430  
FXUS61 KLWX 210801  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
401 AM EDT MON OCT 21 2019  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL BRIEFLY BUILD OVER THE REGION TODAY AS THE  
REMNANTS OF NESTOR HEAD OUT TO SEA. A COLD FRONT WILL APPROACH  
FROM THE WEST TONIGHT BEFORE CROSSING THE REGION LATER TUESDAY  
INTO TUESDAY NIGHT. HIGH PRESSURE WILL BUILD BACK ACROSS THE  
REGION WEDNESDAY. ANOTHER STORM SYSTEM MAY APPROACH THE REGION  
DURING THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF EARLY THIS MORNING, NESTOR'S REMNANT LOW PRESSURE, STILL A  
POTENT EXTRATROPICAL SYSTEM, IS EAST OF OCEAN CITY MD AND  
CONTINUING TO HEAD OUT TO SEA. LOW LEVEL MOISTURE REMAINS HIGH,  
HOWEVER, AND LOW CLOUDS ARE PERSISTENT. THOSE FEW AREAS WHICH  
HAVE SEEN THE LOW CLOUDS BREAK HAVE SEEN PATCHY FOG DEVELOP, AND  
THIS RISK WILL CONTINUE UNTIL AFTER THE SUN RISES. THOSE AREAS  
WHICH REMAIN CLOUDY THROUGH SUNRISE SHOULD SEE THE CLOUDS  
GRADUALLY BREAK AS THE MORNING PROGRESSES THANKS TO A WEAK RIDGE  
OF HIGH PRESSURE BUILDING SOUTHWARD FROM SOUTHERN CANADA, SO  
MOST LOCATIONS SHOULD SEE MORE SUN THAN CLOUDS BY MID AFTERNOON.  
THE SUN WILL AID TEMP RISES, AND WE SHOULD REBOUND WELL INTO THE  
60S ACROSS MOST OF THE REGION, WITH SOME PLACES FLIRTING WITH  
70. WINDS WILL BE NORTHERLY THIS MORNING, BECOMING LIGHT AND  
VARIABLE BY AFTERNOON AS NESTOR'S INFLUENCE WANES.  
 
TONIGHT, MOST AREAS START OUT MOSTLY CLEAR, BUT THE APPROACHING  
SYSTEM FROM THE MIDWEST WILL BEGIN TO SPREAD HIGH CLOUDS ACROSS  
THE REGION. THE SOUTHEASTERLY FLOW WHICH WILL DEVELOP AHEAD OF  
THE SYSTEM WILL ALSO AID LOW-LEVEL MOISTURE ADVECTION, AND LOW  
CLOUDS ARE LIKELY TO DEVELOP TOO. THERE MAY EVEN BE SOME PATCHY  
FOG IN SPOTS, THOUGH IT IS MORE LIKELY TO BE MIST OR EVEN A  
LITTLE DRIZZLE LATER AT NIGHT. A FEW SHOWERS MIGHT REACH WESTERN  
ZONES BY NIGHT'S END, BUT MOST AREAS LIKELY STAY RELATIVELY DRY  
THROUGH TONIGHT. WITH THE SOUTHEASTERLY FLOW AND INCREASING  
CLOUDS, LOWS LIKELY STAY MILD, WITH 50S COMMON.  
 

 
   
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
 
 
COLD FRONT APPROACHING FROM THE WEST IS THE MAIN PLAYER IN THE  
SHORT TERM. GUIDANCE DEPICTS A NEUTRAL OR EVEN WEAKLY POSITIVELY  
TILTED TROUGH ALOFT WITH THE BEST FORCING STAYING NORTH. AT THE  
SURFACE, MOST MODELS DEPICT A WAVE FORMING ALONG THE FRONT TO  
THE SOUTH, WHICH MAY PASS OVER SOUTHERN MD AS THE SYSTEM CROSSES  
THE REGION, THOUGH IT ALSO MIGHT STAY JUST SOUTH. THE  
IMPLICATION HERE IS THAT WHILE RAIN SHOWERS ARE VERY LIKELY, AND  
THERE IS SOME SHEAR PRESENT, THE SURFACE INSTABILITY IS NOT  
SIGNIFICANT AND UPPER-LEVEL FORCING ALSO IS NOT PARTICULARLY  
HELPFUL. THUS, HAVE POPS GOING CATEGORICAL IN THE AFTERNOON AND  
EVENING FROM WEST TO EAST ACROSS THE CWA ON TUESDAY AS THE FRONT  
CROSSES THE REGION AND THE WAVE OF LOW PRESSURE MOVES ON BY, BUT  
HAVE HELD BACK ON ANY THUNDER MENTION THUS FAR. CAN'T RULE IT  
OUT COMPLETELY, BUT ODDS LOOK TO LOW TO INCLUDE IN MAIN FORECAST  
AT THIS POINT. OTHERWISE, THE RELATIVELY LATE ARRIVAL OF THE  
FRONT AND MILD START SHOULD ALLOW MOST OF THE REGION TO REBOUND  
INTO THE 60S BY AFTERNOON, THOUGH LIKELY IT WILL STAY A LITTLE  
COOLER THAN TODAY THANKS TO THE CLOUDS.  
 
FRONT SWEEPS THROUGH DURING THE EVENING AND COOLER AIR MOVES ON  
IN, WITH THE RAIN SHOWERS QUICKLY ENDING. IT WILL BE BREEZY AS  
WELL, BUT NOT PARTICULARLY WINDY BEHIND THIS ONE. HIGH PRESSURE  
WILL THEN DOMINATE THROUGH THE FOLLOWING 24 HOURS, BUT WITH THE  
CENTER STAYING WELL SOUTH, DOWNSLOPE FLOW AND RELATIVELY MILD  
AIR FLOWING OVER THE TOP OF THE HIGH SHOULD KEEP TEMPS FAIRLY  
BENIGN, WITH 60S EXPECTED ONCE AGAIN WEDNESDAY. SOME LOWS MAY  
REACH THE 30S WEDNESDAY NIGHT IN THE COLDER LOCALES, BUT THINK  
IT WON'T BE QUITE AS COLD AS FRIDAY NIGHT WAS. WITH MANY OF OUR  
COLDER ZONES NOW CLEARED FROM FURTHER FROST/FREEZE HEADLINES  
THANKS TO THE WIDESPREAD FREEZE ON FRIDAY NIGHT, DO NOT  
CURRENTLY ANTICIPATE WIDESPREAD FROST/FREEZE HEADLINES FOR  
WEDNESDAY NIGHT.  
 

 
   
LONG TERM /THURSDAY THROUGH SUNDAY/
 
 
SPRAWLING HIGH PRESSURE WILL BUILD FROM THE TENNESSEE VALLEY  
ACROSS THE MID-ATLANTIC THURSDAY INTO FRIDAY WITH MAINLY DRY  
WEATHER ANTICIPATED, THOUGH A WEAK SHORTWAVE LIKELY SWINGS BY TO  
OUR NORTH ON FRIDAY WITH A BIT OF AN INCREASE IN CLOUDS,  
ESPECIALLY NEAR THE MASON-DIXON LINE. HIGH TEMPERATURES  
GENERALLY 65-70 EXPECTED LATE THIS WEEK, WHICH IS RIGHT AROUND  
NORMAL FOR LATE OCTOBER.  
 
MODEL TIMING DISCREPANCIES CONTINUE FOR THE POTENTIAL STORM  
SYSTEM NEXT WEEKEND, THOUGH HAVE MOSTLY BACKED OFF PRECIP  
CHANCES FOR FRIDAY (EXCEPT FOR GFS/GEFS). HAVE FOCUSED POPS  
SATURDAY NIGHT INTO SUNDAY. TIMING UNCERTAINTIES STEM FROM WHEN  
AN UPPER TROUGH APPROACHES FROM THE WEST, WHICH WILL DEPEND ON  
WHETHER OR NOT IT REMAINS ATTACHED TO LARGER SCALE WESTERLY FLOW  
(QUICKER PROGRESSION, TRENDING LESS LIKELY) OR CUTS OFF (SLOWER  
EASTWARD PROGRESSION, TRENDING MORE LIKELY).  
 

 
   
AVIATION /08Z MONDAY THROUGH FRIDAY/
 
 
LOW CIGS IN THE MVFR RANGE LIKELY LINGER INTO THE MORNING HOURS,  
AND LOCATIONS WHICH SEE BREAKS (I.E., CHO) WILL THEN RUN THE  
RISK OF IFR VSBY WITH FOG DEVELOPING. IMPROVEMENT LOOKS LIKELY  
BY LATE MORNING WITH VFR BY EARLY AFTERNOON AT LATEST. HOWEVER,  
SOUTHEASTERLY FLOW MAY BRING LOW CIGS BACK TO THE REGION LATER  
TONIGHT WHICH COULD PERSIST MOST OF TUESDAY INTO TUESDAY  
EVENING, ACCOMPANIED BY SHOWERS BY TUESDAY AFTERNOON. VFR LIKELY  
RETURNS BEHIND A COLD FRONT TUESDAY NIGHT, WHICH SHOULD PERSIST  
UNDER HIGH PRESSURE THROUGH WEDNESDAY NIGHT.  
 
VFR EXPECTED IN SW FLOW THU-FRI.  
 

 
   
MARINE
 
 
SCA GRADUALLY WINDING DOWN EARLY THIS MORNING AS NESTOR'S  
REMNANTS SLOWLY HEAD OUT TO SEA. EXPECT ALL HEADLINES GONE BY  
NOON IF NOT SOONER. LIGHT WINDS LIKELY TONIGHT UNDER HIGH  
PRESSURE, BUT SCA MAY DEVELOP JUST AHEAD OF A COLD FRONT TUESDAY  
AFTERNOON. SCA THEN MORE LIKELY BEHIND THE FRONT TUESDAY NIGHT  
INTO WEDNESDAY BEFORE DROPPING OFF BY WEDNESDAY NIGHT.  
 
GRADIENT SHOULD REMAIN LIGHT ENOUGH TO PRECLUDE ANY SCA LEVEL  
WINDS THURSDAY INTO FRIDAY AS HIGH PRESSURE BUILDS OVERHEAD.  
 

 
   
TIDES/COASTAL FLOODING
 
 
WATER LEVELS HAVE DECREASED ON NORTHEAST TO NORTH FLOW, BUT  
WATER REMAINS PILED (ANOMALIES OF +1.5) AT THE MOUTH OF THE  
CHESAPEAKE BAY. THIS WATER WILL RETURN NORTHWARD THROUGH TUESDAY  
AS WINDS BECOME SOUTHEASTERLY, WHICH WILL LIKELY RESULT IN  
WIDESPREAD MINOR TO PERHAPS NEAR MODERATE FLOODING (MOST LIKELY  
MODERATE FLOODING WOULD BE AT STRAITS POINT AND ANNAPOLIS,  
SLIGHTLY LESS LIKELY BUT NOT OUT OF THE REALM OF POSSIBILITY  
NEAR DC/BALTIMORE).  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...NONE.  
MD...NONE.  
VA...NONE.  
WV...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 9 AM EDT THIS MORNING FOR ANZ532-  
533-539>542.  
SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ534-537-543.  
SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR  
ANZ531.  
 

 
 

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