Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 240004 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 704 PM EST SUN NOV 23 2014 .SYNOPSIS... 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. && .NEAR TERM /THROUGH MONDAY/... AS OF 630 PM EST SUNDAY... WINDS HAVE BEEN GUSTING UP TO 35-40 KTS AT BLF AND WEST...AS CORE OF LLJ MOVES ACROSS THE CENTRAL APPALACHIANS. A FEW MORE HOURS ARE EXPECTED OF HIGHER WINDS IN THE FAVORED WRN SLOPES WITH A SE COMPONENT TO THE WIND. NOT GOING TO ADD SUMMERS OR WESTERN GREENBRIER TO AN ADVISORY BUT WE COULD SEE A SMALL WINDOW REST OF THE EVENING WHERE HIGHER RIDGES COULD GUST TO 45 TO 50 MPH...BUT BY MIDNIGHT FLOW TURNS MORE SOUTH TO SSW...WITH MAIN JET MOVING OUT. RADAR SHOWING MORE OF A SOLID AREA OF RAIN MOVING NWD ACROSS NC INTO SW VA. THE 21Z HRRR SHOWING THIS FAIRLY WELL WITH THE LOCAL WRF NOT TOO FAR OFF...AND ADJUSTED POPS THROUGH MIDNIGHT TO ACCOUNT FOR BETTER THREAT IN THE WEST. REGIONAL RADAR SHOWS THE DRY SLOT MOVING ACROSS ERN AL/WRN GA INTO SRN TN....WITH UPPER SHORTWAVE PUSHING EAST OF MEMPHIS TN. SOLID SHIELD OF RAIN WILL BE LIFTING ACROSS BETWEEN NOW AND 1 AM...AND SHOULD CLEAR OUR CWA AFTER 1-2 AM. ADJUSTED TEMPS DOWN ACROSS THE WEDGE AREAS THIS EVENING AS TEMPS RUNNING COOLER THAN EARLIER FORECAST. STILL LOOKS LIKE WARM FRONT LIFTING NORTH WITH WEDGE BREAKING UNDER THE MODERATE TO HEAVY RAIN SHOULD CAUSE TEMPS TO STEADY OR SLIGHTLY RISE OVERNIGHT...PER PREVIOUS FORECAST. AS FAR AS SVR THREAT FORECAST EFFECTIVE SHEAR AND CAPE SUGGEST THAT OUR CWA WILL BE OUTSIDE THE WIND THREAT...THOUGH SOME HIGHER GUSTS COULD OCCUR AROUND MIDNIGHT SOUTH OF THE DAN/SOUTH BOSTON AREA. PREVIOUS VALID DISCUSSION... WIND ADVISORY REMAINS IN EFFECT FOR THE COUNTIES OF TAZEWELL AND SMYTH IN VIRGINIA AND MERCER IN WEST VIRGINIA. 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. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... 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. && .LONG TERM /THURSDAY THROUGH SUNDAY/... 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. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... AS OF 650 PM EST SUNDAY... WINDS...RAIN AND CLOUDS WILL HINDER AVIATION OPERATIONS THROUGH THE MORNING MONDAY. CIGS WILL BE VARIABLE IN THE IFR/MVFR RANGE WITH LIGHT TO MODERATE RAIN EXPECTED THIS EVENING INTO EARLY OVERNIGHT. THINK THE DECENT RAIN WILL BE EXITING AFTER MIDNIGHT IN THE WESTERN TAF SITES/BLF/LWB...AND LYH/DAN AFTER 07Z. WITH IN SITU WEDGE IN PLACE EARLY THIS EVENING AND STRONG LLJ...WILL SEE A PERIOD OF LOW LVL WIND SHEAR WHICH ENDS AFTER MIDNIGHT...AT ALL SITES. OVERNIGHT...MAIN ISSUE WILL BE WHETHER LEFTOVER MOISTURE CAN LEAD TO FOG...BUT THINK WITH SOUTH TO SSW WINDS APPEARING TO STAY UP WILL BE LIMITED IN FOG DEVELOPMENT. WILL KEEP CIGS MVFR THOUGH OVER MUCH OF THE NIGHT THOUGH SEEING DRY SLOT INTO AL/GA MAY BRING VFR CIGS OR EVEN SCATTERING THEM OUT IN BLF BY DAWN. SW WINDS AHEAD OF THE COLD FRONT TO KEEP VFR AT ALL TAF SITES BY LATE MONDAY MORNING. THE ISSUE WILL BE THE WINDS WITH 10-15 KT SUSTAINED GUSTING TO 20-30 KNOTS AT TIMES. WIND WILL TURN MORE WESTERLY LATE IN THE TAF PERIOD BUT LEFT THAT OUT FOR NOW IN THE TAFS GIVEN SUCH AN ACTIVE FIRST 12-18 HOURS. CONFIDENCE FOR SUB VFR THROUGH TONIGHT IS HIGH...BUT LOW ON TIMING OF IFR VS MVFR WITH RESPECT TO CIG/VSBY...AGAIN FLUCTUATIONS WILL OCCUR BASED ON RAINFALL INTENSITY. CONFIDENCE IS HIGHER MONDAY WITH RETURN TO VFR MOST LOCATIONS...WITH A SMALL WINDOW IN THE MORNING OF MVFR. EXTENDED DISCUSSION... WINDS WILL STAY GUSTY MONDAY NIGHT BEHIND COLD FRONT....WITH POTENTIAL FOR SUB VFR CIGS IN THE MTNS...WHILE VFR IS EXPECTED TO THE EAST. ANOTHER STORM SYSTEM IS EXPECTED TO MOVE UP THE SOUTHEAST COAST BY EARLY WEDNESDAY WHICH MAY BRING WINTRY PRECIP TO THE AREA ALONG WITH SUB VFR AT ALL SITES. LOOKS LIKE FLIGHTS WILL BE IMPACTED GREATLY ACROSS THE MID ATLANTIC INTO THE NORTHEAST WITH THIS SYSTEM WITH STRONG WINDS EXPECTED ALONG WITH WIDESPREAD PRECIPITATION. AROUND HERE LOOKS LIKE WE WILL EXPERIENCE SUB VFR AT LEAST WED INTO EARLY THANKSGIVING BEFORE HIGH PRESSURE WORKS IN FROM THE WEST...THOUGH WINDS MAY STAY UP THROUGH THU NIGHT...WITH UPSLOPE LOWER CIGS AT BLF/LWB. && .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... VA...WIND ADVISORY UNTIL 1 AM EST MONDAY FOR VAZ007-009. NC...NONE. WV...WIND ADVISORY UNTIL 1 AM EST MONDAY FOR WVZ042. && $$ SYNOPSIS...KK/MBS NEAR TERM...KK/WP SHORT TERM...AMS LONG TERM...DS AVIATION...KK/WP EQUIPMENT...RAB

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