858  
FXUS61 KLWX 270051  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
851 PM EDT TUE MAY 26 2020  
   
SYNOPSIS
 
 
HIGH PRESSURE REMAINS IN THE WESTERN ATLANTIC THROUGH  
WEDNESDAY. A TROPICAL DISTURBANCE NEAR THE SOUTHEAST U.S. COAST  
ON WEDNESDAY MORNING WILL MOVE NORTH THROUGH THE APPALACHAINS  
BY THURSDAY MORNING, AND REPLACED BY SLOW MOVING UPPER LEVEL  
TROUGH WHICH LINGERS ACROSS THE CWA THROUGH FRIDAY NIGHT. A  
COLD FRONT WILL MOVE THROUGH OUR REGION FROM THE WEST EARLY  
SATURDAY. HIGH PRESSURE BUILDS INTO THE REGION SUNDAY AND  
REMAINS THROUGH EARLY NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH WEDNESDAY/
 
 
THE CWA IS CAUGHT BETWEEN THE OFFSHORE SURFACE HIGH AND THE  
TROPICAL DISTURBANCE THAT'S WELL TO THE SOUTH; HOWEVER, THE LONG  
SE FETCH WILL CONTINUE TO PUMP MOISTURE INTO THE REGION. AS OF  
THIS EVENING, SATELLITE IMAGERY IS SHOWING HIGH CLOUDS WELL  
AHEAD OF THE TROPICAL DISTURBANCE MOVING INTO THE AREA. ALSO, A  
STRATUS DECK IS APPROACHING FROM THE EASTERN SHORE.  
 
HIGH CLOUDS WILL CONTINUE TO MOVE INTO THE AREA TONIGHT, AND  
WITH A PERSISTENT ONSHORE FLOW, LOW CLOUDS AND AREAS OF DRIZZLE/FOG  
SHOULD SPREAD OVER THE AREA AFTER MIDNIGHT. FOG MAY BE LOCALLY  
DENSE AND ANOTHER DENSE FOG ADVISORY MAY BE NEEDED LATE TONIGHT  
INTO WEDNESDAY MORNING AS MOISTURE GETS TRAPPED UNDERNEATH THE  
NOCTURNAL AND SUBSIDENCE INVERSIONS.  
 
WITH BOTH WARM AIR AND MOISTURE ADVECTION ON WEDNESDAY,  
SCATTERED SHOWERS SHOULD BE DEVELOPING TOMORROW MORNING ACROSS  
THE SOUTHERN PORTION OF THE CWA, AND SPREADING ACROSS THE  
REGION BY LATE AFTERNOON. DO NOT ANTICIPATE TOMORROW TO BE A  
WASHOUT, AS WE'LL WAIT FOR WEDNESDAY NIGHT AND THURSDAY FOR THAT  
POSSIBILITY.  
 

 
   
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/
 
 
HIGHER PRECIPITABLE WATER WITH VALUES AOA 1.5 INCHES CWA-WIDE  
MOVES INTO THE REGION WEDNESDAY EVENING. THESE VALUES ARE EVEN  
GREATER IN THE SW PORTION OF OUR CWA, RISING TO AS MUCH AS 2.0  
INCHES ALONG THE CHESAPEAKE BAY PER THE 26/12Z ECMWF. SHOWERS  
WILL BECOME MORE NUMEROUS AFTER MIDNIGHT WEDNESDAY NIGHT, AND AM  
LOOKING FOR TWO AREAS OF HEAVIER RAINFALL LATE WEDNESDAY NIGHT:  
ONE IN THE SW PORTION OF THE CWA, FOLLOWED BY AN AXIS OF HEAVIER  
RAINFALL ASSOCIATED WITH THE HIGH PWS AND PVA ALONG AND EAST OF  
I-95 TOWARDS DAWN THURSDAY AND LASTING THROUGH THE AFTERNOON.  
ANY SHOWER COULD PRODUCE LOCALLY HEAVY RAINFALL LATE WED NIGHT  
AND THURSDAY, ESPECIALLY DURING THE AFTERNOON HOURS ALONG AND  
EAST OF INTERSTATE 95 WHERE MOISTURE IS MAXIMIZED.  
 

 
   
LONG TERM /FRIDAY THROUGH TUESDAY/
 
 
A POTENT SHORTWAVE WILL DESCEND INTO THE GREAT LAKES ON FRIDAY.  
FURTHER TO THE SOUTH, A DECAYING UPPER LOW WILL THIN OUT INTO AN  
OPEN WAVE AND GRADUALLY BECOME ABSORBED INTO THE LARGER TROUGH  
SITUATED TO OUR NORTHWEST. AS THIS PROCESS OCCURS, THE NORTHERN  
STREAM SYSTEM WILL DRIVE A COLD FRONT SOUTHWARD TOWARD OUR REGION.  
WHILE OUR AREA WON'T BE SITUATED BENEATH THE STRONGEST FORCING FOR  
ASCENT AT UPPER LEVELS, OR IMMEDIATELY AHEAD OF THE SURFACE COLD  
FRONT, GRADUAL HEIGHT FALLS WILL BE OCCURRING ALOFT. WITH WARM AND  
HUMID AIR IN PLACE AT THE SURFACE, THE HEIGHT FALLS IN THE PRESENCE  
OF AN UNSTABLE AIRMASS SHOULD BE SUFFICIENT TO SPARK THE DEVELOPMENT  
OF SHOWERS AND THUNDERSTORMS, ESPECIALLY DURING THE AFTERNOON AND  
EVENING HOURS. GUIDANCE HAS TRENDED DOWNWARD WITH QPF TOTALS ACROSS  
THE AREA, SUGGESTING POTENTIALLY LOWER AREAL COVERAGE OF STORMS.  
STILL THINK THERE WILL BE AT LEAST SOME THREAT FOR LOCALIZED  
FLOODING FOLLOWING A SOAKING RAINFALL ON THURSDAY. PRECIPITABLE  
WATER VALUES WILL BE AROUND 1.5-2 INCHES, SUGGESTING THAT ANY STORMS  
THAT DO FORM ON FRIDAY COULD BE EFFICIENT HEAVY RAINFALL PRODUCERS.  
A STRONGER STORM OR TWO CAN'T BE RULED OUT EITHER, WITH MLCAPE  
VALUES INCREASING TO AROUND 1000 J/KG AND AROUND 20-35 KNOTS OF 0-6  
KM SHEAR IN PLACE. OUTSIDE OF THE THUNDERSTORM ACTIVITY, CONDITIONS  
WILL BE VERY WARM AND HUMID, WITH HIGHS IN THE MID 80S AND DEWPOINTS  
IN THE UPPER 60S TO LOWER 70S.  
 
SATURDAY'S FORECAST WILL LARGELY DEPEND ON THE SOUTHWARD PROGRESSION  
OF THE AFOREMENTIONED SYSTEM'S COLD FRONT. 12Z GUIDANCE HAS THUS FAR  
TRENDED FASTER WITH RESPECT TO THE PROGRESSION OF THE FRONT, WHICH  
WOULD SUGGEST LOWER CHANCES FOR SHOWERS AND STORMS. HOWEVER, THERE'S  
STILL ENOUGH SPREAD IN THE GUIDANCE, THAT LINGERING SHOWERS AND  
STORMS CAN'T BE RULED OUT, ESPECIALLY DURING THE MORNING HOURS. IF  
THE FRONT WERE TO HOLD TO OUR NORTH, THERE COULD ONCE AGAIN BE A  
THREAT FOR LOCALIZED FLOODING OR A STRONGER AFTERNOON STORM, BUT THE  
TREND SEEMS TO BE MOVING AWAY FROM THIS SOLUTION.  
 
A MUCH COOLER AND DRIER AIRMASS WILL WORK IN BEHIND THE FRONT FOR  
SUNDAY AND MONDAY AS UPPER LEVEL TROUGHING DIGS INTO THE EASTERN US.  
MOSTLY SUNNY SKIES ARE EXPECTED, ALONG WITH HIGHS IN THE UPPER 60S  
TO LOWER 70S, AND DEWPOINTS IN THE 40S.  
 

 
   
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
 
 
VFR FOR MOST OF THE TERMINALS THROUGH MIDNIGHT, THEN CONDITIONS  
DETERIORATE TO AOB IFR AFTER MIDNIGHT WITH LOW CIGS LIKELY AND  
POSSIBILITY OF LOW VSBY AND DRIZZLE. THESE IFR CONDITIONS WILL  
LIKELY LAST THROUGH MID- MORNING WEDNESDAY. SUBIFR CONDITIONS  
ARE ALSO POSSIBLE DURING THIS TIME. CIGS/VSBYS SHOULD GRADUALLY  
IMPROVE TO VFR LEVELS LATE IN THE MORNING INTO THE AFTERNOON,  
BUT SCATTERED SHOWERS ARE POSSIBLE THROUGHOUT THE DAY.  
 
SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE FRIDAY INTO FRIDAY  
NIGHT. A COLD FRONT WILL PROGRESS THROUGH THE AREA LATE FRIDAY  
NIGHT INTO SATURDAY. DEPENDING ON THE PROGRESSION OF THE FRONT,  
SHOWERS AND THUNDERSTORMS MAY BE POSSIBLE AGAIN ON SATURDAY, BUT  
THE TREND HAS BEEN FOR THE FRONT TO CLEAR THE AREA EARLIER,  
WHICH WOULD IN TURN LEAD TO DRIER CONDITIONS.  
 

 
   
MARINE
 
 
A SOUTHEAST FLOW WILL CONTINUE THROUGH WEDNESDAY NIGHT, BUT  
WINDS WILL REMAIN BELOW SCA CRITERIA FOR MOST OF THE TIME. FOG  
IS EXPECTED TO DEVELOP TONIGHT ACROSS THE MARYLAND PORTION OF  
THE CHESAPEAKE, REDUCING VSBY BELOW 1 MILES ON THE WATER, AND  
CONTINUE THROUGH MUCH OF THE DAY WEDNESDAY AS DEWPOINTS RISE TO  
MEET OR EXCEED THE WATER TEMPERATURE.  
 
ON THURSDAY, A LOW LEVEL JET WITH 35KTS AT 2.5KFT ON THURSDAY  
IS APPARENT ON THE 12Z BUFKIT PROFILE FOR BWI, BUT IT IS ABOVE  
THE INVERSION. HOWEVER, THE POTENTIAL FOR IT TO MIX DOWN IN  
HEAVIER SHOWERS IS THERE, AND SCA MAY BE REQUIRED THURSDAY.  
 
WINDS MAY APPROACH SCA LEVELS ON FRIDAY IN SOUTHERLY FLOW, BUT  
ARE EXPECTED TO REMAIN MOSTLY SUB- SCA IN MAGNITUDE.  
THUNDERSTORMS WILL BE POSSIBLE OVER THE WATERS FRIDAY INTO  
FRIDAY NIGHT, WITH THE HIGHEST COVERAGE OF STORMS OCCURRING  
DURING THE AFTERNOON AND EVENING HOURS. GUSTY WINDS WILL BE  
POSSIBLE IN ASSOCIATION WITH ANY OF THESE THUNDERSTORMS.  
DEPENDING ON THE PROGRESSION OF THE SYSTEM'S COLD FRONT, SHOWERS  
AND THUNDERSTORMS MAY BE POSSIBLE AGAIN ON SATURDAY. HOWEVER,  
THE TREND HAS BEEN FOR THE COLD FRONT TO MOVE THROUGH QUICKER,  
WHICH WOULD LEAD TO DRIER CONDITIONS.  
 

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

 
 

 
SYNOPSIS...LEE  
NEAR TERM...BJL/LEE  
SHORT TERM...BJL/LEE  
LONG TERM...KJP  
AVIATION...BJL/LEE/KJP  
MARINE...BJL/LEE/KJP  
 
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