169  
FXUS61 KLWX 240037  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
837 PM EDT WED SEP 23 2020  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL WEAKEN AND MOVE SOUTH OF THE AREA THROUGH  
TONIGHT, THEN MOVE OFFSHORE THURSDAY INTO FRIDAY. THE REMNANTS  
OF BETA WILL LIKELY PASS TO THE SOUTH WHILE WEAKENING FRIDAY  
INTO SATURDAY. A COUPLE COLD OF FRONTS ARE EXPECTED TO APPROACH  
FROM THE GREAT LAKES AND OHIO RIVER VALLEY LATE IN THE WEEKEND  
INTO EARLY NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
 
 
HIGH PRESSURE WILL REMAIN CENTERED TO THE SOUTH TONIGHT, AND A  
LIGHT WEST TO SOUTHWEST FLOW WILL ALLOW FOR MILDER CONDITIONS  
COMPARED TO RECENT NIGHTS.  
 
THE REMNANTS OF BETA WILL TRACK THROUGH THE MIDWEST, AND HIGH  
CLOUDS WILL INCREASE OVER THE AREA. LIGHT WINDS AND HIGHER  
DEWPOINTS RELATIVE TO THE LAST FEW NIGHTS MAY RESULT IN PATCHY  
FOG, MAINLY IN RIVER VALLEYS NEAR AND WEST OF THE BLUE RIDGE  
MOUNTAINS. WIDESPREAD FOG IS NOT EXPECTED DUE TO THE INCREASING  
HIGH CLOUDS AND STILL RELATIVELY HIGHER TEMP/DEWPOINT  
DEPRESSIONS THIS EVENING.  
 
LOW TEMPERATURES TONIGHT SHOULD GENERALLY BE IN THE 50S, EXCEPT  
LOWER TO MIDDLE 60S IN DOWNTOWN WASHINGTON AND BALTIMORE AND  
ALONG THE SHORES OF THE CHESAPEAKE BAY AND TIDAL POTOMAC RIVER.  
 

 
   
SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/
 
 
HIGH PRESSURE WILL SHIFT OFFSHORE THURSDAY. THIS WILL LEAD TO A  
LIGHT SOUTHWEST WIND. WARMING FROM THIS RETURN FLOW WILL BE OFFSET  
SOMEWHAT BY INCREASING MID AND HIGH LEVEL CLOUD COVER, RESULTING IN  
SIMILAR HIGH TEMPERATURES TO WEDNESDAY. HRRRX SMOKE PROGS SHOW SOME  
SMOKE MOVING BACK IN ALOFT WHICH MAY RESULT IN A HAZY APPEARANCE TO  
THE SKY THURSDAY, THOUGH THE BACKGROUND CLOUD COVER WILL PROBABLY  
MAKE THIS LESS NOTICEABLE.  
 
GUIDANCE HAS CONTINUED TO NUDGE NORTHWARD WITH RAIN SHOWER ACTIVITY  
TO CLOSE OUT THE WEEK, FOLLOWING THE LEAD OF THE EC GUIDANCE WHICH  
STARTED THIS SHIFT ABOUT 24 HOURS AGO. HAVE RAISED CHANCES FOR  
PRECIPITATION GENERALLY SOUTH OF I-70 FRIDAY AND FRIDAY NIGHT AS A  
RESULT. AT LEAST SOME MEASURABLE RAIN IS APPEARING INCREASINGLY  
LIKELY AT LEAST AS FAR NORTH AS US-50/I-66, THOUGH THE REMNANTS OF  
BETA CAUSING THIS POTENTIAL PRECIP WILL BE IN A WEAKENED STATE AND  
MOVING SWIFTLY TO OUR SOUTH. THIS SHOULD KEEP ANY FLOODING THREAT  
FROM FRESH WATER (RAIN) MINIMAL.  
 
HIGH TEMPERATURES FRIDAY WILL BE DEPENDENT ON THE EXTENT OF PRECIP  
BUT OVERALL SHOULD TREND SEVERAL DEGREES LOWER THAN THURSDAY.  
OVERNIGHT LOWS BOTH THURSDAY NIGHT AND FRIDAY NIGHT LOOK TO HOLD IN  
THE 50S TO LOWER 60S WITH GRADUALLY INCREASING HUMIDITY LEVELS.  
 

 
   
LONG TERM /SATURDAY THROUGH WEDNESDAY/
 
 
THE REMNANTS OF BETA WILL LIKELY MOVE OFFSHORE SATURDAY. WITH  
HIGH PRESSURE OFFSHORE, A PERSISTENT SOUTHERLY FLOW WILL BRING  
IN MOISTURE TO END THE WEEKEND AND CONTINUE INTO EARLY NEXT  
WEEK. HIGHS SATURDAY WILL REACH THE UPPER 70S TO NEAR 80. WHILE  
SUNDAY AND SUNDAY NIGHT LOOKS DRY, IT MAY BE SETTING THE STAGE  
FOR EARLY NEXT WEEK WITH A COUPLE COLD FRONTS. HIGHS SUNDAY  
COULD REACH THE LOWER 80S.  
 
AN UPPER-LEVEL TROUGH IS PROGGED TO STRENGTHEN OVER THE GREAT  
LAKES INTO THE THE MIDWEST AND EASTERN CONUS AS A CLOSED UPPER-  
LEVEL LOW DEVELOPS OVER CANADA. A COLD FRONT WILL ASSOCIATED  
WITH THE TROUGH IS LIKELY TO IMPACT THE AREA MONDAY, BRINGING  
THE CHANCE SHOWERS AND PERHAPS EVEN A THUNDERSTORM.  
 
NOTICEABLY COOLER CONDITIONS ARE EXPECTED FOR THE MIDDLE PORTION  
OF NEXT WEEK AS THE UPPER-LEVEL TROUGH REMAINS OVERHEAD. ANOTHER  
REINFORCING COLD FRONT MAY PASS THROUGH THE AREA TUESDAY AS  
WELL, BRINGING THE POTENTIAL FOR MORE UNSETTLED CONDITIONS.  
 
HEAVIER SHOWERS OR PERHAPS EVEN A STRONGER STORM CANNOT BE RULED  
OUT AHEAD OF THESE COLD FRONTS MONDAY AND TUESDAY, BUT  
CONFIDENCE IS LOW AT THIS TIME.  
 

 
   
AVIATION /01Z THURSDAY THROUGH MONDAY/
 
 
VFR EXPECTED AT ALL TAF SITES THRU THU EVE. LOWER CIGS AND PATCHY  
FOG ARE POSSIBLE MAINLY NEAR KCHO THU NIGHT-FRI NIGHT AS THE  
REMNANTS OF BETA PASS TO THE SOUTH. RAIN SHOWER ACTIVITY MAY MAKE IT  
AS FAR NORTH AS THE METRO TERMINALS FRI-FRI NIGHT.  
 
WINDS WILL SHIFT TO ABOUT 240-260 LATE THIS AFT/EARLY THIS EVE 5-10  
KTS THEN BECOME LIGHT/VARIABLE OVERNIGHT. S/SW FLOW 5-10 KTS  
EXPECTED THU-FRI.  
 
LOW CLOUDS AND PATCHY FOG AS WELL AS SHOWERS ARE POSSIBLE TO  
START SATURDAY, BUT CIGS SHOULD GRADUALLY INCREASE TO VFR  
LEVELS THROUGHOUT THE DAY. RADIATIONAL FOG IS POSSIBLE SATURDAY  
NIGHT INTO SUNDAY, BUT MOST OF THE TIME SHOULD TURN OUT VFR  
LATER SUNDAY MORNING THROUGH MONDAY. HOWEVER, A STRONGER COLD  
FRONT MAY TRIGGER SHOWERS AND PERHAPS A THUNDERSTORM MONDAY.  
 

 
   
MARINE
 
 
HIGH PRESSURE WILL SHIFT OFFSHORE THROUGH THURSDAY. WESTERLY  
WINDS WILL BECOME SOUTHERLY THROUGH THE END OF THE WEEK AT  
GENERALLY LESS THAN 15 KTS. GUSTS TO 20 KTS ARE POSSIBLE LATER  
FRIDAY AND FRIDAY NIGHT ESPECIALLY OVER THE LOWER TIDAL POTOMAC  
RIVER AND THE CHESAPEAKE BAY SOUTH OF NORTH BEACH MD AS WINDS  
TURN A BIT EAST OF SOUTH THANKS FOR THE REMNANTS OF BETA PASSING  
ACROSS SOUTHERN VIRGINIA. THIS REMNANT LOW MAY ALSO BRING  
SHOWERS TO THE WATERS FRIDAY INTO FRIDAY NIGHT.  
 
NO MARINE HAZARDS EXPECTED SATURDAY, BUT SOUTHERLY WINDS LATER  
SUNDAY AND SUNDAY NIGHT MAY APPROACH SCA CRITERIA AHEAD OF AN  
APPROACHING COLD FRONT.  
 

 
   
TIDES/COASTAL FLOODING
 
 
ANOMALIES AROUND 1 TO 1.25 FEET REMAIN TO OUR SOUTH THIS  
EVENING. WITH LIGHT WINDS TONIGHT THEN SOUTHERLY THURSDAY INTO  
FRIDAY, SOME OR ALL OF THIS EXCESS WATER WILL LIKELY RETURN  
NORTH. THEREFORE, MINOR FLOODING SEEMS PLAUSIBLE ESPECIALLY AT  
THE MORE VULNERABLE TIDE LOCATIONS (ANNAPOLIS, DC SW WATERFRONT,  
STRAITS POINT AND POSSIBLY BALTIMORE HARBOR). THE HIGHEST  
ASTRONOMICAL TIDES THE NEXT COUPLE DAYS ARE IN THE EVENING, AND  
IT IS AROUND THESE HIGH TIDES WHEN FLOODING WOULD BE MOST  
LIKELY.  
 
A COASTAL FLOOD ADVISORY IS IN EFFECT FOR ANNE ARUNDEL COUNTY  
TONIGHT, AND WASHINGTON DC WILL BE CLOSE. WILL CONTINUE TO  
MONITOR THE TIDAL ANOMALIES FOR WASHINGTON DC THROUGHOUT LATE  
THIS EVENING.  
 

 
   
EQUIPMENT
 
 
THE KLWX (STERLING, VA) WSR-88D REMAINS OUT OF SERVICE UNTIL FURTHER  
NOTICE. THE OUTAGE IS DUE TO A FAILURE WITHIN THE RADAR DATA  
ACQUISITION FUNCTIONAL AREA THAT OCCURRED EARLY IN THE MORNING ON  
SEPTEMBER 20, 2020.  
 
TECHNICIANS FROM THE NATIONAL WEATHER SERVICE RADAR OPERATIONS  
CENTER WILL ARRIVE IN STERLING ON SATURDAY, SEPTEMBER 26, TO  
DIAGNOSE THE FAILURE. AT THAT TIME, THEY WILL DETERMINE THE FULL  
SCOPE OF THE FAILURE, AND WORK WITH WFO STERLING ELECTRONICS PROGRAM  
STAFF IN TAKING SUBSEQUENT MAINTENANCE ACTIONS. ACTION AND DIAGNOSIS  
INCLUDES REPAIRING THE GEAR BOX AND ASSESSING THE HEALTH OF THE BULL-  
GEAR.  
 
USERS OF KLWX CAN UTILIZE ADJACENT WEATHER RADARS LOCATED IN DOVER  
DE (KDOX), MT. HOLLY NJ (KDIX), PITTSBURGH PA (KPBZ), CHARLESTON WV  
(KRLX), BLACKSBURG VA (KFCX), AND WAKEFIELD VA (KAKQ).  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...NONE.  
MD...COASTAL FLOOD ADVISORY UNTIL 3 AM EDT THURSDAY FOR MDZ014.  
VA...NONE.  
WV...NONE.  
MARINE...NONE.  
 

 
 

 
SYNOPSIS...BJL/DHOF  
NEAR TERM...BJL/DHOF  
SHORT TERM...DHOF  
LONG TERM...KLW  
AVIATION...BJL/KLW/DHOF  
MARINE...BJL/KLW/DHOF  
TIDES/COASTAL FLOODING...BJL/DHOF  
EQUIPMENT...DHOF/JEL  
 
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