Area Forecast Discussion
Issued by NWS Blacksburg, VA

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513 FXUS61 KRNK 050007 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 807 PM EDT WED MAY 4 2016 .SYNOPSIS... AN UPPER LEVEL LOW PRESSURE SYSTEM WILL MOVE OUT OF THE GREAT LAKES AND LINGER OVER THE MID ATLANTIC REGION INTO THE WEEKEND. THIS WILL BRING A GOOD CHANCE OF RAINFALL AND QUITE CHILLY CONDITIONS TO THE REGION INTO THE WEEKEND. UNSETTLED CONDITIONS WILL PERSIST AS WARMER TEMPERATURES WORK INTO THE AREA FOR THE FIRST PART OF NEXT WEEK. && .NEAR TERM /THROUGH THURSDAY/... AS OF 330 PM EDT WEDNESDAY... DIURNAL INSTABILITY COMBINED WITH COOL AIR ALOFT HAVE KEPT WIDELY SCATTERED SHOWERS ON THE RADAR THIS AFTERNOON MAINLY WEST OF THE BLUE RIDGE AND NORTH OF ROUTE 460 IN VIRGINIA. THUNDER HAS BEEN QUITE LIMITED WITH ONLY AN OCCASIONAL LIGHTNING FLASH NOTED ACROSS BUCKINGHAM COUNTY VA. HOWEVER...AN APPROACHING COLD FRONT BEING DRIVEN BY AN UPPER CLOSED LOW MOVING OUT OF THE GREAT LAKES WILL BRING A COHESIVE BAND OF SHOWERS TO OUR WESTERN DOORSTEP BY EARLY THIS EVENING. AS THE SHOWERS PROGRESSIVELY SPREADS ACROSS THE REGION TONIGHT A SURFACE LOW SILL DEVELOP ALONG THE MID ATLANTIC COAST WITH A DEFORMATION ZONE EXTENDING BACK ACROSS THE NORTHEASTERN PORTION OF THE REGION WITH MULTIPLE SHORT WAVE IMPULSES ROTATING AROUND THE UPPER LOW. THIS IS SETTING THE STAGE FOR SOME HEAVY PRECIPITATION TO FALL THROUGH THE END OF THE WEEK WITH CUMULATIVE RAINFALL AMOUNTS OF 1.5 TO 2 IN A RELATIVELY NARROW CORRIDOR IN VIRGINIA FROM NORTHERN CHARLOTTE COUNTY THROUGH APPOMATTOX AND BUCKINGHAM TO AMHERST. THERE IS STILL UNCERTAINTY IN EXACTLY WHERE THE RAIN WILL SET UP AND HOW HEAVY IT WILL BE SO WILL HOLD OFF ON ANY WATCHES UNTIL THE SITUATION COMES INTO SHARPER FOCUS OVER THE NEXT FEW MODEL RUNS. PRECIPITATION ELSEWHERE WILL BE LESS PRONOUNCED WITH AMOUNTS TAILING OFF TOWARD THE FOOTHILLS OF NORTH CAROLINA. WITH THE POOL OF COLD AIR ACCOMPANYING THE UPPER CLOSED LOW LAPSE RATES WILL BE STEEP SO SOME EMBEDDED THUNDER MAY BE PRESENT BUT WILL LEAVE IT OUT OF THE GIRDS FOR NOW SINCE EXPECT IT WILL BE LOCALIZED AND EPHEMERAL. THERE WILL ALSO BE A LITTLE WET SNOW POSSIBLE AT THE HIGHEST PEAKS OF THE GRAYSON HIGHLANDS INTO THE MOUNTAINS OF NORTH CAROLINA BUT JUST SOME WET FLAKES WITH NO ACCUMULATION EXPECTED. NEEDLESS TO SAY TEMPERATURES WILL BE WELL BELOW NORMAL WITH HIGHS ON THURSDAY GENERALLY REMAINING IN THE UPPER 40S/LOWER 50S WEST OF THE RIDGE AND ONLY REACHING THE MID/UPPER 50S TO THE EAST. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... AS OF 330 PM EDT WEDNESDAY... AN UPPER LOW WILL DROP SOUTH INTO OUR REGION AND SLOWLY MOVES EAST ACROSS THE AREA INTO THE WEEKEND. AS A RESULT...COOL...CLOUDY...AND DAMP CONDITIONS EXPECTED INTO THE WEEKEND. RAINFALL THURSDAY NIGHT WILL RANGE FROM 0.15 TO AROUND AN HALF INCH. LOCALLY AMOUNTS AROUND INCH MAY BE POSSIBLE WITH A THUNDERSTORM. HOWEVER...THE BEST INSTABILITY WITH LIS AND CAPE IS TO OUR EAST. THE COLDEST NIGHT DURING THE PERIOD WILL BE THURSDAY NIGHT. LOW TEMPERATURES THURSDAY NIGHT WILL RANGE FROM THE UPPER 30S IN THE MOUNTAINS TO THE UPPER 40S IN THE PIEDMONT. THE CLOSED LOW WILL SLOWLY MOVE EAST FRIDAY. BEHIND THIS LOW...COLD AIR ADVECTION SHOULD ENSUE COURTESY OF A DECENT NORTHWEST WIND WHICH MAY GUST UP TO 30 MPH ALONG THE HIGHEST RIDGETOPS FRIDAY AFTERNOON. HIGH TEMPERATURES FRIDAY WILL VARY FROM AROUND 50 IN THE NORTHWEST MOUNTAINS TO THE MID 60S IN THE PIEDMONT. FRIDAY AFTERNOON INTO FRIDAY NIGHT...SCATTERED SHOWERS SHOULD GRADUALLY WANE. RAIN AMOUNTS FRIDAY WILL VARY FROM THE AROUND A TENTH TO ABOUT 0.75 INCH. THE 3 HOUR FFG WAS AROUND 1.1 INCHES IN THE NORTHWEST TO NEAR 3 INCHES IN THE PIEDMONT. ANY FLOODING POTENTIAL WILL DEPEND ON STORM TRAINING...RAINFALL RATE AND LOCATIONS. LOW TEMPERATURES FRIDAY NIGHT WILL GENERALLY BE FROM LOWER 40S IN THE WEST TO AROUND 50 DEGREES IN THE EAST. THE LATEST ECMWF AND GFS ARE CONSISTENT WITH BREAKING DOWN THE OMEGA BLOCK PATTERN ON SATURDAY. IT WILL BE A WARMER AFTERNOON SATURDAY WITH HIGH TEMPERATURES FROM THE MID 60S IN THE MOUNTAINS TO THE MID 70S IN THE PIEDMONT. ISOLATED TO SCATTERED SHOWERS MAY BE POSSIBLE IN THE WEST SATURDAY NIGHT. THE GFS AND ECMWF HAS COME IN WETTER WITH AMOUNTS UP TO 0.5 INCH. LOW TEMPERATURES SATURDAY NIGHT INTO SUNDAY MORNING WILL DROP INTO THE LOWER 50S IN IN THE WEST TO MID 50S IN THE EAST. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 330 PM EDT WEDNESDAY... CUTOFF LOW OFF THE MID ATLANTIC COAST DRIFTS EAST IN THE ATLANTIC OCEAN AS FLOW ALOFT SLOWLY EVOLVES INTO A MORE PROGRESSIVE PATTERN FOR THE SECOND WEEK OF MAY. A COLD FRONT TO OUR NORTHWEST WILL DROP SOUTH SUNDAY INTO OUR AREA AND STALL SOUTH OF THE REGION SUNDAY NIGHT BEFORE RETURNING AS A WARM FRONT MONDAY INTO TUESDAY. MOISTURE CONVERGENCE ALONG THIS FRONT WILL RESULT IN A RISK FOR SHOWERS AND PERHAPS A FEW THUNDERSTORMS DURING THE PERIOD...BUT NOT CONFIDENT ON TIMING OR AMOUNTS ATTM. IT DOES LOOK LIKE THE BEST CHANCES WILL BE WEST OF INTERSTATE 77 EARLY NEXT WEEK. ON WEDNESDAY...OUR AREA IN THE WARM SECTOR WITH WARM FRONT TO THE NORTH AND COLD FRONT TO OUR WEST IN THE OHIO VALLEY. TEMPERATURES WILL BE NEAR NORMAL FOR SUNDAY...THEN MODERATE INTO MIDWEEK. BEHIND THE COLD FRONT...A COOL DOWN IS POSSIBLE FOR THE END OF THE WEEK. && .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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AS OF 750 PM EDT WEDNESDAY... UPPER LOW WILL MOVE SOUTHEAST OUT OF WISCONSIN AND CLOSE OFF. THIS LOW WILL TRACK INTO WESTERN NORTH CAROLINA THEN ROTATE NORTHEAST INTO MARYLAND. SYNOPTIC MODELS WERE IN GOOD AGREEMENTWITH THE TIMING AND TRACK OF THIS FEATURE. SHOWERS WILL COVER MUCH OF THE REGION AFTER MIDNIGHT. SIMILAR ARRIVAL TIME OF THE SHOWERS IN THE HI-RES MODELS AS WELL AS THE HRRR AND LOCAL WRF. LOWER CONFIDENCE ON THE OCCURRENCE OF ANY THUNDER. HAVE LEFT OUT OF THE TAFS AT THIS TIME. HIGH CONFIDENCE THAT CEILINGS WILL LOWER TO MVFR STARTING IN THE MOUNTAINS OVERNIGHT AND SPREADING EAST THURSDAY MORNING. AT THE SURFACE LOW PRESSURE OVER VIRGINIA ON THURSDAY WILL RESULT IN UPSLOPE CONDITIONS AT KBLF...KLWB...AND KLYH WILL WILL HELP SUPPORT LOWER CEILINGS. EXTENDED DISCUSSION... THE CLOSED UPPER LOW WILL REMAIN OVER THE MID ATLANTIC STATES THROUGH FRIDAY. MVFR OR LOWER CEILINGS AND REDUCED VISIBILITY WITH SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED INTO FRIDAY. SOME VFR IS POSSIBLE EAST OF THE BLUE RIDGE SATURDAY. CONDITIONS WILL BE BETTER ON SATURDAY AS THE UPPER LOW MOVES OFF THE COAST...BUT AS ANOTHER SHORT WAVE REACHES THE AREA FROM THE NORTHWEST ON SATURDAY NIGHT AND SUNDAY MORE SHOWERS AND SUB-VFR CONDITIONS ARE LIKELY.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...WP NEAR TERM...MBS SHORT TERM...KK LONG TERM...KK AVIATION...AMS/JR

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