAK  
SHOULD TRY TO INDUCE LOW PRESSURE DEVELOPMENT ALONG THE FRONT,  
CAUSING MORE WIDESPREAD RAIN TO BREAK OUT AS WE HEAD THROUGH  
THURSDAY INTO THURSDAY NIGHT. SOME GUIDANCE IS HINTING AT SOME  
POTENTIAL HEAVIER RAIN, SO WILL NEED TO KEEP AN EYE ON THIS  
POTENTIAL, BUT WE WILL BE IN THE COOLER, MORE STABLE SIDE OF  
THINGS, WHICH SHOULD HOPEFULLY LIMIT THIS THREAT. SPEAKING OF  
BEING IN THE COOLER AIR, HIGHS ON THURSDAY WILL FEEL MUCH MORE  
AUTUMNAL, WITH READINGS GENERALLY IN THE 60S ALL DAY LONG.  
 

 
   
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/
 
 
WAVE OF LOW PRESSURE WILL PUSH NORTHEASTWARD ALONG THE STALLED  
FRONT THURSDAY NIGHT AND FRIDAY, ALLOWING RAIN TO CROSS THE  
REGION AT NIGHT, THEN PULL AWAY FROM THE REGION ON FRIDAY.  
HOWEVER, THE FRONT WILL LINGER FOR A TIME STILL, SO A FEW  
SHOWERS ARE STILL POSSIBLE FRIDAY. OTHERWISE, FRIDAY SHOULD BE  
AN IMPROVING DAY, WITH SOME BREAKS OF SUN AND TEMPS REBOUNDING A  
BIT BACK, GENERALLY RETURNING TO THE 70S. HIGH PRESSURE WILL  
FINALLY BECOME MORE DOMINANT FRIDAY NIGHT, ALLOWING THE THREAT  
OF RAIN TO FINALLY END.  
 

 
   
LONG TERM /SATURDAY THROUGH TUESDAY/
 
 
A DRY COLD FRONT WILL CROSS THE AREA SAT AFTERNOON. HIGH  
PRESSURE WILL THEN BUILD OVER THE REGION SAT NIGHT AND HOLD  
THROUGH THE MIDDLE OF NEXT WEEK. TEMPS WILL COOL OFF A BIT SUN  
AND MON UNDER HIGH PRESSURE OVERHEAD AND THEN REBOUND SOMEWHAT  
TO THE MID 70S DURING THE MIDDLE OF NEXT WEEK.  
 

 
   
AVIATION /08Z WEDNESDAY THROUGH SUNDAY/
 
 
IFR CIGS/VIS AT TIMES THIS MORNING AS PLENTIFUL LOW LEVEL  
MOISTURE PLAYS HAVOC WITH FLYING CONDITIONS. HIGHER CLOUDS  
MOVING OVERHEAD WILL RESULT IN CHANGEABLE CONDITIONS AS WELL,  
WITH CIGS/VIS POTENTIALLY VARYING BETWEEN IFR AND VFR OVER SHORT  
TIME PERIODS AS CLOUDS HIGHER IN THE ATMOSPHERE ALLOW CLOUDS AND  
FOG TO BREAK, ONLY TO HAVE THEM REDEVELOP AS THOSE CLOUDS MOVE  
AWAY. HOWEVER, PREDOMINANT CONDITIONS APPEAR LIKELY TO BE IFR.  
 
VFR SHOULD RETURN BY MIDDAY OR EARLY AFTERNOON AS SOUTHERLY FLOW  
PICKS UP AHEAD OF APPROACHING COLD FRONT. HOWEVER, THIS  
AFTERNOON AND EVENING WILL STILL LIKELY HAVE SIGNIFICANT FLYING  
ISSUES, BUT THIS TIME IN THE FORM OF GUSTY THUNDERSTORMS WITH  
THE COLD FRONT. BEST TIMING FOR THE BIG 3 TERMINALS IS 21-0Z,  
BUT STILL SOME UNCERTAINTY HERE. WOULD NOT BE SURPRISED IF A  
STORM HAPPENED BEFORE OR AFTER THIS WINDOW.  
 
CIGS MAY GO BACK DOWN BEHIND THE FRONT, ESPECIALLY LATER  
THURSDAY AS ANOTHER WAVE OF LOW PRESSURE RIDES NORTHEAST ALONG  
THE FRONT (WHICH BY THIS TIME WILL BE STALLED TO THE SOUTHEAST).  
RAIN LIKELY LATE THURSDAY/THURSDAY NIGHT.  
 
CONDITIONS LIKELY IMPROVE SIGNIFICANTLY FRIDAY AS THE WAVE MOVES  
AWAY AND HIGH PRESSURE FINALLY STARTS TO BUILD BACK IN.  
 
WINDS WILL SHIFT FROM THE NW TO N BEHIND A DRY FRONTAL PASSAGE  
SAT AFTERNOON. OTHERWISE, NO SIGNIFICANT WX EXPECTED SAT OR SUN.  
 

 
   
MARINE
 
 
LIGHT SOUTHERLY FLOW WILL PREVAIL OVER THE WATERS MUCH OF TODAY.  
THE FLOW MAY INCREASE A BIT THIS AFTERNOON, BUT AT PRESENT DO  
NOT EXPECT SMALL CRAFT ADVISORY CONDITIONS DURING MOST OF THE  
DAY. INSTEAD, THE MAIN CONCERN WILL BE A STRONG COLD FRONT  
APPROACHING FROM THE NORTHWEST, WHICH WILL BRING WITH IT A  
THREAT OF GUSTY THUNDERSTORMS THIS AFTERNOON AND EVENING.  
SPECIAL MARINE WARNINGS MAY BE NECESSARY.  
 
THE FRONT CROSSES THE WATERS TONIGHT, WITH WINDS PICKING UP FROM  
THE NORTH BEHIND IT. HAVE ISSUED SCA FOR MUCH OF THE WATERS  
TONIGHT AND THURSDAY DUE TO INCREASED NORTHERLY THEN  
NORTHEASTERLY FLOW BEHIND THE FRONT. ITS POSSIBLE IT MAY NEED  
EXPANSION TO REMAINING, MORE SHELTERED WATERS, BUT WILL LET DAY  
SHIFT TAKE A LOOK FIRST.  
 
WINDS DIE DOWN THURSDAY NIGHT AND FRIDAY AS A WAVE OF LOW  
PRESSURE PASSES TO THE SOUTHEAST ALONG THE FRONT AND THE  
GRADIENT WEAKENS.  
 
WINDS EXPECTED TO REMAIN 10 KT OR LESS SAT THROUGH MON.  
 

 
   
TIDES/COASTAL FLOODING
 
 
WATER LEVELS WILL REMAIN ELEVATED THROUGH MIDDAY TODAY AND THEN  
BEGIN TO SLOWLY DROP OFF DURING THE AFTERNOON THEN FALL MORE  
RAPIDLY TONIGHT AS WINDS TURN MORE NORTHERLY BEHIND A COLD  
FRONT. CANCELLED WARNING FOR ANNE ARUNDEL AND ALEXANDRIA WHERE  
MODERATE FLOODING IS NO LONGER EXPECTED. OTHER ADVISORIES MAY BE  
ABLE TO BE DROPPED SOONER THAN THEIR CURRENT EXPIRATION TIMES.  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...COASTAL FLOOD WARNING UNTIL 4 PM EDT THIS AFTERNOON FOR DCZ001.  
COASTAL FLOOD WATCH FROM THIS AFTERNOON THROUGH LATE TONIGHT  
FOR DCZ001.  
MD...COASTAL FLOOD ADVISORY UNTIL 6 PM EDT THIS EVENING FOR MDZ018.  
COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR MDZ011-  
014.  
COASTAL FLOOD WARNING UNTIL 6 PM EDT THIS EVENING FOR MDZ017.  
COASTAL FLOOD ADVISORY UNTIL 7 PM EDT THIS EVENING FOR MDZ016.  
COASTAL FLOOD ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR  
MDZ508.  
VA...COASTAL FLOOD ADVISORY UNTIL 7 PM EDT THIS EVENING FOR VAZ057.  
COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR VAZ054.  
WV...NONE.  
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EDT  
THURSDAY FOR ANZ531-539.  
SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM EDT  
THURSDAY FOR ANZ532>534-537-540>543.  
 

 
 

 
SYNOPSIS...RCM  
NEAR TERM...RCM  
SHORT TERM...RCM  
LONG TERM...LFR  
AVIATION...RCM/LFR  
MARINE...RCM/LFR  
TIDES/COASTAL FLOODING...LFR  
 
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