Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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 182005 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 305 PM EST THU DEC 18 2014 .SYNOPSIS... HIGH PRESSURE OVER THE UPPER MIDWEST WILL GRADUALLY BUILD EAST ACROSS THE AREA RESULTING IN OVERALL DRY WEATHER THROUGH FRIDAY EVENING. A WEAK AREA OF LOW PRESSURE WILL EVENTUALLY DEVELOP ALONG THE GULF COAST STATES FRIDAY NIGHT AND MOVE EAST-NORTHEAST OVER THE CAROLINAS ON SATURDAY. THIS SYSTEM WILL BRING A PERIOD OF LIGHT WINTRY PRECIPITATION SATURDAY MORNING...CHANGING TO RAIN OVER THE PIEDMONT IN THE AFTERNOON. && .NEAR TERM /THROUGH FRIDAY/... AS OF 215 PM EST THURSDAY... WAVE ALOFT PASSES EAST OVERNIGHT LEAVING WEAK SUBSIDENCE IN PLACE AS HIGH PRESSURE TO THE NW NOSES BACK IN LATE. THIS WILL ALSO INTRODUCE ANOTHER ROUND OF WEAK COLD ADVECTION ALLOWING UPSLOPE CLOUDS TO REDEVELOP IN THE WEST...PERHAPS REACHING THE BLUE RIDGE BY DAYBREAK. WITH ENOUGH MOISTURE...WESTERN GREENBRIER COULD EDGE OUT A DUSTING TO A HALF OF AN INCH OF SNOW ABOVE 3000 FT. OTHER SOUTHEASTERN WV COUNTIES SHOULD ONLY SEE FLURRIES OVERNIGHT. COUNTIES ALONG THE BLUE RIDGE TO THE PIEDMONT WILL SEE SLOW CLEARING OF THE MID/HIGH CLOUDS FROM WEST TO EAST AFTER MIDNIGHT. CLOUDS THIS AFTERNOON KEPT TEMPERATURES COOL AND THIS SHOULD TRANSLATE TO COOLER TEMPERATURES OVERNIGHT. WITH AFTERNOON DEW POINTS MAINTAINING IN THE L/M 20S...ANY SUBSTANTIAL CLEARING WITH LIGHT WINDS WILL ALLOW OVERNIGHT LOWS TO RADIATE DOWN COLDER THAN FORECASTED. CURRENT THINKING IS TO HAVE SOME CLOUDS AND/OR MIXING OVERNIGHT TO KEEP OVERNIGHT LOWS IN BETWEEN GFS AND NAM MOS. FRIDAY LOOKS TO BE ON THE DRY SIDE AS HIGH PRESSURE STRETCHING FROM THE GREAT LAKES THROUGH THE OHIO RIVER VALLEY REMAINS THE MAIN FEATURE IN OUR WEATHER PATTERN. MOSTLY SUNNY SKIES AND LIGHT NORTHWESTERLY DOWNSLOPE WINDS WILL ALLOW AFTERNOON TEMPERATURES TO RANGE FROM THE MID 30S ALONG THE WESTERN RIDGES...TO AROUND 50 OVER THE SOUTHSIDE AND THE NORTH CAROLINA PIEDMONT. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... AS OF 250 PM EST THURSDAY... MODELS HAVE BEEN TRENDING QUITE A BIT WEAKER WITH THE SHORT WAVE COMING OUT OF ARIZONA AND REACHING THE MID ATLANTIC REGION ON SATURDAY. ISENTROPIC LIFT AND VORTICITY ADVECTION COME THROUGH ON SATURDAY AND WILL BE EAST OF THE FORECAST AREA ON SATURDAY NIGHT. MOST SIGNIFICANT CHANGE IN THE GUIDANCE IS WITH THE AMOUNT OF MOISTURE. 12Z GUIDANCE NOW KEEPS BULK OF THE DEEPER MOISTURE SOUTH OF THE FORECAST AREA...ESPECIALLY THE 12Z NAM. WILL FOLLOW THIS TREND AND LOWER PROBABILITY OF PRECIPITATION IN ALL BUT THE SOUTHERN THIRD OF THE COUNTY WARNING AREA. WILL ALSO CUT BACK ON AMOUNT OF PRECIPITATION. SURFACE HIGH PRESSURE OVER THE UPPER MISSISSIPPI VALLEY WILL GRADUALLY MOVE EAST AND WILL BE OVER THE OHIO VALLEY ON SATURDAY. THE HIGH CONTINUES SLOW PROGRESS TO THE EAST SATURDAY NIGHT AND BY LATE SUNDAY THE RIDGE AXIS WILL BE OFFSHORE. THIS WILL BEGIN TO BRING SURFACE AND LOW LEVEL WINDS AROUND TO THE SOUTH LATE IN THE DAY. SURFACE REFLECTION OF THE SHORT WAVE ON SATURDAY WILL BE AN INVERTED TROF OVER THE SOUTHERN APPALACHIANS. EXPECT CLOUDS AND PRECIPITATION WILL KEEP MAXIMUM TEMPERATURES ON SATURDAY COOLER THAN GUIDANCE. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 230 PM EST THURSDAY... A VERY ACTIVE WEATHER PATTERN EXPECTED DURING THE MEDIUM RANGE WITH ENOUGH MODEL DIFFERENCES TO MAKE THE DETAILS OF THE SENSIBLE WEATHER A GOOD CHALLENGE. AN AREA OF LOW PRESSURE SYSTEM WILL DEVELOP ALONG THE GULF COAST SUNDAY NIGHT...PUSH MOISTURE NORTHWARD AND INTRODUCING ANOTHER CHANCE OF RAIN...AND POTENTIALLY FREEZING PRECIPITATION TO THE MOUNTAINS. UTILIZED THE TOPDOWN APPROACH LEANING TOWARDS GFS FOR TEMPERATURE PROFILES. HELD LOW TEMPERATURES A FEW DEGREES BELOW MOS WITH CLOUDS AND PRECIPITATION. IN GENERAL...SUNDAY NIGHT LOWS WILL RANGE FROM THE UPPER 20S IN THE MOUNTAINS TO THE LOWER 30S IN THE PIEDMONT. FOR MONDAY...A WAVE OF LOW PRESSURE ALONG THE FRONTAL BOUNDARY WILL BE LOCATED ALONG THE NORTH CAROLINA COAST WITH AXIS OF MOISTURE/PRECIPITATION MOVING NORTH ASSOCIATED WITH INCREASING WARM ADVECTION AHEAD OF THE DEVELOPING LONGWAVE TROUGH TO THE WEST. HOW MUCH THE LOW CENTER DEEPENS...ITS ASSOCIATED PRECIPITATION AND PTYPE REMAINS PROBLEMATIC FOR OUR REGION. EACH MODEL HAS A DIFFERENT TAKE ON THE MAGNITUDE OF THE WARM NOSE OVER OUR REGION. WILL MAINTAIN THE RAIN VERSUS FREEZING RAIN FORECAST DURING MUCH OF MONDAY MORNING. THERMAL PROFILES SUGGEST SOME POTENTIAL FOR LIGHT FREEZING RAIN OR SLEET ACROSS THE VIRGINIA HIGHLANDS AND SOUTHERN SHENANDOAH VALLEY. FELT THAT THERE WAS ENOUGH SUPPORT TO RAISE POPS FROM SLIGHT INTO THE CHANCE LEVEL MONDAY. KEPT HIGHS MONDAY COOLER THAN GUIDANCE WITH READINGS FROM THE MID 30S IN THE WEST TO THE MID 40S IN THE EAST. BY MONDAY NIGHT...LOW PRESSURE MOVES INTO THE MIDWEST WITH TRAILING FRONTAL BOUNDARY SOUTH INTO THE MISSISSIPPI VALLEY. A DEEP LONGITUDINAL TROUGH DEVELOPS SOUTH TO THE GULF OF MEXICO BY TUESDAY AFTERNOON WITH INCREASING SOUTHERLY LOW LEVEL FLOW ACROSS OUR REGION...ACCOMPANIED BY INCREASING MOISTURE ADVECTION. USING SUPERBLEND FOR LOW TEMPERATURES MONDAY NIGHT PRODUCED READINGS GENERALLY IN THE UPPER 20S AND LOWER 30S. TEMPERATURES WILL TREND MILDER FOR HIGHS TUESDAY FROM THE MID 40S TO THE LOWER 50S. BY TUESDAY NIGHT INTO WEDNESDAY...BOTH GFS AND ECWMF DEEPEN THE UPPER LOW AND ASSOCIATED TROUGH AND NEGATIVELY TILT THE FEATURE SO THAT THE TROUGH AXIS SHIFTS TO OFF THE NORTH CAROLINA COAST...COINCIDENT TO THE POSITION OF THE ASSOCIATED SURFACE OCCLUDED FRONT...WITH THE TRIPLE POINT PASSING SOMEWHERE NEAR OR JUST SOUTH OF OUR REGION. AT THIS TIME...SPC DOES NOT HAVE ANY THUNDERSTORMS IN ITS DAY 4-8 CONVECTIVE OUTLOOK. IT LOOKS LIKE...THERE IS THE POTENTIAL FOR OUR REGION TO HAVE ACTIVE WEATHER LATE TUESDAY NIGHT INTO WEDNESDAY WITH PLENTY OF SHOWERS...PERHAPS VERY GUSTY WINDS AND A FEW THUNDERSTORMS. COLD AIR PUSHES INTO THE REGION TUESDAY NIGHT INTO WEDNESDAY MORNING...ALLOWING FOR SOME RAIN AND SNOW SHOWERS. IF ENOUGH COLD AIR ARRIVES QUICKLY...THERE COULD BE SOME ACCUMULATING SNOW IN THE WESTERN MOUNTAINS. KEPT THE HIGHEST POPS OF RAIN AND SNOW SHOWERS IN THE WEST AS THE LOW CENTER MARCHES NORTHEAST PUSHES A COLD FRONT TO THE COAST. IN THE WAKE OF THE COLD FRONT A COOLING TRENDS WILL CONTINUE WEDNESDAY INTO THURSDAY...WITH WEST TO NORTHWEST FLOW ALOFT. UPPER FLOW SHIFTS TO THE SOUTHWEST AS TROF CURVES OUT IN THE CENTRAL US WITH SFC INFLECTION OF LOW PRESSURE DEVELOPS OVER THE TENNESSEE VALLEY BY FRIDAY MORNING. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... AS OF 1250 PM EST THURSDAY... MOST OF THE REGION WILL EXPERIENCE VFR CONDITIONS THROUGH THE NEXT 24 HOURS WITH MAINLY INTERVALS OF MID AND HIGH CLOUDS PASSING ACROSS. THE EXCEPTION WILL BE THE THOSE AREAS MAINLY ALONG AND WEST OF A KBLF-KLWB LINE WHERE RETURNING LOW LEVEL MOISTURE WILL MAKE FOR LOWER STRATO-CU CIGS OVERNIGHT INTO FRIDAY MORNING. EXTENDED DISCUSSION... THE FRI NIGHT-SAT SYSTEM NOW HAS TRENDED WEAKER BUT WILL STILL NEED TO BE WATCHED AS IT WILL LIKELY BRING A PERIOD OF SUB VFR WINTRY WEATHER ESPECIALLY FROM THE BLUE RIDGE WEST SAT. AVIATION INTERESTS WILL NEED TO MONITOR THIS SITUATION AS LATER FORECASTS BECOME AVAILABLE. THIS WILL LIKELY HAVE AN IMPACT ON AIR TRAVEL OVER THE WEEKEND...FROM THE SOUTHERN APPALACHIANS AND CAROLINAS NORTH TO THE MID ATLANTIC. ON THE HEELS OF THIS FRIDAY/SATURDAY SYSTEM WILL BE ANOTHER SYSTEM TO POTENTIALLY IMPACT MAINLY THE EASTERN PORTION OF THE REGION MONDAY INTO TUESDAY. ANOTHER AREA OF LOW PRESSURE IS EXPECTED TO HEAD NORTH ALONG THE EAST COAST WITH SCATTERED PRECIPITATION ON ITS WESTERN FLANKS ENTERING THE REGION. AT THIS POINT A WINTRY MIX IS POSSIBLE ALONG WITH LOCALIZED MVFR CIGS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...RCS NEAR TERM...RCS SHORT TERM...AMS LONG TERM...KK AVIATION...JH/RCS

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