485  
FXUS61 KRNK 270536  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
136 AM EDT FRI APR 27 2018  
   
SYNOPSIS
 
 
AN UPPER LEVEL TROUGH WILL CROSS OVER THE MID ATLANTIC AND  
PROVIDE RAIN SHOWERS FOR TONIGHT. HIGH PRESSURE SHOULD ARRIVE  
TO PROVIDE DRIER CONDITIONS FOR THE UPCOMING WEEKEND AND INTO  
EARLY NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH TODAY/
 
 
AS OF 930 PM EDT THURSDAY...  
 
CURRENT SET OF GRIDS STILL LOOK GOOD. AT TIME OF THIS  
UPDATE,SHOWERS HAVE OVERSPREAD MUCH OF THE BLACKSBURG FORECAST  
AREA. HAVE ADJUSTED HOURLY TEMPERATURES AND DEW POINTS TO  
REFLECT LATEST TRENDS AS ONSET OF RAIN AND WET BULBING DRIVE  
TEMPERATURES DOWNWARD - ONLY TO LEVEL OFF AS THE EVENING  
PROGRESSES AS BOUNDARY LAYER SATURATES. MINIMUM OVERNIGHT  
TEMPERATURES STILL LOOK REASONABLE, SO LEFT UNCHANGED.  
 
OTHERWISE, JUST ENOUGH WEAK INSTABILITY MAY TRY TO SNEAK IN  
ACROSS THE EXTREME SOUTHEASTERN PORTION OF THE FORECAST AREA IN  
ADVANCE OF THE APPROACHING SHORT WAVE TO SUPPORT A BRIEF RUMBLE  
OF THUNDER, BUT NOT SUFFICIENT ENOUGH IN EITHER TIME OR SPACE TO  
WARRANT INFUSION INTO FORECAST AT THE PRESENT TIME. ALL  
INDICATIONS ARE THAT BEST INSTABILITY WILL REMAIN LOCKED TO  
AREAS FURTHER TO THE SOUTH AND EAST THROUGH THE NIGHT.  
 
AS OF 315 PM EDT THURSDAY...  
A POTENT UPPER LEVEL SHORTWAVE TROUGH WILL APPROACH  
NORTHWESTERN NORTH CAROLINA THIS EVENING AND CROSS OVERHEAD  
TONIGHT. SHOWERS WILL SPREAD NORTHEASTWARD ALONG THE REFLECTED  
SURFACE LOW PRESSURE AREA FROM THIS TROUGH. DETAILS ARE STILL A  
LITTLE SKETCHY ON THE EXACT QPF AND TIMING OF THE RAINFALL. THE  
GFS IS A LITTLE QUICKER AND WETTER, WHILE THE ECMWF IS SLOWER  
AND DRIER. THE CONSENSUS OF THE HIGH RESOLUTION GUIDANCE FAVORS  
THE GFS SOLUTION MORE BUT APPEARS TO BE DRIVEN TOO MUCH BY  
CONVECTION, AND INSTABILITY IS BARELY THERE TO SUPPORT IT  
ACCORDING TO MODEL SOUNDINGS. WE WILL NEED TO MONITOR RAINFALL  
RATES FOR ANY POSSIBLE MINOR FLOODING OR ANY AGGRAVATION OF THE  
ONGOING RIVER FLOODING SITUATION IN SOUTHSIDE VIRGINIA.  
CONFIDENCE WAS NOT HIGH ENOUGH TO WARRANT A FLOOD WATCH AT THIS  
TIME, SO THE FLOOD THREAT IS MENTIONED IN THE HWO. OVERALL,  
ABOUT A HALF TO ONE INCH OF RAIN IS EXPECTED TONIGHT, BUT THERE  
SHOULD BE LOCALLY HIGHER AMOUNTS IF ANY BANDING OR TRAINING  
TAKES PLACE.  
 
THE SHOWERS SHOULD GRADUALLY FADE DURING THE EARLY MORNING HOURS  
OF FRIDAY, BUT THE LINGERING MOISTURE SHOULD PROVIDE LOW CLOUDS  
AND PATCHY FOG TOWARD SUNRISE. AS THE AREA OF LOW PRESSURE  
DEPARTS FROM THE MID ATLANTIC, WINDS SHOULD SHIFT TOWARD THE  
NORTHWEST AND STEADILY INCREASE DURING THE DAY. THIS MIXING  
SHOULD SCOUR OUT ANY FOG AND LOW CLOUDS ACROSS THE PIEDMONT BY  
MIDDAY. HOWEVER, LINGERING MOISTURE COULD KEEP LOW CLOUDS A  
LITTLE LONGER ALONG AND WEST OF THE BLUE RIDGE. IN ADDITION, THE  
UPSLOPE FLOW SHOULD PROVIDE SHOWERS ALONG THE HIGHER ELEVATIONS  
WEST OF A LINE FROM LEWISBURG TO BOONE THROUGH MOST OF THE  
DAYTIME HOURS. IT WILL BE SLIGHTLY COOLER ON FRIDAY COMPARED TO  
TODAY, BUT TEMPERATURES SHOULD REMAIN NEAR SEASONAL VALUES.  
 

 
   
SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/
 
 
AS OF 230 PM EDT THURSDAY...  
 
A DISTURBANCE OVER THE GREAT LAKES FRIDAY NIGHT WILL SLOWLY TRACK  
EAST TO NEW ENGLAND BY SATURDAY NIGHT. AN INVERTED TROUGH EMERGES  
AHEAD OF THIS SYSTEM AND ALONG THE WESTERN SLOPES OF THE APPALACHIAN  
MOUNTAINS FRIDAY EVENING. THIS TROUGH SHOULD ONLY RESULT IN SOME LOW  
CLOUDS PASSING OVER THE MOUNTAINS INTO SATURDAY MORNING. ALSO AHEAD  
OF THIS SYSTEM, WINDS BACK ACROSS THE TENNESSEE-OHIO VALLEY. WITH  
WEAK FORCING AND LIMITED MOISTURE AS GULF IS BLOCKED, LIGHT SHOWERS  
ARE POSSIBLE ALONG WESTERN SLOPES AND ISOLATED SHOWERS ACROSS THE  
REST OF THE MOUNTAINS SATURDAY AFTERNOON INTO THE EARLY EVENING.  
SHOWERS WILL END QUICKLY AS THE FRONT SLIDES ACROSS THE AREA  
SATURDAY EVENING. EVEN THOUGH DRY AIR ENTRAINS INTO THE REGION, SOME  
LIGHT UPSLOPE RAIN/DRIZZLE IS LIKELY ALONG WESTERN GREENBRIER AS  
SHORT WAVES ROUNDING THE LOW TO THE NORTH PASS OVER THE AREA.  
UPSLOPE PRECIPITATION WILL COME TO AN END SUNDAY MORNING, THEN DRY  
HIGH PRESSURE BUILDS OVER THE REGION.  
 
BEING AHEAD OF THE FRONT FRIDAY NIGHT AND SATURDAY, TEMPERATURES  
WILL REMAIN MILD. OVERNIGHT FRIDAY, 40S WILL BE COMMON TO NEAR 50F  
ACROSS THE PIEDMONT. FOR SATURDAY, NEAR SEASONAL TEMPERATURES  
EXPECTED WITH LOW TO MID 60S WEST AND LOW TO MID 70S EAST. FOLLOWING  
THE FRONT SATURDAY EVENING, TEMPERATURES DROP INTO THE 30S ACROSS  
THE MOUNTAINS AND LOW TO MID 40S EAST.  
 

 
   
LONG TERM /MONDAY THROUGH THURSDAY/
 
 
AS OF 230 PM EDT THURSDAY...  
 
DRY HIGH PRESSURE WILL BE OVERHEAD MONDAY. WITH DRY AIR AND ABUNDANT  
SUNSHINE, TEMPERATURES WILL WARM TO NEAR NORMAL LEVELS. THE CENTER  
OF THE HIGH WILL SLIDE OFF THE SOUTHEAST COAST ON TUESDAY. THE  
ADDITION OF SOUTHERLY FLOW WILL PUSH AFTERNOON TEMPERATURES WELL  
ABOVE NORMAL TUESDAY INTO THURSDAY. EXPECTED TEMPERATURES THROUGH  
THE MIDDLE OF THE WEEK TO RUN 10F WARMER THAN NORMAL.  
 

 
   
AVIATION /06Z FRIDAY THROUGH TUESDAY/
 
 
AS OF 136 AM EDT FRIDAY...  
 
POOR FLYING CONDITIONS THIS MORNING IN LOW CLOUDS, FOG AND  
CONVECTION WILL IMPROVE THIS AFTERNOON INTO TONIGHT.  
 
THE UPPER LEVEL AND ASSOCIATED WIDESPREAD AREA OF SHOWERS WILL  
CONTINUE TO SLOWLY MOVE EAST ACROSS THE REGION TODAY INTO  
TONIGHT. VFR/MVFR CONDITIONS WILL LOW TO IFR/LIFR IN  
LOW CLOUDS, FOG AND SHOWERS THIS MORNING.  
 
GRADUAL IMPROVEMENT BACK TO VFR CONDITIONS EXPECTED BY LATE  
THIS MORNING WITH PASSAGE OF TROF AND WITH ONSET OF DAYTIME  
HEATING/MIXING. WINDS WILL REMAIN TOO LIGHT THROUGHOUT THE VALID  
FORECAST PERIOD TO PRESENT ANY FLIGHT-RELATED CONCERNS, BUT  
COULD PICK UP A LITTLE AS THE AFTERNOON PROGRESSES.  
 
MEDIUM CONFIDENCE IN CEILINGS, VISIBILITIES AND WINDS DURING  
THE TAF PERIOD.  
 
EXTENDED AVIATION DISCUSSION...  
 
HIGH PRESSURE SHOULD BUILD OVERHEAD TONIGHT INTO SATURDAY TO  
BRING VFR CONDITIONS FOR ALL SITES BY SATURDAY AFTERNOON. GOOD  
FLYING WEATHER WILL PERSIST THROUGH THE REMAINDER OF THIS  
WEEKEND AND INTO EARLY NEXT WEEK.  
 

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

 
 

 
SYNOPSIS...PW/WERT  
NEAR TERM...PW  
SHORT TERM...RCS  
LONG TERM...RCS  
AVIATION...KK/WERT  
 
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