534  
FXUS61 KLWX 240041  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
841 PM EDT SAT SEP 23 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL REMAIN IN PLACE THROUGH THE WEEKEND AND THE  
FIRST PART OF THE WEEK. THIS WILL SLOWLY WEAKEN ITS GRIP OVER  
THE AREA BY THE MIDWEEK AS HURRICANE MARIA MOVES NORTHWARD  
THROUGH THE WESTERN ATLANTIC.  
 

 
   
NEAR TERM /TONIGHT/
 
 
 
HIGH PRESSURE IN CONTROL OF THE SYNOPTIC PATTERN BOTH AT THE  
SURFACE AND ALOFT. ANTICIPATE THAT TONIGHT'S WEATHER WILL BE  
COMPARABLE TO LAST NIGHT. GUIDANCE BACKING OFF SLIGHTLY ON FOG  
COVERAGE, WHICH IS SLIGHTLY CURIOUS. WOULD THINK THAT VIRGINIA  
WOULD BE PREFERRED DUE TO LIGHT ONSHORE FLOW. AM CARRYING PATCHY  
COVERAGE, FAVORING THE VALLEYS OF THE PIEDMONT AND FOOTHILLS.  
LOWS IN THE MID 50S-LOWER 60S, EXCEPT 65-70 IN THE URBAN  
CENTERS.  
 

 
   
SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/
 
 
THE SYNOPTIC PATTERN WILL CHANGE LITTLE SUNDAY AND MONDAY. IF  
ANYTHING, RIDGING ALOFT WILL ONLY GROW STRONGER UNTIL A WEAKNESS  
EMERGES AS A RESULT OF MARIA. A SLIGHT WARMING SURFACE THROUGH  
925 MB SUGGESTS THAT UPPER 80S/NEAR 90 WILL BE WITHIN REACH  
SUNDAY AFTERNOON. HIGHS MAY RETREAT A DEGREE OR SO BY MONDAY.  
 
LATEST GUIDANCE DOES SUGGEST THAT MARIA WILL BE APPROACHING THE  
NC COAST TUESDAY. IT IS UNCLEAR HOW CLOSE OR WHAT THE FULL  
IMPACTS WILL BE, ALTHOUGH THEY LIKELY WILL BE MINIMAL THROUGH  
MONDAY NIGHT. HAVE INCREASED CLOUD COVER AND POPS MONDAY  
NIGHT...BUT ONLY ENOUGH FOR PARTLY CLOUDY SKIES AND A SLIGHT  
CHANCE OF PRECIP OVER THE TIP OF SOUTHERN MARYLAND. CONSULT THE  
LATEST BULLETINS FROM NHC ON THE LATEST THINKING ON THE PROGRESS  
OF MARIA.  
 

 
   
LONG TERM /TUESDAY THROUGH SATURDAY/
 
 
HIGH PRESSURE ON THE SURFACE AN ALOFT WILL ALLOW FOR DRY  
CONDITIONS OVER THE REGION PART OF TUESDAY. AT THE SAME TIME  
HURRICANE MARIA WILL BE MOVING NORTH-NORTHWEST TUESDAY.  
GUIDANCE SUGGESTS THAT MARIA WILL GET CLOSE TO THE NC OUTER  
BANKS AND IT WILL STALL THERE TUESDAY NIGHT INTO MAYBE THURSDAY  
WHEN AN UPPER TROUGH/COLD FRONT PUSHES IT OUT TO SEA. MOST  
GUIDANCE DOES NOT SHOW SIGNIFICANT IMPACT TO OUR REGION. PLEASE  
VISIT THE NATIONAL HURRICANE CENTER'S WEBSITE HURRICANES.GOV  
FOR MORE INFORMATION.  
 
THE COLD FRONT THAT IS EXPECTED TO MOVE THROUGH OUR CWA THURSDAY  
WILL INCREASING THE CHANCE OF SHOWERS OVER OUR AREA. DRY  
CONDITIONS RETURN BEHIND IT LATER THURSDAY AND FRIDAY. ANOTHER  
FRONT APPROACHES SATURDAY.  
 

 
   
AVIATION /01Z SUNDAY THROUGH THURSDAY/
 
 
VFR FLIGHT CONDITIONS WILL PREVAIL FOR THE VALID TAF PERIOD,  
ASIDE FROM EARLY MORNING FOG CONCERNS. CHO/MRB TERMINALS WILL BE  
THE MOST IMPACTED. AM FORECASTING MVFR AT THIS POINT. IFR  
POSSIBLE, BUT ITS LIKELY TO BE BRIEF AND WOULD BE TOUGH TO  
PINPOINT.  
 
THE PATTERN WILL BE SIMILAR THROUGH MONDAY. THERE MAY BE AN  
INCREASE IN CLOUD COVER ON MONDAY NIGHT IN ADVANCE OF MARIA; ITS  
EXTENT UNCLEAR AT THIS POINT.  
 
MAINLY VFR CONDITIONS EXPECTED TUESDAY INTO THURSDAY BUT SOME  
SUB-VFR CONDITIONS POSSIBLE LATER WITH MAYBE SOME SHOWERS  
AROUND. A FURTHER DEVIATION NORTHWEST IN THE TRACK OF MARIA  
COULD BRING WORSE CONDITIONS.  
 

 
   
MARINE
 
 
LIGHT NORTH FLOW (10 KT OR LESS) WILL PREVAIL THORUGH MONDAY  
NIGHT. WIND GUSTS INCREASE TUESDAY INTO THURSDAY WITH HURRICANE  
MARIA OVER THE WEST ATLANTIC OCEAN. SMALL CRAFT ADVISORY  
ANTICIPATED. IF THE STORM'S TRACK DEVIATES FURTHER NORTHWEST,  
MORE SIGNIFICANT IMPACTS ARE POSSIBLE (THOUGH NOT LIKELY). REFER  
TO LATEST NHC STATEMENTS FOR UP- TO-DATE INFORMATION ON MARIA.  
 

 
   
TIDES/COASTAL FLOODING
 
 
WATER LEVELS REMAIN BETWEEN A FOOT AND A FOOT AND A HALF ABOVE  
ASTRONOMICAL NORMALS. THERE HAS BEEN A SLIGHT WEAKENING IN THIS  
INFLUX THOUGH, SOMETHING THAT GUIDANCE SUGGESTS WILL CONTINUE.  
WHILE THE PATTERN WILL SUPPORT MINOR INUNDATION FOR SEVERAL  
DAYS, CONFIDENCE IN ANY INUNDATION IS HIGHEST FOR THE UPCOMING  
TIDE CYCLE. ENSEMBLE GUIDANCE SUPPORTS THIS APPROACH.  
 
ADVISORY IN EFFECT FOR THE OVERNIGHT CYCLE FOR DC/ALEXANDRIA  
AND ANNAPOLIS, AND THROUGH SUNDAY MORNING FOR ST MARYS AND  
CALVERT.  
 
BEYOND THAT, WILL NEED TO MONITOR TRENDS AND LATEST GUIDANCE.  
ANTICIPATE THE THREAT OF MINOR INUNDATION AT SENSITIVE  
LOCATIONS WILL BE AN ISSUE FOR SEVERAL DAYS AT LEAST.  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...COASTAL FLOOD ADVISORY UNTIL 2 AM EDT SUNDAY FOR DCZ001.  
MD...COASTAL FLOOD ADVISORY UNTIL 8 AM EDT SUNDAY FOR MDZ017-018.  
COASTAL FLOOD ADVISORY UNTIL 1 AM EDT SUNDAY FOR MDZ014.  
VA...COASTAL FLOOD ADVISORY UNTIL 2 AM EDT SUNDAY FOR VAZ054.  
WV...NONE.  
MARINE...NONE.  
 

 
 

 
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