899  
FXUS61 KLWX 260122  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
922 PM EDT THU APR 25 2019  
   
SYNOPSIS
 
 
A WARM FRONT STALLED IN CENTRAL VIRGINIA TONIGHT WILL LIFT NORTH  
ACROSS THE REGION FRIDAY MORNING. LOW PRESSURE WILL TRACK  
FROM THE OHIO VALLEY TO THE EASTERN GREAT LAKES FRIDAY, PULLING  
A COLD FRONT ACROSS THE AREA FRIDAY AFTERNOON. HIGH PRESSURE  
WILL BUILD IN BEHIND THIS FRONT FOR THE EARLY PART OF THE  
WEEKEND. ANOTHER STORM SYSTEM COULD APPROACH THE REGION SUNDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
 
 
FRONTAL BOUNDARY IS RESIDING IN CENTRAL VIRGINIA THIS EVENING  
WILL MORE OR LESS REMAIN IN PLACE OVERNIGHT. WARM ADVECTION AND  
APPROACHING UPPER TROUGH WILL ENHANCE SHOWER ACTIVITY OVERNIGHT.  
SOME MAINLY ELEVATED INSTABILITY MAY DEVELOP AND AN ISOLATED  
THUNDERSTORM OR TWO IS ALSO POSSIBLE, MAINLY ACROSS EASTERN WV  
AND VA. LOWS TONIGHT WILL RANGE FROM THE MID 50S TO LOW 60S.  
 

 
   
SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/
 
 
SURFACE WARM FRONT WILL REMAIN IN CENTRAL VA EARLY FRIDAY  
MORNING, BUT SHOULD RAPIDLY PROGRESS NORTHEASTWARD THROUGH THE  
AREA DURING THE MID AND LATE MORNING HOURS. MEANWHILE, SURFACE  
LOW PRESSURE WILL MOVE NORTHEASTWARD THROUGH THE EASTERN GREAT  
LAKES DURING THE DAY, WITH ITS ATTENDANT SURFACE COLD FRONT  
CROSSING THE REGION DURING THE AFTERNOON AND EARLY EVENING  
HOURS. SOME SHOWERS AND/OR ELEVATED ISOLATED THUNDERSTORMS MAY  
BE ONGOING EARLY FRIDAY MORNING, WITH ACTIVITY WANING DURING THE  
LATE MORNING HOURS AFTER THE SURFACE WARM FRONT LIFTS NORTH.  
THIS WILL ALLOW FOR TEMPERATURES TO RISE AND CAUSE SURFACE-BASED  
INSTABILITY TO DEVELOP. A FEW MODELS SUGGEST SIGNIFICANT  
INSTABILITY OF GREATER THATN 1500 J/KG, BUT MOST ARE NOT AS  
UNSTABLE, LIKELY DUE TO LINGERING CLOUDS LIMITING INSOLATION.  
HOWEVER, THIS SHOULD BE ADEQUATE, WHEN COMBINED WITH STRONG LOW  
TO MID LEVEL WIND FIELD AND 40 KNOTS OR SO OF BULK SHEAR, TO  
SET THE STAGE FOR STRONG TO LOCALLY SEVERE THUNDERSTORMS, MAINLY  
FROM THE BLUE RIDGE MOUNTAINS EASTWARD, WITH THE HIGHEST  
PROBABILITY OF SEVERE ACROSS PORTIONS OF CENTRAL VA, EASTWARD TO  
DC, AND INTO SOUTHERN MARYLAND WHERE A SLIGHT RISK OF SEVERE  
THUNDERSTORMS WAS INTRODUCED.  
 
SHOWERS/THUNDERSTORMS WILL LIKELY DEVELOP AROUND NOON OR SO  
ACROSS EASTERN WV AND CENTRAL VA, AND MOVE EASTWARD ACROSS THE  
REGION, EXITING EAST OF THE CHESAPEAKE BAY BY 7 PM. THE HIGHEST  
THREAT WINDOW FOR SEVERE THUNDERSTORMS WILL LIKELY EXIST BETWEEN  
2 PM AND 6 PM. SEVERAL DISCRETE CELLS ARE POSSIBLE AHEAD OF WHAT  
MAY BECOME A MORE ORGANIZED DEVELOPING SQUALL LINE. THE PRIMARY  
THREAT WILL BE ISOLATED DAMAGING WIND GUSTS, BUT GIVEN  
LOW LEVEL DIRECTIONAL SHEAR AND RELATIVELY HIGH HELICITY VALUES,  
AN ISOLATED TORNADO IS ALSO POSSIBLE, WITH THE HIGHEST  
PROBABILITIES IN SOUTHERN MD.  
 
HEAVY RAINFALL WILL ALSO OCCUR WITH THESE SHOWERS/THUNDERSTORMS,  
AND WHILE A WIDESPREAD FLOOD EVENT IS NOT LIKELY, AN ISOLATED  
INCIDENT OF FLOODING IS POSSIBLE IF ANY TRAINING THUNDERSTORMS  
OCCUR. THE FLOOD THREAT IS SOMEWHAT LOWER THAN A WEEK AGO SINCE  
THE WEATHER HAS BEEN DRY FOR NEARLY A WEEK NOW.  
 
HIGHS ON FRIDAY WILL RANGE FROM THE 60S TO LOW 70S, WITH COOLEST  
READINGS IN THE MOUNTAINS WHERE THE SURFACE COLD FRONT WILL  
ARRIVE FIRST, FAIRLY EARLY IN THE DAY.  
 
THE FRONT WILL THEN PUSH EASTWARD FRIDAY NIGHT WITH STRONG  
WEST-NORTHWEST FLOW FOLLOWING BEHIND. GUSTY WINDS ARE EXPECTED  
WITH 30-40 MPH LIKELY, ALTHOUGH MIXING MAY BE LIMITED AT NIGHT.  
IT'S POSSIBLE A WIND ADVISORY MAY BE NEEDED, ESPECIALLY ACROSS  
THE HIGHER ELEVATIONS, BUT UNCERTAINTY EXISTS AT THIS TIME. THE  
WIND FIELD BEGINS TO WEAKEN SATURDAY BUT MIXING WILL INCREASE  
DURING THE DAYLIGHT HOURS, SO GUSTY WINDS MAY ACTUALLY MAX OUT  
SATURDAY MORNING. HIGHS SATURDAY IN THE 60S TO AROUND 70F.  
 
A WEAK RIDGE OF HIGH PRESSURE MOVES OVERHEAD SATURDAY EVENING  
BEFORE SHIFTING EASTWARD AND OFFSHORE BY SUNDAY MORNING AS A  
WEAK AREA OF LOW PRESSURE APPROACHES. SOME SHOWERS BECOME  
POSSIBLE SATURDAY NIGHT.LOWS IN THE 40S TO LOW 50S.  
 

 
   
LONG TERM /SUNDAY THROUGH THURSDAY/
 
 
A COLD FRONT WILL CROSS THE AREA SUNDAY AFTERNOON. MOISTURE AND  
INSTABILITY WILL BE LIMITED WITH THE BEST MOISTURE AND  
INSTABILITY FOCUSED TO OUR REGION'S NORTH. RAINFALL AMOUNTS WILL  
BE LIGHT. DRY WEATHER IS EXPECTED SUNDAY NIGHT AS STRONG HIGH  
PRESSURE BUILDS IN FROM THE NORTHWEST.  
 
MOISTURE RETURNS MONDAY NIGHT AS HIGH PRESSURE SHIFTS EAST. A  
DEVELOPING FRONT OVER THE OHIO VALLEY WILL BE THE FOCUS FOR  
SHOWERS AND THUNDERSTORMS. ALTHOUGH DISTURBANCES WILL MOVE ALONG  
THE FRONT, THE FRONT WILL REMAIN NEARLY STATIONARY WITH VERY  
LITTLE SHOWER OR THUNDERSTORM ACTIVITY INITIALLY. EXPECT  
UNSETTLED WEATHER TO REDEVELOP TOWARD THE MIDDLE AND LATTER PART  
OF THE WEEK WITH A CHANCE FOR THUNDERSTORMS.  
 

 
   
AVIATION /01Z FRIDAY THROUGH TUESDAY/
 
 
SHOWERS AND EVEN A FEW ISOLATED THUNDERSTORMS WILL DEVELOP THIS  
EVENING AND CONTINUE INTO FRIDAY MORNING. REDUCTIONS TO MVFR  
ARE EXPECTED, WITH THE HIGHEST PROBABILITIES OF MORE CONSISTENT  
MVFR CEILINGS AT MTN/MRB.  
 
A STRONG COLD FRONT WILL THEN CROSS THE TERMINALS FRIDAY.  
PREDOMINANT VFR/MVFR ANTICIPATED, BUT LOCAL IFR LIKELY WITHIN  
SHOWERS/STORMS. IN ADDITION, LOCAL GUSTY WINDS (40-50 KT)  
POSSIBLE IN STRONGER STORMS. PLACEMENT OF THESE CELLS  
PROBLEMATIC THIS FAR OUT, BUT THE GENERAL TIME FRAME FOR STRONG  
WINDS/WIND SHIFT WILL BE MID AFTERNOON MRB/CHO AND LATE  
AFTERNOON AT THE HUBS (IAD/DCA/BWI).  
 
GUSTY NORTHWEST WINDS WILL CONTINUE BEHIND THE FRONT FRIDAY  
NIGHT INTO SATURDAY BEFORE DIMINISHING SATURDAY NIGHT. GUSTY  
NW WINDS ANTICIPATED ONCE AGAIN SUNDAY AFTERNOON THROUGH SUNDAY  
EVENING BEHIND ANOTHER FRONTAL PASSAGE.  
 
A FEW SHOWERS ARE ALSO POSSIBLE MONDAY NIGHT. CONDITIONS COULD  
BRIEFLY BECOME MVFR IN THESE SHOWERS.  
 

 
   
MARINE
 
 
GENERALLY LIGHT WINDS EXPECTED ON THE WATERS THROUGH TONIGHT.  
FLOW WHICH IS PREDOMINANTLY NORTHERLY THIS AFTERNOON WILL  
BECOME SOUTH THIS EVENING AND TONIGHT AS A WARM FRONT SLOWLY  
CROSSES THE WATERS.  
 
BY FRIDAY, A SHARP COLD FRONT WILL BE APPROACHING THE WATERS.  
WHILE MIXING WON'T BE IDEAL, THERE WILL BE A HEALTHY GRADIENT  
WIND IN ADVANCE OF THIS FRONT. A SMALL CRAFT ADVISORY IS IN  
EFFECT BEGINNING AT 12 NOON. THE ENVIRONMENT WILL ALSO BECOME  
FAVORABLE FOR DEVELOPMENT OF CLUSTERED SHOWERS/THUNDERSTORMS  
FRIDAY AFTERNOON CAPABLE OF PRODUCING GUSTY WINDS IN EXCESS OF  
34 KNOTS AND POSSIBLY UP TO 50 KNOTS, AND SPECIAL MARINE  
WARNINGS MAY BECOME NECESSARY.  
 
IN THE WAKE OF THE COLD FRONT FRIDAY NIGHT INTO SATURDAY THE  
GRADIENT REMAINS TIGHT, WITH 30-35 KT (AND DEPENDING UPON MODEL  
SOLUTION, PERHAPS UP TO 40 KT) STILL AVAILABLE. MOMENTUM  
TRANSFER WILL BE MORE OPTIMAL. A SCA IS IN EFFECT, BUT AN  
UPGRADE TO GALE MAY BE NEEDED. THE STRONG WINDS WILL CONTINUE  
INTO SATURDAY MORNING BEFORE GRADUALLY RELAXING DURING THE  
AFTERNOON HOURS.  
 
SMALL CRAFT ADVISORY CONDITIONS EXPECTED SUNDAY AND SUNDAY  
NIGHT WITH FREQUENT GUSTS TO AROUND 25 KNOTS. WINDS DIMINISH  
BELOW CRITERIA LATER SUNDAY NIGHT THROUGH MONDAY NIGHT.  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...NONE.  
MD...NONE.  
VA...NONE.  
WV...NONE.  
MARINE...SMALL CRAFT ADVISORY FROM 9 AM FRIDAY TO 6 AM EDT SATURDAY FOR  
ANZ530>543.  
 

 
 

 
SYNOPSIS...MM/RCM  
NEAR TERM...MM/RCM  
SHORT TERM...MM/RCM  
LONG TERM...KLW  
AVIATION...MM/KLW/RCM  
MARINE...MM/KLW  
 
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