858  
FXUS61 KLWX 270009  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
809 PM EDT FRI MAY 26 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL BUILD OVERHEAD THIS EVENING BEFORE MOVING  
OFFSHORE TOWARD MORNING. A WARM FRONT WILL STALL OUT OVER THE  
AREA SATURDAY THROUGH SUNDAY BEFORE A COLD FRONT MOVES INTO THE  
AREA MONDAY. HIGH PRESSURE MAY RETURN DURING THE MIDDLE PORTION  
OF NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 7 AM SATURDAY MORNING/
 
 
WEAK RIDGING WILL MOVE OVERHEAD FOR MUCH OF THE NIGHT, LEADING  
TO DRY WEATHER AND SLACKENING WINDS. STRATO-CU FROM EARLIER  
TODAY SHOULD ALSO TEND TO DISSIPATE, ALTHOUGH MID/HIGH CLOUDS  
WILL BE ON THE INCREASE AHEAD OF A DEVELOPING MCS CURRENTLY  
LOCATED OVER INDIANA AT 8 PM. MOVING ALONG A FRONTAL ZONE, REMNANTS  
OF THAT MCS, ALTHOUGH WEAKENING, WILL MOVE INTO THE REGION  
DURING THE LATE NIGHT/EARLY MORNING HOURS WITH INCREASED CHANCES  
FOR RAIN SHOWERS AND POSSIBLY SOME RUMBLES OF THUNDER. NO  
SEVERE THREAT ANTICIPATED. HIGHEST RAIN CHANCES PRIOR TO 8AM  
WILL BE FROM THE ALLEGHENY AND POTOMAC HIGHLANDS INTO EASTERN  
WEST VIRGINIA AND NORTHERN MARYLAND. THERE MAY ALSO BE SOME  
PATCHY FOG IN A FEW AREAS. LOWS TONIGHT GENERALLY IN THE 50S,  
EXCEPT 60S IN THE URBAN CENTERS AND ALONG THE IMMEDIATE  
SHORELINES OF THE CHESAPEAKE AND POTOMAC.  
 

 
   
SHORT TERM /7 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/
 
 
LOW PRESSURE WILL PASS THROUGH THE AREA ON THE STALLED BOUNDARY  
SATURDAY. THE BOUNDARY WILL SEPARATE COOLER MARINE AIR TO THE  
NORTH VS. WARM AND HUMID AIR TO THE SOUTH. TO THE NORTH AND EAST  
OF THE BOUNDARY...MOSTLY CLOUDY SKIES ALONG WITH A FEW SHOWERS  
ARE POSSIBLE DUE TO THE LOW PASSING THROUGH. SHOWERS AND  
THUNDERSTORMS ARE POSSIBLE TO THE SOUTH AND WEST OF THE  
BOUNDARY. SOME THUNDERSTORMS HAVE THE POTENTIAL TO BE SEVERE DUE  
TO MODERATE SHEAR PROFILES. HOWEVER...LATEST GUIDANCE SUGGEST  
THE BOUNDARY WILL BE A BIT FARTHER SOUTH ACROSS THE POTOMAC  
HIGHLANDS INTO CENTRAL VIRGINIA. THIS IS WHERE THE BEST CHANCE  
FOR STRONGER STORMS ARE POSSIBLE SATURDAY AFTERNOON AND EVENING.  
 
THE BOUNDARY WILL REMAIN STALLED OVER OUR AREA THROUGH SUNDAY  
NIGHT. MOST PLACES WILL TURN OUT DRY SATURDAY NIGHT AFTER ANY  
EVENING CONVECTION DISSIPATES. MORE POPUP SHOWERS AND  
THUNDERSTORMS ARE POSSIBLE SUNDAY NEAR THE BOUNDARY. THE BEST  
CHANCE FOR SHOWERS AND THUNDERSTORMS WILL BE IN THE POTOMAC  
HIGHLANDS INTO THE CENTRAL SHENANDOAH VALLEY...WHERE THE  
BOUNDARY IS MOST LIKELY TO SET UP. A COLD FRONT WILL APPROACH  
FROM THE WEST SUNDAY NIGHT. MORE SHOWERS AND A FEW THUNDERSTORMS  
ARE POSSIBLE. RAIN MAY BE LOCALLY HEAVY...ESPECIALLY OVER THE  
ALLEGHENY AND POTOMAC HIGHLANDS WHERE INSTABILITY MAY BE A BIT  
HIGHER.  
 

 
   
LONG TERM /MONDAY THROUGH FRIDAY/
 
 
A COLD FRONT SLOWLY MOVES AWAY FROM OUR REGION  
MONDAY INTO MONDAY NIGHT WITH SOME SHOWERS, AND MAYBE A  
THUNDERSTORM, MAINLY IN THE FIRST PART OF THE DAY. CONDITIONS  
BECOME DRIER INTO TUESDAY BEFORE A WEAK COLD FRONT MOVES  
THROUGH TUESDAY NIGHT INTO EARLY WEDNESDAY... WHICH COULD BRING  
SOME SCATTERED SHOWERS TO OUR AREA. ANOTHER BOUNDARY MOVES  
THROUGH WEDNESDAY NIGHT INTO THURSDAY BEFORE IT STALLS SOUTH OF  
OUR CWA INTO FRIDAY.  
 
HIGH TEMPERATURES WILL BE IN THE 70S AND 80S... SOME 60S AT  
HIGHER ELEVATIONS.  
 

 
   
AVIATION /00Z SATURDAY THROUGH WEDNESDAY/
 
 
VFR CONDITIONS ARE EXPECTED THROUGH TONIGHT. A FEW SHOWERS AND  
THUNDERSTORMS ARE POSSIBLE SATURDAY AS LOW PRESSURE PASSES  
THROUGH. MARINE AND RAIN COOLED AIR BEHIND A BOUNDARY THAT WILL  
STALL OUT OVERHEAD WILL LIKELY CAUSE SUB-VFR CEILINGS AS EARLY  
AS LATE MORNING SATURDAY AT MRB, MID AFTERNOON AT BWI/MTN, AND  
SATURDAY NIGHT ELSEWHERE. POSITION OF BOUNDARY AND PROGRESSION  
OF MORNING RAINFALL WILL GREATLY INFLUENCE LIKELIHOOD/POSITION  
OF REDUCED CEILINGS.  
 
LOW CLOUDS WILL CONTINUE WELL INTO SUNDAY WITH THE BOUNDARY  
LIKELY BEING OFF TO THE SOUTH AND WEST. SHOWERS AND A FEW  
THUNDERSTORMS ARE POSSIBLE SUNDAY NIGHT AS A COLD FRONT  
APPROACHES FROM THE WEST.  
 
SUB-VFR CONDITIONS EXPECTED AT TIMES ON MONDAY WITH  
SOME SHOWERS AND THUNDERSTORMS OVER US AS COLD FRONT MOVES  
THROUGH OUR AREA. CONDITIONS BECOME DRIER/VFR MONDAY NIGHT AND  
INTO WEDNESDAY.  
 

 
   
MARINE
 
 
GUSTY WEST TO NORTHWEST WINDS WILL CONTINUE THROUGH THIS  
EVENING. WINDS WILL QUICKLY DIMINISH AROUND SUNSET. A SMALL  
CRAFT ADVISORY REMAINS IN EFFECT THROUGH THIS EVENING. GUSTS  
AROUND 20-30 KNOTS ARE LIKELY...ESPECIALLY ACROSS THE NORTHERN  
WATERS.  
 
A BOUNDARY WILL STALL NEAR THE WATERS SATURDAY THROUGH SUNDAY  
NIGHT. WINDS SHOULD REMAIN BELOW SCA CRITERIA FOR MOST OF THE  
TIME...BUT IT WILL BE CLOSE SUNDAY NIGHT AS THE PRESSURE  
GRADIENT STRENGTHENS JUST A BIT AHEAD OF AN APPROACHING COLD  
FRONT.  
 
PERIODS OF SHOWERS AND THUNDERSTORMS MOVE THROUGH AT  
TIMES ON MONDAY AS FRONT MOVES ACROSS OUR REGION. CONDITIONS  
BECOME DRIER MONDAY NIGHT INTO WEDNESDAY. WINDS WILL BE BELOW  
THE SCA THRESHOLD MONDAY INTO TUESDAY NIGHT, INCREASING SLIGHTLY  
ON WEDNESDAY TO NEAR 16 KT.  
 

 
   
TIDES/COASTAL FLOODING
 
 
TIDAL ANOMALIES HAVE DROPPED OFF THIS AFTERNOON AND EVENING IN  
THE GUSTY WESTERLY FLOW, BUT STILL LIKELY HIGH ENOUGH TO PRODUCE  
ANOTHER ROUND OF MINOR FLOODING AT STRAITS POINT OVERNIGHT AND  
INTO EARLY SATURDAY MORNING. ANNAPOLIS MAY ALSO APPROACH ITS  
FLOOD STAGE.  
 
THE OFFSHORE FLOW WILL QUICKLY DIMINISH TONIGHT AND AN ONSHORE  
FLOW WILL DEVELOP FOR SATURDAY THROUGH MONDAY. ELEVATED WATER  
LEVELS ARE EXPECTED AND MINOR FLOODING IS LIKELY. MINOR FLOODING  
MAY OCCUR DURING THE HIGH TIDE CYCLES SATURDAY, ALTHOUGH  
CONFIDENCE IS HIGHER FOR SATURDAY NIGHT INTO MONDAY.  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...NONE.  
MD...COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EDT  
SATURDAY FOR MDZ017.  
VA...NONE.  
WV...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR  
ANZ530>543.  
 

 
 

 
SYNOPSIS...BJL  
NEAR TERM...BJL/MM  
SHORT TERM...BJL  
LONG TERM...IMR  
AVIATION...BJL/MM/IMR  
MARINE...BJL/MM/IMR  
TIDES/COASTAL FLOODING...BJL/MM  
 
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