Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 012043 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 343 PM EST SUN MAR 1 2015 .SYNOPSIS... A COLD FRONT WILL CROSS THE AREA TONIGHT. HIGH PRESSURE BUILDS ON MONDAY AND CONTINUES INTO TUESDAY. A WARM FRONT WILL CROSS THE AREA TUESDAY NIGHT INTO WEDNESDAY BRINGING WINTER PRECIPITATION AND THEN RAIN TO THE AREA. ANOTHER ARCTIC FRONT WILL ARRIVE THURSDAY WITH A CHANCE FOR SNOW. && .NEAR TERM /THROUGH MONDAY NIGHT/... AS OF 300 PM EST SUNDAY... WINTER WEATHER ADVISORY HAS BEEN CANCELED BECAUSE TEMPERATURES HAVE WARMED TO OR ABOVE FREEZING LEVELS IN MOST LOCATIONS. THE THREAT FOR WIDESPREAD FREEZING RAIN AND SLEET HAS ENDED. POCKETS OF LIGHT RAIN DRIZZLE AND FOG MAY BE POSSIBLE THIS EVENING INTO TONIGHT. A 1039 MB HIGH WILL CONTINUE TO PUSH EAST INTO THE ATLANTIC OCEAN THIS EVENING INTO MONDAY. WARM AIR WAS ADVANCING EASTWARD INTO THE REGION FROM THE WEST. LEANED POPS THIS EVENING INTO TONIGHT TOWARDS A BLEND OF RNK WRFARW...HIRESW-ARW AND GFS WHICH PULLS MOISTURE OUT OF THE EAST THIS AFTERNOON INTO THIS EVENING...THEN LEANED TOWARDS GFS TONIGHT. UTILIZED WEATHER TOOL WITH GFS TEMPERATURES PROFILE FOR PTYPES. WEAK SUBSIDENCE SPILLS IN BEHIND THE DEPARTING SHORTWAVE WITH THE BATCH OF DEEPER MOISTURE THIS EVENING LEAVING A RESIDUAL AXIS OF WRAP AROUND PRECIPITATION OVER THE WEST AHEAD OF THE UPSTREAM COLD FRONT THAT WILL REACH THE WESTERN SLOPES LATE. SOME SPOTTY LIGHT RAIN...DRIZZLE AND FOG MAY BE POSSIBLE THIS EVENING INTO TONIGHT. CAN NOT COMPLETED RULE OUT AN ISOLATED POCKET OF VALLEY FREEZING DRIZZLE IN THE NORTH. WIDESPREAD ICING PROBLEMS NOT EXPECTED. COLD ADVECTION ARRIVES AFTER MIDNIGHT ON INCREASING NORTHWEST WINDS IN MOUNTAINS WITH THE 85H FRONT CROSSING THE WESTERN SLOPES WHICH SHOULD ALLOW RAIN TO CHANGE TO SNOW SHOWERS BEFORE TAPERING AROUND DAYBREAK. TEMPERATURES SHOULD STEADY IF NOT RISE AHEAD OF THE FRONT OVERNIGHT AS THE WARM ADVECTION BOOTS THE WEDGE OUT BEFORE COLDER AIR ARRIVES LATE ALLOWING TEMPERATURES TO DROP AGAIN AROUND SUNRISE. LOW TEMPERATURES WILL RANGE FROM AROUND 20 DEGREES IN THE NORTH TO AROUND 40 DEGREES IN SOUTH. HIGH PRESSURE BUILDING IN BEHIND THE FRONT ON MONDAY WILL BRING AN END TO UPSLOPE SNOW AND RAIN SHOWERS FOR THE FAR WESTERN SLOPES. SNOW ACCUMULATIONS OF ONE TO TWO INCHES MAY BE POSSIBLE IN THE WESTERN UPSLOPE FAVORED LOCATIONS. HIGH TEMPERATURES ON MONDAY WILL RANGE FROM THE UPPER 20S IN THE NORTHWEST MOUNTAINS TO THE LOWER 50S IN THE PIEDMONT. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 310 PM EST SUNDAY... COMPLICATED AND ACTIVE WEATHER PATTERN EXPECTED TO CONTINUE THROUGH THIS PERIOD AS A BAROCLINIC ZONE BETWEEN ARCTIC AIR TO THE NORTH AND WARMER...SPRINGLIKE AIR TO THE SOUTH OSCILLATES ACROSS THE REGION. HOWEVER...THE MODELS HAVE CONTINUED TO TREND COLDER AND FURTHER SOUTH WITH THE ARCTIC AIR...LEAVING ONLY A BRIEF WINDOW IN THE LATE TUE TO WED TIME FRAME FOR WARM AIR AND LIQUID PRECIPITATION. MONDAY NIGHT BEGINS WITH YET ANOTHER ARCTIC HIGH CENTERED OVER THE REGION. ALOFT...A BROAD UPPER RIDGE IS NOTED ACROSS THE CENTRAL GULF WITH A SERIES OF TROUGHS CARVING OUT A MEAN TROUGH IN THE WESTERN U.S. WITH UPPER RIDGING ON TOP OF AN ARCTIC HIGH...YET AGAIN A FAVORABLE WEDGE SET UP FOR THE MID-ATLANTIC REGION. AS THE ARCTIC HIGH SLIDES TOWARD THE EAST COAST TUE MORNING...A NEW AREA OF ARCTIC AIR WILL BE SPREADING SOUTHWARD INTO THE PLAINS UNDER THE MEAN TROUGH. IN BETWEEN...A STRONG COLD FRONT WILL STRETCH FROM TEXAS TO THE GREAT LAKES...WITH DEEPENING LOWER PRESSURE ACROSS THE WESTERN GREAT LAKES. THE UPPER FLOW IS SW ACROSS THE REGION...LEADING TO AN INITIAL SLOW PROGRESSION OF THE UPPER FEATURES...ALTHOUGH UNDERNEATH...THE COLD...DENSE ARCTIC AIR WILL LIKELY OVERCOME THIS OBSTACLE AT THE SURFACE. SUBSTANTIAL ISENTROPIC LIFT IS EXPECTED TO BEGIN EARLY TUE WITH A FAVORABLE WEDGE SETUP IN PLACE AND THE FIRST OF SEVERAL UPPER DISTURBANCES AND DEEP MOISTURE TRACKING OVER THE SHALLOW COLD AIR. SIMILAR TO THE SITUATION EXPERIENCED SUNDAY MORNING...THIS SHOULD LEAD TO A PERIOD OF SNOW/SLEET/FREEZING RAIN...DEPENDING ON DEPTH AND DURATION OF COLD AIR AT ANY LOCATION. USING THE TOPDOWN WX TOOL...A PREDOMINANCE OF -FZRA WAS INDICATED IN THE WEST AND SOUTH...WITH -FZRA/IP IN THE NORTH. PRECIPITATION SHOULD TRANSITION TO MOSTLY RAIN BY AFTERNOON UNDER THE INFLUENCE OF A STRONG SW LLJ AND CONTINUED WARM AIR INTRUSION EATING AWAY AT THE WEDGE. WITH THE HIGH SHIFTING TO THE SOUTHEAST OF THE REGION AND THE SUBSTANTIAL WARMING ALOFT AND THE STRONG LLJ...WOULD NOT EXPECT THIS NEXT WEDGE TO BE QUITE AS TENACIOUS AS THE ONE TODAY. AFTER THE ISENTROPIC/WARM FRONTAL PRECIPITATION MOVES AWAY TUE EVENING...A DRY SLOT WILL ADVECT INTO MUCH OF THE CWA EAST OF THE ALLEGHANY FRONT. THE NEXT ARCTIC FRONT WILL BE APPROACHING FROM THE WEST...BUT SLOWED BY THE SW/PARALLEL UPPER FLOW. THUS...THE HEAVIEST RAIN SHOULD REMAIN WEST OF THE CWA THROUGH MIDNIGHT TUE. IN ADDITION...THE UPPER SUPPORT ON THIS END WILL BE WANING AS THE NEXT PIECE OF ENERGY ALOFT MOVES OUT OF THE SOUTHERN PLAINS. THIS WILL BRING THE NEXT WAVE OF PRECIPITATION TO THE REGION WED NIGHT INTO THU...THE HEAVIEST QPF OF WHICH TRACKS MORE EAST OF THE ALLEGHANY FRONT. MORE ON QPF ISSUES IN THE HYDRO SECTION BELOW. ARCTIC AIR WILL SPILL INTO THE REGION VERY QUICKLY FROM THE NW BEHIND THE FRONT WED NIGHT/EARLY THU...CHANGING THE PRECIPITATION FROM RAIN TO SNOW. WAVES OF LOW PRESSURE CONTINUE TO DEVELOP ALONG THE SLOWLY SOUTHWARD MOVING FRONT...BY THU MORNING DRAPED FROM NEAR ORF-ATL. THUS...EXPECT PRECIPITATION TO CONTINUE ALONG AND BEHIND THE FRONT FOR SEVERAL HOURS...ESPECIALLY IN LIGHT OF THE CONTINUED LAGGING TROUGH IN THE SOUTHERN PLAINS WITH EJECTED...EMBEDDED SHORT WAVES IN THE MEAN FLOW. THUS...MODERATE RAIN WED NIGHT/EARLY THU COULD QUICKLY CHANGE TO MODERATE SNOW...WITH SEVERAL INCHES OF ACCUMULATION POSSIBLE EVEN BEFORE DAYBREAK THU IN THE WESTERN COUNTIES. THIS WILL NEED TO CONTINUE TO BE EVALUATED IN THE COMING DAYS...BUT OUR NEXT SIGNIFICANT SNOW STORM COULD BE ON THE HORIZON FOR WED NIGHT/THU. HAVE AGAIN LEANED TOWARD THE COLD SIDE OF GUIDANCE GIVEN THE DOMINANCE OF A COLD AIR WEDGE TUE...AND THE RETURN OF ARCTIC AIR LATE WED/EARLY THU. NON-DIURNAL TEMPERATURE TRENDS CAN BE EXPECTED TUE NIGHT AS THE WEDGE DEPARTS CONTINUING INTO EARLY WED AS LOW- LEVEL WARM AIR ADVECTION OVERSPREADS THE AREA. THERE IS A BRIEF WINDOW WED AFTERNOON...WHERE TEMPERATURES COULD SOAR INTO THE 50S ACROSS MUCH OF THE CWA...DEPENDING ON WHETHER OR NOT THE LLJ CAN MIX DOWN TO THE SFC. THIS WILL ESPECIALLY NEED TO BE WATCHED IN SOUTHEAST WV/FAR SW VA IN THE TYPICAL LOCATIONS FOR STRONG SOUTHERLY WINDS. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 130 PM EST SUNDAY... AT SUNRISE THURSDAY...A COLD FRONT WILL BE SOUTHEAST OF OUR REGION. HOWEVER...PRECIPITATION ASSOCIATED WITH IT WILL STILL BE SPREADING WESTWARD ACROSS THE FORECAST REGION. MUCH COLDER AIR WILL BE FLOWING INTO THE AREA ON STRENGTHENING NORTHWEST WINDS. HIGH TEMPERATURES WILL OCCUR AROUND SUNRISE...WITH STEADY OR SLOWING FALLING TEMPERATURES THROUGHOUT THE DAY. A MODERATE SNOWFALL IS POSSIBLE...ESPECIALLY ACROSS THE SOUTHEAST PART OF THE REGION WILL PRECIPITATION AMOUNTS WILL BE HIGHEST CLOSEST TO THE DEPARTING FRONT. BY THE AFTERNOON...COVERAGE IS EXPECTED TO BECOME SCATTERED...WITH AGAIN THE BEST COVERAGE IN THE SOUTHEAST. THURSDAY NIGHT...SOME LINGERING SNOW SHOWER WILL STILL BE POSSIBLE EAST OF THE BLUE RIDGE. HOWEVER...BY MIDNIGHT...PRECIPITATION IS EXPECTED TO COME TO AN END...AND CLOUD COVER ACROSS THE ENTIRE REGION WILL TREND FROM CLOUDY TO PARTLY CLOUDY THROUGH THE NIGHT. LOW TEMPERATURES WILL RANGE FROM THE SINGLE DIGITS TO THE LOWER TEENS ACROSS THE MOUNTAINS WITH MID TO UPPER TEENS ACROSS THE PIEDMONT. FRIDAY INTO SATURDAY...A BROAD AREA OF HIGH PRESSURE IS EXPECTED TO BUILD INTO...OVER...AND THEN EAST OF THE AREA. THIS WILL HAVE THE IMPACT TO KEEP OUR REGION PRECIPITATION FREE WITH A TREND FROM COLDER CONDITIONS TO MILDER CONDITIONS AS WE START GETTING ON THE RETURN SIDE SW-W FLOW OF THE HIGH BY SATURDAY AFTERNOON. THE TREND WILL CONTINUE INTO SUNDAY WITH NO PRECIPITATION AND EVEN MILDER CONDITIONS AS A TROUGH DEEPENS IN THE CENTRAL U.S. AND A SHORTWAVE RIDGE ALOFT BUILDS OVER THE REGION. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... AS OF 1240 PM EST SUNDAY... SCT-BKN MVFR CLOUDS WITH POCKETS OF IFR IN FREEZING RAIN...SLEET AND LIGHT RAIN/DRIZZLE THIS AFTERNOON INTO TONIGHT. TEMPERATURES WILL CREEP ABOVE FREEZING THIS AFTERNOON AS WARM AIR SPREADS EAST ACROSS THE REGION. EXPECTED LOW CLOUDS TO REDEVELOPED THIS EVENING INTO TONIGHT WITH POCKETS OF FOG AND STRATUS. POOR FLYING CONDITIONS WILL CONTINUE TONIGHT WITH RESIDUAL LOW LEVEL MOISTURE IN PLACE AHEAD OF A COLD FRONT TO THE WEST. APPEARS WIDESPREAD MVFR/IFR CIGS AND VSBYS LIKELY OVERNIGHT WITH ANOTHER ROUND OF DRIZZLE...THEN AN INCREASE IN RAIN/SNOW SHOWERS WEST ALONG AND BEHIND THE FRONT. A SHARP COLD FRONT WILL CROSS THE AREA MONDAY WITH NORTHWEST WINDS INCREASING ALONG WITH UPSLOPE MVFR CIGS/VSBYS IN SNOW SHOWERS AT KBLF/KLWB. LOW TO MEDIUM CONFIDENCE IN CEILINGS...VISIBILITIES AND WIND DURING THE TAF PERIOD. .EXTENDED FORECAST... ANOTHER POTENTIALLY POTENT SYSTEM THAT MAY IMPACT ALL OR PARTS OF THE REGION TUESDAY INTO WEDNESDAY WITH SUB- VFR DEVELOPING IN MOST LOCATIONS LATER TUESDAY INTO WEDNESDAY...WITH POST FRONTAL MVFR TO IFR POSSIBLE IN RAIN/SNOW ON THURSDAY. && .HYDROLOGY... AS OF 340 PM EST SUNDAY... CONCERN FOR THE PAST SEVERAL DAYS HAS BEEN POTENTIAL COMBINATION OF SNOW MELT AND HEAVY RAINFALL ACROSS OUR SOUTHEAST WEST VIRGINIA COUNTIES AND THROUGH THE JAMES RIVER BASIN NEAR THE I-64 CORRIDOR WHERE UP TO TWO FEET OF SNOW HAS FALLEN DURING THE PAST COUPLE OF WEEKS...MOST OF WHICH REMAINS INTACT DUE TO PERSISTENT SUB- FREEZING TEMPERATURES...AND THE ADDED EFFECTS OF WARM TEMPERATURES AND HEAVY RAIN MID-WEEK. AS NOTED IN THE DISCUSSIONS ABOVE...THE PERIOD OF WARM TEMPERATURES WILL BE LIMITED TO AN APPROXIMATELY 24-36 HOUR WINDOW LATE TUE INTO WED EVENING BEFORE ARCTIC AIR RETURNS. PRIOR TO TUE...LITTLE IF ANY MELTING OF THE SNOW PACK IS EXPECTED DUE TO PERSISTENT ARCTIC AIR IN PLACE. MODELS ARE ALSO CONSISTENTLY SHOWING THAT THE HEAVIER PRECIPITATION WILL TRACK CLOSER TO THE INITIAL SFC LOW TRACK FROM THE WESTERN TN/OH VALLEY TOWARD THE GREAT LAKES. THE EASTERN EDGE OF THIS COULD AFFECT OUR FAR WESTERN COUNTIES WHICH HAVE SOME OF THE GREATEST SNOW PACK. LOCALLY GENERATED AND WPC QPF IN OUR WESTERN MOST AREAS FOR THE WED TIME FRAME WHEN THE HEAVIEST RAINFALL IS EXPECTED IS IN THE 1.5 TO 2.5 INCH RANGE. THIS COULD STILL RESULT IN MINOR RISES ON AREA CREEKS AND STREAMS...BUT MAJOR FLOODING IS NOT ANTICIPATED AT THIS POINT BASED ON THE CURRENT PROJECTIONS. THE NEXT WAVE OF HEAVIER PRECIPITATION SHOULD TRACK ACROSS THE PIEDMONT...WHERE THERE IS LITTLE TO NO SNOWPACK OF CONCERN. ONE OTHER ISSUE MIGHT BE POTENTIAL ICE JAMS ON LOCAL STREAMS AND RIVERS...GIVEN THE FACT THAT MUCH OF THE LAST THREE WEEKS HAVE BEEN WELL BELOW FREEZING...WITH MANY DAYS BELOW 20. THIS COULD EXACERBATE THE FLOODING IN CERTAIN SPOTS AND WILL NEED TO BE MONITORED...BUT OVERALL...A MAJOR FLOOD THREAT IS NOT FORESEEN AT THIS TIME. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK NEAR TERM...KK SHORT TERM...RAB LONG TERM...DS AVIATION...JH/KK/PM HYDROLOGY...RAB

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