056  
FXUS61 KRNK 251350  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
950 AM EDT SUN JUN 25 2017  
   
SYNOPSIS
 
 
WEAK HIGH PRESSURE WILL LINGER OVER THE REGION THROUGH MONDAY.  
AN UPPER TROUGH AND ASSOCIATED COLD FRONT WILL SWEEP THROUGH THE  
AREA TUESDAY WITH A FEW SHOWERS FOLLOWED BY A COOLER, DRIER AIR  
MASS. TOWARD THE END OF THE WEEK, HIGH PRESSURE WILL MOVE EAST  
OF THE REGION INTO THE WESTERN ATLANTIC, ALLOWING MUCH WARMER  
AND MORE HUMID AIR TO RETURN TO THE REGION ALONG WITH INCREASING  
CHANCES FOR SHOWERS AND THUNDERSTORMS.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 945 AM EDT SUNDAY...  
 
THIS MORNING'S LIMITED PATCHY FOG HAS DISSIPATED. CLOUD COVER  
CONTINUES TO STREAM SOUTHWEST TO NORTHEAST ACROSS MAINLY CENTRAL  
AND EASTERN PARTS OF THE AREA. AS HIGH PRESSURE CONTINUES TO  
BUILD INTO THE AREA, THE EXTENT OF THIS CLOUD COVER WILL TREND  
EASTWARD AS THE DAY PROGRESSES. NO SIGNIFICANT CHANGES TO THE  
OVERALL FORECAST ARE BEING MADE THIS MORNING. HAVE MADE MINOR  
ONLY ADJUSTMENTS IN THE HOURLY TEMPERATURES, DEW POINTS, WINDS,  
AND SKY COVER TO REFLECT THE LATEST OBSERVATIONS AND EXPECTED  
TRENDS INTO THE EARLY AFTERNOON.  
 
AS OF 330 AM EDT SUNDAY...  
 
A DIFFUSE FRONTAL BOUNDARY IS EVIDENT ACROSS THE EXTREME  
SOUTHERN PARTS OF THE CWA OR TOWARD THE I-40 CORRIDOR IN NORTH  
CAROLINA. THERE IS QUITE A RANGE IN DEWPOINTS THIS HOUR FROM THE  
MID 50S ACROSS THE ALLEGHANYS AND THE NORTHWEST PART OF THE CWA  
TO NEAR 70 YET ACROSS THE SOUTHEAST PART OF THE CWA, SAY  
CASWELL/HALIFAX AREAS TOWARD YADKIN. A BROAD UPPER TROUGH WILL  
CONTINUE TO DEEPEN ACROSS THE GREAT LAKES TODAY PUSHING THE  
BAROCLINIC BOUNDARY FURTHER SOUTH, SUCH THAT BY EVENING, IT  
SHOULD BE LOCATED FROM EAST CENTRAL NC INTO CENTRAL SC, THEN  
WEST INTO CENTRAL GA. ANY SHOWERS OR THUNDERSTORMS TODAY WILL BE  
NEAR AND SOUTH OF THE FRONT, LEAVING OUR ENTIRE CWA RAIN FREE  
TODAY WITH LOWER HUMIDITY LEVELS AND SLIGHTLY COOLER  
TEMPERATURES, SINCE NOT ONLY DO THE DEWPOINTS DROP INTO THE 50S  
NORTH TO 60S SOUTH BY EVENING, BUT THE 850MB TEMPERATURES SHOW  
A MARKED DROP FROM +18C OF THE PAST FEW DAYS TO AROUND +8C BY  
MONDAY MORNING. SOME CIRRUS CAN BE EXPECTED AS A RESULT OF THE  
PREVAILING SOUTHWEST FLOW ALOFT AS WE REMAIN ON THE EAST SIDE OF  
THE BROAD UPPER TROUGH ANCHORED OVER THE GREAT LAKES, BUT SC/CU  
DEVELOPMENT BECOMES LESS OF A CONCERN WITH TIME, EVEN IN THE  
UPSLOPE AREAS OF EASTERN WV.  
 
AS NOTED ABOVE, TEMPERATURES WILL BE ON A COOLING TREND THANKS  
TO COLD ADVECTION AT 850MB AND THE DEEPENING UPPER TROUGH. HIGH  
TEMPERATURES TODAY WILL RANGE FROM THE 70S IN THE NORTHWEST TO  
LOWER 80S IN THE SOUTHEAST, ON AVERAGE ABOUT 5 DEGREES COOLER  
THAN WHAT WE SAW SATURDAY, WITH ELEVATIONS ABOVE 3000 FT. LIKELY  
ONLY SEEING HIGH TEMPERATURES IN THE 60S TODAY. LOWS TONIGHT  
WILL BE VERY PLEASANT FOR THE END OF JUNE WITH WIDESPREAD LOWS  
IN THE 50S. A FEW 40S FOR LOWS IN PLACES LIKE LEWISBURG, BURKES  
GARDEN, AND SIMILAR ACROSS THE MOUNTAIN VALLEYS IN THE WEST  
WOULD NOT BE UNPRECEDENTED AT ALL. HOWEVER, THE COOLEST AIR OF  
THE WEEK WILL COME AFTER A SECONDARY FRONT MOVES THROUGH THE  
AREA TUESDAY.  
 

 
   
SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/
 
 
AS OF 330 AM EDT SUNDAY...  
 
AN UPPER LEVEL LOW OVER THE GREAT LAKES WILL BRING AN INCREASE IN  
CLOUDS MONDAY AFTERNOON AND A CHANCE FOR RAIN TUESDAY. THIS LOW WILL  
OPEN INTO A TROUGH TUESDAY NIGHT AS IT CONTINUES TO TRACK EAST AND  
OFF THE NEW ENGLAND COAST. COOL HIGH PRESSURE WILL SETTLE OVER THE  
REGION ON WEDNESDAY.  
 
MODELS VARY GREATLY FOR TUESDAY'S RAIN CHANCES IN TIMING, CONFIDENCE  
AND RAINFALL AMOUNTS. THE MOST AGRESSIVE IS THE ECM WHICH HAS RAIN  
ENTERING THE MOUNTAINS BEFORE SUNRISE TUESDAY. THE GFS HAS RAIN IN  
THE MOUNTAINS DURING THE MORNING WHILE THE NAM HOLDS EVERYTHING OFF  
UNTIL LATE IN THE AFTERNOON. THE ECM IS VERY CONFIDENT ON RAIN  
CHANCES TUESDAY WITH POPS 80-90%. THE GFS CONFIDENCE IS 30-50% FOR  
THE MOUNTAINS AND ZERO EAST OF THE BLUE RIDGE. THE NAM HAS LIKELY  
POPS (60%) FOR ONLY THE MOUNTAIN IN THE AFTERNOON. MODEL RAINFALL  
AMOUNTS RANGE FROM HALF AN INCH (ECM) TO A COUPLE OF HUNDREDTHS  
(GFS/NAM).  
 
WE FAVORED THE GFS SOLUTION FOR A FEW REASONS. FIRST, AS THE UPPER  
LEVEL TROUGH AXIS PIVOTS OVER THE OHIO VALLEY AND MID ATLANTIC  
REGION, THE ASSOCIATED SHORT WAVES TRACK ACROSS CENTRAL VA AND NOT  
DOWN INTO NC. THIS PATTERN AND NORTHWEST DOWNSLOPING FLOW WILL LIMIT  
RAIN CHANCES EAST OF THE BLUE RIDGE. SECOND, WHILE THE UPPER LEVEL  
TROUGH IS IN PLAY, OUR FLOW WILL BE FROM THE NORTHWEST. THE MOISTURE  
SOURCE WILL BE LIMITED COMING FROM EITHER THE GREAT LAKES OR  
RESIDUAL SOIL MOISTURE FROM TS CINDY'S TRACK ACROSS WV/OH. THERE IS  
NO RETURN FLOW FROM THE GULF OR THE ATLANTIC FOR RAINFALL AMOUNTS TO  
MATCH THAT OF THE ECM.  
 
WHILE UNDER THE INFLUENCE OF AN UPPER LEVEL TROUGH AND COOL  
NORTHWEST FLOW, TEMPERATURES MONDAY AND TUESDAY WILL RUN 5F-10F  
COOLER THAN NORMAL. WEDNESDAY'S TEMPERATURES WILL ALSO BE SLIGHT  
COOLER THAN NORMAL BUT WILL BEGIN A WARMING TREND FOR THE END OF THE  
WEEK.  
 

 
   
LONG TERM /THURSDAY THROUGH SATURDAY/
 
 
AS OF 230 PM EDT SATURDAY...  
 
TROUGH LIFTS OUT MIDWEEK WITH HEIGHT BUILDING ACROSS THE SOUTHERN  
U.S. SURFACE HIGH WILL SLIDE EAST OF THE REGION WEDNESDAY NIGHT.  
DIGGING TROUGH OVER THE UPPER MIDWEST TO START TO BUILD A LITTLE  
MORE OF HEAT RIDGE IN THE SOUTHEAST WITH 591 HEIGHTS. WILL STAY  
MAINLY DRY BUT HEATING UP WITH THREAT OF TYPICAL SUMMERTIME  
CONVECTION AS EARLY AS THURSDAY OVER THE WV MOUNTAINS, WITH BETTER  
THREAT FRIDAY-SATURDAY. SOUTHWEST FLOW ALOFT INCREASES BY SATURDAY  
WITH A FRONTAL BOUNDARY SLOWLY MOVING TOWARD THE OHIO VALLEY. SHOULD  
SEE AN UPTICK IN COVERAGE IN CONVECTION OVER THE WEEKEND ACROSS  
THE MOUNTAINS.  
 
THURSDAY WILL SEE MOISTURE INCREASE WITH HIGHS BUMPING UP ANOTHER 5  
DEGREES WITH UPPER 70S/LOWER 80S WEST, MID TO UPPER 80S EAST. THESE  
WARMER TEMPERATURES WHICH ARE CLOSE TO NORMAL FOR THE END OF JUNE  
WILL STICK AROUND INTO JULY 1ST, BUT THE HUMIDITY WILL BE MORE  
NOTICABLE AS WELL.  
 

 
   
AVIATION /14Z SUNDAY THROUGH THURSDAY/
 
 
AS OF 745 AM EDT SUNDAY...  
 
MOVING INTO AN EXTENDED PERIOD OF MOSTLY VFR CONDITIONS ACROSS  
THE REGION OVER THE NEXT FEW DAYS. THE WEAK FRONT HAS PUSHED  
SOUTHEAST OF THE AREA DOWN TOWARD THE I-40 CORRIDOR TAKING THE  
SHOWERS AND THUNDERSTORMS WITH IT, ALONG WITH THE DEEPER  
MOISTURE. FLOW ALOFT IS STILL BROAD WEST-NORTHWEST UNDER THE  
INFLUENCE OF A BROAD UPPER TROUGH DEEPENING ACROSS THE GREAT  
LAKES. THIS WILL CONTINUE UNTIL TUESDAY WHEN A SHORT WAVE ROUNDS  
THE BASE OF THE UPPER TROUGH. FOLLOWING THE PASSAGE OF THIS  
FEATURE, THE FLOW BEGINS TO RELAX, BECOME MORE ZONAL, AND  
EVENTUALLY SOUTHWEST AS THE TROUGH WEAKENS AND LIFTS OUT.  
 
THE ONLY POTENTIAL THROUGH THE PERIOD FOR ANY NON-VFR CONDITIONS  
WOULD BE DURING THE LATE NIGHT/EARLY MORNING HOURS WHEN ANY  
OF THE TYPICAL SPOTS THAT DECOUPLE AND RADIATE EFFECTIVELY WILL  
SEE FOG DEVELOPMENT. KDAN WAS ON THE EDGE OF DEEPER MOISTURE ALL  
NIGHT AND RAINFALL LATE IN THE DAY SATURDAY. AS A RESULT, THEY  
FOGGED IN JUST AFTER MIDNIGHT LAST NIGHT AND REMAINED LIFR-VLIFR  
MUCH OF THE NIGHT IN DENSE FOG. A SLIGHT NORTHWEST WIND AND  
INCREASED MID/HIGH CLOUDS HAVE ALLOWED THE FOG TO FINALLY BREAK  
UP THERE. GIVEN A DIFFERENT SYNOPTIC SITUATION MONDAY MORNING,  
DO NOT SEE A REPEAT OF THIS. GIVEN THE MOIST GROUND FROM RECENT  
RAINFALL AND THE COOLER/DRIER AIR MASS MOVING INTO THE REGION  
FOR THE FIRST HALF OF THE WEEK, FOG SEEMS LIKE A REASONABLE  
POSSIBILITY AT SITES SUCH AS KLWB AND KBCB, BUT LESS SO  
ELSEWHERE. NOT OVERLY CONFIDENT ABOUT SUCH TONIGHT BECAUSE AIR  
MASS HAS NOT FULLY TRANSITIONED YET AND THERE ARE SOME HIGH  
CLOUDS SKIRTING THE AREA. WILL CONTINUE TO ADVERTISE MVFR BR FOR  
KBCB AND KLWB MONDAY MORNING AS AIR MASS MAY MORE EFFECTIVELY  
RADIATE TONIGHT WITH LESS CLOUDS AND NEAR CALM WINDS.  
 
WINDS WILL BE WNW-NW AT SPEEDS OF 3-6KTS BEFORE 13Z, THEN  
INCREASE TO 6-11KTS WITH LOW END GUSTS AT MOST LOCATIONS DURING  
THE 14Z-22Z TIME FRAME, DIMINISHING OR BECOMING CALM AFTER 00Z.  
 
MEDIUM TO HIGH CONFIDENCE IN CEILINGS THROUGH THE TAF VALID  
PERIOD.  
MEDIUM TO HIGH CONFIDENCE IN VISIBILITIES THROUGH THE TAF VALID  
PERIOD.  
MEDIUM TO HIGH CONFIDENCE IN WIND SPEED/DIRECTION THROUGH THE  
TAF VALID PERIOD.  
 
EXTENDED AVIATION DISCUSSION...  
 
A WEAK DISTURBANCE DROPPING IN FROM THE NORTHWEST MAY BRING A  
PERIOD OF MVFR CIGS ALONG WITH A FEW SHOWERS TO THE MOUNTAINS  
LATE MONDAY NIGHT INTO TUESDAY. OTHERWISE EXPECTING OVERALL VFR  
FOR MONDAY THROUGH THURSDAY WITH SOME BRIEF LATE NIGHT/EARLY  
MORNING MOUNTAIN AND RIVER VALLEY FOG POSSIBLE.  
 
ON FRIDAY, THE POTENTIAL WILL INCREASE FOR SOME BRIEF, LOCALIZED  
SUB-VFR CONDITIONS AS SHOWER AND THUNDERSTORM CHANCES INCREASE.  
MORE WIDESPREAD, STILL DIURNALLY DRIVEN CONVECTION EXPECTED  
SATURDAY.  
 

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

 
 

 
SYNOPSIS...RAB  
NEAR TERM...DS/RAB  
SHORT TERM...RCS  
LONG TERM...RCS/WP  
AVIATION...RAB  
 
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