Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 051012 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 512 AM EST THU MAR 5 2015 .SYNOPSIS...
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ARCTIC AIR WILL PUSH INTO THE REGION TODAY BEHIND A LOW PRESSURE SYSTEM THAT WAS CENTERED OVER NORTHWEST NORTH CAROLINA. THIS LOW WILL MOVE SOUTHEAST...FOLLOWED BY HIGH PRESSURE FOR TONIGHT AND FRIDAY. WINTER PRECIPITATION WILL BE WIDESPREAD BY THIS AFTERNOON ACROSS THE REGION.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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425 AM EST THURSDAY... PRIMARY SURFACE LOW WAS OVER WILKESBORO AT 2AM WITH THE FRONT EXTENDING EAST ALONG THE SOUTHERN BORDER OF THE FORECAST AREA AND SOUTHWEST INTO LOUISIANA. MSAS ANALYSIS WAS NOT SHOWING MUCH PRESSURE FALLS BUT THERE WAS A SOUTHWARD PUSH OF THE COLD AIR INTO THE LOWER MISSISSIPPI VALLEY SINCE MIDNIGHT. AT 00Z THE 850MB FRONT WAS JUST NORTH OF THE FORECAST AREA. MODELS BRING THIS THROUGH THE COUNTY WARNING AREA BY 12Z/7AM...DROPPING TEMPERATURES TO -5 IN THE NORTHWEST. BY THE END OF THE DAY 850 MB TEMPERATURES WILL BE BELOW ZERO AS FAR SOUTH AS THE VIRGINIA / NORTH CAROLINA BORDER. TEMPERATURE PROFILES FROM THE MODELS SHOWED DIFFERENT TIMING OF HOW FAST THE WARM NOSE ERODES. LEANING TOWARD THE RAP AND NAM WHICH COOL THE WARM NOSE A LITTLE SLOWER THAN THE NAM. BIGGEST CHANGE WILL TO ADJUST THE TIMING AND SLOW DOWN THE CHANGE OVER TO MIXED WINTER PRECIPITATION AND THEN SNOW. EXTENDED IN TIME THE WINTER STORM WARNING FOR AMHERST AND BUCKINGHAM COUNTIES TO ACCOUNT FOR THE TIMING OF WHEN THE SNOW ENDS. ALSO ADDED A WINTER WEATHER ADVISORY FOR THE REMAINING COUNTIES IN NORTH CAROLINA. THE AMOUNT OF FREEZING RAIN HAS BEEN INCREASED FOR MUCH OF THE COUNTY WARNING AREA. AT THE SURFACE...RUC GUIDANCE HAD THE BEST HANDLE ON THE CURRENT TEMPERATURE TRENDS SO USED THIS AS A GUIDE FOR THE FALLING TEMPERATURES DURING THE DAY AND THEREFORE THE TRANSITION TIMES.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
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AS OF 300 AM EST THURSDAY... DURING EARLY EVENING...PRECIPITATION WILL QUICKLY BE MAKING THE TRANSITION FROM SLEET TO SNOW ACROSS THE SOUTHSIDE AND NORTH CAROLINA PIEDMONT...JUST AHEAD OF THE BACK EDGE OF THE SNOW WHICH WILL BE RACING EAST ACROSS THE PIEDMONT. EXPECT WE WILL HAVE ALL MEASURABLE SNOWFALL OUT OF OUR AREA BY 10 PM...WITH DECREASING CLOUDS THEREAFTER. ARCTIC HIGH PRESSURE WILL THEN BUILD EAST UP THE OHIO RIVER VALLEY...MAKING FOR MOSTLY CLEAR SKIES AND LIGHT WINDS BY SUNRISE FRIDAY...IDEAL CONDITIONS FOR STRONG RADIATIONAL COOLING. THIS WILL RESULT IN ONE LAST SHOT OF FRIGID AIR FOR THE FORESEEABLE FUTURE AS WE START FRIDAY MORNING OFF WITH TEMPERATURES RANGING FROM NEAR ZERO ALONG THE INTERSTATE 64 CORRIDOR...TO THE LOW 20S ACROSS THE FOOTHILLS AND PIEDMONT OF NORTH CAROLINA. THE ARCTIC AIRMASS WILL KEEP FRIDAY AFTERNOON TEMPERATURES WELL BELOW NORMAL...WITH HIGHS RANGING FROM THE UPPER 20S NORTH TO AROUND 40 SOUTH. TEMPERATURES WILL BEGIN TO MODERATE FOR FRIDAY NIGHT AND SATURDAY AS WINDS SHIFT MORE WEST SOUTHWESTERLY AHEAD OF AN APPROACHING WEAK COLD FRONT...CAUSING THE COLDER AIR TO RETREAT BACK TO THE NORTH. WILL START SATURDAY OFF WITH LOWS IN THE UPPER TEENS AND LOW 20S FOR MUCH OF THE REGION...WITH ABUNDANT SUNSHINE HELPING AFTERNOON HIGHS WARM INTO THE 40S ACROSS THE MOUNTAINS AND THE LOW TO MID 50S EAST OF THE BLUE RIDGE. THE WARMUP WILL CONTINUE INTO SUNDAY...ALBEIT WITH INCREASING CLOUDS BUT OTHERWISE DRY CONDITIONS. AFTERNOON HIGHS WILL RANGE FROM THE MID/UPPER 40S WEST TO THE MID/UPPER 50S EAST. WILL BE KEEPING AN EYE ON AN UPPER LEVEL DISTURBANCE PASSING ACROSS THE SOUTHEAST STATES SUNDAY NIGHT...WHICH HAS THE POTENTIAL OF BRINGING LIGHT RAIN EARLY IN THE NIGHT...CHANGING OVER TO A LIGHT WINTRY MIX TOWARD SUNRISE MONDAY.
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&& .LONG TERM /MONDAY THROUGH WEDNESDAY/...
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AS OF 300 PM EST WEDNESDAY... THERE HAS BEEN CONSIDERABLE VARIATION IN THE MODEL GUIDANCE DURING THE SUNDAY NIGHT THROUGH TUESDAY TIME PERIOD. WHILE EACH IS FAIRLY CONSISTENT THAT A LONG WAVE TROUGH WILL DEVELOP ACROSS THE EASTERN THIRD OF CONUS...THERE HAVE BEEN INCONSISTENCIES AS TO WHETHER OR NOT...AND WHEN...AND WHAT TRACK A SOUTHERN STREAM SYSTEM MAY GET PICKED UP ON THE EAST SIDE OF THIS TROUGH AND PROGRESS NORTHEAST ACROSS OUR AREA. THE GFS HAS NOT BEEN FAVORABLE OF THIS OCCURRENCE. THE ECMWF WAS OPTIMISTIC ON AN ARRIVAL A SOUTHERN SYSTEM ON MONDAY. OUR FORECAST TODAY WILL REFLECT TEMPERATURES CONTINUING TO MODERATE THROUGH MONDAY...WITH THE THINKING THAT THE DEVELOPING TROUGH AXIS WILL REMAIN TO OUR WEST...AND WE WILL CONTINUE IN WARM AIR ADVECTION AT THE SURFACE. IT WILL ALSO REFLECT THE POTENTIAL FOR SOME ISOLATED TO SCATTERED UPSLOPE SNOW SHOWERS ACROSS SOUTHEAST WEST VIRGINIA WHERE 850 MB FLOW WILL BE MORE W-NW. IT WILL ALSO ALLOW FOR A SLIGHT CHANCE OF A SOUTHERN STREAM SYSTEM IMPACTING THE AREA ON TUESDAY WITH RAIN OR FREEZING RAIN. THE LATEST GUIDANCE FOR THE EARLY TO MIDDLE PART OF NEXT WEEK CONTINUES TO FLUCTUATES IN REGARDS TO THE TIMING AND TRACK OF A SOUTHERN STREAM SYSTEM. THE LATEST TRENDS BRING THE GFS INTO PLAY NOW FOR BRINGING A SYSTEM THROUGH THE AREA ON WEDNESDAY...THE CANADIAN AND ECWMF STILL A LITTLE EARLIER. IN ADDITION TO THE SMALL CHANCE OF PRECIPITATION ON TUESDAY...WE WILL ALSO ADD WEDNESDAY INTO THE MIX TO REFLECT THE MODEL VARIATIONS AND A SMALL POTENTIAL EACH DAY FOR A LOW AND ITS ASSOCIATED PRECIPITATION TO PROGRESS OVER OR NEAR THE REGION. WHILE MOST OF THE REGION SHOULD EXPERIENCE RAIN ON WEDNESDAY...A FEW SPOTS IN THE SOUTHEAST WEST VIRGINIA MAY BE COLD ENOUGH FOR A BRIEF PERIOD OF FREEZING RAIN. HIGH TEMPERATURES ON WEDNESDAY WILL BE MILDER THAN THOSE OF TUESDAY. EXPECT A RANGE OF LOW TO MID 50S ACROSS THE MOUNTAINS WITH UPPER 50S TO LOWER 60S ACROSS THE PIEDMONT.
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&& .AVIATION /10Z THURSDAY THROUGH MONDAY/... AS OF 1125 PM EST WEDNESDAY... FLYING CONDITIONS WILL CONTINUE TO DETERIORATE OVER THE MOUNTAINS OVERNIGHT AND IN THE EAST BY DAYBREAK THURSDAY. THIS WILL RESULT IN WIDESPREAD MVFR TO IFR CIGS OVER THE MOUNTAIN LOCATIONS WITH PERIODIC MVFR VSBYS AND PERHAPS IFR AT TIMES AT KBLF/KLWB. BRIEF MVFR MAY OCCUR AT KROA AND POINTS EAST OVER THE NEXT FEW HOURS BEFORE TRENDING TO OVERALL MVFR OVERNIGHT. WINDS WILL SHIFT NW-N BEHIND THE FRONT. THE PRECIPITATION WILL GRADUALLY TRANSITION FROM RAIN TO A RAIN/SLEET MIX...TO A SNOW/SLEET MIX TO MAINLY ALL SNOW BEFORE ENDING OUT EAST THURSDAY AFTERNOON. THIS TRANSITION WILL START FIRST AROUND 06Z/1AM AROUND KBLF...AND THE LAST LOCATION TO TRANSITION TO ALL SNOW WILL BE KDAN AROUND 22Z/5PM. BY LATE IN THE AFTERNOON THURSDAY...CIGS/VSBYS WILL START TO IMPROVE IN THE WEST. A CLEARING TREND IS EXPECTED THURSDAY EVENING...ESPECIALLY IN THE EAST WITH VFR TO MVFR CIGS LIKELY LINGERING IN THE WEST THURSDAY EVENING. MEDIUM CONFIDENCE ON CEILINGS...VISIBILITIES AND WINDS DURING THE TAF PERIOD. EXTENDED FORECAST... FRIDAY TO SUNDAY WILL SEE A RETURN TO HIGH PRESSURE AND VFR WEATHER. SOME RAIN AND SNOW SHOWERS ARE POSSIBLE ON MONDAY IN THE WESTERN MOUNTAINS WITH BRIEF MVFR EXPECTED. && .HYDROLOGY...
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AS OF 330 AM EST THURSDAY FLOODING WAS WIDESPREAD ACROSS MERCER AND TAZEWELL COUNTIES OVERNIGHT. RAINFALL ACROSS THE AREA WEDNESDAY RANGED FROM ONE /1.00/ TO ONE AND A HALF /1.50/ INCHES. THE RAINFALL...COMBINED WITH EXISTING SNOWMELT...CAUSING EXTENSIVE LOWLAND FLOODING. IN TERMS OF THE RIVERS...THE BLUESTONE AND CLINCH HAVE BEEN THE MOST AFFECTED. MODERATE FLOOD LEVELS WERE REACHED AT SPANISHBURG AND PIPESTEM...WITH MINOR FLOODING AT RICHLANDS. THESE LOCATIONS MAY CONTINUE TO EXPERIENCE FLOODING TODAY. FOR TODAY...THE BIG QUESTION IS HOW MUCH MORE LIQUID PRECIPITATION OCCURS BEFORE THE TRANSITION TO FROZEN. CURRENT THINKING IS THAT ALL PRECIPITATION ACROSS WEST VIRGINIA...AND ALL THE BORDERING COUNTIES WITH VIRGINIA...WILL TRANSITION OVER TO SNOW AFTER DAYBREAK THIS MORNING. THIS SHOULD SIGNIFICANTLY STABILIZE THE HYDROLOGIC SITUATION...LIMITING FURTHER RUNOFF AND ALLOWING RIVERS AND SMALL STREAMS TO RECEDE.
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&& .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR VAZ007- 009>018-022-034. WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR VAZ019- 020-023-024. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR VAZ032-033-043>046-058-059. WINTER STORM WARNING UNTIL 10 PM EST THIS EVENING FOR VAZ035- 047. NC...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR NCZ001- 002-018. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR NCZ003-019. WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 10 PM EST THIS EVENING FOR NCZ004>006-020. WV...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR WVZ042>044-507-508.
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&& $$ SYNOPSIS...AMS NEAR TERM...AMS/WP SHORT TERM...NF LONG TERM...DS AVIATION...AMS/DS/JH/KK HYDROLOGY...PM

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