566  
FXUS61 KRNK 221138  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
738 AM EDT THU AUG 22 2019  
   
SYNOPSIS
 
 
A COLD FRONT FROM NEW ENGLAND TO THE MID MISSISSIPPI VALLEY WILL  
MOVE SLOWLY SOUTH TODAY AND FRIDAY. BY SATURDAY THE FRONT WILL  
EXTEND FROM THE CAROLINAS TO THE SOUTHERN PLAINS. COOLER HIGH  
PRESSURE WILL BUILD INTO THE MID ATLANTIC REGION SUNDAY AND  
MONDAY.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 315 AM EDT THURSDAY...  
 
A COLD FRONT EXTENDED FROM NEW YORK TO SOUTHERN MISSOURI THIS  
MORNING. THE FRONT WILL BE DROPPING SLOWLY SOUTH TODAY AND WILL  
REACH CENTRAL WEST VIRGINIA TO NORTHERN VIRGINIA LATE TONIGHT.  
WARM, HUMID AND UNSTABLE AIR WILL STILL BE IN PLACE AHEAD OF THE  
FRONT TODAY.  
 
A CLUSTER OF THUNDERSTORMS TRACKING ACROSS SOUTHERN INDIANA EARLY  
THIS MORNING WILL REACH THE CENTRAL APPALACHIANS JUST AFTER  
15Z/11AM. THIS TIMING IS BASED OF THE SPC HREF AND HIRESARW  
GUIDANCE. THESE THUNDERSTORMS WILL EITHER CONTINUE ACROSS SOUTHWEST  
VIRGINIA AND NORTHERN CAROLINA INTO THE AFTERNOON, OR IF THEY WEAKEN  
THROUGHOUT THE MORNING, ANY RESIDUAL OUTFLOW WILL BE THE FOCUS FOR  
THUNDERSTORM DEVELOPMENT DURING THE AFTERNOON. OTHERWISE UNSTABLE  
AIR MASS WILL SUPPORT DEVELOPMENT OF ISOLATED TO SCATTERED  
THUNDERSTORMS DURING THE AFTERNOON AND INTO THE EVENING. NO  
PARTICULAR CONSENSUS IN THE GUIDANCE OF WHAT THE AREAL COVERAGE  
OF STORMS WILL LOOK LIKE AROUND 21Z/5PM BUT SOME AGREEMENT THAT  
AFTER 00Z/8PM A MAJORITY OF THE ACTIVITY WILL BE EAST OF US 29.  
 
WILL BE STAYING CLOSE TO NATIONAL BLEND GUIDANCE WHICH HAS BEEN  
DOING WELL OVER THE PAST FEW RUNS FOR MAXIMUM TEMPERATURES.  
LOCATIONS IN THE FOOTHILLS AND PIEDMONT OF VIRGINIA AND NORTH  
CAROLINA THAT STAY DRY FOR A MAJORITY OF THE DAY WILL BE CLOSE TO  
THE MID 90S. HEATING WILL BE CURTAILED IN SPOTS THAT HAVE RAIN IN  
THE AFTERNOON. WITH NO CHANGE IN AIR MASS TONIGHT, WILL USE  
PERSISTENCE AS GUIDANCE FOR OVERNIGHT LOWS.  
 

 
   
SHORT TERM /FRIDAY THROUGH SUNDAY/
 
 
AS OF 300 AM EDT THURSDAY...  
 
A SOUTHWARD-SAGGING, WEST-EAST ORIENTED COOL FRONT WILL INTERACT  
WITH POORLY-DEFINED VORT MAXIMA AND LEAD TO WHAT SHOULD BE AN ACTIVE  
CLOSE TO THE WORKWEEK FRIDAY INTO FRIDAY NIGHT. INCREASING 500 MB  
HEIGHT GRADIENT SHOULD ALSO SUPPORT INCREASING MID-LEVEL WINDS INTO  
THE 30 TO 35 KT TERRITORY AREAWIDE. WHILE THIS INCREASES EFFECTIVE  
SHEAR MAGNITUDES INTO THE 30 KT RANGE, THE SOMEWHAT STRONGER FLOW  
WILL ALSO IN ALL LIKELIHOOD CONTRIBUTE TO A CONSIDERABLE EXTENT OF  
MID-LEVEL CLOUD COVER STREAMING IN FROM THE WEST THAT MAY HAMPER  
DESTABILIZATION DURING THE PEAK-HEATING HRS. WHILE LOW-LEVEL  
MOISTURE ON SOUTHWEST WINDS WILL HELP DESTABILIZE THINGS TO AN  
EXTENT, EVEN FOR A MOST-UNSTABLE PARCEL ASCENT CAPES ARE ONLY  
PROGGED TO BE AROUND 1000-1500 J/KG. MODEL RADAR SIMULATIONS FOR  
FRIDAY GIVE A MULTICELL/BROKEN LINE SETUP FOR AREAS EAST OF THE BLUE  
RIDGE - WHICH MAKES SENSE GIVEN THE EFFECTIVE SHEAR VALUES, WITH  
BETTER ORGANIZATION AND SLIGHTLY GREATER SEVERE WEATHER POTENTIAL  
INTO OUR EASTERN THIRD OF COUNTIES BUT ESPECIALLY INTO EASTERN VA  
AND NORTHEAST NC. FURTHER WEST, EARLY-DAY SHOWERS/EMBEDDED RUMBLES  
OF THUNDER POSES LESS OF A SEVERE WEATHER CONCERN THAN POINTS EAST.  
 
TALL, SKINNY CAPE PROFILES FORECAST AND HUMID, ELEVATED-PWAT  
AIR MASS WILL ALSO CONTRIBUTE TO HEAVY RAIN POTENTIAL PRETTY  
MUCH AREAWIDE, EVEN INTO THE NIGHTTIME HOURS AS THE EAST-WEST  
FRONT SAGS SOUTH. FLASH FLOOD GUIDANCE CONTINUES TO RUN ON THE  
HIGH SIDE (ABOUT 2-3" IN AN HOUR'S TIME, AND 2.5-4" IN 3 HOURS),  
AND THAT SHOULD PRECLUDE A GREATER SHORT-FUSED FLOOD THREAT.  
PATTERN SUGGESTS TRAINING IS A POSSIBILITY GIVEN AN EAST-WEST  
FRONT ORIENTED SOMEWHAT MORE PARALLEL TO THE MID-LEVEL FLOW, AND  
IT WOULD BE FOR THOSE AREAS THAT WOULD HAVE TO BE WATCHED FOR  
HYDRO ISSUES. GIVEN THE EFFICIENT RAIN POTENTIAL AND THE  
ENVIRONMENT SUPPORTING TRAINING, I DO THINK IT'S WORTH INCLUDING  
HEAVY RAIN WORDING IN THE GRIDS AREAWIDE, EVEN INTO THE  
EVENING. AFTER COORDINATION, WPC'S ALSO INCREASED THE EXCESSIVE  
RAIN CATEGORY TO THE SLIGHT LEVEL IN EASTERN VA/NC WITH A  
MARGINAL ELSEWHERE FOR FRIDAY. WHILE WE SHOULD HAVE SOME STRONG  
TO SEVERE STORMS WITH GUSTY TO DAMAGING WINDS IN A CORRIDOR FROM  
LYNCHBURG TO MARTINSVILLE TO DANBURY AND EASTWARD, WITH MORE  
CLOUD COVER/LESS CLOUD BREAKS AND RESULTING LOWER INSTABILITY  
VALUES, I DON'T THINK THE CONFIDENCE IN THE SEVERE THUNDERSTORM  
POTENTIAL IS GREAT ENOUGH TO INCLUDE ENHANCED WORDING FOR GUSTY  
WINDS ATTM. SPC HAS HIGHLIGHTED THE ABOVE CORRIDOR IN A MARGINAL  
RISK FOR SEVERE WEATHER FOR FRIDAY.  
 
A WEAK SURFACE WAVE LOW/MESOLOW OVERNIGHT FRIDAY INTO EARLY SATURDAY  
MAY BRIEFLY STALL THE FRONT'S SOUTHWARD PROGRESS. THIS SUGGESTS  
OPENING WITH LIKELY POPS ON SATURDAY MORNING AT LEAST TO SOUTHSIDE  
SEEMS REALISTIC, LOWER POPS NORTH. NORTHERLY/NORTHEAST FLOW ON THE  
COOL SIDE OF THE FRONT AND RAIN FALLING ON THE SOUTH SIDE OF THE  
FRONTAL ZONE SHOULD HELP SHIFT THE FRONT'S POSITION INTO NORTH-  
CENTRAL NC TOWARD SATURDAY AFTERNOON WITH FALLING POPS TOWARD SLIGHT  
CHANCE OR DRY.  
 
BIGGEST FORECAST CHALLENGES SATURDAY ARE TIMING THE FRONT'S  
PASSAGE INTO CENTRAL NC, AND ON TEMPERATURES DUE TO VARIATION IN  
CLOUD COVER. TO THE LATTER POINT, COOLER/DRIER AIR SHOULD  
FILTER IN ON THE NORTHEAST FLOW, WITH LOWERING DEWPOINTS TO MUCH  
MORE COMFORTABLE LEVELS. NAM/GFS BUFKIT PROFILES SHOW A SHALLOW  
STRATUS LAYER AROUND 4000' THAT COULD KEEP DAYTIME HEATING  
POST- FRONTAL AT LEAST MORE MUTED. MOS HIGHS ARE SOME 10 DEGREES  
COLDER THAN CLIMO GIVEN THE CLOUD COVER AND 850 MB TEMPS  
DIPPING INTO THE LOW TO MID TEENS CELSIUS. IF THAT CLOUD LAYER  
DOESN'T MATERIALIZE THEN WE COULD SEE HIGHS CLOSER TO THE LOW  
80S. WILL STICK CLOSER TO THE UPPER 70S (COOLER 60S IN THE HIGH  
TERRAIN), THOUGH CONFIDENCE IN THE TEMPERATURE FORECAST IS LOWER  
THAN IT WOULD OTHERWISE BE.  
 
SATURDAY NIGHT INTO SUNDAY LOOK A LOT QUIETER, WITH SUNDAY BEING THE  
PICK OF THE WEEKEND FOR OUTDOOR ACTIVITIES WITH HIGH PRESSURE  
RIDGING DOWN THE CENTRAL APPALACHIANS. SKIES LOOK VARIABLY CLOUDY  
WITH SOME ENHANCED EAST FLOW AND SOME HIGHER MODEL RH MEANING  
POTENTIAL FOR GREATER CLOUDINESS INTO OUR NC COUNTIES. HOWEVER MUCH  
OF VA AND WV SHOULD SEE LESS CLOUDS, WITH TEMPERATURES A FEW DEGREES  
COOLER THAN NORMAL ALONG WITH COMFORTABLE DEWPOINTS.  
 
FORECAST CONFIDENCE IS OVERALL MODERATE FOR THIS PERIOD.  
 

 
   
LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/
 
 
AS OF 300 PM EDT WEDNESDAY...  
 
IF THE FRONT SINKS SOUTH INTO THE CAROLINAS SATURDAY, COOL NORTHEAST  
WINDS WILL KEEP THE AREA DRY INTO MONDAY (ECM). THE LATEST GFS HAS  
AN UPPER LEVEL TROUGH MOVING NORTHEASTWARD ACROSS THE OHIO VALLEY  
WITH OVERRUNNING WARM MOIST AIR MOVING OVER A WEDGE OF COOLER AIR.  
WE THINK THE GFS IS OVERDONE ON MEASURABLE PRECIPITATION, BUT THINK  
IT HAS THE RIGHT IDEA WITH INCREASING CLOUD COVER. THE WEDGE IS  
EXPECTED TO HANG OVER THE REGION INTO TUESDAY MORNING THEN ERODE  
WITH THE PASSING OF A WEAK FRONT.  
 
TEMPERATURES WILL RUN 10F OR COOLER THAN NORMAL SUNDAY AND MONDAY.  
TEMPERATURE RETURN TO NORMAL WEDNESDAY.  
 

 
   
AVIATION /12Z THURSDAY THROUGH MONDAY/
 
 
AS OF 725 AM EDT THURSDAY...  
 
MID AND HIGH CLOUDS WILL ALSO BE INCREASING FROM THE WEST IN  
THE MORNING. STILL ENOUGH HEATING EXPECTED FOR THE AIR MASS TO  
BECOME UNSTABLE, ESPECIALLY IN THE VIRGINIA AND NORTH CAROLINA  
PIEDMONT WHERE BUFKIT FORECAST SOUNDINGS WERE SHOWING CONVECTIVE  
AVAILABLE POTENTIAL ENERGY AS HIGH AS 2000 J/KG THIS AFTERNOON  
AT KLYH.  
 
SPC HREF AND HI-RESARW MODELS HAD THE LEADING EDGE OF SHOWERS  
AND THUNDERSTORMS CROSSING OHIO AND KENTUCKY REACHING KBLF AND  
KLWB BETWEEN 14Z/10AM AND 16Z/NOON. THUNDERSTORMS WILL CONTINUE  
TO DEVELOP AS THIS RESIDUAL OUTFLOW MOVES EAST ACROSS VIRGINIA  
AND NORTH CAROLINA. MVFR CONDITIONS ARE EXPECTED WITH THE  
THUNDERSTORMS THIS AFTERNOON DUE TO REDUCED VISIBILITY FROM HEAVY  
RAIN.  
 
THE MAJORITY OF THE THUNDERSTORMS WILL BE EAST OF KLYH AND KDAN  
BY MIDNIGHT. LOCATIONS THAT GET RAIN DURING THE AFTERNOON MAY  
HAVE FOG IN THE EVENING OR OVERNIGHT. MORE SHOWERS AND  
THUNDERSTORMS WILL BE APPROACHING THE CENTRAL APPALACHIANS FROM  
THE WEST LATE TONIGHT WHICH MAY LOWER CEILINGS TO MVFR AT KLWB  
AND KBLF WELL AFTER MIDNIGHT.  
 
CONFIDENCE ON THE OCCURRENCE OF THUNDERSTORMS THIS AFTERNOON IS  
ABOVE AVERAGE, ALTHOUGH CONFIDENCE ON THE EXACT TIMING AND  
LOCATION IS AVERAGE.  
 
CONFIDENCE ON CEILING, VISIBILITY AND WIND TONIGHT IS AVERAGE.  
 
   
EXTENDED AVIATION DISCUSSION
 
 
WEATHER PATTERN WILL CONTINUE TO PROMOTE SCATTERED SHOWERS AND  
THUNDERSTORMS. A COLD FRONT WILL APPROACH FROM THE NORTHWEST  
FRIDAY AND SATURDAY, RESULTING IN SCATTERED TO NUMEROUS  
THUNDERSTORM WITH POTENTIAL FOR ORGANIZED CLUSTERS OF  
THUNDERSTORMS TO TRACK ACROSS THE OHIO VALLEY INTO THE MID-  
ATLANTIC REGION.  
 
IMPROVING CONDITIONS WITH MORE IN THE WAY OF VFR WILL BE  
POSSIBLE FOR SUNDAY, PENDING JUST HOW FAR SOUTH OF THE MID  
ATLANTIC AREA THE FRONT PROGRESSES. SOME MVFR SHOWERS ARE  
POSSIBLE IN THE SOUTHWEST VIRGINIA AND NORTHWEST NORTH CAROLINA  
ON MONDAY.  
 
NO OBSERVATIONS WERE AVAILABLE FOR KLWB SO "AMD NOT SKED" HAS  
BEEN ADDED TO THE TAF. NIGHTIME MICROPHYSICS SATELLITE IMAGES  
SUGGEST THERE MAY BE FOG IN THE GREENBRIER VALLEY AND MVFR OR  
LOWER VISIBILITY AT KLWB.  
 

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

 
 

 
SYNOPSIS...AMS  
NEAR TERM...AMS  
SHORT TERM...AL  
LONG TERM...RCS  
AVIATION...AMS/PM  
 
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