Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KRNK 010851 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 451 AM EDT MON SEP 1 2014 .SYNOPSIS... THE REGION WILL STAY BETWEEN A LARGE HIGH PRESSURE SYSTEM OVER THE SOUTHEAST UNITED STATES AND A COMPLEX LOW PRESSURE SYSTEM CROSSING THE GREAT LAKES. DISTURBANCES PASSING BETWEEN THESE TWO FEATURES WILL COMBINE WITH HEAT AND HUMIDITY TO RESULT IN PERIODIC CHANCES OF SHOWERS AND THUNDERSTORMS. A COLD FRONT DROPS IN FROM THE NORTH LATE TUESDAY INTO WEDNESDAY...THEN LIFTS NORTH THURSDAY. ANOTHER COLD FRONT ARRIVES DURING THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 400 AM EDT MONDAY... IN THE WAKE OF THIS MORNINGS SHORTWAVE...WEST TO SOUTHWEST FLOW WILL CONTINUE TODAY WITHOUT MUCH FORCING WELL IN ADVANCE OF THE NEXT UPSTREAM 5H TROF/COLD FRONT TO THE NW. A DEEP WESTERLY FLOW WILL RESULTS IN DRYING ALOFT/LOWERING PWATS ESPECIALLY WEST THIS AFTERNOON AND A LEE TROUGH ACROSS THE PIEDMONT. THE GFS...NAM AND ECMWF HIGHLIGHTED THE BEST CHANCES OF CONVECTION IN THE WEST WITH THE OROGRAPHIC LIFT AND WEAK SHORTWAVE ARRIVING AROUND THE TIME OF MAX HEATING. WHILE IN THE EAST...WEAKER LAPSES...LACK OF DEEP INSTABILITY AND EASTERN DOWNSLOPE FLOW WILL LIMIT OVERALL COVERAGE. WITH A WARM START...THIS COULD BE ONE OF THE WARMEST DAYS SEEN IN A WHILE WITH 85H TEMPS PUSHING +21C OVER DECENT DOWNSLOPE AND UNDER AFTERNOON SUNSHINE. HIGH TEMPERATURES THIS AFTERNOON WILL RANGE FROM THE LOWER 80S IN THE WESTERN MOUNTAINS TO THE LOWER TO MID 90S IN THE SOUTHEAST. WEAK HIGH PRESSURE BUILDS IN TONIGHT...CUT BACK POPS OVERNIGHT. WITH LIGHT WINDS AND LOW LEVEL MOISTURE...EXPECT PATCHY FOG DEVELOP IN SOME OF THE MOUNTAIN VALLEYS OVERNIGHT. LOW TEMPERATURES WILL BE IN THE LOWER 60S IN THE MOUNTAINS TO THE LOWER 70S IN THE PIEDMONT. && .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... AS OF 415 AM EDT MONDAY... THROUGH THE PERIOD...THE MAIN BELT OF WESTERLIES AND THUS THE STORM TRACK...WILL REMAIN NORTH OF THE CWA AS A BROAD SUBTROPICAL RIDGE HOLDS ALONG AND SOUTH OF 40 DEG LATITUDE. A STRONG SHORT WAVE AND ASSOCIATED FRONTAL SYSTEM WILL TRACK ALONG TO JUST NORTH OF THE FORECAST AREA TUE AFTERNOON/EVENING. THE AIR MASS WILL REMAIN SUFFICIENTLY MOIST AND HOT...HENCE UNSTABLE...FOR ANOTHER ROUND OF THUNDERSTORMS. HOWEVER...ALL OF THE MODELS FOCUS ON THE BULK OF THE PRECIPITATION REMAINING WEST OF THE ALLEGHANY FRONT...WITH A STRONG DOWNSLOPE COMPONENT TO THE EAST...WHICH WILL PUT A DAMPER ON CONVECTION ACROSS THE NEW RIVER VALLEY AND THE PIEDMONT. THIS PATTERN IS CONSISTENT WITH TIMING AS WELL...WITH THE BULK OF THE CONVECTION ARRIVING IN THE 18Z-00Z TIME FRAME...REACHING AREAS EAST OF THE ALLEGHANY FRONT AFTER THE LOSS OF DAYTIME INSOLATION. NONETHELESS...SCATTERED CONVECTION COULD LINGER ACROSS THE PIEDMONT INTO THE EARLY MORNING HOURS. FOR WED...THE FRONTAL BOUNDARY HAS PUSHED JUST SOUTH OF THE CWA...LIKELY STALLING FROM MIDDLE/EASTERN TN EASTWARD THROUGH CENTRAL NC. WITH THE BROAD UPPER RIDGE REMAINING IN PLACE...LITTLE SUPPORT FOR THE FRONT TO PUSH ANY FURTHER SOUTH. MOISTURE WILL REMAIN CLOSE TO THE SOUTH/SOUTHWEST...WHICH BY AFTERNOON WILL BEGIN TO CREEP BACK TO THE NORTHEAST INTO SW VA/NW NC. THUS...HAVE INTRODUCED CHC POPS IN THESE AREAS...BUT AREAS FURTHER NORTH/EAST SHOULD REMAIN DRY FOR WED. BY THU...THE FRONT RETURNS QUICKLY BACK TO THE NORTHEAST OF THE REGION IN RESPONSE TO THE UPPER RIDGE AMPLIFYING FURTHER ACROSS THE EASTERN U.S...592 DM INTO TN BY THU...591 OVER VA BY FRIDAY. THIS LEAVES THE REGION IN A VERY TYPICAL MID-SUMMER LIKE AIR MASS...NAMELY UNSEASONABLY WARM...HUMID...WITH LIMITED DYNAMICS...BUT AMPLE THERMODYNAMICS FOR POPUP AFTERNOON SHOWERS/THUNDERSTORMS...ESPECIALLY IN CONJUNCTION WITH DIFFERENTIAL HEATING THROUGH THE MOUNTAINS. AGAIN...THE HIGHEST POPS SHOULD REMAIN ACROSS THE WESTERN/SOUTHERN PARTS OF THE CWA. TEMPERATURES WILL CHANGE LITTLE THROUGH THE PERIOD AND AVERAGE WELL ABOVE NORMAL...BOTH LOWS AND HIGHS. AFTER MANY BELOW NORMAL DAYS THIS PAST SUMMER AND NOW THAT IT IS SEPTEMBER AND NORMALLY STARTING TO GET COOLER...WE ARE INSTEAD LOOKING NOW AT AN EXTENDED PERIOD OF TEMPERATURES WELL ABOVE NORMAL...WITH HIGHS IN THE 80S WEST TO 90S EAST AND LOWS IN THE 60S AND 70S. NORMAL HIGH TEMPERATURES BY NOW SHOULD BE IN THE 70S WEST AND 80S EAST WITH LOWS IN THE 50S WEST AND 60S EAST...SO WE WILL BE SEEING READINGS A GOOD 10 DEGREES ABOVE NORMAL THROUGH THE WEEK. && .LONG TERM /FRIDAY THROUGH SUNDAY/... AS OF 435 AM MONDAY... THE NEXT IN THE SERIES OF UPPER SHORT WAVES WILL TRACK ACROSS THE REGION FRI-SAT. IN RESPONSE...THE CENTER OF THE STRONG SUBTROPICAL RIDGE WILL BACK OFF TO THE WEST INTO THE SOUTH CENTRAL STATES...ALBEIT BRIEFLY...ONLY TO SURGE BACK INTO THE AREA EARLY NEXT WEEK. THIS CHANGE WILL ALLOW A FRONTAL SYSTEM TO PUSH THROUGH THE AREA BY SAT...BRINGING OUR NEXT BEST CHANCE OF SHOWERS/THUNDERSTORMS TO THE REGION. AGAIN THIS BOUNDARY WILL STALL JUST SOUTH OF THE REGION...RETURNING NORTH BY SUN OR MON. THE SYNOPTIC SITUATION HAS MANY SIMILARITIES TO THE TUE-WED SET UP EARLIER IN THE WEEK. ANY COOLING BEHIND THE FRONT OVER THE WEEKEND WILL BE MODEST AS 850 TEMPS HOVER IN THE +18C RANGE...EVEN BEHIND THE FRONT. WHILE THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS WILL OCCUR WITH THE FRONT FRI-SAT...EVEN THEREAFTER THE AIR MASS WILL REMAIN SUFFICIENTLY MOIST AND UNSTABLE FOR SCATTERED DIURNAL CONVECTION...BUT NOTHING WELL ORGANIZED WITH THE BROAD UPPER RIDGE REMAINING JUST TO THE SOUTH...AMPLIFYING BACK INTO THE REGION BY EARLY NEXT WEEK. THUS...OVERALL EXPECT CONTINUED ABOVE NORMAL TEMPERATURES AND UNSEASONABLY HIGH HUMIDITY AS WELL. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... AS OF 127 AM EDT MONDAY... A SHORTWAVE WILL LIFT NORTHEAST THIS MORNING ACROSS THE REGION. A FEW SHOWERS WILL MOVE EAST ACROSS THE REGION THIS MORNING. THE BEST CHANCE OF A SHOWER WILL OCCUR AT BLF AND LWB. IN THE WAKE OF THE SHORTWAVE...THE OVERALL THREAT OF SHOWERS WILL FADE WITH A SCT/BKN MID DECK LINGERING. PATCHY FOG MAY DEVELOP THIS MORNING...BUT THE MID DECK SHOULD LIMIT HOW FAR DOWN VSBYS DROP. WILL KEEP MOST TAF SITES NO WORSE THAN MVFR THIS MORNING WITH LWB DROPPING OCCASIONALLY TO IFR AFTER 10Z. AHEAD OF THE UPSTREAM COLD FRONT...DEEP WESTERLY FLOW COMBINED WITH LACK OF FOCUS AND DECENT MIXING SHOULD INHIBIT MUCH CONVECTION TODAY ESPECIALLY IF EARLY MID DECK PERSISTS. THIS SUPPORTS GOOD FLYING CONDITIONS FOR MUCH OF LABOR DAY AFTER EARLY LOW CLOUDS/FOG FADE WITH ONLY ISOLATED CONVECTION LIKELY. MEDIUM CONFIDENCE ON CEILINGS...VISIBILITIES AND WINDS DURING THE TAF PERIOD. EXTENDED DISCUSSION... UPPER TROUGH AND ITS ASSOCIATED COLD FRONT WILL APPROACH FROM THE NORTHWEST TUESDAY WITH SIMILAR ISOLATED SHOWERS/STORMS EXPECTED DURING THE DAY AHEAD OF THE BOUNDARY. FRONT SETTLES CLOSER TUESDAY NIGHT INTO WEDNESDAY...WHEN BETTER COVERAGE OF SHRA/TSRA IS EXPECTED...AND THEN ACROSS THE SOUTH THURSDAY WHERE THE BOUNDARY STALLS. HOWEVER LOW CONFIDENCE ON THE TIMING AND SOUTHWARD POSITION OF THE BOUNDARY AT THIS POINT. THUS APPEARS MAINLY VFR ON TUESDAY...WITH PERIODS OF MVFR WEDNESDAY-THURSDAY IN MORE ORGANIZED MAINLY AFTERNOON/EVENING CONVECTION...AND MVFR/IFR UNDER EARLY MORNING FOG IN THE VALLEYS AND WHERE EARLIER HEAVY RAIN OCCURRED. FRONT WASHES OUT TO THE SOUTH OF THE AREA FRIDAY WITH MORE DIURNAL NATURE SHOWERS AND STORMS...OTRW VFR. && .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...KK NEAR TERM...KK/WP SHORT TERM...RAB LONG TERM...RAB AVIATION...JH/KK/WP EQUIPMENT...RAB

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.