Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 300834 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 434 AM EDT THU OCT 30 2014 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD ACROSS THE REGION TODAY PROMOTING MOSTLY CLEAR SKIES AND LIGHT WINDS...FAIR WEATHER PERSISTING THROUGH THE FIRST HALF OF THE DAY FRIDAY. WEATHER CONDITIONS WILL RAPIDLY DETERIORATE FRIDAY EVENING AS A FAST MOVING CLIPPER SYSTEM FROM CANADA MOVES SOUTHEAST ACROSS THE OHIO VALLEY...AND TRIGGERING THE DEVELOPMENT OF A STRONG AREA OF LOW PRESSURE IN THE UPPER LEVELS OF THE ATMOSPHERE AS IT CROSSES THE MID ATLANTIC REGION FRIDAY NIGHT AND SATURDAY. WINTER STORM CONDITIONS ARE POSSIBLE IN THE HIGH COUNTRY OF NORTH CAROLINA...AND INTO THE HIGHER ELEVATIONS OF FAR WESTERN VIRGINIA VICINITY OF MOUNT ROGERS FRIDAY NIGHT AND SATURDAY. ELEVATIONS ABOVE 3000 FEET WILL SEE THE GREATEST WINTRY IMPACT.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 400 AM EDT THURSDAY... THE NEXT 24-36 HOURS WILL BE THE CALM BEFORE THE STORM. 1022MB SURFACE HIGH PRESSURE CENTERED OVER THE OH/TN VALLEYS THIS MORNING WILL DRIFT EAST ACROSS THE AREA TODAY AND TONIGHT PROMOTING MOSTLY CLEAR SKIES AND LIGHT WINDS. THE AIRMASS IS SEASONALLY COOL AND DRY. PATCHY FROST IS A GOOD BET TONIGHT BUT THE BIGGER STORY IS THE STORM SYSTEM THAT MODELS ARE ZEROING IN ON FOR HALLOWEEN NIGHT...WITH INGREDIENTS COMING TOGETHER FOR A TRICK OR TREAT.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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AS OF 400 AM EDT THURSDAY... OUR FIRST WINTER STORM OF THE SEASON IS POSSIBLE FRIDAY NIGHT INTO SATURDAY. MODEL CONCENSUS IS FOR THE GREATEST WINTRY IMPACT TO OCCUR AT ELEVATIONS ABOVE 3000 FEET...AND PRIMARILY ACROSS THE NORTH CAROLINA HIGH COUNTRY AND INTO FAR SOUTHWESTERN VIRGINIA VICINITY OF MOUNT ROGERS. NOT A GOOD WEEKEND TO VENTURE INTO THE HIGHER ELEVATIONS UNLESS YOU ARE PREPARED...BACKPACKERS/CAMPERS HEAD CAUTION. A DEEP UPPER LEVEL TROUGH DROPS SOUTH FROM THE WESTERN GREAT LAKES THURSDAY NIGHT...BECOMING A CLOSED LOW AS IT CROSSES THE OHIO RIVER NEAR CINCINNATI FRIDAY EVENING. THE LOW CENTER REACHES CHARLOTTE/COLUMBIA FRIDAY NIGHT INTO SATURDAY MORNING. A SECONDARY SURFACE CYCLOGENESIS OCCURS ALONG THE NORTH CAROLINA COAST SATURDAY INTO SATURDAY NIGHT. ALL MODELS ARE IN AGREEMENT THAT THIS SYSTEM WILL BRING THE COLDEST AIR WE HAVE SEEN THIS AUTUMN...AND THAT THE SYSTEM WILL PASS RAPIDLY ACROSS OUR AREA. RAIN SHOWERS WILL BECOME WIDESPREAD FRIDAY AFTERNOON. 850MB TEMPERATURES WILL GRADUALLY DROP THROUGH THE DAY AS THE UPPER LOW APPROACHES...WITH THE AIR BECOMING COLD ENOUGH FRIDAY EVENING INTO FRIDAY NIGHT TO RESULT IN A MIXTURE OF RAIN AND SNOW. THE HIGHEST ELEVATIONS WILL HAVE THE BEST CHANCE FOR SNOW AND EVENTUALLY CHANGE OVER TO ALL...SNOW ACROSS MUCH OF THE AREA BY EARLY SATURDAY. TOO EARLY FOR CONFIDENCE IN SNOW ACCUMULATIONS WITH WARM GROUND...UNCERTAINTY WITH SNOW RATES AND QUESTIONS IN ACTUAL TRACK OF THE LOW CENTER. AT THIS POINT LOOKS LIKE NORTHWEST SNOW EVENT WITH SNOW ADVISORY LEVEL ACCUMULATIONS POSSIBLE ALONG THE WESTERN SLOPES THE MOUNTAINS...AND WARNING LEVEL ACCUMULATION AT ELEVATIONS ABOVE 3000 FEET. SNOW TOTALS IN THE LOWER ELEVATIONS NOT AN ISSUE DUE TO WARMER GROUND...AND ONCE YOU GET EAST OF THE BLUE RIDGE NOT EXPECTING ANY ACCUMULATION AT ALL...JUST A COLD RAIN. BY EARLY SATURDAY AFTERNOON...THE UPPER LOW WILL PUSH OFF THE NORTH CAROLINA COAST...CAUSING PRECIPITATION TO FADE FROM EAST TO WEST OVER OUR AREA AS WINDS BECOME NORTHWESTERLY. WIND SPEEDS WILL INCREASE DRASTICALLY AS THE PRESSURE GRADIENT BETWEEN THE DEPARTING LOW AND HIGH PRESSURE APPROACHING FROM THE WEST INCREASES TO 10MB TO 12MB. THESE HEALTHY 6 HOUR PRESSURE RISES SHIFT EASTWARD SATURDAY NIGHT TOWARDS THE ATLANTIC COAST...THEN WIND SPEEDS WILL DECREASE AS THE PRESSURE GRADIENT BEGINS TO RELAX OVERNIGHT. WE WILL ALSO HAVE TO CONSIDER WIND HEADLINES FRIDAY NIGHT INTO SATURDAY NIGHT. SNOW SHOWERS WILL LINGER IN THE MOUNTAINS SATURDAY NIGHT...WITH SNOW SHOWERS FADING QUICKLY IN THE NORTHWESTERLY DOWNSLOPE FLOW EAST OF THE BLUE RIDGE. MOISTURE WILL BECOME INCREASINGLY SHALLOW THROUGH THE NIGHT ACROSS THE WESTERN RIDGES... SO ACTUALLY MAY SEE PRECIPITATION TRANSITION MORE TO LIGHT FREEZING DRIZZLE AS OPPOSED TO SNOW SHOWERS. TEMPERATURES BY SATURDAY WILL BE 10-15 DEGREES BELOW NORMAL ACROSS THE REGION.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 407 PM EDT WEDNESDAY... TEMPERATURES WILL MODERATE OVER THE FIRST FEW DAYS OF NEXT WEEK AS THE UPPER LOW MOVES AWAY FROM OUR AREA. HIGH PRESSURE WILL BUILD SOUTHEAST ACROSS OUR REGION SUNDAY. HIGH PRESSURE WILL PASS OVERHEAD ON SUNDAY NIGHT...SO TEMPERATURES STILL PRETTY CHILLY SUNDAY AND SUNDAY NIGHT. AS THE HIGH SHIFTS TOWARD THE CAROLINA COAST ON MONDAY...WINDS WILL SHIFT SOUTHWESTERLY... WHICH WILL BEGIN TO CARRY WARMER AIR FROM THE GULF OF MEXICO NORTHWARD ALONG THE APPALACHIAN CHAIN. THE HIGH CENTER WILL SLIDE OFF INTO THE ATLANTIC OCEAN ON MONDAY NIGHT AS A COLD FRONT APPROACHES FROM THE WEST. THE COLD FRONT WITH CONVECTION AHEAD AND ALONG IT WILL TRAVEL THROUGH OUR REGION ON WEDNESDAY. && .AVIATION /09Z THURSDAY THROUGH MONDAY/...
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AS OF 400 AM EDT THURSDAY... HIGH PRESSURE WILL BUILD OVERHEAD TODAY AND TONIGHT PROMOTING MAINLY VFR CONDITIONS. SOME RIVER VALLEY FOG IS POSSIBLE IN THE MOUNTAINS EARLY THIS MORNING. STRATUS AND FOG IS ALSO LIKELY THROUGH MID MORNING OVER PARTS OF CENTRAL VIRGINIA...MAINLY NORTHEAST OF KLYH. THERE IS A SLIGHT RISK FOR BRIEF PD OF IFR AT KLYH AND KDAN AROUND DAYBREAK THIS MORNING...BUT WILL LEAVE OUT OF THE TAFS ATTM. CONFIDENCE IS MEDIUM ON CIGS/VSBYS. EXTENDED AVIATION DISCUSSION... EXPECTATION IS FOR VFR CONDITIONS TO PERSIST THROUGH THE FIRST HALF OF THE DAY FRIDAY...THEN DETERIORATING AS A STRONG STORM SYSTEM MOVES IN FROM THE NORTHWEST. THIS SYSTEM WILL BRING A PROLONGED PERIOD OF POTENTIALLY IFR-LIFR CIGS AND PRECIPITATION...WITH SNOW IN THE MOUNTAINS OF NC/WV/AND FAR WESTERN VA...AND RAIN IN THE VALLEYS. ATTM IT LOOKS LIKE SIGNIFICANT IMPACT TO AVIATION WILL DEVELOP WITHIN THE VICINITY OF THE NC MTNS AND UP INTO THE HIGHER ELEVATIONS OF FAR WRN VA AND WV. MODELS SUGGEST THIS STORM SYSTEM WILL BE VERY DYNAMIC WITH LOW FREEZING LEVELS AND HEAVY WET SNOW UNDERNEATH THE CORE OF THE STORM WHICH IS PROGGED TO PASS DIRECTLY OVER THE NC MTNS. IN ADDITION...STRONG WINDS ARE EXPECTED TO DEVELOP SATURDAY IN THE WAKE OF THIS DEPARTING STORM SYSTEM. STRONG CROSS BARRIER FLOW...50 KTS...IS EXPECTED OVER THE MOUNTAINS...RESULTING IN SURFACE WIND GUSTS OF 30 KTS LEE OF THE BLUE RIDGE SATURDAY AFTERNOON AND EVENING. THIS STORM WILL QUICKLY MOVE AWAY FROM THE AREA SUNDAY WITH VFR CONDITIONS RETURNING FOR MONDAY AND TUESDAY.
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&& .EQUIPMENT... THE AC UNITS FOR THE RADAR SHELTER ARE BAD. RADAR OPERATION WILL BE INTERMITTENT UNTIL SUCH TIME THE AC UNITS ARE FIXED. IF SHELTER TEMPERATURES RISE ABOVE CRITICAL LEVELS WE WILL PLACE THE RADAR INTO STANDBY TO AVOID DAMAGE TO THE TRANSMITTER. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WINTER STORM WATCH FROM FRIDAY EVENING THROUGH SATURDAY EVENING FOR VAZ007-009-015. NC...WINTER STORM WATCH FROM FRIDAY EVENING THROUGH SATURDAY EVENING FOR NCZ001-018. WV...NONE.
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&& $$ SYNOPSIS...PM NEAR TERM...AMS/PM SHORT TERM...PM/KK LONG TERM...KK AVIATION...PM EQUIPMENT...PM

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