960  
FXUS61 KLWX 192352  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
752 PM EDT WED SEP 19 2018  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH THURSDAY  
BEFORE MIGRATING OVER THE WESTERN ATLANTIC ON FRIDAY. A COLD  
FRONT WILL APPROACH FROM THE NORTHWEST TOWARD THE END OF THE  
WEEK BEFORE STALLING NEAR OR OVER THE REGION THROUGH THE  
WEEKEND.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
A SECONDARY COLD FRONT IS DECAYING OVER THE MID-ATLANTIC AS OF  
EARLY WEDNESDAY EVENING. SURFACE HIGH PRESSURE IS BUILDING OVER  
THE REGION IN ITS PLACE. ANY CONVECTIVE ACTIVITY HAS WANED.  
 
PATCHY FOG SEEMS LIKELY TONIGHT GIVEN LIGHT WINDS, A MAINLY  
CLEAR SKY AND WET GROUND, ESPECIALLY WEST OF I-95. SOME FOG MAY  
BE LOCALLY DENSE.  
 

 
   
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
 
 
HIGH PRESSURE WILL BEGIN SHIFTING TO THE EAST THURSDAY, WITH  
LIGHT EASTERLY OR SOUTHEASTERLY RETURN FLOW. A POP UP SHOWER  
CAN'T BE RULED OUT NEAR/OVER THE HIGHER TERRAIN AGAIN, BUT  
THUNDER POTENTIAL SHOULD BE LOWER WITH RIDGING MORE DIRECTLY  
OVERHEAD THROUGH THE DAY.  
 
LOW PRESSURE WILL PASS NORTH OF THE GREAT LAKES ON FRIDAY,  
CONTINUING ITS PATH NORTHEASTWARD TO CLOSE OUT THE WORK WEEK.  
THE ASSOCIATED FRONTAL BOUNDARY WILL APPROACH OUR REGION FROM  
THE NORTHWEST LATE FRIDAY AND INTO FRIDAY NIGHT. CURRENT  
PROGRESSION OF THE FRONT BY MODEL GUIDANCE KEEPS PRECIPITATION  
MOSTLY NORTHWEST OF THE CWA THROUGH THE DAY ON FRIDAY, WITH  
COVERAGE INCREASING FRIDAY NIGHT. AS SUCH, HAVE PUSHED BACK THE  
TIMING AND HAVE LOW END CHANCE POPS FRIDAY AFTERNOON FOR ONLY  
OUR FAR NORTHWESTERN ZONES (EASTERN WV/WESTERN MD). THERE IS A  
SEVERE RISK MAINLY NORTH OF THE PA BORDER WHERE BETTER  
FORCING/SHEAR WILL BE, AND THIS RISK SHOULD DECREASE WITH  
SOUTHWARD EXTENT TOWARDS OUR AREA AS MORE FAVORABLE PARAMETERS  
EJECT TOWARDS NEW ENGLAND.  
 
RAIN CHANCES INCREASE FURTHER EAST FRIDAY NIGHT AS THE FRONT  
SAGS SOUTHWARD. TEMPERATURES THURSDAY THROUGH FRIDAY WILL RUN  
IN THE LOW TO MID 80S FOR HIGHS AND LOWS GENERALLY IN THE 60S,  
WITH NEAR 70 DEGREE READINGS FRIDAY NIGHT AHEAD OF THE FRONT.  
 

 
   
LONG TERM /SATURDAY THROUGH WEDNESDAY/
 
 
A COLD FRONT WILL BE MOVING SOUTHWARD ACROSS THE AREA ON  
SATURDAY. SHOWERS AND PERHAPS A FEW THUNDERSTORMS WILL BE  
POSSIBLE NEAR THE BOUNDARY. IT DOES APPEAR THE SURFACE BOUNDARY  
WILL MOVE SOUTH OF THE AREA BEFORE STALLING DURING THE LATTER  
PART OF THE WEEKEND, WHICH WILL PUT THE FORECAST AREA ON THE  
STABLE SIDE OF THE BOUNDARY. HOWEVER, THE FRONTAL ZONE ALOFT  
WILL LIKELY REMAIN NEAR OR PERHAPS EVEN NORTH OF THE AREA. AT  
THE SAME TIME, SURFACE HIGH PRESSURE WILL BE BUILDING OVER NEW  
ENGLAND, RESULTING IN A COLD AIR DAMMING PATTERN. ASSUMING THE  
FRONTAL ZONE ALOFT REMAINS NEARBY, MOIST ASCENT OVER THE SURFACE  
WEDGE WILL RESULT IN PLENTIFUL CLOUDS AND THE POTENTIAL FOR  
LIGHT TO MODERATE RAIN AT TIMES. TEMPERATURES (ESPECIALLY HIGHS)  
WILL LIKELY FALL BELOW NORMAL...AND THERE'S POTENTIAL HIGHS  
DON'T GET OUT OF THE 60S FOR SOME AREAS BY SUNDAY AND MONDAY. IT  
IS WORTH NOTING THAT THERE IS SOME POTENTIAL THE FRONTAL ZONE  
GETS FAR ENOUGH SOUTH AT SOME POINT TO PRECLUDE APPRECIABLE RAIN  
CHANCES, BUT IF THE PATTERN OVER THE PAST SEVERAL MONTHS  
INDICATES ANYTHING, THAT WON'T BE THE CASE.  
 
THE FRONTAL ZONE WILL BE LIFTING NORTH EARLY NEXT WEEK AS LOW  
PRESSURE MOVES THROUGH THE UPPER GREAT LAKES. IF/WHEN WE BREAK OUT  
OF THE SURFACE WEDGE, IT WILL RESULT IN A SLIGHT WARMING TREND.  
HOWEVER, MOIST SOUTHWEST FLOW AHEAD OF A BROAD TROUGH MOVING INTO  
THE PLAINS WILL CONTINUE TO RESULT IN CLOUDS AND CHANCES FOR SHOWERS  
AND SOME THUNDERSTORMS. THE NEXT COLD FRONT REMAINS WELL TO OUR  
NORTHWEST THROUGH WEDNESDAY, WITH ITS PASSAGE OCCURRING AFTER THE  
END OF THE FORECAST PERIOD. GIVEN THE MULTIPLE DAYS OF RAIN AND  
PRECIPITABLE WATER REBOUNDING TO 1.5-2.0 INCHES BY TUESDAY AND  
WEDNESDAY, SOME HYDRO CONCERNS ARE NOT OUT OF THE QUESTION.  
 

 
   
AVIATION /00Z THURSDAY THROUGH MONDAY/
 
 
PATCHY FOG IS LIKELY WEST OF I-95 TONIGHT, COULD BE LOCALLY  
DENSE ESPECIALLY INVOF MRB/CHO. LOW CLOUDS ALSO DEVELOPING OFF  
THE NEW JERSEY COAST WILL ADVECT SOUTHWEST TOWARDS TERMINALS  
EAST OF I-95 BY TOMORROW MORNING, AND COULD BRING CIGS DOWN TO  
NEAR IFR. CONDITIONS SHOULD IMPROVE BY MID MORNING.  
 
OTHERWISE, MAINLY VFR CONDITIONS EXPECTED AT ALL TERMINALS  
THROUGH THURSDAY NIGHT AS HIGH PRESSURE MOVES OVERHEAD.  
 
A COLD FRONT WILL APPROACH THE TERMINALS LATE FRIDAY AND FRIDAY  
NIGHT, INCREASING RAIN CHANCES. AT THIS TIME, MRB WOULD SERVE  
TO SEE THE HIGHEST CHANCE OF RESTRICTIONS WITH THE REMAINING  
TERMINALS LIKELY HOLDING OFF UNTIL SATURDAY MORNING. NORTHERLY  
BREEZES TODAY WILL SUBSIDE TONIGHT, VEERING SOUTHEASTERLY ON  
THURSDAY AT LESS THAN 10 KNOTS, THEN TURNING SOUTHERLY AND  
INCREASING ON FRIDAY AHEAD OF THE FRONT.  
 
THERE WILL BE A CHANCE OF SHOWERS AND PERHAPS A THUNDERSTORM AS A  
COLD FRONT DROPS INTO THE AREA THROUGH THE WEEKEND. THE FRONTAL  
ZONE WILL REMAIN NEARBY (PERHAPS FOCUSED OVER CENTRAL VA), AND  
SHOWERS MAY REDUCE VISIBILITY AT TIMES THROUGH THE PERIOD.  
CEILINGS MAY EVENTUALLY DROP BELOW VFR LEVELS AS WELL IN  
POSSIBLE COOL AIR WEDGE AS HIGH PRESSURE BUILDS TO THE NORTH.  
 

 
   
MARINE
 
 
WINDS HAVE DIMINISHED. SUB SCA CONDITIONS SHOULD PREVAIL THROUGH  
THURSDAY NIGHT. SCA CONDITIONS MAY RETURN ON FRIDAY AS SOUTHERLY  
FLOW INCREASES AHEAD OF A COLD FRONT APPROACHING FROM THE GREAT  
LAKES AND PENNSYLVANIA.  
 
THE COLD FRONT WILL DROP ACROSS THE WATERS ON SATURDAY, THEN  
STALL NEARBY THROUGH EARLY NEXT WEEK. THIS FRONT WILL BRING A  
WIND SHIFT TO THE NORTH, THEN EVENTUALLY EASTERLY. WINDS MAY BE  
THE STRONGEST MONDAY AS HIGH PRESSURE BUILDS INTO NEW ENGLAND.  
SHOWERS WILL BE POSSIBLE THROUGH THE PERIOD, WITH THE HIGHEST  
CHANCE OF THUNDERSTORMS (THOUGH STILL LOW) ON SATURDAY.  
 

 
   
TIDES/COASTAL FLOODING
 
 
ONSHORE FLOW WILL CAUSE TIDAL ANOMALIES TO INCREASE THURSDAY  
NIGHT INTO FRIDAY, POSSIBLY PERSISTING THROUGH THE WEEKEND. THIS  
WILL LIKELY LEAD TO A RENEWED THREAT FOR COASTAL FLOODING,  
ESPECIALLY GIVEN INCREASING ASTRONOMICAL TIDES.  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...NONE.  
MD...NONE.  
VA...NONE.  
WV...NONE.  
MARINE...NONE.  
 

 
 

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