878  
FXUS61 KLWX 061907  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
307 PM EDT MON APR 6 2020  
   
SYNOPSIS
 
 
A FRONT WILL STALL SOUTH OF THE AREA TONIGHT WHILE HIGH PRESSURE  
BUILDS TO THE NORTH. THE FRONT WILL GRADUALLY LIFT NORTH TUESDAY  
AND TUESDAY NIGHT, FOLLOWED BY A COLD FRONT CROSSING WEDNESDAY  
AFTERNOON. A SECOND STRONGER COLD FRONT WILL MOVE THROUGH THE  
AREA THURSDAY MORNING. HIGH PRESSURE WILL BUILD OVER THE REGION  
TOWARD THE END OF THE WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
 
 
CONVERGENCE DUE TO THE ORIENTATION OF THE FRONTAL ZONE TO OUR  
SOUTH ALONG WITH LINGERING LOW LEVEL MOISTURE HAS RESULTING IN  
NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS GENERALLY SOUTH OF  
I-64 THIS AFTERNOON. THE AMOUNT OF MOISTURE AND DRY ADVECTION  
WILL HAS BEEN A LIMITING FACTOR, SO WHILE SOME LOCALLY GUSTY  
WINDS ARE POSSIBLE, ANY SEVERE WEATHER IS LOOKING UNLIKELY. THIS  
ACTIVITY SHOULD PUSH TO THE SOUTHEAST BY 5 PM OR SO.  
 
HIGH PRESSURE WILL BE LOCATED NORTH OF THE AREA TONIGHT WHILE  
THE SURFACE FRONT STALLS TO OUR SOUTH. HOWEVER, CLOUDS WILL  
LIKELY INCREASE BACK NORTHWARD THROUGH THE NIGHT AS MOISTURE  
ADVECTION BEGINS ACROSS THE FRONTAL ZONE ALOFT. PATCHY FOG IS  
POSSIBLE IN CENTRAL VIRGINIA WHERE THE HIGHEST DEW POINTS WILL  
BE LOCATED, POSSIBLY AIDED BY ANY SHOWERS THIS AFTERNOON. LATE  
TONIGHT, SOME SHOWERS MAY ADVECT ALONG THE FRONTAL ZONE FROM THE  
NORTHWEST, THOUGH THEY WILL LIKELY BE WEAKENING AS THEY DO SO.  
LOWS WILL BE IN THE MID 40S TO LOWER 50S.  
 

 
   
SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/
 
 
TUESDAY AND WEDNESDAY WILL OFFER CHANCES FOR CONVECTION AS THE  
WARM FRONTAL ZONE LINGERS ACROSS THE AREA, BEFORE LOW PRESSURE  
PASSES TO THE NORTH TUESDAY NIGHT AND DRAGS A COLD FRONT  
SOUTHWARD ON WEDNESDAY. AS IS TYPICAL THIS TIME OF YEAR, DETAILS  
ARE A BIT MUDDY IN REGARDS TO TIMING, LOCATION, AND STRENGTH OF  
ANY THUNDERSTORMS. SOME GUIDANCE HINTS AT POTENTIALLY TWO ROUNDS  
OF CONVECTION TUESDAY: ONE DURING THE MIDDAY TO AFTERNOON HOURS,  
THEN A SECOND AFTER DARK. IT'S POSSIBLE EITHER OR BOTH OF THESE  
COULD BE ELEVATED IN NATURE, ESPECIALLY IF/WHERE THE SURFACE  
FRONT GETS HUNG UP AND/OR IF THEY OCCUR OUTSIDE OF PEAK DIURNAL  
HEATING. HOWEVER, MID-LEVEL FLOW WILL BE SUFFICIENTLY STRONG FOR  
STORM ORGANIZATION IF DEVELOPMENT OCCURS. SPC HAS UPGRADED MOST  
OF THE AREA TO A SLIGHT RISK FOR THIS REASON, WITH A RISK OF  
DAMAGING WINDS AND LARGE HAIL. THE RISK APPEARS TO DECREASE  
NORTHEASTWARD FROM THE POTOMAC RIVER, WHICH WILL LIKELY BE IN  
SLIGHTLY MORE STABLE AIR.  
 
IT'S POSSIBLE ADDITIONAL SHOWERS AND THUNDERSTORMS WILL DEVELOP  
WEDNESDAY AS THE SURFACE FRONT MOVES THROUGH, ALTHOUGH TIMING  
WILL LIKELY PRECEDE PEAK HEATING ACROSS MUCH OF THE AREA, AND  
THERE MAY BE TOO MUCH DRY AIR FOR STORM INITIATION. GIVEN THE  
CONDITIONAL NATURE OF THE RISK, A MARGINAL RISK FROM SPC IS IN  
EFFECT FOR THIS TIME PERIOD.  
 
MOST OF WEDNESDAY NIGHT WILL BE DRY WITH WEAK RIDGING. THE  
CHANCE OF SHOWERS MAY ARRIVE LATE AT NIGHT IN THE POTOMAC  
HIGHLANDS AHEAD OF AN APPROACHING STRONGER COLD FRONT.  
 
TEMPERATURES TUESDAY WILL HAVE A WIDE RANGE DUE TO THE CLOUDS,  
PRECIP, AND FRONTAL ZONE, RANGING FROM LOW 60S NORTH TO MID 70S  
SOUTH. WITH MORE SUN WEDNESDAY AFTERNOON, MOST AREAS SHOULD  
REACH THE 70S. OVERNIGHT LOWS WILL BE MILD IN THE UPPER 40S AND  
50S.  
 

 
   
LONG TERM /THURSDAY THROUGH SUNDAY/
 
 
FOR THURSDAY, A STRONG COLD FRONT WILL PUSH THROUGH THE REGION IN  
THE LATE MORNING/EARLY AFTERNOON TIME FRAME. A POTENT UPPER-LOW WILL  
BE DIVING OUT OF CENTRAL CANADA INTO THE GREAT LAKES, WITH MOST  
ENERGY PASSING BY TO OUR NORTH AS THE FRONT PUSHES THROUGH. STILL  
THINK THERE WILL BE JUST ENOUGH JET ENERGY, AND STRONG ENOUGH  
SURFACE FORCING, TO GET SHOWERS, AND POSSIBLY A FEW THUNDERSTORMS.  
WINDS ALOFT THOUGH WILL BE STRONG, WITH 40-50 KNOTS IN THE 850-700MB  
LAYER. ADDITIONALLY, CAPE VALUES AROUND 500 J/KG OR SO WILL BE  
ENOUGH TO GET THINGS GOING. SO ANY STORMS WILL HAVE THE POTENTIAL  
FOR DAMAGING WIND GUSTS. HODOGRAPHS IN MODEL GUIDANCE ARE NOT  
SUPPORTIVE OF A TORNADO THREAT, AND WITH THIN CAPE PROFILES AS WELL,  
THE HAIL THREAT SHOULD BE MINIMAL. COOLER AIR WILL THEN PUSH INTO  
THE REGION THURSDAY NIGHT, WITH LOWS REACHING THE MID TO UPPER 30S  
FOR MOST (LOWER 40S FOR URBAN AREAS).  
 
FRIDAY WILL BE MOSTLY QUIET, AS HIGH PRESSURE BUILDS INTO THE  
REGION. HOWEVER, AREAS ALONG/WEST OF THE ALLEGHENY FRONT MAY BE  
DEALING WITH SOME UPSLOPE RAIN/SNOW SHOWERS, AS THE UPPER TROUGH  
SWINGS THROUGH. ANY SNOW WOULD LIKELY BE EARLY IN THE DAY, BEFORE  
TEMPERATURES RISE. EVERYWHERE EAST OF THAT THOUGH WILL REMAIN DRY,  
BUT THERE WILL BE SOME MID-UPPER LEVEL CLOUDS AS THE TROUGH PASSES.  
HIGHS ONLY REACH THE MID 50S. SKIES THEN BEGIN TO CLEAR FRIDAY NIGHT  
INTO SATURDAY MORNING AS THE UPPER TROUGH MOVES OFF TO THE EAST AND  
HIGH PRESSURE SETTLES OVERHEAD. LIGHT WINDS AND CLEARING SKIES WILL  
LEAD TO COOLER TEMPERATURES FRIDAY NIGHT INTO SATURDAY, WITH LOWS  
DOWN INTO THE MID 30S (UPPER 30S FOR URBAN AREAS). THIS WOULD BRING  
ABOUT WIDESPREAD FROSTING CONCERNS, SO THIS WILL NEED TO BE WATCHED.  
 
THINKING MUCH OF SATURDAY WILL STAY DRY AND SEASONABLE AS WELL, WITH  
HIGHS IN THE LOW 60S. THIS AS A RESULT OF HIGH PRESSURE PASSING  
OVERHEAD AND THEN OFFSHORE BY THE AFTERNOON/EVENING. SOUTHERLY  
WINDS, THANKS TO HIGH PRESSURE OFFSHORE, WILL BRING LOW TEMPS BACK  
INTO THE UPPER 30S TO LOW 40S ON SATURDAY NIGHT, SO STILL CHILLY,  
BUT NOT AS SURE ABOUT FROST RISK AT THIS TIME.  
 
SUNDAY IS WHEN THINGS BECOME INTERESTING. A CUTOFF UPPER LOW THAT  
HAD BEEN OVER THE DESERT SOUTHWEST WILL EJECT INTO SOUTHEASTERN US  
BY SUNDAY NIGHT. ATTENDANT SURFACE LOW WILL FORM OVER THE ARKLATEX,  
AND GENERALLY MOVE TOWARDS OUR AREA. NOT GOING TO GO INTO SPECIFICS,  
BUT THIS SYSTEM HAS THE POTENTIAL TO EITHER BE A HEAVY RAIN MAKER,  
OR A SEVERE WEATHER THREAT, DEPENDING ON THE TRACK. ADDITIONALLY,  
THE TIMING IS STILL VERY SPREAD OUT, WITH THE GFS NOT BRINGING RAIN  
UNTIL MONDAY OR SO, WHILE THE EURO BRINGS RAIN IN BY SUNDAY EVENING.  
JUST TOO FAR OUT RIGHT NOW TO BE SURE, BUT THIS LOOKS TO BE AN  
IMPACTFUL STORM SYSTEM IN SOME FASHION FOR AT LEAST PORTIONS OF THE  
REGION, SO THIS WILL NEED TO BE WATCHED CLOSELY IN THE COMING  
DAYS.  
 

 
   
AVIATION /19Z MONDAY THROUGH SATURDAY/
 
 
VFR CONDITIONS WITH N/NW FLOW LESS THAN 10 KT THROUGH TONIGHT.  
ANY RISK OF A SHOWER AT CHO SHOULD WIND DOWN BY 4 PM. THERE'S A  
LOW CHANCE OF MVFR CEILINGS OR FOG AT CHO TONIGHT, BUT THINK IT  
SHOULD LARGELY STAY SOUTH OF THE TERMINAL.  
 
INCREASING RISK OF SHOWERS AND THUNDERSTORMS TUE AFTERNOON AND  
NIGHT. TWO ROUNDS OF CONVECTION ARE POSSIBLE (MIDDAY/AFTERNOON,  
THEN AGAIN AFTER DARK...THOUGH OVERALL COVERAGE, TIMING, AND  
SEVERITY ARE HIGHLY UNCERTAIN) WHICH MAY CAUSE TEMPORARY  
RESTRICTIONS IN CIGS AND VSBY. WINDS WILL BECOME SOUTHERLY BUT  
REMAIN LIGHT. A COLD FRONT WILL CROSS THE AREA WED AFTERNOON  
WITH WINDS STRENGTHENING AND SHIFTING TO NW. THERE IS A LOWER  
RISK OF SHOWERS AND THUNDERSTORMS AS THE FRONT CROSSES ON  
WEDNESDAY.  
 
A COLD FRONT WILL SWING THROUGH THE AREA ON THURSDAY DURING THE LATE  
MORNING/EARLY AFTERNOON. AS A RESULT, EXPECT GUSTY WESTERLY TO WEST-  
NORTH WESTERLY FLOW TO DEVELOP BEHIND IT. GUSTS IN THE 20-30 KNOT  
RANGE ARE NOT OUT OF THE QUESTION BEHIND THIS FRONT, WITH SUSTAINED  
WINDS EVEN REACHING 15-20 KNOTS. ALSO WITH THIS FRONTAL PASSAGE  
COMES THE THREAT OF THUNDERSTORMS, WHICH COULD CONTAIN DAMAGING  
WINDS.  
 
GUSTY WINDS CONTINUE FRIDAY AFTERNOON AS WELL, BUT PROBABLY ABOUT 10  
KNOTS LESS OVERALL COMPARED TO THURSDAY. NO STORM THREAT ON FRIDAY  
EITHER.  
 

 
   
MARINE
 
 
WINDS WILL REMAIN FAIRLY LIGHT THROUGH WEDNESDAY WITH A WEAK  
FRONT STALLED ACROSS THE AREA. HOWEVER, MULTIPLE ROUNDS OF  
SHOWERS AND POSSIBLE THUNDERSTORMS WILL CROSS BETWEEN MIDDAY  
TUESDAY AND WEDNESDAY AFTERNOON, WHICH COULD NECESSITATE SPECIAL  
MARINE WARNINGS.  
 
SMALL CRAFT ADVISORIES ARE EXPECTED BY THURSDAY NIGHT. COULD EVEN  
START AS EARLY AS THURSDAY AFTERNOON, BUT A LITTLE LESS CERTAIN AT  
THIS POINT, GIVEN AN INVERSION PRESENT OVER THE WATERS THAT MAY BE  
TOUGH FOR STRONGER WINDS TO GET THROUGH. HOWEVER, SHOWERS AND  
THUNDERSTORMS ARE EXPECTED WITH A COLD FRONT LATE THURSDAY MORNING  
INTO THE EARLY AFTERNOON. THESE WOULD POSE A THREAT FOR STRONG GUSTY  
WINDS, WHICH COULD NECESSITATE SPECIAL MARINE WARNINGS.  
 
GUSTY WINDS CONTINUE ON FRIDAY, WITH SCA CONDITIONS LIKELY TO  
CONTINUE THROUGHOUT THE DAY AND EVEN INTO THE OVERNIGHT HOURS.  
 

 
   
TIDES/COASTAL FLOODING
 
 
WATER LEVELS CONTINUE TO RECEDE. HAVE CANCELLED THE ADVISORY FOR  
ALEXANDRIA SINCE THE THREAT OF MINOR FLOODING HAS SIGNIFICANTLY  
LOWERED THERE. IT'S LOOKING DOUBTFUL THAT DC SW WATERFRONT WILL  
REACH THIS EVENING EITHER, BUT LEFT THE ADVISORY IN EFFECT FOR  
NOW SINCE IT WILL BE WITHIN A FEW INCHES.  
 
WATER LEVELS WILL REMAIN ELEVATED FOR THE NEXT SEVERAL DAYS, SO  
WILL HAVE TO MONITOR FOR POTENTIAL FLOODING, BUT ODDS ARE LOW AT  
THIS TIME.  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...COASTAL FLOOD ADVISORY UNTIL 10 PM EDT THIS EVENING FOR DCZ001.  
MD...NONE.  
VA...NONE.  
WV...NONE.  
MARINE...NONE.  
 

 
 

 
SYNOPSIS...ADS  
NEAR TERM...ADS  
SHORT TERM...ADS  
LONG TERM...CJL  
AVIATION...ADS/CJL  
MARINE...ADS/CJL  
TIDES/COASTAL FLOODING...ADS  
 
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