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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KRNK 262005 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 405 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/... AS OF 400 PM EDT THURSDAY... A STRONG COLD FRONT LOCATED JUST TO OUR WEST THIS AFTERNOON WITH PREFRONTAL LINE OF CONVECTION AND ANAFRONT RAIN WELL BEHIND THE FRONTAL BOUNDARY WILL MOVE EAST TONIGHT INTO FRIDAY. THE COLD AIR WEDGE FINALLY ERODED THIS AFTERNOON WITH HEATING AND MIXING. ANTICIPATING THAT ADDITIONAL CONVECTION WILL DEVELOP AHEAD AND ALONG THE FRONT THIS AFTERNOON INTO TONIGHT AS IT MOVES EAST. SKINNY CAPE AND INSTABILITY MAKES CONVECTION FORECAST PROBLEMATIC WITH THIS BOUNDARY. USED A BLEND OF THE NAM AND HRRR FOR POPS THIS AFTERNOON INTO TONIGHT. THERE IS SOME UNCERTAINTY IF CONVECTION DEVELOP EXACTLY AS PROGGED ALONG BLUE RIDGE MOUNTAINS BY HIGHER RESOLUTION MODELS LIKE THE RNKWRFARW...HRRR AND HIRESW-ARW. FOR THE WINDOW FOR THUNDERSTORM DEVELOPMENT IS SMALL. ANOTHER ISSUE IS WHETHER THE COLD AIR CATCHES FRONTAL MOISTURE ASSOCIATED WITH THE FRONT SLOWED BY LOW PRESSURE WAVE MOVING ALONG THE BOUNDARY LATE TONIGHT INTO FRIDAY. THE RATE OF FALL IS ALSO IMPORTANT FOR LATE TONIGHT INTO FRIDAY MORNING FOR POTENTIAL COOLING OF TEMPERATURES. BELIEVE THAT ENOUGH COLD AIR CATCHES SOME MOISTURE LATE TONIGHT INTO FRIDAY TO CREATE SOME MOUNTAIN SNOW SHOWERS AND SNOW FLURRIES. ANY SNOW ACCUMULATIONS WILL GENERALLY BE LIGHT AND MAINLY IN THE WESTERN UPSLOPE FAVOR AREAS. THE STRONG COLD AIR ADVECTION COMBINED WITH PRESSURE RISES OF 5 TO 10MB/6HRS WILL RESULT IN GUSTY WINDS TONIGHT. LOW TEMPERATURES WILL DROP INTO THE MID 20S IN THE NORTHWEST MOUNTAINS TO THE MID 40S IN THE PIEDMONT TONIGHT. THE FRONTAL WAVES BEING DRIVEN BY UPPER LEVEL SHORT WAVE ENERGY 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. && .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 URFACE 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 DURNG 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 /20Z THURSDAY THROUGH TUESDAY/... AS OF 150 PM EDT THURSDAY... VFR AND MVFR CEILINGS WILL LOWER THIS AFTERNOON INTO TONIGHT. MIXING HAS ERODED THE COLD WEDGE IN MOST AREAS EXCEPT A NARROW PATCH ALONG THE SOUTHERN BLUE RIDGE. WITH HEATING AND MIXING THIS AFTERNOON...LIGHT WINDS WILL BECOME GUSTY OUT OF THE SOUTHWEST THIS AFTERNOON. HIGH CONFIDENCE THAT A STRONG COLD FRONT WILL CROSS THROUGH THE REGION JUST AROUND 00Z/7PM AT KLWB AND KBLF. THE FRONT IS EXPECTED TO REACH KLYH AROUND 04Z/MIDNIGHT AND KDAN AROUND 05Z/1AM. SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP ALONG AND BEHIND THE FRONT. VISIBILITY MAY DROP TO MVFR LEVELS IN THE HEAVIER RAIN SHOWERS. WINDS WILL BECOME NORTHWEST BEHIND THE FRONT WITH GUSTS AT 20 TO 30 KNOTS. SHOWERS AND GUSTY WINDS WILL CONTINUE THROUGH FRIDAY AS MUCH COLDER AIR SURGES INTO THE REGION. SNOW SHOWERS AND SNOW FLURRIES ARE LIKELY WITH MVFR CEILINGS AND VISIBILITIES IN THE WESTERN UPSLOPE AREAS OF THE MOUNTAINS LATE TONIGHT THROUGH FRIDAY NIGHT. MEDIUM TO HIGH CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS DURING THE TAF PERIOD. 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 SHORT TERM...SK LONG TERM...SK AVIATION...AMS/KK CLIMATE...SK

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