Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 291653 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1253 PM EDT FRI AUG 29 2014 .SYNOPSIS... A WEAK FRONT WILL BE STATIONARY FROM NORTH CAROLINA TO MISSOURI TODAY. THIS FRONT WILL LIFT NORTH INTO THE OHIO VALLEY TONIGHT. A STRONGER SYSTEM WILL BRING A BETTER THREAT FOR SHOWERS AND STORMS FOR SUNDAY AND MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1247 PM EDT FRIDAY... LATEST LAPS DATA ARE SHOWING SURFACE BASED LI OF -2 TO -3 AND CAPS AROUND 500 J/GS ACROSS TAZEWELL AND SMYTH COUNTIES. HIGHER VALUES EXIST WEST OF THE FORECAST AREA IN SOUTHERN WEST VIRGINIA AND NORTHEAST TENNESSEE. NO SHOWERS DETECTED YET ON REGIONAL RADARS IN THAT REGION...BUT VISIBLE SATELLITE IMAGERY IS STARTING TO SHOW THE DEVELOPMENT OF CUMULUS CLOUDS...SO AM NOT EXPECTING TOO LONG OF WAIT FOR THE FIRST SHOWERS TO DEVELOP. LATEST HRRR AND RNK WRF-ARW ARE ON TARGET FOR ABOUT A 18-19Z/2PM-3PM INITIATION TIME. THE OTHER AREA OF THE REGION THAT WE HAVE BEEN WATCHING FOR DEVELOPMENT IS SOUTHSIDE VIRGINIA AND NEIGHBORING NORTH CENTRAL NORTH CAROLINA. THIS REGION HAS HAD DECENT CLOUD COVER OVER IT FOR THE MORNING...AND NOW THE EARLY AFTERNOON. LAPS...AS EXPECTED...STILL HAS THE AREA STABLE. FOR OUR FORECAST...HAVE DELAYED THE ONSET OF ANY ISOLATED SHOWER OR THUNDERSTORM ACTIVITY UNTIL LATER IN THE AFTERNOON...PERHAPS STARTING AROUND OR AFTER 21Z/5PM. HAVE ALSO LOWERED EXPECTED HIGH TEMPERATURES IN THIS AREA BY A COUPLE OF DEGREES THANKS TO THE CLOUDS. HAVE RAISE FORECAST HIGHS IN THE FAR WESTERN PARTS OF THE ARE BASED UPON CURRENT TEMPERATURES AND CONTINUED WARMING TREND THROUGH THE AFTERNOON. AS OF 947 AM EDT FRIDAY... LATEST MESOSCALE MODELS STILL OFFERING BEST CHANCE FOR CONVECTION TODAY TO BE ACROSS THE WESTERN QUARTER OF THE REGION. LATEST LAPS DATA SHOW SURFACE BASED LI VALUES HAVE JUST DROPPED BELOW ZERO AND A FEW HUNDRED SURFACE BASED CAPE HAVE DEVELOPED IN WESTERN TAZEWELL AND SMYTH COUNTIES. THIS AREA AND THE SURROUNDING AREA IS EXPECTED TO BECOME MORE UNSTABLE WITH THE HEATING OF THE AFTERNOON. INITIAL CONVECTION TIME IS EXPECTED TO BE SOMEWHERE BETWEEN 17Z-18Z/1PM-2PM IN THIS REGION AND MAINTAIN THROUGH THE AFTERNOON. ANOTHER AREA WE ARE STILL WATCHING IS SOUTHSIDE VIRGINIA AND NEIGHBORING PORTIONS OF NORTH CENTRAL NORTH CAROLINA. WHILE STILL STABLE AT THE SURFACE...THIS AREA IS EXPECTED TO BECOME UNSTABLE THIS AFTERNOON IN PROXIMITY TO THE STALLED FRONTAL BOUNDARY. NO MAJOR CHANGES TO THE FORECAST. AS OF 400 AM EDT FRIDAY... STATIONARY FRONT TRAILED FROM NORTHEAST NORTH CAROLINA TO NORTH CENTRAL TENNESSEE EARLY THIS MORNING. ALONG THE BOUNDARY AND WEST OF THE BLUE RIDGE MODELS WERE SHOWING A CHANCE OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING. WILL BE STARTING OFF THE DAY CAPPED. EVEN IF THE CAP DOES BREAK...AS SUGGESTED BY BUFKIT NAM/RAP GUIDANCE...NOT MUCH INSTABILITY...AND NOT UNTIL AFTER 18Z. WITH THE SHORT WAVE ENERGY WELL WEST AND NORTH OF THE FORECAST AREA...LITTLE TO AIDE IN THE FORCING TODAY. AXIS OF POOLED MOISTURE AND LOW LEVEL CONVERGENCE ALONG THE WEAK BOUNDARY PIVOTS NORTHEAST TONIGHT AND WILL EXTEND FROM OHIO INTO EASTERN NORTH CAROLINA BY SATURDAY MORNING. WILL HAVE BEST PROBABILITY OF SHOWERS AND THUNDERSTORMS IN THE EXTREME SOUTHWEST COUNTY WARNING AREA. AREAL COVERAGE OF PRECIPITATION SHOULD ONLY BE ISOLATED TO SCATTERED. STORM MOTION WOULD BRING THE STORMS INTO SOUTHEAST WEST VIRGINIA AND POSSIBLY THE NEW RIVER VALLEY AROUND 00Z. BUT NOT MUCH INSTABILITY LEFT BY THAT TIME. SOUTHEAST WINDS AT THE SURFACE THROUGH LOW LEVELS...BRING 850-1000MB RELATIVE HUMIDITY UP TODAY AND BY TONIGHT LOW CLOUDS ARE EXPECTED TO ADVANCE TOWARD THE EAST SIDE OF THE APPALACHIANS. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... AS OF 310 AM EDT FRIDAY... UPPER RIDGE EXPECTED TO SHIFT EAST AS STRONGER UPPER TROUGH MOVES FROM THE UPPER MIDWEST INTO THE GREAT LAKES. MODELS AGREE THAT A SOUTHERN STREAM UPPER SHORTWAVE WITH ENHANCEMENT IN THE JET WILL STREAK OVER THE GULF COAST STATES AND ACROSS THE WESTERN SLOPES OF THE APPALACHIANS SUNDAY. FOR SATURDAY THOUGH...MAINLY LOOKING WEAK FLOW ALOFT WITH SOME CONVERGENCE ACROSS THE MTNS PER SOUTH-SOUTHEAST FLOW. MODELS ARE FAVORING A BIT OF CONVECTION WITH THE LEE TROUGH IN THE EAST...MAINLY FROM THE EASTERN WV PANHANDLE SOUTHEAST TOWARD THE TIDEWATER. THINK THE AIRMASS WILL BE UNSTABLE AND MOIST ENOUGH TO TRIGGER A FEW STORMS BUT OVERALL UPPER SUPPORT IS LACKING SO ONLY SEEING ISOLATED COVERAGE OVER THE MTNS AND NORTH OF A ROANOKE TO DANVILLE LINE. MORE SUN SATURDAY WILL BRING TEMPS TOWARD 90 OUT EAST WITH MID 80S WEST. SAT NIGHT...MAIN AXIS OF CONVECTION WILL RUN FROM MS-KY...WITH LITTLE TO NO CHANCE OF SHOWERS EAST OF THE BLUE RIDGE AFTER EVENING STORMS WANE. WITH THE UPPER SUPPORT TRACKING CLOSER WILL HAVE AT LEAST SLIGHT CHANCE INTO THE MOUNTAINS LATE. SUNDAY LOOKS ACTIVE AS THE SHORTWAVE AXIS SHIFTS ACROSS KY INTO NORTHERN WV...WITH STRONG CONVERGENCE AND LIFT. WILL SEE HIGH CHANCE/LIKELY POPS. LOOKS LIKE CLOUD COVER COULD ARRIVE SOON ENOUGH TO KEEP INSTABILITY LOWER...BUT ENOUGH UPPER SUPPORT/SHEAR WHERE A FEW STORMS COULD PRODUCE GUSTY WINDS. THE SHORT WAVE AXIS SLOWLY SHIFTS TO THE EAST AND WITH A LEE TROUGH...CONVECTION FIRES LATE IN THE AFTERNOON AND MAY REMAIN OVER SOUTHSIDE UNTIL MIDNIGHT. HIGHS SUNDAY WILL RANGE FROM THE UPPER 70S MOUNTAINS TO UPPER 80S TOWARDS SOUTHSIDE. OVERALL...LABOR DAY WEEKEND LOOKING VERY WARM/HOT/HUMID. SATURDAY NOT TOO BAD RAIN WISE...BUT STAY COOL WHILE DRINKING PLENTY OF WATER IF OUTDOORS. SUNDAY APPEARS POOR FOR OUTDOOR ACTIVITIES. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 PM EDT THURSDAY... MUCH OF THE LONG TERM PERIOD WILL BE INFLUENCED BY A MEAN UPPER RIDGE THAT WILL INITIALLY RESIDE ALONG AND OFF THE SOUTHEAST COAST...WHICH GRADUALLY RETROGRESSES AND EXPANDS WESTWARD INTO THE GULF COAST STATES BY THE END OF THE FORECAST PERIOD. SOUTHEASTERN RIDGE WILL INITIALLY BE STRONG ENOUGH TO DEFLECT ANY NORTHERN STREAM ENERGY AWAY FROM THE BLACKSBURG FORECAST AREA...WITH MAIN BAROCLINIC ZONE REMAINING FROM THE NORTHERN PLAINS EAST INTO AND THROUGH THE GREAT LAKES INTO NEW ENGLAND. HOWEVER...TAP OF TROPICAL MOISTURE RIDING AROUND PERIPHERY OF SOUTHEASTERN RIDGE LIKELY TO REMAIN OVER/NEAR THE BLACKSBURG FORECAST AREA THROUGH AT LEAST MONDAY OR MONDAY NIGHT...MAINTAINING THREAT FOR MAINLY DIURNALLY DRIVEN SCATTERED SHOWERS AND THUNDERSTORMS...SOME OF WHICH MAY BE ACCOMPANIED BY LOCALLY HEAVY RAIN CONSIDERING RELATIVELY HIGH PRECIPITABLE WATER VALUES EXPECTED OVER THE AREA. GRADUAL RETROGRESSION OF UPPER RIDGE INTO NORTHERN GULF COAST REGION DURING THE MIDWEEK PERIOD SHOULD BE SUFFICIENT TO ALLOW WINDS ALOFT TO VEER SUCH THAT INFLUENCE OF TROPICAL MOISTURE TAP GRADUALLY WANES...ONLY TO BE REPLACED BY MORE AGGRESSIVE SOUTHWARD INTRUSION OF NORTHERN STREAM ENERGY AND ASSOCIATED SCATTERED SHOWERS/STORMS IN ADVANCE OF AN ACCOMPANYING DECAYING COOL FRONT INTO THE MID APPALACHIAN AND MID ATLANTIC REGION IN TUESDAY-WEDNESDAY TIMEFRAME. PUSH OF POST-FRONTAL SLIGHTLY DRIER AIR MAY BE STRONG ENOUGH TO REDUCE THREAT FOR PRECIPITATION ACROSS AREAS NORTH OF INTERSTATE 64 BY THURSDAY...BUT WITH AT LEAST A CHANCE THREAT FOR SHOWERS/STORMS REDEVELOPING BY AFTERNOON ACROSS THE SOUTHWESTERN MOUNTAINS CLOSER TO DECAYING FRONTAL BOUNDARY AND PROXIMITY TO HIGHER THETA-E AIR. PLENTY OF CLOUD COVER AND DEWPOINTS PRIMARILY IN THE 60S SHOULD ENSURE THAT TEMPERATURES REMAIN CLOSE TO SEASONAL AVERAGES...MAINLY MID 70S TO LOWER 80S ACROSS THE HIGHER ELEVATIONS BY DAY WITH UPPER 80S ACROSS THE PIEDMONT...WITH MAINLY 60S AT NIGHT. INTRUSION OF SLIGHTLY COOLER/DRIER POST-FRONTAL AIR FROM THE NORTHEAST MAY ALLOW TEMPERATURES TO BE A FEW DEGREES COOLER ON THURSDAY. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 745 AM EDT FRIDAY... A STATIONARY FRONT EXTENDED FROM AROUND NORTH CAROLINA TO MISSOURI. THIS FRONT WILL MOVE LITTLE TODAY THEN WILL PUSH NORTH TONIGHT...INTO THE OHIO VALLEY BY SATURDAY MORNING. STRATOCUMULUS HAD FILLED IN OVER SOUTHERN VIRGINIA AND NORTHERN NORTH CAROLINA EARLY THIS MORNING WITH MVFR TO LOW END VFR CEILINGS. EXPECT THESE CLOUDS TO BECOME SCATTERED BY THIS AFTERNOON. THE BEST PROBABILITY OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING WILL JUST SOUTH OF KBLF AND KBCB. STORM MOTION MAY TAKE THE STORMS CLOSE TO THESE AIRPORTS AROUND 00Z/8PM...BUT PROBABILITY IS TOO LOW AT THIS TIME TO MENTION IN THE TAFS. MODELS SHOWED HIGH AMOUNTS OF LOW NEAR THE SURFACE ALONG AND EAST OF THE BLUE RIDGE LATE TONIGHT. HIGH CONFIDENCE OF AT LEAST MVFR CEILINGS AT KLYH AND KDAN AFTER 06Z/2AM. NOT AS MUCH A SURE THING AT KROA...BUT STILL CONFIDENT ENOUGH TO ADD MVFR CEILINGS TO THE TAF. IT IS POSSIBLE THAT CEILINGS MAY LOWER ALL THE WAY TO IFR LEVELS BEFORE THE 12Z/8AM END OF THE TAF PERIOD AS THIS STRATUS EXPANDS TO THE WEST. EXTENDED DISCUSSION... WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL AFFECT THE REGION AGAIN ON SATURDAY...MAINLY DURING THE LATE AFTERNOON AND EARLY EVENING. SHOULD ONE OF THESE STORMS DEVELOP NEAR A TAF LOCATION IT COULD RESULT IN A BRIEF PERIOD OF SUB VFR CONDITIONS. AN AREA OF LOW PRESSURE IS FORECAST TO MOVE THROUGH THE GREAT LAKES SATURDAY NIGHT AND SUNDAY...THE ASSOCIATED COLD FRONT TRAILING SOUTH AND MOVING ACROSS THE OHIO/TN VALLEYS. SHOWERS AND THUNDERSTORMS WILL LIKELY BE ASSOCIATED WITH THIS FRONT...THIS ACTIVITY SPREADING EAST INTO THE CENTRAL APPALACHIANS SUNDAY AND MONDAY. SHOWER COVERAGE SUNDAY THROUGH TUESDAY IS EXPECTED TO BE MORE WIDESPREAD AS COMPARED TO FRIDAY AND SATURDAY. && .EQUIPMENT... AS OF 730 AM EDT FRIDAY ... THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS/DS SHORT TERM...RCS LONG TERM...WERT AVIATION...AMS/CF EQUIPMENT...AMS

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