666  
FXUS61 KRNK 191838  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
238 PM EDT FRI APR 19 2019  
   
SYNOPSIS
 
 
A STRONG COLD FRONT WILL BRING SHOWERS AND THUNDERSTORMS THROUGH  
TONIGHT. UPSLOPE SHOWERS COULD LINGER WEST OF THE BLUE RIDGE FOR  
SATURDAY AND EARLY SUNDAY. HIGH PRESSURE WILL ARRIVE BY EARLY  
NEXT WEEK TO PROVIDE DRIER CONDITIONS.  
 

 
   
NEAR TERM /THROUGH SATURDAY/
 
 
AS OF 230 PM EDT FRIDAY...  
 
A SPECIAL 15Z SOUNDING WAS CONDUCTED TO GAUGE THE SEVERE WEATHER  
THREAT, AND THE SHEAR NUMBERS HAVE SIGNIFICANTLY INCREASED SINCE  
THE PREVIOUS 12Z SOUNDING. THE 0-1 KM WIND SHEAR IN THIS  
SPECIAL RNK SOUNDING REACHES 55 KT, WHILE THE 0-6 KM WIND SHEAR  
IS UP TO 74 KT. THIS SHEAR ENVIRONMENT IS EXTREMELY FAVORABLE  
FOR SUPERCELLS CAPABLE OF DAMAGING WINDS, HAIL, AND TORNADOES.  
THE SOUNDING ALSO REVEALS SURFACE CAPE OF ABOUT 700 J/KG, SO  
THERE IS STILL ENOUGH INSTABILITY FOR THESE STORMS TO FIRE  
DESPITE THE PREVALENT CLOUD COVER OVERHEAD. REPORTS OF  
SIGNIFICANT STRUCTURAL DAMAGE HAVE ALREADY BEEN RELAYED TO US  
SOUTH OF ROCKY MOUNT, VIRGINIA. A TORNADO WATCH REMAINS IN  
EFFECT FOR MOST OF SOUTHWEST VA AND NORTHWEST NC UNTIL 5 PM EDT.  
NEEDLESS TO SAY, EVERYONE SHOULD REMAIN ALERT THROUGH THIS  
EVENING AS THESE SHOWERS AND THUNDERSTORMS TRACK NORTHEASTWARD.  
 
IN ADDITION, THESE THUNDERSTORMS WILL PRODUCE HEAVY RAIN THAT  
COULD LEAD TO HYDROLOGICAL ISSUES. WHILE THEY ARE MOVING AT  
SPEEDS UP TO 50 KT, IT WILL BE REPEATED ROUNDS OF RAIN FROM  
PREFRONTAL CONVECTION AND THE EVENTUAL LINE ALONG THE COLD FRONT  
ALONG WITH THE POTENTIAL FOR TRAINING THAT MAY LEAD TO  
LOCALIZED FLASH FLOODING AND URBAN/SMALL STREAM FLOODING.  
PRECIPITABLE WATER VALUES HAVE CLIMBED TO 1.25 INCHES, BUT THERE  
IS CONSIDERABLE MOISTURE ADVECTION STILL ONGOING FROM THE GULF  
OF MEXICO COURTESY OF DEEP SOUTHERLY FLOW ALOFT. THE HYDRO  
THREAT COULD LINGER FURTHER INTO TONIGHT AFTER THE SEVERE  
THREATS TAPER BEYOND SUNSET. IT IS TOO EARLY TO TELL WHETHER ANY  
RIVER FLOODING THREATS WILL MATERIALIZE, BUT THIS FACET WILL BE  
CLOSELY MONITORED.  
 
THE CULPRIT RESPONSIBLE FOR THE PREVIOUSLY MENTIONED MULTITUDE  
OF WEATHER HAZARDS IS A STRONG COLD FRONT APPROACHING THE MID  
ATLANTIC. A CLOSED UPPER LEVEL LOW IN ASSOCIATION WITH THIS  
COLD FRONT IS IN THE PROCESS OF TILTING NEGATIVELY. AFTER THE  
FRONTAL PASSAGE PROJECTED TO BE AROUND MIDNIGHT TONIGHT, NOTABLY  
COOLER AIR SHOULD ARRIVE. PLENTIFUL LOW CLOUDS SHOULD SHUT DOWN  
THE LOW-LEVEL INSTABILITY, BUT LINGERING SHOWERS MAY CONTINUE  
THROUGHOUT THE DAY ALONG AND WEST OF THE BLUE RIDGE. HIGH  
TEMPERATURES BY SATURDAY AFTERNOON MAY NOT ESCAPE THE 40S IN THE  
HIGHER ELEVATIONS.  
 

 
   
SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/
 
 
AS OF 230 PM EDT FRIDAY...  
 
BY SATURDAY NIGHT, THE CLOSED UPPER LEVEL LOW WILL SLOWLY TRACK  
OVERHEAD. WITH 850 MB TEMPERATURES FALLING BELOW FREEZING  
OVERNIGHT, LINGERING RAIN SHOWERS IN THE HIGHEST ELEVATIONS  
WEST OF THE BLUE RIDGE COULD CHANGE OVER TO LIGHT SNOW SHOWERS.  
ANY PRECIPITATION SHOULD DISSIPATE BY SUNDAY AS THE UPPER LEVEL  
LOW HEADS TOWARD THE NORTHEAST. LOW CLOUDS COULD LINGER ALONG  
AND WEST OF THE BLUE RIDGE UNTIL LATER IN THE AFTERNOON, BUT  
CONFIDENCE IS HIGHER THAT DRIER CONDITIONS SHOULD ENSUE BY  
SUNDAY NIGHT. HIGH PRESSURE WILL BUILD OVER THE MID ATLANTIC TO  
PROVIDE SUNSHINE FOR MONDAY. THE UPPER LEVEL PATTERN WILL BE  
CHANGING AS WELL DUE TO RIDGING ALOFT, SO EXPECT MILDER AIR TO  
ARRIVE FOR MONDAY AND MONDAY NIGHT.  
 

 
   
LONG TERM /TUESDAY THROUGH FRIDAY/
 
 
AS OF 230 PM EDT THURSDAY...  
 
ANOTHER COLD FRONT SHOULD CROSS OVER THE OHIO RIVER VALLEY BY  
TUESDAY, WHILE ITS ASSOCIATED UPPER LEVEL TROUGH SWINGS THROUGH  
THE NEW ENGLAND STATES. THE RETURN FLOW OF MOISTURE ALONG WITH  
DIURNAL HEATING COULD SPARK A SLIGHT CHANCE OF SHOWERS AND  
THUNDERSTORMS IN THE MOUNTAINS BY THE AFTERNOON. IT IS WORTH  
NOTING THAT THE ECMWF MODEL IS A LITTLE SLOWER AND DRIER FOR  
TUESDAY, WHILE THE GFS INDICATES THIS SLIGHT CHANCE. WEDNESDAY  
APPEARS TO BE MORE FAVORABLE FOR SHOWERS AND THUNDERSTORMS AS  
THE COLD FRONT MOVES CLOSER.  
 
THE MODEL SOLUTIONS DIVERGE NOTABLY BY THURSDAY AS THE ECMWF  
BECOMES MORE PROGRESSIVE AS IT PUSHES THE COLD FRONT OFFSHORE TO  
BRING HIGH PRESSURE BY FRIDAY, BUT THE GFS STALLS THE FRONTAL  
BOUNDARY TO THE NORTH OF THE CWA DURING BOTH DAYS. GIVEN THAT  
BOTH MODELS PRODUCE MOS HIGH TEMPERATURES IN THE 60S AND 70S FOR  
THURSDAY AND FRIDAY AND THE POTENTIAL PROXIMITY OF THIS BOUNDARY,  
THERE APPEARS TO BE ENOUGH INSTABILITY TO ADVERTISE A GENERAL  
THREAT FOR AFTERNOON SHOWERS AND THUNDERSTORMS THROUGHOUT THIS  
TIMEFRAME. LATER MODEL RUNS WILL HOPEFULLY PAINT MORE DETAILS TO  
ADD CONFIDENCE FOR THIS PORTION OF THE FORECAST.  
 

 
   
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
 
 
AS OF 230 PM EDT FRIDAY...  
 
THE THREAT FOR NUMEROUS SHOWERS AND THUNDERSTORMS THIS  
AFTERNOON INTO EARLY TONIGHT HAS NECESSITATED PUTTING THUNDER IN  
ALL TAF SITES. SOME OF THESE STORMS COULD BECOME SEVERE AND  
POSE A SIGNIFICANT THREAT TO AVIATION WITH STRONG WINDS ALOFT,  
ESPECIALLY ALONG AND EAST OF THE BLUE RIDGE. MVFR/IFR CONDITIONS,  
HEAVY RAIN, AND SIGNIFICANT TURBULENCE WILL LIKELY ACCOMPANY  
THESE STORMS AS WELL.  
 
THE CONVECTIVE THREAT SHOULD WANE AFTER 04Z AS A STRONG COLD  
FRONT PASSES EAST OF KLYH AND KDAN. HOWEVER, LINGERING SHOWERS  
AND LOW CLOUDS POINT TO A HIGH CONFIDENCE OF MVFR CEILINGS. IT  
IS POSSIBLE THAT SOME CEILINGS MAY DIP LOWER TOWARD IFR, BUT A  
DECENT SURFACE SOUTH WIND OVERNIGHT MAY PREVENT IT FROM ACTUALLY  
OCCURRING. CONDITIONS SHOULD SLOWLY IMPROVE ON SATURDAY  
MORNING, BUT IT WILL BE QUESTIONABLE IF ANY OF THE TAF SITES CAN  
LEAVE THE MVFR CATEGORY.  
 
EXTENDED AVIATION DISCUSSION...  
 
A CLOSED UPPER LEVEL LOW SHOULD MOVE OVERHEAD DURING SATURDAY  
NIGHT, WHICH WILL KEEP MVFR CEILINGS AND LINGERING SHOWERS ALONG  
AND WEST OF THE BLUE RIDGE INTO SUNDAY MORNING. VFR CONDITIONS  
APPEAR LIKELY TO RETURN BY SUNDAY EVENING. HIGH PRESSURE SHOULD  
BRING GOOD FLYING WEATHER FOR MONDAY AND MOST OF TUESDAY.  
HOWEVER, THE CHANCE OF AFTERNOON SHOWERS AND THUNDERSTORMS WILL  
INCREASE BY WEDNESDAY.  
 

 
   
RNK WATCHES/WARNINGS/ADVISORIES
 
 
VA...NONE.  
NC...NONE.  
WV...NONE.  
 

 
 

 
SYNOPSIS...PW  
NEAR TERM...PW  
SHORT TERM...PW  
LONG TERM...PW  
AVIATION...PW  
 
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