Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 142343 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 743 PM EDT SUN SEP 14 2014 .SYNOPSIS... HIGH PRESSURE OVER THE MID ATLANTIC TODAY WILL SHIFT EAST TOMORROW BRINGING WARMER TEMPERATURES AS WINDS SHIFT MORE SOUTHWEST. THE NEXT COLD FRONT MOVES THROUGH EARLY TUESDAY MORNING BRINGING COOLER THAN NORMAL TEMPERATURES FOR THE REMAINDER OF THE WEEK. A FEW SHOWERS OR A STRAY THUNDERSTORM COULD FORM AHEAD OF THIS LATE MONDAY AND MONDAY NIGHT. && .NEAR TERM /THROUGH MONDAY/... AS OF 725 PM EDT SUNDAY... WARM AIR ADVECTION OVER THE WEDGE WILL CONTINUE TO LOWER CLOUD BASES TONIGHT WITH NO SIGNS OF CLEARING. IF ANY CLEARING DOES TAKE PLACE...FOG LIKELY TO DEVELOP. SINCE WARM AIR IS PUSHING IN ALOFT...TEMPERATURES MAY ONLY FALL A FEW DEGREES FROM WHERE THEY ARE NOW. EVEN THOUGH LOW LEVEL FLOW IS WEAK TO CALM...ANY SOUTHEASTERLY COMPONENT IN THIS MOISTURE ATMOSPHERE WILL HAVE THE POTENTIAL TO PRODUCE LIGHT RAIN/DRIZZLE ALONG EASTERN SLOPES. THE POTENTIAL FOR THIS PRECIP WILL BE ACROSS THE NORTH CAROLINA HIGHLANDS AND SOUTHWESTERN VIRGINIA BLUE RIDGE. AS OF 345 PM EDT SUNDAY... 500MB FLOW REMAINS ZONAL TONIGHT AND MONDAY. SHORT WAVE IN NORTHERN KENTUCKY WILL CROSS THROUGH THE REGION DURING THIS TIME FRAME. AT THE SURFACE...HIGH PRESSURE OVER THE OHIO VALLEY WILL MOVE EAST AND WILL BE CENTERED OFF THE NEW ENGLAND COAST BY LATE IN THE DAY MONDAY. STILL EXPECTING SOME SURFACE BASED CONVERGENCE AND INCREASING DEW POINTS IN THE WESTERN COUNTY WARNING AREA LATE THIS AFTERNOON. WILL LEAVE IN A LOW PROBABILITY OF PRECIPITATION IN THE FAR WEST. DEEPER MOISTURE IN THE SOUTHERN COUNTY WARNING AREA COMES IN ON MONDAY ALONG WITH AN ELONGATED SHORT WAVE OVER THE TENNESSEE VALLEY. MODELS HOLD MID AND HIGH CLOUDS ASSOCIATED WITH THE APPROACHING COLD FRONT WEST OF THE FORECAST AREA. WEDGE BREAKS ON MONDAY AND SOUTHWEST FLOW WILL PROVIDE SOME WARM AIR ADVECTION...BRINGING 850 TEMPERATURES CLOSE TO +15. MODELS SHOWED ENOUGH INSTABILITY ON MONDAY FOR ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS...ALTHOUGH NO ORGANIZED MECHANISM TO TRIGGER THE PRECIPITATION. MOST FAVORABLE LOCATION FOR DEVELOPMENT WILL BE ALONG THE RIDGES. CAPES UP TO 500 J/KG ARE POSSIBLE AS FAR NORTH AS BLUEFIELD AND ROANOKE. WINDS BECOME LIGHT AND VARIABLE TONIGHT SO LOW TEMPERATURES WILL BE HIGHLY DEPENDENT ON CLOUD COVER. BIAS CORRECTED MAV GUIDANCE WAS REASONABLE. USED A BLEND OF MET AND MAV GUIDANCE FOR MAXIMUM TEMPERATURES ON MONDAY. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... AS OF 345 PM EDT SUNDAY... A FAST MOVING COLD FRONT...ASSOCIATED WITH AN UPPER LEVEL NORTHERN STREAM WAVE MOVING THROUGH THE EASTERN GREAT LAKES INTO THE NORTHEAST U.S....WILL MOVE THROUGH OUR AREA MONDAY NIGHT. MODELS HAVE SIGNIFICANTLY BACKED OFF THE AMOUNT OF PRECIPITATION GENERATED BY THIS SYSTEM...AND WITH A SOUTHWEST/WEST MID LEVEL FLOW...MOISTURE WILL BE SHALLOW AND PRECIP WILL BE WIDELY SCATTERED IN COVERAGE. AS A RESULT...LOWERED POPS AND QPF MONDAY NIGHT. ON TUESDAY...THERE WILL BE ENOUGH RESIDUAL MOISTURE ALONG THE WESTERN SLOPES OF SOUTHEAST WV TO GENERATE WIDELY SCATTERED SHOWERS EARLY TUESDAY. ANOTHER REGION TO MONITOR FOR POTENTIAL LIGHT PRECIP WILL BE THE SOUTHERN BLUE RIDGE AND HIGH COUNTRY OF NC. WHILE THE SURFACE BOUNDARY PUSHES INTO SOUTHERN NC...THE SOUTHERN PORTION OF OUR FORECAST AREA RESIDES ON THE NORTHERN FRINGE OF THE LOW LEVEL THETA-E AXIS. IN ADDITION...THE 00Z ECMWF AND 12Z GFS CREATE LOW LEVEL CONVERGENCE IN THIS AREA WITH A WEAK EAST FLOW EAST OF THE BLUE RIDGE. DESPITE THE FRONTAL PASSAGE....CONTINUED THE TREND OF WARMING HIGHS ON TUESDAY WITH DOWNSLOPING WINDS EAST OF THE BLUE RIDGE. A LARGE AREA OF HIGH PRESSURE BEGINS TO FILTER DOWN FROM THE NORTH...USHERING IN DRIER AIR WITH DEW POINTS FALLING WELL INTO THE 40S IN THE MOUNTAINS. COOP MOS GUIDANCE...SUGGESTS LOWS IN THE LOWER 40S POSSIBLE IN SOME OF THE MOUNTAIN VALLEYS LIKE BURKES GARDEN. BROUGHT DOWN LOWS A COUPLE OF DEGREES FOR WEDNESDAY MORNING. AS THE HIGH CONTINUES TO BUILD ON WEDNESDAY...DRIER AIR CONTINUES TO INFILTRATE SOUTH. LOW LEVEL EAST/NORTHEAST FLOW PUSHES AXIS OF LOW LEVEL MOISTURE AGAINST THE SOUTHERN BLUE RIDGE/NW NC MOUNTAINS...WHICH AGAIN MAY GENERATE A FEW SHOWERS. CONTINUED TO GO BELOW GUIDANCE FOR HIGHS WITH POTENTIAL UPSLOPE CLOUDS. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 345 PM EDT SUNDAY... FOR MOST OF THE LONG TERM PERIOD A BROAD UPPER TROF WILL CONTINUE TO HOLD OVER THE EASTERN U.S. WITH SFC HIGH PRESSURE EXTENDING FROM THE NORTHEAST THROUGH THE MID-ATLANTIC...KEEPING A WEDGE IN PLACE THROUGH THE PERIOD. A REINFORCING SHOT OF DRIER AIR ARRIVES THURSDAY AS A NORTHERN STREAM WAVE BRIEFLY AMPLIFIES THE UPPER TROF. ECMWF/GFS ENSEMBLE MEANS AND DETERMINISTIC RUNS NOW SHOW AN UPPER RIDGE TRYING TO BUILD LATE IN THE LONG TERM PERIOD (SATURDAY/SUNDAY) WHICH WILL WEAKEN THE WEDGE OF HIGH PRESSURE AT THE SFC AND ALLOW TEMPS TO MODERATE. UNTIL THEN...TEMPS WILL BE BELOW NORMAL AND MORNING LOWS IN THE 40S WILL BE COMMON FOR MANY MOUNTAIN VALLEY LOCATIONS. OUTSIDE OF UPSLOPE SHOWERS IN THE SOUTHERN BLUE RIDGE/NW NC MOUNTAINS AND FOOTHILLS THURSDAY...MOST AREAS SHOULD REMAIN DRY. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... AS OF 725 PM EDT SUNDAY... WARM AIR ADVECTION OVER THE WEDGE WILL CONTINUE TO LOWER CLOUD BASES TONIGHT WITH NO SIGNS OF CLEARING. IF ANY CLEARING DOES TAKE PLACE...FOG LIKELY TO DEVELOP. EVEN THOUGH LOW LEVEL FLOW IS WEAK TO CALM...ANY SOUTHEASTERLY COMPONENT IN THIS MOISTURE ATMOSPHERE WILL HAVE THE POTENTIAL TO PRODUCE LIGHT RAIN/DRIZZLE ALONG EASTERN SLOPES. THE POTENTIAL FOR THIS PRECIP WILL BE ACROSS THE NORTH CAROLINA HIGHLANDS AND SOUTHWESTERN VIRGINIA BLUE RIDGE. ON MONDAY...ONCE THE FOG AND STRATUS LIFT...CEILINGS AND VISIBILITIES WILL BE VFR FOR THE REST OF THE DAY. MEDIUM CONFIDENCE ON THE TIMING OF IMPROVEMENT UP TO VFR. EXTENDED AVIATION DISCUSSION... WEAK UPPER SHORT WAVE AND ASSOCIATED WEAK SFC FRONT SLIDE THROUGH AND MAY BRING AN ISOLATED SHOWER TO THE MOUNTAINS MONDAY NIGHT AND TUESDAY. A BROAD UPPER TROUGH DEVELOPS ACROSS THE NORTHERN STATES...WITH THE RNK CWA ON ITS SOUTHERN EDGE AND TRENDING TOWARD A MORE NW FLOW ALOFT AS THE WEEK PROGRESSES. THIS SHOULD PUSH THE PESKY DEEP MOISTURE FURTHER SOUTH AWAY FROM THE REGION. THIS PATTERN WOULD BE DRY WITH LIGHT NW WINDS...BUT MAY TEND TO KEEP MVFR CIGS IN THE WEST. THE NEXT COLD FRONT CROSSES THROUGH THE AREA ON THURSDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PH NEAR TERM...AMS/RCS SHORT TERM...PH LONG TERM...PH AVIATION...AMS/RCS

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