Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 300050 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 850 PM EDT FRI AUG 29 2014 .SYNOPSIS... A STALLED FRONTAL BOUNDARY NEAR THE SOUTH CAROLINA...NORTH CAROLINA BORDER WILL MOVE GRADUALLY NORTH TONIGHT THROUGH SATURDAY...AND BE POSITIONED OVER NORTHERN VIRGINIA BY SATURDAY AFTERNOON. A MORE SUBSTANTIAL COLD FRONT WILL APPROACH THE AREA SATURDAY NIGHT AND MOVE THROUGH THE AREA SUNDAY AND SUNDAY NIGHT. && .NEAR TERM /THROUGH SATURDAY/... AS OF 820 PM EDT FRIDAY... EVENING SOUNDINGS SHOW MOISTURE TRAPPED BENEATH THE INVERSION AT 85H AIDED BY SHALLOW SE FLOW NORTH OF THE RESIDUAL FRONT TO THE SOUTH. MOST INSTABILITY THIS EVENING REMAINS OVER THE FAR SW WHERE STILL HAVE A FEW SHOWERS ONGOING NEAR THE FRONT. THUS LEAVING IN SOME CHANCE POPS THERE A WHILE LONGER AS THE HRRR SHOWS SOME OF THIS COVERAGE SLIDING NORTH THROUGH MIDNIGHT. OTRW SATELLITE DEPICTING LOW CLOUDS SPREADING BACK NORTH FROM SOUTHERN VIRGINIA ATTM AHEAD OF THE BOUNDARY THAT WILL LIFT SLOWLY BACK NORTH OVERNIGHT. MOST LATEST MODEL SOLUTIONS SHOW LOW CLOUDS REMAINING ALONG/EAST OF THE BLUE RIDGE THROUGH MORNING WITH ONLY THE FAR SOUTH AND WEST STAYING MORE PC ALONG THE PERIMETER OF THE WEAK WEDGE. SHOWER CHANCES ELSW REMAIN IFFY GIVEN LOSS OF HEATING WITH THE BOUNDARY ACROSS THE REGION LATE. LATEST NAM AND TO SOME DEGREE THE HRRR WANT TO DEVELOP A FEW SHRA CLUSTERS ALONG AND JUST EAST OF THE BLUE RIDGE AFTER MIDNIGHT...WHILE MOST OTHERS DRY OR FARTHER SOUTH WITH ISOLATED COVERAGE. SINCE ALREADY HAVE SOME ISOLATED POPS GOING AND SEEING SOME INSTABILITY ABOVE THE INVERSION...WILL LEAVE IN AND EXTEND INTO SOUTHSIDE VIRGINIA OVERNIGHT. OTRW FOG/LOW CLOUDS LOOK ON TRACK WITH JUST SOME UPWARD ADJUSTS TO LOW TEMPS GIVEN THE CLOUD CANOPY AND MOIST DEWPOINTS OVERNIGHT. WE EXPECT A BREAK IN THE PRECIPITATION SATURDAY MORNING WITH THE FORCING ASSOCIATED WITH THE FRONT NORTH OF THE REGION. HOWEVER...BY THE AFTERNOON...ENOUGH DAYTIME HEATING IS EXPECTED TO REFIRE SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE NORTHERN PARTS OF THE REGION CLOSEST TO THE NEW LOCATION OF THE STALLED FRONT. ALSO...INCREASING SOUTHERLY WINDS WILL FOCUS UPSLOPE ISOLATED SHOWER AND THUNDERSTORM POTENTIAL ALONG THE CREST OF THE BLUE RIDGE. LOW TEMPERATURES TONIGHT WILL BE A MIX OF LOW TO MID 60S ACROSS THE MOUNTAINS WITH MID TO UPPER 60S ACROSS THE PIEDMONT. ON SATURDAY...HIGH TEMPERATURES IN THE LOW TO MID 80S WILL BE COMMON IN THE MOUNTAINS WITH UPPER 80S TO NEAR 90 ACROSS THE PIEDMONT. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... AS OF 330 PM EDT FRIDAY... UPPER LEVEL RIDGE FORECAST OVER THE SOUTHEASTERN CONUS TO REMAIN IN PLACE IN THE SHORT-TERM WITH THE MAIN WEATHER FEATURE A SERIES OF SOUTHERN STREAM SHORT-WAVES EXPECTED TO TRACK FROM THE GULF COAST NORTHEAST INTO THE OHIO VALLEY. 12Z MODEL RUNS OF GFS/NAM/EURO SHOWING THIS FEATURE OR SERIES OF FEATURES TRACKING SOMEWHAT FURTHER WEST THAN PREVIOUS RUNS DUE PARTLY TO THE STRONG RIDGE. AXIS OF HEAVIEST RAINFALL SHOULD STAY WEST OF OUR CWA BUT STILL HAVE LIKELY POPS IN THE FAR WEST ON SUNDAY TAPERING TO CHANCE ACROSS THE PIEDMONT ON SUNDAY. RIDGE FLATTENS SOMEWHAT ON MONDAY AS UPPER TROUGH ENERGY REMAINS WILL NORTH BUT WILL STILL BE CHANCES FOR MAINLY AFTERNOON SHOWERS AND SCATTERED THUNDERSTORMS MONDAY AFTERNOON. TEMPS WILL REMAIN WARM THROUGH THE PERIOD WITH MAINLY 80S FOR HIGHS AND 60S FOR LOWS EVEN WITH CONSIDERABLE CLOUDS ON SUNDAY. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... AS OF 330 PM FRIDAY... FLAT UPPER RIDGE IS EXPECTED TO DOMINATE OUR MID-WEEK WEATHER PATTERN ACROSS THE CENTRAL APPALACHIAN AND MID-ATLANTIC REGION. THIS SHOULD MAINTAIN SUMMER-LIKE TEMPERATURES THROUGH THE ENTIRE PERIOD WITH HIGHS NEAR 90F IN THE PIEDMONT AND MID-80S IN THE MOUNTAINS ALONG WITH NIGHT-TIME LOWS IN THE 60S TO LOW 70S. COULD END UP BEING ONE OF THE WARMEST WEEKS OF THE SUMMER EVEN AS THE SO-CALLED METEOROLOGICAL SUMMER ENDS ON AUGUST 31. PRECIPITATION WILL ALSO GENERALLY BE OF SUMMER-LIKE CHARACTER WITH DIURNALLY DRIVEN CONVECTION PROVIDING THE BEST CHANCES FOR RAINFALL. WEDNESDAY AFTERNOON LOOKS LIKE THE MOST PROMISING DAY FOR STORMS AS WEAK FRONTAL BOUNDARY PUSHES ACROSS THE CWA. THURSDAY AND FRIDAY LIKELY TO BE DRIER ALTHOUGH WIDELY SCATTERED SHOWERS STILL POSSIBLE. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... AS OF 645 PM EDT FRIDAY... VISIBILITY SENSOR AT KDAN REMAINS INOPERABLE. PARTS ARE ON ORDER. UNTIL REPAIRS COMPLETE...NO AMENDMENTS WILL BE SCHEDULED. ISOLATED SHOWERS AND STORMS...MAINLY SW OF KBLF HAVE ALL BUT FADED THIS EVENING WITH OUTFLOW DRIVEN ADDITIONAL SHRA HOW FARTHER WEST. HOWEVER STILL SOME POTENTIAL TO SEE A FEW ADDED SHRA DEVELOP MAINLY SW SO MAY LEAVE IN A VCSH MENTION AT KBLF OVER THE NEXT HOUR OR TWO. OTRW MAIN CONCERN OVERNIGHT WITH THE DEVELOPMENT OF LOW CIGS AND FOG AS THE WEAK FRONT TO THE SOUTH SLIDES NORTH INTO THE AREA BY MORNING. MODELS SHOW A FEW SHRA DEVELOPING ACROSS THE CENTRAL AND NORTH LATE TONIGHT BUT IFFY GIVEN LACK OF INSTABILITY AND AFTER LOSS OF HEATING. LOW LEVEL MOISTURE WILL INCREASE AND BECOME TRAPPED UNDER THE INVERSION ALOFT. ANTICIPATE MOST OF THE REGION TO DEVELOP MVFR CIGS WITH SOME REGIONS OF IFR PER LATEST NAM. VSBYS WILL ALSO DECREASE WITH MOST AREAS HAVING MVFR WITH POCKETS OF IFR NEAR THE BLUE RIDGE. HOWEVER GIVEN CURRENT TRENDS OFF SATELLITE IN ALREADY SEEING CLOUDS PUSH NORTH ACROSS EASTERN SECTIONS...WILL INTRODUCE MVFR CIGS A BIT SOONER THERE BUT DELAY SOME FROM KBCB WESTWARD WHERE THINGS ARE MORE MIXED. ANY SUB-VFR CONDITIONS WILL BE FAIRLY SLOW TO IMPROVE TO VFR AFTER SUNRISE SATURDAY. 15Z/11AM IS THE MOST LIKELY TIME MOST OF THE REGION WILL BE BACK TO VFR BUT MAY TAKE UNTIL MID AFTERNOON FOR KROA/KLYH TO IMPROVE. THINK MOST SHOULD FINALLY GO TO A SCATTERED CU FIELD ONCE LOW CIGS IMPROVE WITH ANY CONVECTION VERY ISOLATED GIVEN THE FRONT TO THE NE. EXTENDED DISCUSSION... ANY ISOLATED OR SCATTERED SHOWERS AND STORMS WILL BE MAINLY CONFINED TO AN AREA ALONG AND NORTH OF A KHSP-KFVX LINE SATURDAY EVENING...JUST SOUTH OF THE AGAIN STALLED FRONTAL BOUNDARY. LATE SATURDAY NIGHT THROUGH SUNDAY EVENING AN AREA OF LOW PRESSURE WILL HEAD EASTWARD THROUGH THE GREAT LAKES REGION TOWARD NEW ENGLAND. ITS ASSOCIATED COLD FRONT WILL SWEEP THROUGH THE REGION BRINGING A GENEROUS COVERAGE OF SHOWERS AND SOME STORMS. SUB-VFR CONDITIONS ARE EXPECTED TO ACCOMPANY THE SYSTEM AND PRECIPITATION. ANOTHER COLD FRONT IS EXPECTED TO PRODUCE SIMILAR CIRCUMSTANCES TUESDAY INTO WEDNESDAY. HOWEVER...MODEL GUIDANCE FOR THIS ONE OFFERS PRECIPITATION IN A MORE SCATTERED DISTRIBUTION. AS SUCH...THE MAGNITUDE OF SUB-VFR CONDITIONS MAY BE LESS. && .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...DS NEAR TERM...DS/JH SHORT TERM...PC LONG TERM...PC AVIATION...DS/JH EQUIPMENT...AMS

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