590  
FXUS61 KRNK 010335  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
1135 PM EDT SUN APR 30 2017  
   
SYNOPSIS
 
 
A COLD FRONT MOVES THROUGH THE EASTERN UNITED STATES MONDAY.  
WEAK HIGH PRESSURE FOLLOWS THE FRONT WITH DRIER WEATHER FOR  
TUESDAY AND WEDNESDAY.  
 

 
   
NEAR TERM /THROUGH MONDAY/
 
 
AS OF 1123 PM EDT SATURDAY...  
 
MADE MINOR CHANGES TO THE FORECAST TO ACCOUNT FOR LOCATION OF  
SHOWERS OVER THE NW NC FOOTHILLS/PIEDMONT. HRRR AND RAP SHOWING  
MOST SHOWER ACTIVITY THROUGH EARLY MORNING TO STAY ACROSS THE  
BLUE RIDGE SOUTH OF FLOYD INTO THE NC MOUNTAINS/FOOTHILLS.  
 
UPPED WINDS A LITTLE AS WELL BUT THINK ADVISORY LEVELS SHOULD  
NOT BE REALIZED, EXCEPT PERHAPS AT THE HIGHER PEAKS OF FAR SW  
VA. SPECIAL WX STATEMENT ISSUED EARLIER TO ACCOUNT FOR GUSTS UP  
TO 45 MPH THANKS TO 50-55 KT LOW LEVEL JET MOVING IN AFTER 05Z.  
 
PREVIOUS DISCUSSION FROM EARLY EVENING...  
 
SATELLITE/RADAR SHOWING LIMITED COVERAGE FOR SHOWERS,  
MUCH LESS THUNDER IN OUR FORECAST AREA EARLY THIS EVENING. SMALL  
AREA OF LOW LEVEL CONVERGENCE SITUATED OVER SOUTHSIDE VA  
HELPING WITH A FEW SHOWERS THERE. OTHERWISE WILL WAIT UNTIL  
MIDNIGHT OR SO TO SEE BETTER LIFT/ENHANCEMENT ACROSS THE  
SOUTHERN BLUE RIDGE FOR MORE SHOWER DEVELOPMENT.  
 
PREVIOUS DISCUSSION FROM MID AFTERNOON...  
DEEP UPPER CLOSED LOW OVER WESTERN OKLAHOMA THIS MORNING WILL  
TRACK NORTHEAST TO SOUTHEAST IOWA BY MONDAY MORNING THEN TO  
NORTHEAST WISCONSIN BY MONDAY EVENING. MONDAY IN GOOD AGREEMENT  
WITH THE TIMING AND TRACK OF THE LOW.  
 
CHALLENGING TO PINPOINT WHERE ISOLATED TO WIDELY SCATTERED STORMS  
WILL DEVELOP THIS AFTERNOON. SOME OF THE HI-RES GUIDANCE INCLUDING  
SPC-HRRR SUGGESTS FAVORED AREAS NORTH OF LYNCHBURG AND LEWISBURG AND  
ANOTHER IN SOUTHWEST NORTH CAROLINA WITH THE STORMS TRACKING TO THE  
NORTH AND NORTHEAST. ANY THUNDERSTORMS WILL DISSIPATE SHORTLY AFTER  
SUNSET WITH LOSS OF HEATING.  
 
WINDS INCREASE FROM THE SSW, ESPECIALLY JUST ABOVE THE SURFACE  
TONIGHT. LOW LEVEL IS AROUND 60 KNOTS AT BOONE AND BLUEFIELD BY  
MONDAY MORNING. ENOUGH LOW LEVEL MOISTURE AGAIN TONIGHT FOR A LAYER  
OF LOW CLOUDS. BAND OF DEEPER MOISTURE ALONG THE FRONT CROSSES WEST  
TO EAST OVER THE REGION ROUGHLY BETWEEN 15Z/11AM THROUGH 03Z/11PM,  
WITH THE GFS STILL A COUPLE HOURS FASTER THAN THE NAM. THIS SLOWS  
DOWN THE HIGHER PROBABILITY OF PRECIPITATION ON MONDAY MORNING. WIND  
SHIFT TO THE WEST WILL BEHIND THE FRONT. THIS LOOKS LIKE LATE IN THE  
DAY FOR SOUTHEAST WEST VIRGINIA.  
 
STILL NOT CLEAR HOW MUCH PRE-FRONTAL PRECIPITATION THERE WILL BE.  
QUESTIONABLE HOW MUCH INSTABILITY WILL INCREASE ON MONDAY IF MOST OF  
THE MOUNTAINS START OUT CLOUDY AND THE CLOUDS SPREAD EAST DURING THE  
DAY. TEMPERATURES AT MID LEVEL NOT QUITE AS WARM JUST AHEAD OF THE  
FRONT. BUFKIT FORECAST SOUNDINGS SHOWED ENOUGH SLOW LEVEL HEATING TO  
BREAK THE CAP BY 20Z/4PM MONDAY ACROSS SOUTHWEST VIRGINIA, NORTHERN  
NORTH CAROLINA, AND SOUTHEAST WEST VIRGINIA. OFF THE 12Z NAM AND GFS  
THE FORECAST LIFTED INDEX VALUES ARE -4 TO -6 WITH CONVECTIVE  
AVAILABLE POTENTIAL ENERGY AROUND 1500 J/KG WITH THE PUSH EAST OF  
MORE STABLE AIR IN THE LATE AFTERNOON AND EVENING FROM WEST TO EAST.  
 
SIMILAR TO PAST COUPLE OF NIGHTS, FORECAST AREA WILL REMAIN IN THE  
MILD HUMID AIR MASS AND WITH INCREASING CLOUD COVER LATE TONIGHT  
MINIMUM TEMPERATURES WILL BE ABOVE NORMAL. ALSO SLIGHTLY INCREASED  
THE MAXIMUM TEMPERATURES FOR MONDAY SINCE FRONT IS COMING THROUGH A  
LITTLE LATER IN THE DAY.  
 

 
   
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/
 
 
AS OF 310 PM EDT SUNDAY...  
 
FORECAST MODELS SHIFT A COLD FRONT EAST OF OUR FORECAST AREA AROUND  
06Z (2 AM EDT) TUESDAY. IN ITS WAKE, A BRIEF PERIOD OF 40-50KT 850MB  
WINDS ARE EXPECTED, BUT PRESSURE RISES DIMINISH DURING THE PRE-DAWN  
HOURS TUESDAY AND THE FORECAST INVERSION HEIGHT SHOULD KEEP THE  
STRONGEST WINDS ALOFT. THEREFORE WILL CONTINUE TO HIGHLIGHT GUSTY  
WINDS IN THE MOUNTAINS IN THE HWO, BUT NOT ISSUE HEADLINES.  
 
BREEZY CONDITIONS CONTINUE ON TUESDAY, AND DESPITE COOLER 850MB  
TEMPS, DOWNSLOPING WIND SHOULD PUSH TEMPS UP TO NEAR NORMAL VALUES  
FOR EARLY MAY.  
 
LEANED TOWARD THE COOLER GUIDANCE VALUES FOR LOWS WEDNESDAY MORNING  
AS A LARGE HIGH NOSES INTO THE WESTERN POTION OF THE AREA. A WEAK  
RETURN FLOW WEDNESDAY WILL BRING CLOUDS AND AN INCREASE IN DEW  
POINTS TO THE SOUTHERN POTION OF THE FORECAST AREA LATE IN THE DAY.  
DESPITE WEAK LOW LEVEL CONVERGENCE LATE IN THE SOUTHERN BLUE RIDGE,  
FORECAST SOUNDINGS SHOW A HEALTHY AMOUNT OF DRY AIR IN THE LOW  
LEVELS, THEREFORE KEPT A DRY FORECAST IN PLACE.  
 

 
   
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
 
 
AS OF 245 PM EDT SUNDAY...  
 
THIS PERIOD OF THE FORECAST WILL BE DOMINATED BY A HIGH AMPLITUDE  
UPPER TROF/CUT OFF LOW THAT LIFTS OUT OF THE SOUTHERN PLAINS EARLY  
IN THE PERIOD, AND INTO NEW ENGLAND BY THE END OF THE WEEKEND. WHILE  
THERE ARE STILL SOME DIFFERENCES IN THE MODELS WITH REGARD TO  
INTENSITY AND TIMING, THERE IS GROWING CONSENSUS THAT WIDESPREAD  
SHOWERS AND THUNDERSTORMS IMPACT OUR AREA SOMETIME FROM THURSDAY  
INTO FRIDAY WITH UPSLOPE SHOWERS LINGERING INTO SUNDAY AS  
REINFORCING SHORTWAVES ROTATE SOUTHWARD ON THE WEST SIDE OF THE UPPER  
LOW. ENSEMBLE MEMBERS SEEM TO BE CENTERING AROUND LATE  
THURSDAY/EARLY FRIDAY MORNING FOR THE BEST CHANCE FOR PRECIPITATION.  
 
THE 12Z GFS IS SHOWING BETTER RUN TO RUN CONSISTENCY, BUT ALSO  
ALIGNING MORE WITH THE 00Z ECMWF WITH A SLIGHTLY LESS AMPLIFIED  
UPPER TROF AND MORE NORTHERN PLACEMENT OF THE UPPER LOW. FOR OUR  
AREA, CHANCES FOR STRONG STORMS APPEAR BEST WHEN INSTABILITY AND  
LIFT ALIGN ON FRIDAY, BUT A GREATER CONCERN MAY BE FOR THE POTENTIAL  
FOR FLOODING, AS NAEFS AND GEFS ENSEMBLES OFF THE METEOROLOGICAL  
MODEL ENSEMBLE RIVER FORECASTS SHOW SOME CONFIDENCE IN THE POTENTIAL  
FOR FLOODING IN OUR AREA LATE THURSDAY/FRIDAY. WILL INCLUDE THE  
MENTION FOR POSSIBLE FLOODING DURING THIS TIME IN THE HWO.  
 
AFTER BEING WEDGED IN THURSDAY, WARMEST TEMPS FOR THIS PERIOD WILL  
BE FRIDAY BEFORE BELOW NORMAL TEMPS ARRIVE SATURDAY INTO SUNDAY  
UNDER THE INFLUENCE OF THE UPPER TROF.  
 

 
   
AVIATION /04Z MONDAY THROUGH FRIDAY/
 
 
AS OF 705 PM EDT SUNDAY...  
 
SHOULD STAY VFR THIS EVENING AT ALL SITES, THEN LOW LEVELS  
MOISTEN UP AS SOUTHEAST TO SOUTH FLOW INCREASES WITH MOST SITES  
FALLING TO MVFR OR LOWER AFTER 06Z, ESPECIALLY NEAR THE BLUE  
RIDGE, WHILE BLF STAYS VFR.  
 
TIMING OF FRONT AND PRE-FRONTAL SHOWERS AND THUNDERSTORMS LOOKS  
TO BE STARTING AROUND 15Z BLF/LWB TO 17Z BCB/ROA AND 19-20Z  
LYH/DAN. ENDING TIME WILL BE BY 20Z BLF/LWB TO 23Z ROA/BCB AND  
BEYOND THIS TAF PERIOD OUT EAST.  
 
THUNDER CHANCES ARE GOOD, BUT COULD BE LIMITED BY LOW LEVEL  
CLOUD COVER. FOR NOW WILL KEEP VCTS IN THE TAFS WITH MODERATE  
RAIN SHOWERS WITH MVFR CIGS, WITH GOOD POSSIBILITY FOR IFR  
CIGS/VSBYS IN HEAVY DOWNPOURS.  
 
SPC HAS MARGINAL TO SLIGHT RISK OF SEVERE STORMS, SO FLYING  
CONDITIONS WILL BE TURBULENT AND POOR IN THE REGION TOMORROW.  
 
WINDS WILL ALSO BE STRONG FROM THE SOUTH TONIGHT INTO MONDAY,  
THEN STAY GUSTY BEHIND THE FRONT MONDAY AFTERNOON/EVENING.  
 
EXTENDED AVIATION DISCUSSION...  
 
THE COLD FRONT WILL MOVE EAST OF KLYH AND KDAN BY 03Z BRINGING  
THE WINDS AROUND TO THE SOUTHWEST THEN WEST. SOUTHEAST WEST  
VIRGINIA MAY HAVE MVFR UPSLOPE CLOUDS INTO EARLY TUESDAY. VFR  
CONDITIONS RETURN TUESDAY AND WILL CONTINUE UNDER HIGH PRESSURE  
TUESDAY NIGHT AND WEDNESDAY.  
 
A SLOW MOVING LOW PRESSURE SYSTEM WILL BRING WIDESPREAD  
PRECIPITATION AND SUB-VFR CONDITIONS TO THE MID ATLANTIC REGION  
THURSDAY AND FRIDAY.  
 

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

 
 

 
SYNOPSIS...AMS  
NEAR TERM...AMS/WP  
SHORT TERM...PH  
LONG TERM...PH  
AVIATION...AMS/JH/WP  
 
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