482  
FXUS61 KLWX 130755  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
355 AM EDT TUE APR 13 2021  
   
SYNOPSIS
 
 
A WEAK AREA OF HIGH PRESSURE WILL MOVE IN TODAY, BEFORE AN  
UPPER LEVEL LOW IMPACTS OUR AREA DURING THE MIDDLE TO LATTER  
PORTIONS OF THE WEEK.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
A FEW VERY LIGHT SHOWERS PERSIST EARLY THIS MORNING ACROSS  
EASTERN AREAS ON THE BACKSIDE OF AN UPPER LOW SPINNING OFF OF  
THE DELMARVA COAST, BUT SHOULD DISSIPATE SOON AS MID-LEVEL  
SUBSIDENCE STRENGTHENS. OTHERWISE, WEAK SURFACE HIGH PRESSURE  
AND MID-UPPER LEVEL RIDGING WILL BUILD OVER THE AREA DURING THE  
NEXT 24 HRS AND SUPPORT FAIR WEATHER CONDITIONS. HOWEVER, VERY  
COOL MID-LEVEL TEMPS AND RESIDUAL LOW-LEVEL MOISTURE COMBINED  
WITH DAYTIME HEATING WILL SUPPORT BKN STRATOCUMULUS FIELD AND,  
HENCE, MOSTLY CLOUDY SKIES.  
 
SOME PATCHY FOG IS POSSIBLE LATE TONIGHT ESPECIALLY IN AREAS  
THAT HAVE RECEIVED THE MOST RAIN LATELYT. MID- HIGH LEVEL  
CLOUDS WILL INCREASE LATE TONIGHT IN ADVANCE OF CLOSED UPPER LOW  
DROPPING FROM THE GREAT LKS.  
 

 
   
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
 
 
A LOW PRESSURE CENTER AND ASSOCIATED FRONTAL ZONE IS EXPECTED TO  
DEVELOP WED AFTERNOON INTO THU ACROSS SRN VA AND THE CAROLINAS  
AS HEIGHTS FALL IN ADVANCE OF UPPER LOW DROPPING FROM THE GREAT  
LKS INTO THE NORTHERN MID-ATLC IN AN AREA OF INCREASING UPPER  
LEVEL DIFFLUENCE. SHOWERS ARE EXPECTED WED INTO THU ALONG  
STRENGTHENING FRONTAL ZONE AND DEVELOPING LOW PRESSURE CENTER.  
 
SHOWERY AND UNSETTLED WX WILL PERSIST THU INTO FRI IN THE  
VICINITY OF UPPER LOW OVER THE NRN MID-ATLC BUT GUIDANCE HAVE  
TRENDED DRIER FOR THURSDAY GIVEN MORE NORTHWARD TRACK OF UPPER  
LOW AWAY FROM OUR AREA. SOME SNOW MAY ACCUMULATE ACROSS THE  
HIGHEST ELEVATIONS THU NIGHT WITH PASSAGE OF UPPER TROUGH AXIS.  
 

 
   
LONG TERM /FRIDAY THROUGH MONDAY/
 
 
BY FRIDAY, THE AFOREMENTIONED LOW PRESSURE SYSTEM WILL BE DEPARTING  
TO THE EAST AS THE STRONG UPPER LOW SLOWLY PUSHES OFFSHORE.  
MEANWHILE, WELL TO OUR WEST, ANOTHER UPPER LEVEL SHORTWAVE WILL  
BE EXITING THE CENTRAL/SOUTHERN ROCKIES, INDUCING SURFACE  
CYCLOGENSIS ACROSS THE CENTRAL PLAINS. THIS WILL MOVE IN OUR  
DIRECTION LATER IN THE WEEKEND. FOR OUR AREA, THOUGH, SHOULD  
REMAIN DRY ON FRIDAY FOR THE MOST PART. HOWEVER, COULD SEE SOME  
SHOWERS ASSOCIATED WITH THE UPPER LOW, PARTICULARLY ALONG/WEST  
OF THE ALLGHENY FRONT AND ALONG THE MASON-DIXON LINE.  
 
AN UPPER RIDGE MOVES INTO THE REGION BRIEFLY ON FRIDAY NIGHT AND  
SATURDAY, LEADING TO A BRIEF DRY PERIOD AREA-WIDE. LOWS FRIDAY NIGHT  
WILL BE RIGHT AROUND SEASONAL AVERAGES, WITH LOWS IN THE LOWS 30S IN  
THE MOUNTAINS AND LOW 40S ELSEWHERE. AS THE UPPER RIDGE BUILDS IN  
SATURDAY, AND THE AFOREMENTIONED LOW OVER THE CENTRAL PLAINS  
APPROACHES, TEMPERATURES ARE EXPECTED TO WARM SLIGHTLY INTO THE  
MID 60S.  
 
FOR SATURDAY NIGHT THROUGH SUNDAY, THE FORECAST BECOMES A BIT MORE  
UNCERTAIN, ALBEIT WITH A LOW IMPACT REGARDLESS. FLOW ALOFT BECOMES  
RATHER ZONAL ACROSS THE ENTIRE SOUTHERN UNITED STATES, WITH THE  
SHORTWAVE MOVING OUT OF THE CENTRAL PLAINS BECOMING SOMEWHAT  
WASHED OUT. A WEAK SURFACE LOW WILL TRAVERSE THE SOUTHEASTERN  
UNITED STATES, THOUGH IT COULD TRACK JUST FAR ENOUGH NORTH TO  
BRING SOME SHOWERS TO THE REGION. MOST LIKELY TIMEFRAME WOULD BE  
SUNDAY, AND WOULD, PERHAPS, BE MORE ASSOCIATED WITH SOME  
FAVORABLE JET DYNAMICS OVER THE REGION RATHER THAN THE SURFACE  
LOW ITSELF, PERHAPS SPARKING SOME SHOWERS. HIGHS ON SUNDAY AGAIN  
IN THE MID 60S, BUT PERHAPS SLIGHTLY WARMER THAN SATURDAY, WITH  
OVERNIGHT LOWS SATURDAY AND SUNDAY NIGHT IN THE MID 30S  
(MOUNTAINS) TO MID 40S (ELSEWHERE).  
 
ANOTHER UPPER LOW MAY IMPACT THE REGION DURING THE BEGINNING PORTION  
OF NEXT WEEK, WHICH COULD BRING ANOTHER CHANCE FOR SOME LIGHT  
PRECIPITATION TO THE REGION.  
 

 
   
AVIATION /07Z TUESDAY THROUGH SATURDAY/
 
 
GENERALLY EXPECTING VFR CONDITIONS ON FRIDAY AND SATURDAY. SOME  
LINGERING SHOWERS COULD CAUSE SOME BRIEF REDUCED VSBYS EARLIER IN  
THE DAY FRIDAY, BUT SHOULDN'T BE TOO MUCH OF AN ISSUE, AS LOW  
PRESSURE IS OFFSHORE BY THIS TIME. WINDS BEHIND THAT AREA OF LOW  
PRESSURE COULD BE GUSTY ON FRIDAY, WITH GUSTS TO 25 KNOTS POSSIBLE.  
 
WINDS WILL RELAX FRIDAY NIGHT INTO SATURDAY AS AN UPPER RIDGE BUILDS  
IN OVERHEAD. SHOULD SEE DRY CONDITIONS DURING THIS PERIOD AS  
WELL.  
 

 
   
MARINE
 
 
WINDS WILL BEGIN TO STRENGTHEN WED AFTERNOON AND EVENING WITH A  
BRIEF LULL LATE WED NIGHT AND THU MORNING IN THE VICINITY OF  
DEVELOPING LOW PRESSURE. WINDS STRENGTHEN AGAIN THU NIGHT WITH  
SOLID SCA CONDITIONS EXPECTED. RISK OF GALES APPEARS LOW AT THIS  
TIME.  
 
SMALL CRAFT ADVISORIES ARE LIKELY GOING TO BE NEEDED ON FRIDAY, AND  
PERHAPS INTO FRIDAY NIGHT, IN THE WAKE OF A LOW PRESSURE SYSTEM  
PUSHING OFFSHORE. HOWEVER, AS THE GRADIENT LOOSENS OVERNIGHT FRIDAY  
INTO SATURDAY, AND AN UPPER RIDGE BUILDS IN, EXPECT WINDS TO LIGHTEN  
UP INTO SATURDAY. NO MARINE HAZARDS ARE EXPECTED ON SATURDAY.  
 

 
   
TIDES/COASTAL FLOODING
 
 
WATER LEVELS ARE ON THE RISE WITH ANOMALIES RUNNING AROUND A  
FOOT IN THE UPPER BAY TO 1.5 FT IN ANNAPOLIS TO 1.9 FT AT  
DAHLGREN. MINOR COASTAL FLOODING WILL CONTINUE TO BE A CONCERN  
INTO THU MORNING UNTIL WINDS BECOME MORE NW.  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...COASTAL FLOOD ADVISORY FROM 7 AM THIS MORNING TO NOON EDT  
TODAY FOR DCZ001.  
MD...COASTAL FLOOD ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR  
MDZ016-017.  
COASTAL FLOOD ADVISORY UNTIL 11 AM EDT THIS MORNING FOR MDZ014.  
VA...COASTAL FLOOD ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR  
VAZ057.  
WV...NONE.  
MARINE...NONE.  
 

 
 

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