Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 011750 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 150 PM EDT FRI AUG 1 2014 .SYNOPSIS... AN UPPER TROUGH OF LOW PRESSURE WILL CONTINUE TO RETROGRADE WEST TO THE MISSISSIPPI RIVER VALLEY...AND THE CENTER OF SURFACE HIGH PRESSURE WILL SHIFT TO OUR EAST TODAY. AN UPPER DISTURBANCE TRACKING JUST SOUTHEAST OF THE AREA WILL BRING MORE IN THE WAY OF WIDESPREAD RAINFALL INTO THIS AFTERNOON. LINGERING MOISTURE IN THE WAKE OF THIS FEATURE WILL COMBINE WITH HEATING TO RESULT IN MORE SHOWERS AND STORMS OVER THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1050 AM EDT FRIDAY... TWO SHORT WAVES MOVING INTO GEORGIA AND WET VIRGINIA WILL CONTINUE TO PROVIDE LIFT ACROSS THE FORECAST AREA THIS AFTERNOON. MAXIMUM RAINFALL AMOUNT ALONG THE FOOTHILLS FROM HENRY COUNTY THROUGH WILKES COUNTY WITH 1.5 TO 2.0 INCHES OF RAIN. FOR THE REST OF THE REGION MAINLY EAST OF A LINE FROM HOT SPRINGS TO BOONE...AMOUNTS HAVE BEEN GENERALLY FROM ONE THIRD TO THREE QUARTERS OF AN INCH. UNUSUAL WIDESPREAD RAIN EVENT FOR MID SUMMER LOOKS IN STORE FOR MUCH OF TODAY AS SHORTWAVE ENERGY CURRENTLY OVER SOUTHERN S CAROLINA TRACKS NE CROSSING THE EASTERN PORTIONS OF THE CWA BY THIS EVENING. THIS WILL CONTINUE TO ENHANCE THE OVERRUNNING OF WARM/MOIST AIR ON SE FLOW OVERTOP A DEVELOPING COOL WEDGE EARLY THIS MORNING...WITH SOME DEGREE OF PRECIP SPREADING NORTH AND WEST ACROSS MUCH OF THE REGION BY 12Z. STILL APPEARS THAT THE HEAVIEST RAINFALL WILL BE ACROSS SOUTHERN SECTIONS AND ENHANCED ALONG THE SOUTHERN BLUE RIDGE BY UPSLOPE FLOW OF NEAR 2 INCH PWATS INTO THIS AFTERNOON. HOWEVER APPEARS CONVECTION ALONG THE COASTAL CAROLINAS CONTINUES TO DISRUPT THE DEEPER SE TRAJECTORY WITH MORE CONVECTIVE NATURE COVERAGE FARTHER TO THE SOUTH IN CONJUNCTION WITH THE HIGHER THETA-E AIR BEING ADVECTED ACROSS THE FRONT INTO THE N CAROLINA COASTAL PLAINS. THIS MAY HAVE ALSO CAUSED THE MODEL INIT TO BE TOO FAR WEST WITH THE CORE OF HEAVIER RAINFALL BUT EXPECT THE CURRENT AXIS TO PIVOT MORE NORTH-SOUTH ORIENTED SIMILAR TO THE LATEST HRRR AS THE WAVE HELPS SHARPEN THE TROF WHILE BACKING THE FLOW ALOFT THIS MORNING. QUESTION IS WHETHER OR NOT WILL GET ENOUGH HEAVIER RAINFALL OVER A PROLONGED PERIOD TO PRODUCE FLOOD ISSUES GIVEN DRY CONDITIONS PER LATEST FFG SHOWING 6 HOUR AMOUNTS OF 3.5-4.5 INCHES TO CAUSE FLOODING. SINCE EXPECTING MOST OF THE RAINFALL TO REMAIN MORE STRATIFORM WITH EMBEDDED HEAVIER DOWNPOURS WONT POST A WATCH OVER THE SW FOR NOW BUT EXPECT UPSLOPE MAY CAUSE A GOOD 2-3+ INCHES ALONG THE EASTERN SLOPES. BEST LIFT SPREADS NE WITH THE WAVE THIS AFTERNOON CAUSING THE SOLID AXIS OF PRECIP TO SHIFT ACROSS EASTERN/NE SECTIONS DURING THE AFTERNOON WITH SOME TAPERING TO LIGHTER SHRA WEST/SW. COULD EVEN SEE A FEW BREAKS DEVELOP FAR WEST ON THE PERIMETER OF THE COOL AIR OTRW CLOUDY AND VERY COOL TO START AUGUST. HIGHS QUITE TRICKY AS SOME SPOTS MAY SEE MORE OF A WINTER CAD EVENT WITH TEMPS ONLY RISING A FEW DEGREES AT MOST ALONG THE BLUE RIDGE WHERE KEEPING IT IN THE 60S FOR THE MOST PART. THINK SPOTS OVER THE PIEDMONT INCLUDING SW VA INTO SE WVA MAY BE ABLE TO BUMP VALUES INTO THE LOW/MID 70S ESPCLY IF THE RAINFALL DIMINISHES A BIT FASTER AND THINGS BRIGHTEN SLIGHTLY. IMPULSE EXITS THIS EVENING LEAVING THE REGION WITHIN THE RESIDUAL WEDGE BUT UNDERNEATH A CONTINUED DIFFLUENT PATTERN ALOFT ON THE FRONT OF THE 5H TROF. LITTLE UPPER SUPPORT REMAINING OVERNIGHT FOR MUCH ADDED RAINFALL ESPCLY AFTER MIDNIGHT BUT LIKELY ENOUGH WEAK UPSLOPE TO KEEP LIKELY OR HIGHER POPS GOING BLUE RIDGE INTO LATE THIS EVENING. FLOW BEHIND THE DEPARTING WAVE MAY ACTUALLY TURN WESTERLY ENOUGH TO SHUT OFF SHRA WESTERN HALF LATE SO CUT POPS BACK TO MAINLY CHANCE AFTER MIDNIGHT WHEN MAY BE MORE DRIZZLE/FOG OUT EAST. CONTINUED COOL WITH LOWS LIKELY ONLY FALLING A FEW DEGREES BUT AFTER A CHILLY DAY WONT TAKE MUCH TO GET INTO THE 50S WEST AND LOW 60S EAST. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... AS OF 314 AM EDT FRIDAY... A BERMUDA HIGH REMAINS OVER THE WESTERN ATLANTIC WHILE AN UPPER LEVEL TROUGH IS DRAPED OVER THE MISSISSIPPI VALLEY THIS WEEKEND. WITH THE FORECAST AREA IN BETWEEN THESE TWO SYNOPTIC FEATURES...IMPULSES WITH TROPICAL MOISTURE WILL KEEP A GOOD CHANCE FOR SHOWERS AND SCATTERED THUNDERSTORMS IN THE AREA OVER THE WEEKEND. COMPARED TO YESTERDAY...MODELS HAVE SHIFTED THE AXIS OF HEAVY STEADY RAIN EAST ALONG THE COAST. THE FORECAST AREA WILL STILL SEE A FAIR AMOUNT OF RAIN OVER THE WEEKEND...BUT WILL BE MORE CONFIDED TO THE AFTERNOON AND EVENING HOURS. DESPITE THE MODELS TRENDING DRIER...KEEP POPS THROUGH THE ENTIRE PERIOD WITH LOW CHANCE DURING NON-DIURNAL HEATING HOURS AND HIGH CHANCE-LIKELY DURING THE AFTERNOON AND EVENING. ALSO WITH THE DRIER MODEL SOLUTIONS...EDGE TEMPERATURES UP A FEW DEGREES EACH AFTERNOON. DESPITE WARMING THE FORECAST TEMPERATURES...THEY WILL REMAIN COOLER THAN NORMAL BY AT LEAST 10F FOR THE FIRST WEEKEND IN AUGUST. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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AS OF 1230 PM EDT FRIDAY... AT THE SURFACE TUESDAY...HIGH PRESSURE SITS OVER WEST VIRGINIA WHILE A SLOW MOVING COLD FRONT IS ACROSS THE OHIO VALLEY. TS BERTHA OR WHAT IS REMAINING OF IT IS FORECAST TO REMAIN WELL OFF SHORE AND WILL NOT BE A FACTOR IN OUR REGION NEXT WEEK. AN UPPER LEVEL TROUGH REMAINS SITUATED ACROSS THE EASTERN US. THE UPPER LEVEL FLOW WILL BECOME MORE ZONAL BY THE END OF THE PERIOD. THE FRONT ACROSS THE OHIO VALLEY WILL SLOWLY DRIFT AND PARTIALLY STALL OUT ACROSS NORTHERN PORTIONS OF OUR CWA BY THURSDAY INTO FRIDAY. WHILE PWATS ARE NOT IMPRESSIVE...GENERALLY 0.75-1.25 INCHES DEPENDING ON THE LOCATION...EXPECT ISOLATED TO SCATTERED THUNDERSTORMS EACH AFTERNOON BEGINNING DURING PEAK HEATING AND TAPERING OFF AROUND SUNSET. FOCUS OF THE LOW CHANCE POPS ARE ACROSS THE MOUNTAINS AND GENERALLY NORTH OF ROUTE 460. SURFACE TEMPS WILL BE RIGHT AROUND NORMAL FOR THE PERIOD. 850MB TEMPS OF +15-17C WILL CORRESPOND TO SURFACE HIGHS OF MID TO UPPER 80S EAST OF THE BLUE RIDGE AND LOWER 80S ACROSS THE MOUNTAINS. DEWPTS IN THE UPPER 50S TO LOWER 60S WILL KEEP NIGHT TIME TEMPS UP A BIT.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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AS OF 145 PM EDT FRIDAY... COMBINATION OF UPSLOPE LOW LEVEL FLOW AND LOFT FROM TWO SHORT WAVES CROSSING THE AREA...POOR FLYING CONDITIONS WILL CONTINUE ACROSS MUCH OF THE REGION TONIGHT. THE BEST COVERAGE OF RAIN WILL BE ALONG AND EAST OF THE BLUE RIDGE BEFORE 06Z/2AM TONIGHT. AFTER SUNSET...CEILINGS WILL DROP AND REMAIN AT IFR TO LIFR LEVELS WITH AREAS OF FOG AND DRIZZLE. BOTH THE NAM AND GFS SHOWED THE MAJORITY OF THE HEAVIER PRECIPITATION MOVING NORTHEAST AND OUT OF SOUTHWEST VIRGINIA BY 09Z/5AM. LOWER CONFIDENCE ON HOW FAST WEDGE WILL ERODE ON SATURDAY. BUFKIT FORECAST SOUNDINGS SUGGEST SURFACE AND LOW LEVEL WINDS WILL COME AROUND TO THE SOUTHWEST AFTER 15Z/11AM. EXPECT KLYH WILL BE THE LAST AIRPORT TO LIFT OUT OF IFR CONDITIONS. EXTENDED AVIATION DISCUSSION... THE BROAD UPPER TROUGH OF LOW PRESSURE WILL LINGER ACROSS THE EASTERN UNITED STATES THROUGH SUNDAY CONTINUING TO RETROGRADE FROM THE EASTERN/CENTRAL GREAT LAKES TO THE WESTERN GREAT LAKES BY THE WEEKEND. SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED AGAIN ON SUNDAY. FOR MONDAY AND TUESDAY...THE AIR MASS WILL SLOWLY BECOME WARMER AND MORE UNSTABLE. ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED IN THE AFTERNOON AND EVENING...ESPECIALLY TUESDAY...WITH BRIEF PERIODS OF MVFR- IFR CIGS/VSBYS EXPECTED IN SHRA/TSRA. A WEAK COLD FRONT MOVES SLOWLY SOUTH FROM THE OHIO VALLEY ACROSS THE MID ATLANTIC REGION...THIS WILL ALSO BRING A CHANCE OF SHOWERS AND THUNDERSTORMS.
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&& .HYDROLOGY...
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AS OF 330 AM EDT FRIDAY... RAINFALL TOTALS OF 1-3 INCHES IS EXPECTED ALONG THE ENHANCED UPSLOPE REGIONS OF THE BLUE RIDGE AND FOOTHILLS MAINLY SOUTH OF ROANOKE WITH A GOOD 1-2 INCHES ELSW OVER THE PIEDMONT SECTIONS OF NORTHWEST NORTH CAROLINA INTO SOUTHSIDE VIRGINIA BY THIS AFTERNOON. GIVEN THE VERY DRY ANTECEDENT CONDITIONS OF LATE AND THE OVERALL LACK OF HEAVIER RAINFALL RATES...WIDESPREAD FLOODING OR FLASH FLOODING IS NOT EXPECTED BUT LOCALIZED SMALL STREAM AND POOR DRAINAGE FLOODING COULD OCCUR ESPCLY WHERE HEAVIER DOWNPOURS ARE REALIZED. RAINFALL TOTALS WILL QUICKLY TAPER OFF HEADING INTO FAR WESTERN VIRGINIA AND SE WEST VIRGINIA WHERE ONLY UP TO A HALF INCH LOOKS POSSIBLE WITH AN INCH OR MORE LIKELY IN AREAS AROUND LYNCHBURG.
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&& .EQUIPMENT...
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AS OF 100 PM EDT FRIDAY... THE NOAA WEATHER RADIO AT WYTHEVILLE VA...WZ2500...BROADCASTING ON A FREQUENCY OF 162.450 MHZ...IS BACK ON THE AIR.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/NF NEAR TERM...AMS/JH SHORT TERM...RCS LONG TERM...CF AVIATION...JH/AMS HYDROLOGY...JH EQUIPMENT...AMS

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