Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 232038 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 338 PM EST SUN NOV 23 2014 .SYNOPSIS...
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A WARM FRONT WILL LIFT NORTH ACROSS THE REGION TONIGHT. THE RAIN MAY BE HEAVY AT TIMES THIS EVENING AND EARLY TONIGHT...AND WINDS WILL BECOME QUITE GUSTY ACROSS THE MOUNTAIN EMPIRE REGION AND OTHER HIGH ELEVATIONS WEST OF THE BLUE RIDGE. UNSEASONABLY WARM CONDITIONS ARE EXPECTED MONDAY IN THE WAKE OF THIS SYSTEM...BEFORE A COLD FRONT MOVES THROUGH MONDAY NIGHT INTO TUESDAY...RETURNING TEMPERATURES TO BELOW NORMAL FOR THE REST OF THE WEEK. THERE IS THE POTENTIAL FOR A COASTAL STORM TO IMPACT PARTS OF THE MID ATLANTIC FOR MID WEEK.
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&& .NEAR TERM /THROUGH MONDAY/...
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AS OF 330 PM EST SUNDAY... WIND ADVISORY REMAINS IN EFFECT FOR THE COUNTIES OF TAZEWELL AND SMYTH IN VIRGINIA AND MERCER IN WEST VIRGINIA...WHERE THERE IS THE POTENTIAL FOR THE STRONG LOW LEVEL SOUTHEAST JET TO TRANSLATE TO LOWER ELEVATIONS. BOTH THE GFS AND NAM PIVOT THE THE 85O MB JET JUST TO OUR WEST THIS EVENING INTO TONIGHT. THE WARM FRONT OVER THE SOUTHEAST STATES WILL SLOWLY LIFT NORTH THIS AFTERNOON INTO TONIGHT. THE ADVANCE OF THIS FRONTAL BOUNDARY IS QUITE SLOW. REGIONAL WSR-88D IMAGES INDICATED THAT LIGHT RAIN HAS ADVANCE NORTHWARD ACROSS THE MUCH OF THE FORECAST AREA. THE RAIN WILL CONTINUE TO SPREAD NORTHWARD ACROSS THE AREA INTO TONIGHT. THE RAIN MAY BE HEAVY AT TIMES THIS EVENING AND EARLY TONIGHT. NOT EXPECTING ANY FLOODING PROBLEMS WITH FORECASTED RAIN RATES. THE SWODY1 HAS THE CHANCE OF A GENERAL THUNDERSTORM FOR OUR REGION BUT CLOUDS AND RAIN ARE HINDERING THE INSTABILITY...DESPITE THE HEALTHY SHEAR. WILL HOLD OFF ON ADDING ANY EMBEDDED THUNDERSTORM AT THIS TIME...BUT CAN NOT COMPLETELY RULE OUT AN ISOLATED THUNDERSTORM IN THE SOUTHEAST. TONIGHT...THE 850 MB FRONT IS EXPECTED TO SURGE INTO AND ACROSS THE AREA THIS EVENING INTO TONIGHT. ONCE THE WARM FRONT SURGES THROUGH TONIGHT...A DRY SLOT WILL WORK IN FROM THE WEST AND SHOULD TAPER OFF PRECIPITATION OVERNIGHT INTO MONDAY MORNING. USED A NON-DIURNAL CURVE FOR TEMPERATURES TONIGHT WITH LOWS GENERALLY FROM THE LOWER 40S TO THE LOWER 50S. BROAD UPPER LEVEL 500H TROUGH WILL ENCOMPASS MUCH OF THE CENTRAL CONUS FOR MONDAY TO START THE WORKWEEK. A COLD FRONT WILL APPROACH FROM THE WEST MONDAY. A WARM SECTOR SOUTHERLY WINDS WILL RESULT IN A BREEZY MILD MONDAY. 1000-500MB THICKNESS VALUES OF 565-570DM AND 850H TEMPERATURES AROUND PLUS 10C SUPPORT SURFACE TEMPERATURES FROM AROUND 60 DEGREES IN THE MOUNTAINS TO THE LOWER 70S IN THE PIEDMONT. THE SURFACE COLD FRONT CROSSES THE MOUNTAINS LATE IN THE DAY... WITH GFS SOLUTION A LITTLE QUICKER THAN THE NAM/ECMWF.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
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AS OF 338 PM EST SUNDAY... ON MONDAY NIGHT LOW LEVEL MOISTURE IS BANKED UP AGAINST THE WESTERN SLOPES OF THE APPALACHIANS. MODELS ERODE LOW LEVEL MOISTURE ON TUESDAY MORNING. OVERALL PATTERN THIS TIME FRAME IS FOR SPLIT FLOW WITH AN ACTIVE NORTHERN STREAM ALONG THE CANADIAN/NORTHERN U.S. BORDER AND SOUTHERN STREAM THAT HAS A STRONG SHORT WAVE AT THE BASE OF THE TROF OVER THE LOWER MISSISSIPPI VALLEY BY LATE TUESDAY. EVOLUTION AND TIMING OF LONG WAVE TROF FROM POSITIVE TILT TO NEGATIVE TILT AND AMOUNT OF PHASING BETWEEN THE TWO JET STREAMS WILL IMPACT THE RESULTING TRACK OF THE GULF TO EAST COAST SURFACE LOW AND LOCATION OF THE HEAVIEST PRECIPITATION. AT THIS TIME SPREAD IN DIFFERENT MODELS IS LARGE. HIGHEST CONFIDENCE IS WITH THE TIMING BUT MUCH LOWER WITH THE LOCATION AND TYPE OF PRECIPITATION. WILL BE LEANING TOWARD BLEND OF THE ECMWF AND GFS AS SUGGESTED BY WPC. MODELS SHOW MID ATLANTIC REGION IN THE RIGHT REAR QUADRANT OF A 170 KNOT UPPER JET BY LATE TUESDAY NIGHT. AT THE SURFACE THE COLD FRONT MOVES OFF THE EAST COAST MONDAY NIGHT THEN HIGH PRESSURE BUILDS FROM THE TENNESSEE VALLEY INTO THE MID ATLANTIC STATES ON TUESDAY. LOW PRESSURE DEVELOPS IN THE GULF OF MEXICO ON TUESDAY...THEN TRACKS ACROSS FLORIDA TUESDAY NIGHT. THE LOW SHOULD BE OFF THE SOUTH CAROLINA COAST ON WEDNESDAY MORNING AS IT MOVES NORTHEAST AND BEGINS TO DEEPEN. ONCE THE LOCATION OF THE PRECIPITATION IS DETERMINED...TEMPERATURES WILL INFLUENCE WHAT TYPE OF PRECIPITATION WILL OCCUR. EVEN TAKING THE COOLER MET/SREF GUIDANCE FOR TEMPERATURES ON TUESDAY NIGHT AND WEDNESDAY...SURFACE VALUES MAY STILL BE TOO WARM EAST OF THE BLUE RIDGE TO SUPPORT ANYTHING BUT RAIN. HAVE USED PARTIAL THICKNESS VALUES...MAINLY FROM THE GFS/ECMWF TO PLACE RAIN/SNOW LINE. THIS WILL CHANGE AS THE EVENT DRAWS CLOSER. LOOKED AT PROBABILITY FOR SNOW AND CORRELATION WITH PAST ANALOG EVENTS. APPEARS THERE IS AT LEAST THE POTENTIAL FOR SOME WINTER PRECIPITATION. SINCE WEDNESDAY IS A MAJOR TRAVEL DAY WILL MENTION POTENTIAL FOR WINTER PRECIPITATION IN THE HAZARDOUS WEATHER OUTLOOK.
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&& .LONG TERM /THURSDAY THROUGH SUNDAY/...
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AS OF 130 PM EST SUNDAY... THIS PORTION OF THE FORECAST STARTS WITH THE AFTERMATH OF WHAT UNFOLDS TUESDAY NIGHT INTO WEDNESDAY EVENING. GIVEN THERE STILL IS GENEROUS UNCERTAINTY IN THOSE EVENTS...THE EVENTS AFTERWARDS ARE EQUALLY CHALLENGING. THE GENERAL CONSENSUS IS FOR A LOW/TROUGH TO DEEPEN ACROSS THE GREAT LAKES/OHIO VALLEY AS THE SYSTEM ALONG THE COAST HEADS NORTHEAST...AND MAKES WAY FOR THE UPSTREAM SYSTEM TO ENTER OUR REGION. THE PAST FEW DAYS...GUIDANCE HAS TRANSITIONED THIS SYSTEM FROM A SLOWER...MORE AMPLIFIED SYSTEM INTO ONE THAT IS MORE PROGRESSIVE AND THE BULK OF ITS ENERGY REMAINS NORTH OF THE REGION AS IT MOVES EASTWARD. THAT TREND CONTINUES TODAY. OUR FORECAST WILL REFLECT LITTLE CHANGE FROM THE PRIOR DURING THE THURSDAY THROUGH FRIDAY TIMEFRAME. THE HIGHLIGHTS HERE ARE UPSLOPE RAIN/SNOW SHOWERS ACROSS SOUTHEAST WEST VIRGINIA AND NEIGHBORING COUNTIES OF SOUTHWEST VIRGINIA. A DECENT NORTHWEST FLOW WILL HELP CLOUDS TO A MINIMUM EAST OF THE CREST OF THE BLUE RIDGE AND ADD A TOUCH OF A WARMING INFLUENCE. PARTLY TO MOSTLY CLOUDY SKIES AND COOLER TEMPERATURES WILL BE THE RULE FOR THE MOUNTAINS. SATURDAY INTO SUNDAY THE REGION TRANSITIONS INTO MORE OF A ZONAL PATTERN. THERE IS CONSISTENCY IN EACH MODEL CONCERNING THAT FEATURE. WHAT VARIES SIGNIFICANTLY IS THE TIMING...TRACK AND SPEED OF A DISTURBANCE MOVING WITHIN THIS ZONAL FLOW THAT MAY OR MAY NOT IMPACT OUR REGION. AT THIS TIME...HAVE PLACED THE GREATEST FORECAST WEIGHT ON A MODEL CONSENSUS THAT OFFERS A SMALL CHANCE OF LIGHT RAIN/SNOW MAINLY IN THE WESTERN PARTS OF THE AREA SATURDAY NIGHT INTO EARLY SUNDAY WITH TEMPERATURES TRENDING MILDER OVER THE WEEKEND.
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&& .AVIATION /21Z SUNDAY THROUGH FRIDAY/... AS OF 1250 PM EST SUNDAY... WINDS...RAIN AND CLOUDS WILL HINDER AVIATION OPERATIONS THIS AFTERNOON INTO MONDAY. WARM FRONT OVER THE SOUTHEAST STATES WILL LIFT NORTH THIS AFTERNOON INTO TONIGHT. RAIN WILL SPREAD NORTH ACROSS OUR AREA THIS AFTERNOON INTO TONIGHT. AS THE AFTERNOON PROGRESSES...CLOUD BASES WILL LOWER WITH MVFR CIGS DEVELOPING AT ALL RNK TERMINAL FORECAST POINTS. ONSET OF RAIN MAY RESULT IN RAPID DETERIATION OF FLIGHT CONDITIONS TO IFR BY SUNSET WITH CONTINUATION OF LOW CIGS/VSBYS THROUGH THE OVERNIGHT TONIGHT. EXPECT PERIODS OF MDT AND HEAVY RAIN FROM THE BLUE RIDGE EAST THIS EVENING INTO TONIGHT. THERE IS THE POTENTIAL FOR LOW LVL WIND SHEAR ESPECIALLY IN THE WEST AS LOW LEVEL JET INCREASES TO AOA 50KTS TONIGHT. A BRIEF RETURN TO VFR DURING MONDAY OUTSIDE OF THE MOUNTAINS AS A DRY SLOT DEVELOPS BETWEEN THE EXITING FRONT FROM SUNDAY AND THE NEXT UPSTREAM COLD FRONT. MEDIUM CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS DURING THE PERIOD. EXTENDED DISCUSSION... MONDAY INTO TUESDAY LOOK TO FEATURE QUITE A BIT OF WIND. NW FLOW INTO MAY KEEP SUB VFR CIGS INTO BLF AND POSSIBLE LWB...WITH VFR TO THE EAST. ANOTHER STORM SYSTEM IS EXPECTED TO MOVE UP THE SOUTHEAST COAST BY WEDNESDAY WHICH MAY BRING WINTRY PRECIP TO THE AREA ALONG WITH SUB VFR AT ALL SITES. && .EQUIPMENT... AS OF 215 PM EST FRIDAY... THE VISIBILITY SENSOR AT KLYH...LYNCHBURG AIRPORT...WILL BE OUT OF SERVICE UNTIL PARTS ARRIVE TO REPLACE THE SENSOR. UNTIL THEN THE VISIBILITY WILL ONLY BE REPORTED WHEN THE CONTROL TOWER IS STAFFED. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WIND ADVISORY UNTIL 1 AM EST MONDAY FOR VAZ007-009. NC...NONE. WV...WIND ADVISORY UNTIL 1 AM EST MONDAY FOR WVZ042.
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&& $$ SYNOPSIS...KK/MBS NEAR TERM...KK SHORT TERM...AMS LONG TERM...DS AVIATION...KK/PM EQUIPMENT...RAB

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