Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 270051 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 851 PM EDT THU MAR 26 2015 .SYNOPSIS... A STRONG COLD FRONT TO OUR WEST WILL TRAVEL EAST THIS EVENING AND PUSH THROUGH THE AREA TONIGHT. MUCH COLDER AIR WILL BE MOVING IN BEHIND THE COLD FRONT FOR THIS WEEKEND. && .NEAR TERM /THROUGH FRIDAY/...
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AS OF 845 PM EDT THURSDAY... COLD FRONT IS SLOWLY WORKING ITS WAY ACROSS THE FORECAST AREA. AS OF 800 PM IT WAS GENERALLY ALIGNED WITH THE BLUE RIDGE. A LINE OF CONVECTIVE SHOWERS WITH EMBEDDED THUNDERSTORMS WAS ASSOCIATED WITH THE FRONT...AND HAVE HAD A FEW REPORTS OF PEA SIZE HAIL. THE RNK BALLOON RELEASE WENT UP 30 MINUTES PRIOR TO FRONTAL PASSAGE AND PROVIDES A GOOD REPRESENTATION OF THE PRE- SHOWER/STORM ENVIRONMENT. THE CAPE IS WEAK...650 J/KG...BUT CERTAINLY SUPPORTIVE OF THE LINE OF CONVECTIVE SHOWERS ONGOING. TEMPERATURES AHEAD OF THE FRONT ACROSS SOUTHSIDE VA AND THE PIEDMONT OF NC REMAIN IN THE 60S. BEHIND THE FRONT TEMPERATURES HAVE TUMBLED THROUGH THE 50S...AND WILL MOST LIKELY REACH THE LOWER TO MID 40S ACROSS THE HIGHLANDS OF VA/WV BY MIDNIGHT. FORWARD PROGRESSION OF THE FRONT IS EXPECTED TO COME TO A SLOW CRAWL...LESS THAN 10 MPH. AS SUCH WILL MAINTAIN HIGH POPS...EVEN ACROSS SOUTHSIDE VA AND THE PIEDMONT...MOISTURE CONVERGENCE ALONG THE FRONT SUPPORTING CONTINUED DEVELOPMENT OF SHOWERS AS THE FRONT MOVES EAST. LINGERING PRECIPITATION IS ALSO LIKELY BEHIND THE FRONT...IN THE FORM OF LIGHT RAIN...OR RAIN MIXED WITH SNOW ONCE THE TEMPERATURES GETS COLD ENOUGH LATER TONIGHT. ANY SNOW ACCUMULATIONS WILL GENERALLY BE LIGHT AND MAINLY CONFINED TO THE HIGHER ELEVATIONS IN THE FAR WESTERN PART OF THE CWA. BY SUNRISE FRIDAY TEMPERATURES WEST OF THE BLUE RIDGE ARE EXPECTED TO BE IN THE 30S....POSSIBLY AS LOW AS THE UPPER 20S AT ELEVATIONS ABOVE 3500 FEET. EAST OF THE BLUE RIDGE...THE TEMPERATURE TUMBLE WILL BE A LITTLE DELAYED...BUT STILL DIPPING INTO THE 40S BY DAYBREAK. A WAVE OF LOW PRESSURE ALONG THE FRONT WILL KEEP RESIDUAL PRECIPITATION ACROSS THE EAST FRIDAY. MEANWHILE... NORTHWEST WINDS WILL BE GENERATING UPSLOPE PRECIPITATION WEST OF THE BLUE RIDGE AS MUCH COLDER COLDER AIR MOVES IN. SNOW ACCUMULATION IN THE WESTERN MOUNTAINS WILL BE LIMITED BY THE STRENGTH OF THE SUN THIS TIME OF YEAR AND WARM ANTECEDENT CONDITIONS. WPC IN DAY 1 PAINT UP TO 2 INCHES POSSIBLE IN WESTERN GREENBRIER AND THE POTENTIAL UP TO AN INCH IN THE WESTERN MOUNTAINS. HIGH TEMPERATURES FRIDAY WILL RANGE FROM THE MID 30S IN THE NORTHWEST MOUNTAINS TO THE LOWER 50S IN THE PIEDMONT.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... AS OF 340 PM EDT... MAIN ISSUE FOR THE WEEKEND IS THE INFLUENCE OF THE DEEP UPPER TROUGH AND ANOMALOUSLY COLD AIR MASS. FIRST...LINGERING LIGHT ACCUMULATING SNOW SHOWERS ON WESTERN SLOPES OF APPALACHIANS FOR FRIDAY NIGHT AND PERHAPS INTO FIRST PART OF SATURDAY ASSOCIATED WITH COLD ADVECTION AND AIDED BY SOME SLIGHTLY DEEPER LIFT WHEN THE UPPER VORTICITY MAX AND TROUGH AXIS SWING THROUGH BETWEEN MIDNIGHT AND DAYBREAK SATURDAY. THEN WITH COLD AIR MASS IN PLACE...INCLUDING COLDER THAN MINUS 10 C AT 850MB OVER MUCH OF THE AREA SATURDAY...HIGH TEMPS SATURDAY WILL BE 15-20 F BELOW AVERAGE...AND WE COULD BE CLOSE TO RECORD LOWS FOR SUNDAY MORNING THE 29TH...SEE CLIMATE SECTION BELOW. WENT WITH COLDER MAV AND ECMWF GUIDANCE COMPARED TO MET...WHICH BOTH KEEPING TRENDING DOWN...AND WAS TEMPTED TO GO EVEN COLDER THAN GUIDANCE WITH THE SURFACE HIGH RIGHT OVERHEAD SUNDAY MORNING. ONE CAUTION IS THAT WARM ADVECTION ALOFT BEGINS AGAIN AND THERE COULD BE SOME THIN CIRRUS DRIFTING AHEAD OF WARM FRONT...MOST LIKELY ACROSS THE WEST...SO WILL WAIT ANOTHER 24 HRS BEFORE DECIDING TO GO BELOW GUIDANCE OR NOT. ALSO WITH UPPER TROUGH OVERHEAD AND SOME WEAK MID LEVEL INSTABILITY...SOME MODELS SHOWING VERY LIGHT SHOWERS ACROSS CENTRAL THROUGH FIRST HALF OF SATURDAY...SO INTRODUCED A SLIGHT CHC POP THERE. TEMPS SHOULD MODERATE NICELY DURING THE DAY SUNDAY WITH RETURN OF WARM ADVECTION...BUT STILL BELOW NORMAL. COULD SEE HAVING TO TWEAK THOSE UP A FEW DEGREES BETWEEN NOW AND SUNDAY. NEXT CLIPPER SYSTEM MAY ARRIVE AS EARLY AS SUNDAY NIGHT IN WEST BUT THINK GFS IS A BIT TOO FAST WITH THIS GIVEN POSITION OF LARGER TROUGH STILL OFF EAST COAST...SO LEANING TOWARD SLOWER ECMWF AND HOLDING OFF ON BEST PRECIP CHANCES UNTIL MONDAY...BUT DO HAVE LOW CHANCE FAR WEST BY AFTER MIDNIGHT. && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 355 PM EDT... STILL SOME UNCERTAINTY IN TIMING OF THE CLIPPER SYSTEM AND AMOUNT OF PRECIP GIVEN CURRENT MODEL DIFFERENCES...BUT ECMWF AND CANADIAN ON SAME PAGE WITH MORE OF A DAYTIME MONDAY TIMING...AND ECMWF TRENDS SHOWING LITTLE WETTER SOLUTION AND BETTER CHANCES FOR PRECIP TO SPREAD INTO PIEDMONT AT SOME POINT...SO HAVE INCREASED POPS TO LOW CHC FOOTHILLS AND SLIGHT CHC INTO ALL OF PIEDMONT...AND MAY EVENTUALLY HAVE TO GO HIGHER IF TIMING HOLDS STEADY. PLENTY MILD ENOUGH FOR ALL RAIN WITH THIS SYSTEM...WITH THE POSSIBLE EXCEPTION OF HIGHEST TERRAIN IN WEST VIRGINIA MONDAY MORNING...BUT DO NOT THINK THERE WILL BE ANY ISSUES WITH ACCUMULATING SNOW EVEN ON HIGHEST RIDGES. LARGE SCALE PATTERN KEEPS SOME CLIPPER ENERGY HEADING TOWARD THE APPALACHIANS AGAIN FOR TUESDAY OR TUES NIGHT...BUT THIS COULD REMAIN TO THE NORTH...WHICH IS WHAT CURRENT ECWMF SOLUTION SUGGESTS...AND THERE IS A TREND TO FLATTEN THE PATTERN A BIT SO EVEN THE WETTER GFS MAY NOT BRING US MUCH OF ANYTHING...AND WOULD MOST LIKELY DO SO ONLY ON WESTERN SLOPES. AFTER THAT NEXT BEST CHANCE FOR PRECIP COMES BY WED NIGHT INTO THURSDAY WITH BETTER FRONTAL PASSAGE AND TAP OF SOME GULF MOISTURE AS MODELS SHOWING SOME ATTEMPT TO PHASE A SOUTHERN SHORT WAVE WITH YET ANOTHER COMING OUT OF THE NORTHERN PLAINS. AT THIS POINT...THINK THE GFS IS OVERDOING THE STRENGTH OF THE SOUTHERN PIECE OF ENERGY GIVEN A LOT OF POTENTIALLY SPURIOUS CONVECTION NEAR THE GULF COAST EARLIER WEDNESDAY...SO ONCE AGAIN WILL LEAN TOWARD ECMWF WHICH IS SOMEWHAT DRIER AND NOT AS LIKELY TO SPREAD PRECIP EAST. OBVIOUSLY WITH THIS BEING 6 TO 7 DAYS OUT...THERE IS MUCH UNCERTAINTY WITH DETAILS...AND WITH WARMING TREND THROUGHOUT THE WEEK TOWARD OR ABOVE AVERAGE TEMPERATURES ONCE AGAIN...THIS MID WEEK SYSTEM SHOULD NOT POSE ANY PRECIP TYPE ISSUES...NOR DOES IT LOOK TO HAVE MUCH CHANCE OF GENERATING ANY SEVERE WEATHER GIVEN EITHER A WEAK WEDGE IN PLACE IF GOING MORE WITH GFS...OR A VERY LIMITED MOISTURE TAP IF GOING MORE WITH ECMWF. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... AS OF 745 PM EDT THURSDAY... A COLD FRONT IS STARTING TO MAKE HEADWAY INTO THE FORECAST AREA. THE FRONT HAS REACHED ROUGHLY A KVJI...KBCB...KROA...KCHO LINE. NUMEROUS SHOWERS...SOME MODERATE TO HEAVY...ARE FORMING ALONG IT CURRENTLY. ADDITIONAL AREAS OF LIGHT TO MODERATE RAIN WERE TRAILING THE COLD FRONT...BETWEEN IT AND THE ASSOCIATED 850 MB FRONT. AS THE NIGHT PROGRESSES....FLIGHT CATEGORIES ARE EXPECTED TO TREND DOWNWARD INTO THE MVFR RANGE FOR BOTH CIGS AND VSBYS ALONG WITH POCKETS OF IFR. AFTER ROUGHLY 06Z...MAINLY IFR CONDITIONS ARE EXPECTED ACROSS THE MOUNTAINS...WITH A MIX OF MVFR AND IFR ACROSS THE PIEDMONT. COLDER AIR WILL WORK ITS WAY INTO THE AREA OVERNIGHT...MAINLY ONCE THE 850 MB FRONT WORKS PROGRESSES THROUGH THE REGION. LOOK FOR RAIN MIXED WITH...OR CHANGED TO...LIGHT SNOW BETWEEN ROUGHLY A KBLF-KLWB LINE BY DAYBREAK. INCREASING 850 MB FLOW WILL HELP YIELD UPSLOPE CONDITIONS ACROSS THE PREFERRED WESTERN SLOPES OF SOUTHEAST WEST VIRGINIA...SOUTH INTO THE NORTHERN MOUNTAINS OF NORTH CAROLINA. LOOK FOR MVFR CONDITIONS TO PREVAIL IN THIS REGION FOR MUCH OF THE DAY...ALONG WITH ISOLATED TO SCATTERED RAIN/SNOW SHOWERS. EAST OF THE CREST OF THE BLUE RIDGE...THE SAME NORTHWEST WINDS WILL YIELD DOWNSLOPE CONDITIONS...AND GRADUAL INCREASE IN CLOUD COVER...WITH FLIGHT CATEGORIES IMPROVING TO VFR. AS OF 150 PM EDT THURSDAY... WINDS WILL DIMINISH SATURDAY WITH VFR CONDITIONS AS HIGH PRESSURE BUILDS INTO THE AREA. SCATTERED MVFR SHOWERS ARE POSSIBLE SUNDAY NIGHT INTO MONDAY. VFR WEATHER IS EXPECTED TUESDAY. && .CLIMATE... RECORD LOWS FOR MARCH 29: ROA19 BCB17 LYH23 DAN23 BLF19 LWB18 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK NEAR TERM...KK/PM SHORT TERM...SK LONG TERM...SK AVIATION...AMS/DS/KK CLIMATE...SK

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