Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 021425 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1025 AM EDT TUE JUN 2 2015 .SYNOPSIS... A COLD FRONT NEAR THE APPALACHIANS WILL STALL ALONG THE BLUE RIDGE TODAY INTO TONIGHT BEFORE DRIFTING SOUTH INTO THE CAROLINAS ON WEDNESDAY. THIS IN COMBINATION WITH WAVES OF LOW PRESSURE RIDING UP ALONG THE BOUNDARY...AND A DEVELOPING WEDGE OF COOL AIR WILL KEEP PERIODIC ROUNDS OF SHOWERS...AND STORMS GOING INTO MIDDLE OR LATE WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1015 AM EDT TUESDAY... FRONTAL BOUNDARY DRAPED FROM THE CENTRAL VA PIEDMONT...SOUTHWEST INTO THE MTNS OF NE TN THIS MORNING...WITH BEST THETA-E RIDGING ACROSS THE PIEDMONT AND COASTAL AREAS. LIGHT SHOWERS MOVING NWD FROM SOUTH OF THE TRIAD IN NC TO THE ERN CWA. HIGH-RES MODELS ARE FAVORING A SHIFT TO THE WEST THIS MORNING...BUT THINK ANOTHER 1-2 HOURS WILL OCCUR BEFORE THIS TAKES PLACE...SO MADE SOME DOWNWARD ADJUSTMENTS TO POPS. SUNSHINE RETURNING TO THE CWA IS LOW...THOUGH THE CMC AND HRRR DO SHOW SOME BREAKS RETURNING TO THE MTNS. WITH LIMITED SUNSHINE...INSTABILITY WILL BE LIMITED...THEREFORE...CUT BACK WORDING OF THUNDER TO CHANCE INSTEAD OF LIKELY. STILL LOOKS LIKE ENOUGH VERTICAL MOTION AHEAD OF THE UPPER TROUGH AND SOMEWHERE IN VICINITY OF FRONT TO ALLOW FOR HIGHER POPS THIS AFTERNOON FROM THE BLUE RIDGE EAST. TEMPS WILL BE IMPACTED BY THE CLOUD COVER...SO NO MAJOR CHANGES TO FORECAST HIGHS. PREVIOUS DISCUSSION FROM EARLY MORNING... OVERALL FORECAST REMAINS A RATHER WET ONE OVER THE NEXT 24 HOURS BUT COMPLICATED IN REGARDS TO PLACEMENT OF DEEPER CONVECTION TODAY AND WHETHER OR NOT WILL SEE WIDESPREAD ENOUGH PRECIP FOR FLOODING CONCERNS ESPCLY BLUE RIDGE EAST OVERNIGHT. MAIN CULPRITS REMAIN WITH A CUTOFF 5H LOW JUST WEST OF THE MOUNTAINS TODAY...AND A WEAK SURFACE FRONT DRIFTING EAST TOWARD THE BLUE RIDGE THAT WILL INTERACT WITH DEEP PWATS TO GET BANDS OF CONVECTION GOING THIS AFTERNOON AFTER EARLY SHRA FADES. LATEST GUIDANCE SUGGESTS BEST CHANCES FOR SLOW MOVING SHRA/TSRA TO TAKE SHAPE OVER THE EAST AHEAD OF THE FRONT BY THIS AFTERNOON...AND THEN ACROSS THE SW LATER AS THE BOUNDARY SWINGS OVER A BIT MORE IN BACKDOOR FASHION UNDER COOLER AIR ALOFT. THIS SUPPORTED BY BETTER DIFFLUENCE ALONG THE EASTERN QUADRANT OF THE UPPER DYNAMICS OUT WEST...AND WITH CONVERGENCE AHEAD OF THE BOUNDARY EAST WHERE WILL SLOWLY GET TRAJECTORIES SWITCHING AROUND TO A MORE EASTERLY COMPONENT UNDER THE 85H THETA-E GRADIENT LATER ON. BEST INSTABILITY ALTHOUGH WEAK ALSO PROGGED OVER THE SOUTH AND EAST WITH BROAD UPPER DIFFLUENCE THAT COULD EVENTUALLY CAUSE SHRA/TSRA TO MERGE ALONG/EAST OF THE BLUE RIDGE BY THIS EVENING PER LATEST ENSEMBLES. THUS APPEARS BEST CHANCES FOR ISOLATED PULSE SEVERE MAINLY SOUTH/EAST WITH THE CORRIDOR OF HEAVIER RAINFALL SE-SW BUT GRADUALLY FILLING IN ALONG THE BLUE RIDGE AS THE FLOW TURNS MORE UPSLOPE LATE. THIS SUPPORTS UPPING POPS FROM CHANCE AFTER A LULL THIS MORNING TO LIKELY/CATEGORICAL IN ALL EXCEPT THE FAR NW THIS AFTERNOON WHERE WILL STAY JUST BEHIND THE FRONT. HIGH TEMPS REMAIN TRICKY GIVEN A MILD START BUT WITH MORE CLOUDS AND IFFY TIMING OF ONSET OF THE DEVELOPING WEAK WEDGE LATER TODAY. MOS VALUES HAVE COOLED QUITE A BIT BUT LIKELY ARE TOO COOL PARTS OF THE WEST/SOUTH WHERE THINK ANY COOL ADVECTION WILL HOLD OFF UNTIL THIS EVENING. HOWEVER LIKELY ENOUGH EARLY CLOUDS AND LIGHT SHOWERS FOLLOWED BY SOME AFTERNOON CONVECTION TO LIMIT RISES TO SOME DEGREE. THUS TRENDED WITH THE WARMER MAV WHICH STILL KEEPS MOST IN THE 70S THIS AFTERNOON ALTHOUGH MAY SEE SOME LOCATIONS OVER THE WEST NOT GET OUT OF THE 60S IF CLOUDS LOWER SOONER. CONVERGENCE LOOKS TO GET PINNED IN ALONG A CORRIDOR FROM THE VA BLUE RIDGE EAST OVERNIGHT WITH A CONVEYOR BELT OF DEEP MOISTURE RUNNING IN FROM THE SE ALONG THE STALLED 85H FRONT AND UNDER THE 5H LOW. THIS WITHIN A BROAD AREA OF UPPER DIFFLUENCE THAT SHOULD BE ENHANCED BY UPSLOPE FLOW AS THE WEDGE DEEPENS. SOUNDINGS SUGGEST MUCH OF THIS SHOULD BE MORE STRATIFORM IN NATURE GIVEN DEEP SATURATION AND AN INVERSION ALOFT. HOWEVER CANT TOTALLY RULE OUT ELEVATED CONVECTION PER COOLNESS ALOFT AND PROGGED LIFT ON THE EAST SIDE OF THE 5H LOW. THIS WOULD MAKE A DIFFERENCE IN RAINFALL RATES OVERNIGHT AS COULD BE ENOUGH FOR FLOODING ISSUES PENDING THE COVERAGE OF HEAVIER SHRA/TSRA TODAY. SINCE COVERAGE COULD AGAIN BE MORE SCATTERED NATURE UNTIL LATE THIS AFTERNOON...AND OVERALL FFG RATHER HIGH...WILL HOLD OFF ON ISSUING A FLOOD WATCH FOR NOW. OTRW KEEPING PERSISTENT LIKELY TO CATEGORICAL POPS GOING IN A SWATH ROUGHLY FROM THE BLUE RIDGE EAST IN VA TONIGHT AND CHANCE ELSEWHERE. LOW TEMPS SHOULD BE A LITTLE COOLER WITHIN THE WEDGE WITH LOWS MOSTLY UPPER 50S TO LOWER 60S. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 310 AM EDT TUESDAY... A WELL DEFINED UPPER LOW CENTERED ON THE CENTRAL KENTUCKY/TENNESSEE BORDER THIS MORNING SLOWLY SHIFTS EASTWARD ACROSS THE SOUTHERN APPALACHIANS INTO THE CAROLINAS. ON WEDNESDAY MORNING...THE UPPER LOW IS LOCATED IN EASTERN TENNESSEE AND TRAVELS EASTWARD TO THE SPINE OF THE APPALACHIANS AND OPENED UP INTO MORE OF AN UPPER TROUGH BY THURSDAY NIGHT. ALONG THE LOW/TROUGH AXIS AND ON ITS EASTERN FLANKS...EXPECT DAILY SHOWERS AND THUNDERSTORMS ACROSS THE REGION. THE BEST CHANCE OF PRECIPITATION WILL OCCUR ACROSS THE EASTERN HALF OF THE REGION. AT THE SURFACE...HIGH PRESSURE WILL PUSH SOUTH ALONG THE LEE OF THE APPALACHIANS ON WEDNESDAY...RESULTING IN COOL WEDGE. LOW LEVEL STABLE AIR WILL LIMIT THE POTENTIAL FOR THUNDERSTORMS ON WEDNESDAY. HIGH TEMPERATURES ON WEDNESDAY WILL BE COOLER THAN TUESDAY WITH READINGS FROM THE LOWER 60S IN THE NORTH TO THE LOWER 70S IN THE SOUTH. CLOUDY SKIES WITH SCATTERED SHOWERS CONTINUING WEDNESDAY NIGHT. LOW TEMPERATURES WEDNESDAY NIGHT WILL VARY FROM THE LOWER 50S IN THE NORTHWEST MOUNTAINS TO AROUND 60 DEGREES IN THE PIEDMONT. THE COVERAGE OF STORMS WILL INCREASE AGAIN ON THURSDAY THE AXIS OF THE UPPER TROUGH PASSES OVERHEAD...AND CONVECTION BECOMES ENHANCED BY THE STEEP LAPSE RATE OF THE CORRESPONDING COLD POOL ALOFT...DESPITE RELATIVE STABILITY CLOSER TO THE SURFACE. KEPT HIGH TEMPERATURES COOL ON THURSDAY WITH VALUES FROM THE UPPER 60S IN THE MOUNTAINS TO THE MID 70S IN THE PIEDMONT. SHAPED POPS THURSDAY NIGHT TOWARDS SUPERBLEND WITH SLIGHT CHANCE IN THE WEST TO SCATTERED IN THE EAST. LOW TEMPERATURES THURSDAY NIGHT WILL RANGE FROM THE MID 50S IN THE WEST TO THE LOWER 60S IN THE EAST. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 230 PM EDT MONDAY... THE AXIS OF THE UPPER LOW WILL CONTINUE ITS SLOW PROGRESSION EASTWARD. THIS WILL KEEP THE AREA IN A REGIME PRONE TO ADDITIONAL SCATTERED SHOWERS AND STORMS. COVERAGE WILL BECOME MORE DIURNAL IN NATURE HEADING INTO THE WEEKEND AS THE UPPER LEVEL SUPPORT SHIFTS EAST OF THE COAST. SUNDAY INTO MONDAY...WE EXPECT ANOTHER INCREASE IN COVERAGE ACROSS THE AREA AS A SHORTWAVE TROUGH ENTERS AND MOVES THROUGH THE AREA FROM THE GREAT LAKES REGION. TEMPERATURES DURING THIS PORTION OF THE FORECAST ARE EXPECTED TO BE SLIGHTLY MILDER THAN NORMAL AND SLIGHTLY COOLER THAN NORMAL. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... AS OF 1045 AM EDT TUESDAY... WIDE RANGE OF CONDITIONS ACROSS THE REGION THIS MORNING RANGING FROM IFR/LIFR IN FOG IN SPOTS WHERE HEAVY RAIN OCCURRED ON MONDAY...TO MVFR/IFR CIGS OUTSIDE OF THE FOG...TO VFR IN MID DECK. HOWEVER ALREADY SEEING THE NEXT WAVE OF MOISTURE STARTING TO LIFT BACK NORTH FROM THE CAROLINAS WHICH SHOULD EXPAND ACROSS THE REGION THIS MORNING RESULTING IN BANDS OF SHOWERS...AND LIKELY MORE IN THE WAY OF MVFR CIGS ONCE ANY FOG FADES BY MID MORNING. CLOUDINESS INCLUDING MVFR TO VFR CIGS EXPECTED THROUGH MUCH OF THE AFTERNOON PER UPPER TROUGH OF LOW PRESSURE WHICH IS FORECAST TO BE CENTERED OVER THE CENTRAL APPALACHIANS. THIS WILL LEAD TO ANOTHER AFTERNOON OF NUMEROUS SHOWERS/STORMS...ESPCLY FOR THE AFTERNOON AND EVENING HOURS PENDING THE DEGREE OF HEATING. FRONT BOWING SOUTH INTO THE REGION WILL ALSO MAKE FOR A LINGERING CONVERGENCE AXIS WITH MORE CONVECTIVE NATURE PRECIP TO THE SOUTH TOWARD THE NC/VA BORDER...AND THE DEVELOPMENT OF LOWER IFR TYPE STRATUS OVER THE NORTH WHERE WILL SEE NE FLOW KICK IN. THIS MAY ALSO TEND TO LIMIT DEEP CONVECTION TO SOUTHERN/EASTERN AREAS EARLY THIS AFTERNOON BEFORE SHIFTING WEST OF THE BLUE RIDGE AS THE FRONT PIVOTS SW UNDER THE DEVELOPING WEDGE. THUS WILL INCLUDE A PERIOD OF MVFR IN CONVECTION AT ALL LOCATIONS THIS AFTERNOON BUT WITH MORE SHRA AND ONLY A VCTS MENTION GIVEN LACK OF DEEP INSTABILITY. WEDGE DEEPENS TONIGHT WHILE THE FLOW TURNS MORE SE OVER THE COOL POOL MAKING FOR A GOOD OVERRUNNING SETUP TO THE EAST OF THE UPPER LOW ALONG THE MOUNTAINS. IN ADDITION...UPSLOPE COMBO LIKELY TO CAUSE WIDESPREAD IFR CIGS WITH MVFR/IFR VSBYS IN FOG AND ADDED SHRA/RA INTO AT LEAST THIS EVENING. EXTENDED DISCUSSION... MODEL TRENDS SUGGEST THE UPPER TROUGH WILL STALL OVER THE REGION FOR MOST OF THE WEEK (THROUGH AT LEAST THURSDAY) RESULTING IN A PROLONGED PERIOD OF LOW CIGS (MVFR AND POSSIBLE IFR) AND OPPORTUNITY FOR SHOWERS AND THUNDERSTORMS. THE TROUGH OF LOW PRESSURE IS EXPECTED TO WEAKEN BY THE WEEKEND. THIS WILL ALLOW FOR HIGHER CLOUD BASES...HOWEVER...THERE WILL BE A CONTINUED THREAT FOR DIURNALLY DRIVEN SHOWERS/STORMS IN ADDITION TO LATE NIGHT-EARLY MORNING FOG. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/WP NEAR TERM...JH/WP SHORT TERM...KK LONG TERM...DS AVIATION...JH/PM

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