814  
FXUS61 KRNK 071857  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
257 PM EDT TUE JUL 7 2020  
   
SYNOPSIS
 
 
A SLOW MOVING AREA OF LOW PRESSURE WILL PROGRESS FROM THE SOUTHEAST  
U.S., NORTHEAST ALONG THE EAST COAST THROUGH THURSDAY NIGHT. FOR  
FRIDAY THROUGH MONDAY, A COUPLE OF DISTURBANCES WILL MOVE INTO AND  
THROUGH THE REGION FROM THE GREAT LAKES REGION. BOTH OF THESE  
PATTERNS WILL PROVIDE FOR MULTIPLE OPPORTUNITIES FOR THE AREA TO HAVE  
SHOWERS AND STORMS IN THE FORECAST.  
 

 
   
NEAR TERM /THROUGH WEDNESDAY NIGHT/
 
 
AS OF 230 PM EDT TUESDAY...  
 
TONIGHT INTO WEDNESDAY WE WILL BE TRACKING AN UPPER LEVEL LOW OVER  
THE SOUTHEAST U.S. THAT WILL SLOWLY TRACK NORTHEAST TO OVER THE  
COAST OF THE CAROLINAS BY MID-DAY WEDNESDAY. THE COMBINATION OF  
DIURNAL HEATING AND INCREASED EASTERLY MOISTURE CONVECTION OFF THE  
ATLANTIC ON THE NORTH SIDE OF THE LOW, WILL ALLOW FOR THE  
DEVELOPMENT OF SHOWERS AND STORMS. COVERAGE WILL BE GREATEST DURING  
THE PEAK HEATING OF THE THIS AFTERNOON AND WEDNESDAY AFTERNOON  
THROUGH THE EARLY EVENING OF EACH DAY. GIVEN THE EXPECTED SLOW  
MOTION OF ANY SHOWERS AND STORMS THAT DEVELOP, TRAINING OF  
CONSECUTIVE CELLS IS POSSIBLE, AND LEAD TO VERY LOCALIZED FLOODING.  
GIVEN THE ISOLATED NATURE OF ANY POTENTIAL FLOODING, NO WATCH IS  
WARRANTED AT THIS TIME. GIVEN THE STRONG INFLUX OF MOISTURE, DEW  
POINTS ARE RUNNING HIGHER THAN NORMAL FOR THIS TIME OF THE YEAR.  
THIS WILL ALLOW LOW TEMPERATURES TONIGHT TO LIKEWISE AVERAGE A FEW  
DEGREES ABOVE NORMAL. HIGH TEMPERATURES WEDNESDAY WILL BE NEAR  
NORMAL FOR THIS TIME OF YEAR.  
 
CONFIDENCE IN THE ABOVE WEATHER SCENARIO IS MODERATE TO HIGH.  
 

 
   
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
 
 
AS OF 155 PM EDT TUESDAY...  
 
THE SUB-TROPICAL LOW PRESSURE CENTER WILL SLOWLY LIFT FROM NEAR THE  
CAROLINA COAST WED NIGHT NORTHEASTWARD UP TOWARD THE NEW ENGLAND  
COAST BY LATE FRIDAY, THUS OUR REGION WILL REMAIN ON THE WEST SIDE  
OF THIS THROUGH THE PERIOD, BUT IT IS NOT CLEAR HOW MUCH INSTABILITY  
THERE WILL BE WITH THE LIGHT NORTHEAST FLOW AND DEGREE OF CLOUDINESS  
ACROSS THE PIEDMONT AREAS.  
 
THURSDAY MOST MODELS DO BRING AT LEAST SOME LIGHT SHOWER ACTIVITY  
INTO THE FAR SOUTHEAST LATE THURSDAY BUT SEEM TO SUGGEST MORE  
INSTABILITY THAN EXPECTED GIVEN LIKELY CLOUD COVER. MORE SUNSHINE IS  
LIKELY IN MOUNTAINS BUT COULD ALSO BE SOME SUBSIDENCE TRYING TO  
SUPPRESS CONVECTION. SOME LIFT ALONG THE RIDGES WITH LIGHT  
EASTERLY FLOW MAY BE WHAT IT TAKES TO GET ANY CONVECTION TO  
DEVELOP IN THE MOUNTAINS. SO AT THIS TIME STILL EXPECTING  
HIGHEST POPS IN THE EAST EVEN THOUGH PROBABLY MAINLY LIGHT RAIN  
AMOUNTS AND LIMITED DEEP CONVECTION, WITH MORE LOW TO MID CHANCE  
POPS FAR WEST WITH POSSIBLE HEAVIER BUT MORE HIT AND MISS  
SHOWERS/STORMS. HOWEVER, WOULD NOT BE SURPRISED IF THIS ENDS UP  
BEING A MOSTLY DRY DAY FOR MUCH OF THE WESTERN HALF OF THE  
FORECAST AREA WITH SUBSIDENCE WINNING.  
 
BY FRIDAY AS THE LOW PRESSURE SYSTEM MOVES FARTHER UP THE COAST AND  
AWAY, SUBSIDENCE AND NORTHEAST FLOW, POSSIBLY ALONG WITH LINGERING  
CLOUD COVER COULD KEEP SHOWER AND STORM ACTIVITY TO A MINIMUM IN THE  
EAST, BUT IN THE WEST WITH APPROACHING WEAK UPPER TROUGH AND LATE  
RETURN OF WEAK WESTERLY FLOW AND RESULTANT CONVERGENCE THERE COULD  
BE A BETTER CHANCE FOR SCATTERED SHOWERS AND STORMS FORMING LATE IN  
THE DAY. THUS ULTIMATELY WENT HIGHER POPS FAR WEST, WITH  
ADMISSION THAT CONFIDENCE IS STILL RELATIVELY LOW GIVEN  
UNCERTAINTIES IN HOW QUICKLY THIS LOW WILL MOVE AWAY AND THE  
DEGREE TO WHICH LINGERING CLOUD COVER AND BACK-SIDE SUBSIDENCE  
COULD INFLUENCE AFTERNOON CONVECTION OR LACK THEREOF. IF THE LOW  
SLOWS DOWN, BETTER PRECIP CHANCES COULD BE IN THE FAR NORTHEAST  
WITH MINIMAL CHANCES IN THE WEST. MOST LIKELY HIGH TEMPS WILL  
BE A BIT WARMER ON FRIDAY COMPARED TO THURSDAY, ESPECIALLY IN  
THE EAST, BUT THIS WILL ALSO BE DEPENDENT ON HOW SOON THIS LOW  
MOVES ON UP THE COAST.  
 

 
   
LONG TERM /SATURDAY THROUGH MONDAY/
 
 
AS OF 125 PM EDT TUESDAY...  
 
MOST GUIDANCE IN GOOD AGREEMENT THAT A SERIES OF SHORT WAVE  
DISTURBANCES DROPPING IN FROM THE MIDWEST WILL HELP TO MAINTAIN A  
WEAK LARGE SCALE TROUGH OVER THE APPALACHIAN REGION THROUGH AT LEAST  
EARLY NEXT WEEK. THE FIRST AND WEAKER DISTURBANCE IS MOST LIKELY  
OVER THE REGION ON SATURDAY, WITH THE SECOND AND STRONGER  
DISTURBANCE DIGGING A DEEPER TROUGH OUT BY MONDAY AND POSSIBLY  
LASTING INTO TUESDAY OR BEYOND. EXACT TIMING OF WHEN THESE WILL  
RESULT IN THE MOST INSTABILITY GIVEN SLIGHTLY COOLER UPPER LEVELS  
AND PERHAPS LOWER-LEVEL MOISTURE ADVECTION WITH MORE OF A SOUTHERLY  
OR SW COMPONENT IS STILL UNCERTAIN, BUT THERE IS CURRENT SOME DEGREE  
OF CONSENSUS THAT SATURDAY AND THEN MONDAY WOULD HAVE THE BETTER  
CHANCES OF WIDER COVERAGE OF AFTERNOON/EVENING SHOWERS AND STORMS.  
SUNDAY COULD SEE A RELATIVE BREAK IF BETWEEN WAVES, AND TUESDAY AS  
WELL IF TROUGH IS PROGRESSIVE ENOUGH TO PUSH DEEPER MOISTURE EAST.  
CONFIDENCE NOT HIGH ENOUGH THIS FAR OUT TO REFLECT ANYTHING LOWER  
THAN LOW CHANCE POP VALUES ON THOSE TWO RELATIVE DOWN DAYS, BUT  
KEEPING WITH HIGH CHANCE TO LOW LIKELY POPS ON SATURDAY AND MONDAY.  
 
DESPITE WEAK TROUGH OVERHEAD MAX TEMPS EXPECTED TO BE NEAR OR A  
LITTLE ABOVE SEASONABLE READINGS BUT WILL DEPEND ON AMOUNT OF CLOUD  
COVER AND THUS COULD SEE MONDAY AND TUESDAY ENDING UP A LITTLE  
COOLER THAN SATURDAY AND SUNDAY WITH DEEPER TROUGH OVERHEAD AND  
PERHAPS MORE CLOUD COVER EARLIER IN THE DAY.  
 
AT THIS ANY THREAT OF SIGNIFICANT OR WIDESPREAD IMPACTS FROM  
ANY STORMS APPEARS LOW THROUGH THE SATURDAY TO TUESDAY TIME  
FRAME, WITH THE POSSIBLE EXCEPTION ON MONDAY DEPENDING ON HOW  
STRONGLY THE TROUGH DIGS AND TIMING OF WHEN ANY SURFACE  
BOUNDARY OR EMBEDDED WAVE MOVES THROUGH.  
 

 
   
AVIATION /19Z TUESDAY THROUGH SUNDAY/
 
 
AS OF 145 PM EDT TUESDAY...  
 
CLOUD COVER IS BOTH ADVECTING NORTHWARD INTO THE REGION, AND  
DEVELOPING WITH THE HEATING OF THE DAY. WITH SURFACE DEW POINT  
DEPRESSIONS BETWEEN 10 AND 15 DEGREES F, LCL VALUES HAVE BEEN  
PLACING NEW DEVELOPED CLOUDS IN THE HIGH END OF MVFR AND LOW END  
OF VFR ACROSS THE AREA. ISOLATED SHOWERS WERE ALSO DEVELOPING  
OVER OR MOVING INTO THE SOUTHERN PARTS OF THE REGION. ISOLATED  
THUNDERSTORMS ARE ALSO POSSIBLE. AS THE AFTERNOON PROGRESSES,  
WE EXPECT THE SHOWER ACTIVITY TO EXPAND AND SPREAD NORTHWARD,  
AND FOR CEILING HEIGHTS TO INCREASE SLIGHTLY AS THE SURFACE  
WARMS AND LCLS INCREASE A BIT.  
 
THIS EVENING AND INTO THE OVERNIGHT, SHOWER AND STORM ACTIVITY  
WILL DECREASE, BUT CLOUD COVER WILL REMAIN RATHER ROBUST OVER AT  
LEAST THE SOUTHERN THIRD OF THE REGION, WITH DECREASING COVERAGE  
HEADING NORTH ACROSS THE FORECAST AREA. WE ARE EXPECTING ANOTHER  
NIGHT WITH THE DEVELOPMENT OF IFR/MVFR FOG, ESPECIALLY IN THE  
RIVER AND MOUNTAINS VALLEYS, AND ANY LOCATION THAT GETS AT LEAST  
A FEW HUNDREDTHS OF AN INCH OF RAIN THIS AFTERNOON OR EVENING.  
CEILINGS WILL TREND LOWER THROUGH THE NIGHT INTO THE IFR/MVFR  
RANGE FOR MOST OF THE REGION.  
 
FOR WEDNESDAY, WE ARE EXPECTING ADDITIONAL SHOWERS TO DEVELOP OR  
MOVE INTO THE AREA IN ASSOCIATION WITH AN AREA OF LOW PRESSURE  
THAT WILL BE HEADING SLOWLY NORTHEAST ALONG THE SOUTHEAST COAST  
OF THE U.S. CEILINGS WILL IMPROVE TO MVFR OR LOW END VFR BY THE  
CONCLUSION OF THE VALID TAF PERIOD, 18Z/2PM WEDNESDAY.  
 
WINDS THROUGH THE FORECAST PERIOD WILL BE MAINLY CALM OR LIGHT  
AND VARIABLE.  
 
CONFIDENCE IN THIS AVIATION SCENARIO IS MODERATE.  
 
EXTENDED AVIATION DISCUSSION...  
 
THE SLOW MOVING UPPER LOW ALONG THE EAST COAST WILL HELP  
MAINTAIN THE PATTERN OF MAINLY DIURNAL SHOWERS AND STORMS ACROSS  
THE REGION THROUGH AT LEAST THURSDAY OR THURSDAY NIGHT. POCKETS  
OF SUB-VFR CONDITIONS ARE EXPECTED, ESPECIALLY UNDER THE HEAVIER  
SHOWERS AND STORMS, AND THEN THROUGH THE OVERNIGHT HOURS AS  
MOISTURE IS TRAPPED UNDER THE DEVELOPING NOCTURNAL INVERSION.  
 
ADDITIONAL SHOWERS AND STORMS ARE POSSIBLE WILL FRIDAY THROUGH  
SUNDAY THANKS TO A SERIES OF NORTHWEST FLOW SHORTWAVE TROUGHS  
CROSSING THE AREA. COVERAGE WILL LIKELY BE GREATEST ACROSS THE  
MOUNTAINS. CEILINGS HAVE A GREATER POTENTIAL OF BEING SUB-VFR  
ACROSS THE MOUNTAINS AS COMPARED TO THE PIEDMONT REGION.  
 

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

 
 

 
SYNOPSIS...DS  
NEAR TERM...DS  
SHORT TERM...SK  
LONG TERM...SK  
AVIATION...DS  
 
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