707  
FXUS61 KRNK 161426  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
1026 AM EDT TUE JUL 16 2019  
   
SYNOPSIS
 
 
WEAK HIGH PRESSURE OVER THE SOUTHERN APPALACHIANS WILL SLOWLY  
MOVE EAST TODAY WHILE A FRONT ACROSS NORTHERN VIRGINIA MOVES TO  
THE NORTHERN MID-ATLANTIC. LOW PRESSURE THAT WAS ONCE TROPICAL  
STORM BARRY WILL PUSH ACROSS THE OHIO VALLEY WEDNESDAY. A  
FRONTAL BOUNDARY MOVES THROUGH THE REGION THURSDAY MORNING.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 1015 AM EDT TUESDAY...  
 
ONLY MINOR TWEAKS TO EXISTING GRIDS THIS MORNING AS SCATTERED  
SHOWERS AND THUNDERSTORMS STILL POSSIBLE TODAY BUT POPS REMAIN  
ONLY IN THE 20-30 PERCENT CHANCE RANGE. AIR MASS REMAINS  
SEASONABLY MOIST WITH PWAT OF 1.41 INCHES ON 12Z KRNK SOUNDING  
WHICH IS DOWN SLIGHTLY FROM YESTERDAY EVENING BUT STILL ABOVE  
MID-JULY CLIMO AT ABOUT 75TH PERCENTILE. ANY SLOW-MOVING STORMS  
WOULD STILL BE CAPABLE OF PRODUCING DECENT RAIN TOTALS. SEEING  
MORE CLOUDS FROM THE REMAINS OF BARRY THIS MORNING WHICH MAY  
HOLD DOWN INSTABILITY SOME BUT UNLIKELY TO SUPPRESS ALL  
CONVECTION.  
 
AS OF 250 AM EDT TUESDAY...  
 
UPPER RIDGE CONTINUES TO STAY OVER THE SOUTHEAST TODAY, WHILE  
THE FRONT THAT WAS OVER NORTHERN VIRGINIA LIFTS NORTHEAST TODAY  
AHEAD OF THE REMNANTS OF BARRY. FOR OUR AREA, WILL SEE ISOLATED  
TO SCATTERED CONVECTION ONCE AGAIN FIRING UP AROUND MIDDAY, THEN  
SHIFTING SLOWLY MAINLY IN AN EAST TO NORTHEAST FASHION. HOWEVER  
WIND FLOW WILL BE WEAK, SO NOT OF THE QUESTION TO SEE HEAVY  
RAINERS AND LOCALIZED FLOODING. AS FAR AS THE SEVERE THREAT,  
CANNOT RULE OUT ISOLATED STRONG TO SEVERE STORMS WITH DOWNBURSTS  
THE MAIN THREAT. THE STORM PREDICTION CENTER HAS JUST A GENERAL  
THUNDERSTORM OUTLOOK FOR US, AND GIVEN SUCH AN ISOLATED THREAT,  
THIS MAKES SENSE.  
 
HIGHEST POPS TODAY WILL BE ALONG THE SOUTHERN BLUE RIDGE AS NUMEROUS  
MODELS AGREE ON CONVECTION FIRING HERE WITH OROGRAPHIC EFFECTS, SO  
WENT 40-50 HERE...AND THIS COULD BE ANOTHER AREA TO WATCH FOR  
LOCALIZED FLOODING IF THUNDERSTORMS ARE SLOW AND STAY ANCHORED ON  
THE MOUNTAINS.  
 
BY THIS EVENING, THE SHOWERS AND STORMS FADE AGAIN TOWARD MIDNIGHT.  
THE UPPER RIDGE BEGINS TO BREAK DOWN AS UPPER TROUGH/LOW ASSOCIATED  
WITH BARRY MOVES CLOSER TOWARD THE OHIO VALLEY. SHOULD SEE CLEARING  
SKIES AND FOG POTENTIAL AGAIN WHERE IT RAINED AND IN TYPICAL  
MOUNTAIN VALLEYS.  
 
EXPECT HIGH TEMPS CLOSE TO WHAT WE HAD MONDAY WITH LOWER 80S NC  
MOUNTAINS AND PORTIONS OF THE ALLEGHANYS ALONG THE WV/VA BORDER,  
FIGURING THUNDERSTORMS ARE GOING TO FIRE UP HERE EARLIER, WITH MID  
TO UPPER 80S ELSEWHERE IN THE MOUNTAINS. ROANOKE AND POINTS EAST  
WILL REACH THE LOWER TO MID 90S. DEWPOINTS SHOULD DROP INTO THE  
UPPER 60S THIS AFTERNOON, RESULTING IN HEAT INDICES OF 95 TO 99,  
WITH THE HIGHER HEAT INDICES ABOVE 100 EXPECTED EAST OF A FARMVILLE  
VA TO DURHAM NC LINE.  
 
LOWS TONIGHT AGAIN NOT CHANGING MUCH AS PERSISTENT PATTERN/AIRMASS  
SHOULD KEEP TEMPS IN THE MID TO UPPER 60S IN THE MOUNTAINS, TO  
AROUND 70 TO LOWER 70S EAST.  
 
FORECAST CONFIDENCE IN TEMPS/WIND AND SKY IS ABOVE NORMAL, WITH  
AVERAGE CONFIDENCE ON STORM COVERAGE.  
 

 
   
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
 
 
AS OF 210 AM EDT TUESDAY...  
 
WEATHER FOR MID-WEEK WILL FEATURE REMNANTS FROM BARRY, THE CRUX OF  
THE UPPER SUPPORT PASSING TO OUR NORTH, BUT WITH AN AXIS OF  
VORTICITY TRAILING TO THE SOUTH AS THE CLOSED FEATURE BEGINS TO  
SHEAR INTO AN OPEN WAVE. INSTABILITY FROM WEDNESDAY INTO THURSDAY IS  
EXPECTED TO BE PLENTIFUL, SO ANTICIPATE SCATTERED TO NUMEROUS  
SHOWERS WITH EMBEDDED THUNDERSTORMS.  
 
MODELS SUGGEST THE MOST FAVORABLE TIME FRAME FOR MEASURABLE RAINFALL  
DIRECTLY ASSOCIATED WITH THE TROPICAL REMNANTS WILL BE FROM  
WEDNESDAY AFTERNOON THROUGH THURSDAY MORNING, THE VORTICITY AXIS  
PASSING OVERHEAD AT THAT TIME. QPF IS FORECAST TO BE THE HEAVIEST  
FROM THE OHIO VALLEY INTO THE WESTERN SLOPES WHERE WESTERLY FLOW  
ALOFT WILL ACT TO ENHANCE THE RAINFALL, BUT AS THE SYSTEM CROSSES  
THE APPALACHIANS, PRECIP PRODUCTION IS EXPECTED TO GO DOWN PER  
WESTERLY DOWNSLOPE FLOW. AT THE MOMENT, OUR DAY 2-3 FORECAST RAIN  
TOTALS AVERAGE FROM ABOUT AN INCH OF QPF ON THE WESTERN SLOPES TO A  
GENERAL QUARTER OF AN INCH ACROSS THE PIEDMONT. KEEP IN MIND PWATS  
ARE RUNNING AROUND 2 INCHES, THEREFORE LOCALIZED TORRENTIAL  
DOWNPOURS ARE POSSIBLE. TEMPERATURES ARE EXPECTED TO BE SEASONALLY  
WARM, TEMPERED TO SOME DEGREE BY THE SHOWERS AND ANTICIPATED CLOUD  
COVER. THE HIGH DEWPOINTS HOWEVER, WITH READINGS FORECAST IN THE  
70S, WILL MAINTAIN THE MUGGINESS.  
 
A FRONTAL BOUNDARY WILL SLOWLY MOVE ACROSS THE REGION THURSDAY  
MORNING, STALLING OVER THE PIEDMONT IN THE AFTERNOON. BEHIND THIS  
BOUNDARY, PWATS FALL TO AROUND 1.50 INCHES WHILE AHEAD THEY REMAIN  
NEAR 2.00 INCHES. RIDGING ALOFT BEGINS TO BUILD EASTWARD THROUGH THE  
DAY, WHICH SHOULD LIMIT CONVECTIVE ACTIVITY. HOWEVER, DIURNAL  
HEATING AND A STALLED BOUNDARY/LEE TROUGH COULD PRODUCE SOME STORMS  
ALONG AND EAST OF ROUTE 29 WHICH MAY CONTAIN HEAVY DOWNPOURS DURING  
THE AFTERNOON AND EVENING HOURS.  
 

 
   
LONG TERM /FRIDAY THROUGH MONDAY/
 
 
AS OF 345 PM EDT MONDAY...  
 
FOR FRIDAY AND INTO THE UPCOMING WEEKEND... THE UPPER RIDGE  
STRENGTHENS WITH POTENTIAL FOR 500 MB HEIGHTS TO TEST 595 DM.  
AS SUCH, PATTERN FAVORS SOME VERY WARM TEMPERATURES FOR THE  
WEEKEND, 85H TEMPS OF +23 TO +24 DEG C, YEILDING SURFACE  
READINGS WELL INTO THE 90S EAST OF THE BLUE RIDGE. DEWPOINTS  
ARE ALSO EXPECTED TO REMAIN ELEVATED, SO HEAT INDICES MAY  
ECLIPSE 100 FOR SEVERAL DAYS IN A ROW...POTENTIALLY TESTING 105  
DEGREES BY SATURDAY. SOME RELIEF MAY COME FROM POP-UP  
AFTERNOON/EVENING SHOWERS AND THUNDERSHOWERS, BUT COVERAGE IS  
EXPECTED TO BE LIMITED PER LACK OF ANY SIGNIFICANT FORCING  
MECHANISM AND OVERALL SUBSIDENCE FROM THE UPPER LEVEL RIDGING.  
 

 
   
AVIATION /14Z TUESDAY THROUGH SATURDAY/
 
 
AS OF 720 AM EDT TUESDAY...  
 
EXPECT THE LITTLE BIT OF FOG AT LWB/BCB TO BE GONE BY 13Z. VFR  
CONDITIONS THROUGH THE DAY STILL EXPECTED AND INTO TONIGHT.  
SCATTERED DEVELOPMENT FOR SHOWERS/STORMS ACROSS THE MOUNTAINS  
EARLY THIS AFTERNOON WILL SHIFT EAST TOWARD THE PIEDMONT THROUGH  
LATE AFTERNOON. ABOUT 30 PERCENT COVERAGE SO ADDED VCTS AT ALL  
SITES EXCEPT DAN.  
 
STORMS SHOULD BE GONE BY LATE EVENING WITH MAINLY VFR MID AND  
HIGH CLOUDS. POTENTIAL FOR FOG EXISTS AGAIN WHERE IT RAINS, BUT  
CONFIDENCE ONLY HIGH ENOUGH TO HAVE MVFR VSBYS AT LWB/BCB, BUT  
POTENTIAL IS THERE FOR LOWER VSBYS IF WE CLEAR OUT ENOUGH.  
 
FORECAST CONFIDENCE OUTSIDE THE STORMS IS GOOD THROUGH THE  
PERIOD.  
   
EXTENDED AVIATION DISCUSSION
 
 
THE OCCURRENCE OF SUB-VFR CONDITIONS WILL INCREASE WEDNESDAY  
INTO THURSDAY AS A SHORTWAVE TROUGH APPROACHES AND THE CROSSES  
THE AREA, BRINGING ALONG WITH IT THE TROPICAL MOISTURE  
ASSOCIATED WITH THE REMNANTS OF BARRY. EXPECT AN INCREASE IN  
SHOWER AND THUNDERSTORM COVERAGE, AND SUBSEQUENT LATE  
NIGHT/EARLY MORNING STRATUS/FOG.  
 
BY FRIDAY INTO SATURDAY, A SHORTWAVE RIDGE RETURNS OVERHEAD, AND  
THIS WILL CURTAIL, BUT NOT REMOVE THE POTENTIAL FOR DIURNALLY  
BASED SHOWERS AND STORMS, WITH THE FOCUS FOR MOST ACTIVITY  
ACROSS THE MOUNTAINS. DEPENDING UPON GROUND MOISTURE FOR THE  
DAYS HEADING INTO THE WEEKEND, LATE NIGHT/EARLY MORNING FOG  
COULD AGAIN BE A POSSIBILITY.  
 
CONFIDENCE IN THE ABOVE AVIATION SCENARIO IS MODERATE.  
 

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

 
 

 
SYNOPSIS...DS/WP  
NEAR TERM...PC/WP  
SHORT TERM...RCS  
LONG TERM...PM  
AVIATION...AL/WP  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab VA Page
The Nexlab WV Page
The Nexlab NC Page Main Text Page