838  
FXUS61 KLWX 151854  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
254 PM EDT SUN JUL 15 2018  
   
SYNOPSIS
 
 
HIGH PRESSURE OFF THE CAROLINA COAST WILL REMAIN OVER THE  
WESTERN ATLANTIC THROUGH MONDAY. A COLD FRONT IS POISED TO  
PASS THROUGH THE AREA LATE TUESDAY, WITH HIGH PRESSURE BUILDING  
INTO THE REGION IN ITS WAKE THEN MIGRATING EAST OF CAPE COD LATE  
WEEK.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
SCATTERED SHOWERS AND STORMS HAVE DEVELOPED ACROSS THE CWA, WITH  
MLCAPE 1500-2000 J/KG WEST OF THE BLUE RIDGE, AND 20-25KTS  
EFFECTIVE BULK SHEAR. SATELLITE IS SHOWING THICK, HIGH CLOUDS  
REGION-WIDE, WHICH HAS LIMITED HEATING THIS AFTERNOON. STORMS  
WILL BE SCATTERED THROUGH EARLY EVENING, AND PERHAPS ONE OR TWO  
MAY BECOME SEVERE, PARTICULARLY WEST OF THE BLUE RIDGE.  
HOWEVER, WITH THE MID CLOUD AND RAINFALL FROM THE CONVECTION  
EARLIER TODAY, THE BOUNDARY LAYER SHOULD STABILIZE PREVENTING  
WIND GUSTS TO GET FROM THE SURFACE EAST OF I-95. ADDITIONALLY,  
THE 17Z HRRR HAS THE CONVECTION MAINLY WEST OF THE BLUE RIDGE  
AND DYING OFF RAPIDLY AFTER 6 PM.  
 
EXPECTING CONVECTION TO RAPIDLY QUIET DOWN EARLY THIS EVENING,  
BUT MID-TO-HIGH CLOUDS WILL PERSIST OVERNIGHT. AREAS THAT  
RECEIVED RAINFALL THIS AFTERNOON AND EVENING WILL LIKELY SEE FOG  
DEVELOPMENT TONIGHT; ADDITIONALLY, WITH STRONG SURFACE MOISTURE  
ADVECTION, USUAL VALLEY LOCATIONS SUCH AS AROUND CHO AND MRB  
WILL LIKE SEE FOG DEVELOPING AFTER MIDNIGHT. OVERNIGHT TEMPS  
WILL BE SLIGHTLY ABOVE NORMAL WITH THE HIGHER DEWPOINTS.  
 

 
   
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
 
 
MONDAY WILL SEE INCREASING CHANCES OF CONVECTION AS ADDITIONAL  
HEAT AND HUMIDITY BUILD BACK INTO THE REGION. CONVECTION SHOULD  
BE MINIMAL UNTIL NOONTIME, WHEN CAM MODELS SUCH AS THE HREF SHOW  
MEAN SURFACE CAPE IN THE 2000-3000 J/KG RANGE IN THE AFTERNOON.  
EXPECTING LESS CLOUD COVER TOMORROW THAN WE HAD TODAY (SUNDAY),  
SO AFTERNOON MAX TEMPS SHOULD ONCE AGAIN BE IN THE LOWER 90S,  
WITH THE MID 90S IN THE I-95 CORRIDOR, WHICH WILL AID IN  
CONVECTIVE DEVELOPMENT.  
 
TUESDAY A COLD FRONT WILL APPROACH FROM THE WEST, AND AHEAD OF  
IT MOISTURE WILL CONTINUE TO INCREASE. THE 12Z NAM HAS  
PRECIPITABLE WATER FORECASTS GREATER THAN 2.25", AND THE NAEFS  
HAS THAT PARAMETER MAXING OUT FROM A CLIMATOLOGICAL  
PERSPECTIVE. ADDITIONALLY, BUFKT PROFILE SOUNDINGS FROM THE NAM  
SHOW THE POTENTIAL FOR SLOW MOVING, TRAINING CELLS WITH MBE  
VELOCITY VECTORS AT OR BELOW 10 KTS. DESPITE THE DRY CONDITIONS  
OVER THE PAST COUPLE OF WEEKS, FLASH FLOOD WATCHES MAY NEED TO  
BE CONSIDERED FOR TUESDAY AFTERNOON PRIOR TO THE COLD FRONTAL  
PASSAGE WITH THE COMBINATION OF MOISTURE AVAILABILITY, LIFT FROM  
THE FRONT, AND SLOW MOVING MESO BETA CONVECTIVE ELEMENTS. THE  
BULK OF THE STORMS TUESDAY SHOULD FALL BETWEEN NOON AND 6 PM,  
AS THE COLD FRONT IS PROGGED TO BE SOUTHEAST OF WASHINGTON DC  
METRO BY MID- EVENING TUESDAY AS DEPICTED BY THE 12Z ECMWF.  
 

 
   
LONG TERM /WEDNESDAY THROUGH SUNDAY/
 
 
HIGH PRESSURE WILL BUILD OVERHEAD ON WEDNESDAY, AND REMAIN OVER  
THE REGION THROUGH THURSDAY. EXPECT DRY AND MUCH LESS HUMID  
CONDITIONS TO BE THE RESULT. MAX TEMPERATURES CAN ALSO BE  
EXPECTED AROUND, TO JUST BELOW SEASONAL AVERAGES, WITH HIGHS  
EXPECTED TO BE IN THE MID 80S ACROSS THE REGION. CLEAR SKIES AND  
LOW TEMPERATURES IN THE LOW TO MID 60S CAN ALSO BE EXPECTED  
BOTH WEDNESDAY AND THURSDAY NIGHT.  
 
THE HIGH PRESSURE LOOKS TO MOVE OFF OF THE NORTHEAST COAST THURSDAY  
NIGHT INTO FRIDAY, WHICH WILL SHIFT WINDS TO EASTERLY. EARLY IN THE  
DAY, RAIN CHANCES LOOK TO REMAIN FAIRLY SLIM FOR MUCH OF THE REGION,  
THOUGH THE HUMIDITY MAY BEGIN TO CREEP UP THANKS TO RETURN FLOW FROM  
THE DEPARTING SURFACE HIGH. HIGH TEMPERATURES SHOULD AGAIN REMAIN IN  
THE MID 80S, WITH OVERNIGHT LOWS IN THE MID 60S.  
 
LATER IN THE DAY FRIDAY, THINGS BECOME A LITTLE MORE UNCLEAR AT THIS  
TIME. THE LATEST RUNS OF BOTH THE OPERATIONAL GFS AND EURO SHOW TWO  
SURFACE LOWS THAT COULD AFFECT THE REGION LATE FRIDAY THROUGH THE  
WEEKEND. THE FIRST OF WHICH FORMS OVER THE GREAT LAKES REGION, WHICH  
THE GFS SHOWS HAVING MORE OF AN IMPACT ON OUR AREA. THE GFS BRINGS  
THE COLD FRONT ASSOCIATED WITH THIS SYSTEM TOWARDS THE REGION ON  
SATURDAY, EVENTUALLY MOVING THROUGH THE REGION SUNDAY. THE  
ASSOCIATED SOUTHERLY FLOW WOULD BRING IN ABUNDANT MOISTURE TO THE  
REGION. THEN, THERE SHOULD BE PLENTY OF UPPER LEVEL FORCING TO AID  
IN SHOWER AND THUNDERSTORM DEVELOPMENT, THANKS TO A VERY STRONG  
CUTOFF UPPER LOW OVER THE NORTHERN GREAT LAKES. THE SECOND SYSTEM IS  
A COASTAL LOW THAT BEGINS FORMING ON FRIDAY ALONG A STALLED FRONT  
OFF THE SOUTHEAST COAST. THE SYSTEM LOOKS TO SLIDE NORTH ALONG THE  
EAST COAST THROUGH THE DAY ON SATURDAY. THIS WOULD ONLY ADD TO THE  
MOISTURE IN THE REGION. THE EURO HAS A SLIGHTLY MORE QPF OVER OUR  
REGION ASSOCIATED WITH THIS SYSTEM, EVEN THOUGH BOTH HAVE PRETTY  
SIMILAR TRACKS AND INTENSITIES OF THIS PARTICULAR SYSTEM. THE KEY  
TAKEAWAY FROM THIS IS THAT THE PATTERN IS BECOMING MORE ACTIVE  
AGAIN, AND THE WEEKEND IS LOOKING WET, SO CHANCE POPS WILL BE IN THE  
FORECAST FRIDAY NIGHT THROUGH SUNDAY FOR NOW.  
 

 
   
AVIATION /18Z SUNDAY THROUGH FRIDAY/
 
 
GENERALLY VFR CONDITIONS FOR ALL TERMINALS, WITH THE EXCEPTION  
OF BRIEF PERIOD OF MVFR DUE TO LOWEIRNG CEILINGS DUE TO SHOWERS  
AND TSTMS THROUGH 6 PM TODAY. GREATEST LIKELIHOOD OF THIS  
OCCURING WILL BE AT KIAD, KCHO AND KMRB. PATCHY FOG WILL LIKELY  
DEVELOP OVERNIGHT IMPACTING KCHO FOR MVFR CONDITINS BETWEEN 08Z  
AND 12Z MONDAY.  
 
FOR PLANNING PURPOSES, MORE CONVECTION IS EXPECTED ON MONDAY  
AFTERNOON WITH THE CHANCE AT ALL TERMINALS, AND THEN EVEN MORE  
INCREASING CHANCES OF MVFR TO EVEN IFR CONDITIONS ON TUESDAY.  
 
VFR CONDITIONS EXPECTED FRIDAY AND SATURDAY. A GUSTY NORTHWEST WIND  
ON FRIDAY SHOULD DIMINISH SATURDAY.  
 

 
   
MARINE
 
 
SCA FOR MORE SOUTHERLY CHANNELING IN THE MARYLAND PORTION OF  
THE CHESAPEAKE TONIGHT. LOOK FOR MORE WIDESPREAD THREAT OF  
SHOWERS AND THUNDERSTORMS CREATING MARINE HAZARDS BOTH MONDAY  
AND TUESDAY AFTERNOON ACROSS ALL COASTAL WATERS.  
 
SMALL CRAFT ADVISORIES MAY BE NECESSARY FRIDAY IN THE WAKE OF LOW  
PRESSURE MOVING NORTHEAST ALONG THE MAINE COAST. WINDS LIKELY  
DIMINISH A BIT SATURDAY.  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...NONE.  
MD...NONE.  
VA...NONE.  
WV...NONE.  
MARINE...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT MONDAY  
FOR ANZ532>534-537-540-541-543.  
 

 
 

 
SYNOPSIS...LEE  
NEAR TERM...LEE  
SHORT TERM...LEE  
LONG TERM...CJL  
AVIATION...LEE/CJL  
MARINE...LEE/CJL  
 
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