Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 160004 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 804 PM EDT WED APR 15 2015 .SYNOPSIS... A FRONTAL BOUNDARY WILL REMAIN STALLED ACROSS THE CAROLINAS INTO AT LEAST THURSDAY. WEAK WAVES OF LOW PRESSURE RIDING NORTHEAST ALONG THE FRONT WILL COMBINE WITH A STRONG WEDGE OF HIGH PRESSURE TO KEEP COOL AND DAMP CONDITIONS IN PLACE OVER THE NEXT COUPLE OF DAYS. SLIGHTLY WARMER AIR RETURNS BY WEEKS END AHEAD OF ANOTHER COLD FRONT THAT WILL CROSS THE AREA OVER THE WEEKEND. && .NEAR TERM /THROUGH THURSDAY/... AS OF 230 PM EDT WEDNESDAY... HIGH PRESSURE CENTER WILL TRACK TO NEW ENGLAND BY THIS EVENING AND CONTINUE TO WEDGE DOWN THE EAST OVERNIGHT. MEANWHILE...THERE IS A NEGATIVE-TILTED TROUGH LINGERING OVER THE NORTHERN PLAINS TO THE OZARKS. THIS TROUGH IS SENDING GULF SHORT WAVES OVER THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS MOUNTAINS. FOR THE IMMEDIATE FORECAST AREA...THERE IS AN ON-GOING BATTLE BETWEEN DRY COOL AIR WEDGING SOUTH AND WARM MOIST AIR TRACKING NORTHWARD. THE SOUTHERN PORTION OF THE FORECAST AREA HAS BEEN DOMINATED BY RAIN TODAY WITH THE HELP OF A MODEST SHORT WAVE...WHILE THE NORTHERN HALF BECAME CLOUDY WITH ONLY VERY LIGHT RAIN/SPRINKLES. WEAK SHORT WAVES WILL CONTINUE TO TRACK OVER THE WEDGE TONIGHT WHILE DRIER AIR PENETRATES SOUTH. WITH THE LACK OF LIFT FROM THESE WEAK SHORT WAVES...WE WILL DECLARE THE DRIER AIR THE WINNER TONIGHT WITH ONLY A SMALL AREA RECEIVING MEASURABLE RAINFALL. THE BEST CHANCE FOR RAIN WILL OCCUR THIS EVENING ALONG AND SOUTH OF THE NC-VA BORDER...THEN GETS SHUNTED SOUTH BY MIDNIGHT. THE UPPER LEVEL TROUGH WILL TRACK EAST TO THE OHIO VALLEY THURSDAY BUT WILL WEAKEN. ALSO THROUGH THE DAY THURSDAY...THE PARENT HIGH PRESSURE CENTER WILL DRIFT OFF THE NEW ENGLAND COAST. SHORT WAVES FROM THE UPPER LEVEL TROUGH WILL OVERRUN THE LINGERING WEDGE THURSDAY AFTERNOON...TO BRING ANOTHER ROUND OF RAIN TO THE AREA. THE BEST CHANCE FOR RAIN WILL OCCUR NORTH OF HIGHWAY 460 WITH THE HIGHEST AMOUNTS...UP TO A HALF INCH...FALLING NORTH OF I64. WITH CLOUDS REMAINING OVERNIGHT...THE COOL AIR WILL ALLOW TEMPERATURES TO DROP TO SEASONAL LEVELS...BUT WILL SEEM COLDER WITH OUR RECENT WARM SPELL. TEMPERATURES THURSDAY WILL REMAIN COLD AND AROUND 10F BELOW NORMAL. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... AS OF 345 PM EDT WEDNESDAY... WELL DEFINED SHORT WAVE OVER THE MID MISSISSIPPI VALLEY REACHES THE FORECAST AREA ON THURSDAY NIGHT. HIGHEST CONFIDENCE FOR RAINFALL THIS PART OF THE FORECAST IS FOR THURSDAY NIGHT. DEEPER MOISTURE LIFTS FROM SOUTHWEST TO NORTHEAST OUT OF THE COUNTY WARNING AREA DURING THURSDAY NIGHT. EXPECT THE WEDGE TO HOLD THROUGH AT LEAST 12Z/8AM FRIDAY THEN SURFACE WINDS WILL BECOME SOUTHWEST AHEAD OF THE FRONT DURING THE DAY. LIKELY THAT THERE WILL BE A LARGE SPREAD IN HIGH TEMPERATURES ON FRIDAY DEPENDING ON WHEN AND WHERE THE WEDGE ERODES. HAVE COOLEST MAXES FROM THE NEW RIVER VALLEY INTO THE NORTHEAST PART OF THE COUNTY WARNING AREA. A COLD FRONT CROSSES THROUGH THE FORECAST AREA FRIDAY. SURFACE HIGH PRESSURE BUILDS IN ON SATURDAY AND WITH THE AXIS OF THE HIGH OVER THE COUNTY WARNING AREA SATURDAY AFTERNOON. LARGE SPREAD IN THE MODELS WITH HOW MUCH PRECIPITATION THERE MAY BE ON FRIDAY THROUGH SATURDAY. WILL STAY WITH LOWER PROBABILITY OF PRECIPITATION... ESPECIALLY FOR SATURDAY AND SATURDAY NIGHT. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 145 PM EDT WEDNESDAY... 00Z GFS AND ECMWF AND THEIR ENSEMBLES HAD DECENT CONSENSUS FOR THE EXTENDED PERIOD. CENTRAL ROCKIES LOW OPENS AND LIFTS INTO THE UPPER MISSISSIPPI VALLEY SATURDAY NIGHT THROUGH MONDAY. THEN CLOSED LOW IN THE NORTHERN STREAM REMAINS OVER THE GREAT LAKES THROUGH WEDNESDAY. LOW PRESSURE OVER THE MISSISSIPPI VALLEY WILL BRING WARM FRONT ACROSS THE MID ATLANTIC REGION SUNDAY NIGHT AND MONDAY. SURFACE PATTERN WILL BE MORE COMPLICATED. MODELS WERE SHOWING SOME INDICATIONS OF SURFACE BASED COLD AIR DAMMING. A TRIPLE POINT LOW DEVELOPS ON MONDAY OVER VIRGINIA THEN TRACKS TOWARD NEW JERSEY COAST. A SURGE OF COLDER AIR COMES IN ON WEDNESDAY. LIFT FROM THE SURFACE LOW CROSSING THE MID ATLANTIC STATES AND A PROLONGED PERIOD OF INFLOW OFF THE ATLANTIC WILL RESULT IN A HIGH PROBABILITY OF PRECIPITATION SUNDAY AND SUNDAY NIGHT. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... AS OF 800 PM EDT WEDNESDAY... HIGH PRESSURE WILL CONTINUE TO BUILD ACROSS THE MID ATLANTIC THIS EVENING...PROVIDING A SURGE OF DRIER AIR INTO THE LOW LEVELS OF THE ATMOSPHERE WHILE MORE MOISTURE LADEN AIR PASSES ACROSS IN THE MID LEVELS. WEATHER FORECAST MODELS ARE MORE OPTIMISTIC THAT LOW LEVELS WILL REMAIN DRY ENOUGH OVERNIGHT TO MAINTAIN PREDOMINANTLY VFR CONDITIONS FOR TAF SITES...POSSIBLY WITH MVFR CONDITIONS IN A FEW SPOTS ACROSS THE MOUNTAINS. MVFR TO IFR CONDITIONS CAN BE EXPECTED FOR THE HIGHLANDS AND FOOTHILLS OF NORTH CAROLINA...WHERE RAIN SHOWER ACTIVITY WILL PERSIST THROUGH LATE EVENING. HIGH PRESSURE WILL REMAIN BANKED AGAINST THE APPALACHIANS ON THURSDAY...WITH WINDS BECOMING EAST SOUTHEASTERLY IN THE AFTERNOON. SUBTLE UPPER LEVEL DISTURBANCES PASSING ACROSS THE AREA WILL SUPPORT ON AND OFF SHOWER ACTIVITY...AS WELL AS CAUSING CEILINGS TO GRADUALLY LOWER DURING MID AFTERNOON AS RAINFALL ADDS MOISTURE TO THE LOW LEVELS OF THE ATMOSPHERE. EXTENDED AVIATION... ON FRIDAY...LOW LEVEL FLOW TURNS TO THE SOUTHWEST IN ADVANCE OF A COLD FRONT. ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE IN THE AFTERNOON...ESPECIALLY ONCE HIGH PRESSURE WEDGED AGAINST THE EASTERN FACE OF THE APPALACHIANS MOVES AWAY. A COLD FRONT WILL PASS ACROSS THE AREA FRIDAY NIGHT...WITH DRIER HIGH PRESSURE BUILDING IN BEHIND FOR SATURDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...RCS NEAR TERM...RCS SHORT TERM...AMS LONG TERM...AMS AVIATION...NF

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