Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 010102 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 902 PM EDT SAT APR 30 2016 .SYNOPSIS...
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HIGH PRESSURE TO THE NORTH WILL MAINTAIN A COOL WEDGE ACROSS THE REGION OVERNIGHT AHEAD OF A WARM FRONT APPROACHING FROM THE SOUTH LATE. THIS WARM FRONT WILL MOVE NORTH OF THE AREA SUNDAY AFTERNOON...FOLLOWED BY A COLD FRONT MONDAY. A STRONGER COLD FRONT WILL THEN MOVE THROUGH THE REGION BY MIDWEEK.
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&& .NEAR TERM /THROUGH SUNDAY/...
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AS OF 840 PM EDT SATURDAY... DEEPER MOISTURE HAS CONTINUED TO SLOWLY INCREASE FROM SW TO NE THIS EVENING AS BACKING ALOFT OVER THE WEDGE HAS RESULTED IN PROGRESSIVELY WETTER SOUNDINGS PER PWATS NOW OVER AN INCH. HOWEVER THE LOW LEVEL CAD REMAINS FIRMLY ENTRENCHED WITH THE EVENING RNK RAOB SHOWING EASTERLY FLOW UP TO ABOVE 9H WHILE GUIDANCE INDICATES LITTLE EROSION UNTIL LATE AND MAINLY ACROSS THE SW PERIMETER. THIS WILL CONTINUE TO SUPPORT BANDS OF CONVECTION DEVELOPING TO THE SOUTH WITHIN MORE INSTABILITY...AND THEN RIDING OVER THE COOL POOL IN ELEVATED FASHION OVERNIGHT IN CONJUNCTION WITH MORE ISENTROPIC LIFT NATURE LIGHT RAIN FARTHER NORTH. LATEST HRRR SUPPORTS THIS TREND OVER THE NEXT FEW HOURS WITH ANY CONVECTION WEAKENING BEFORE RAMPING UP DURING THE EARLY MORNING HOURS WHEN THE WARM FRONT TO THE SOUTH GETS CLOSER AND MOISTURE CONVERGENCE ENHANCES. APPEARS COULD BE A COUPLE ROUNDS OF HEAVIER SHOWERS WITH ISOLATED TSRA POSSIBLE MAINLY SOUTH/WEST AS WARMING ALOFT DEEPENS A BIT BUT STILL UNCERTAINTY WITH THE DEGREE OF ANY PROLONGED HEAVY RAIN. THUS WONT HOIST ANY FLOOD WATCHES ESPCLY GIVEN LIGHTER TOTALS SO FAR AND LITTLE OUT EAST WHERE THE DEEPER WEDGE CONTINUES TO LIMIT PRECIP. OTRW HAVE AGAIN TRENDED POPS LOWER EAST OF THE BLUE RIDGE TO INIT BEFORE INCREASING TO LIKELY/CATEGORICAL OVERNIGHT AS DEEPER MOISTURE FINALLY NUDGES EAST. FOG ALSO REMAINS AN ISSUE ALONG THE BLUE RIDGE BUT WITH RAIN INCREASING EXPECTING SOME IMPROVEMENT FROM SW TO NE. THUS STAYING WITH THE GOING SPS FOR AREAS OF DENSE FOG WITHOUT HEADLINES FOR NOW. LOWERED TEMPS A LITTLE MORE GIVEN CONTINUED LOW LEVEL COOL ADVECTION AND LIGHT RAIN/DRIZZLE THROUGH THE COLUMN WHICH HAS COOLED MOST BACK INTO THE CHILLY/DAMP LOW/MID 50S THIS EVENING. UPDATE AS OF 620 PM EDT SATURDAY... WITH THE MAJORITY OF THE MEASURABLE RAINFALL MAINLY ACROSS THE FAR NW AND EXTREME SW SECTIONS...UPDATED TO LOWER POPS BACK TO CHANCE ELSEWHERE FOR A COUPLE HOURS INTO THIS EVENING. APPEARS MOST SIGNIFICANT RAINFALL WILL OCCUR OVER THE NW NC MOUNTAINS/FOOTHILLS WHERE CONVECTION DEVELOPING IN A MORE UNSTABLE ENVIRONMENT TO THE SW PUSHES INTO/OVER THE WESTERN PERIPHERY OF THE WEDGE OVER THE NEXT FEW HOURS. THIS WARM ADVECTION HAS ALSO CAUSED CLOUD BASES TO LOWER ALLOWING FOR MORE WIDESPREAD DENSE FOG ALONG PARTS OF THE SOUTHERN BLUE RIDGE. THIS TREND MAY DEVELOP FARTHER NORTH AS WARM AIR ALOFT DEEPENS OVER THE WEDGE AND AIDED BY SATURATED LOW LEVELS PER RAINFALL. ALSO LOWERING LOW TEMPS A FEW DEGREES MOST LOCATIONS SINCE CLOSE TO CURRENT FORECAST VALUES OVERNIGHT ALTHOUGH NOT EXPECTING VALUES TO FALL MUCH MORE AS RAINFALL INCREASES. PREVIOUS DISCUSSION AS OF 330 PM EDT SATURDAY... STRONG WEDGE IN PLACE THIS AFTERNOON WILL HOLD AS WE HEAD THRU THE NIGHT. MEANWHILE...UPPER LEVEL DIVERGENCE AHEAD OF SHORTWAVE WILL SET UP ACROSS THE CENTRAL AND SOUTHERN APPALACHIANS THIS EVENING WITH RAINFALL OVERSPREADING THE MOUNTAINS. LOOKING AT OVERNIGHT WE START TO SEE MODELS EMPHASIZE STRONG LOW LVL CONVERGENCE WITH UPPER DIVERGENCE ACROSS THE SOUTHERN CWA...WITH ENHANCED RAINFALL AMOUNTS IN THE SOUTHERN APPALACHIANS. ATTM...LOOKS LIKE AT LEAST MOST OF THE AREA WILL SEE RAIN OVERNIGHT WITH ONE HALF TO THREE QUARTERS OF AN INCH SETTING UP ACROSS THE SOUTHERN BLUE RIDGE. WILL NOT ISSUE A FLOOD WATCH AT THIS POINT...BUT WILL BEAR MONITORING TO SEE IF ANY DEEP CONVECTION DEVELOPS AND TRAINS ACROSS THIS AREA LATE TONIGHT. WILL MAINTAIN ISOLATED FLOOD THREAT IN THE HWO. AS FAR AS THUNDERSTORMS...AM KEEPING THEM OUT OF THE FORECAST THROUGH TONIGHT GIVEN LACK OF INSTABILITY AND WEDGE. AS WE HEAD TO SUNDAY WILL BE HARD PRESSED TO CLEAR SKIES IN THE NORTH AND EAST BUT MODELS FAVOR QUICKER EROSION OF THE WEDGE. WILL BE SLOWER...THEN INTRODUCE A CHANCE OF STORMS IN THE AFTERNOON. SPC CONTINUES TO HIGHLIGHT MARGINAL RISK FOR MOST OF THE CENTRAL AND SOUTHERN APPALACHIANS INTO THE PIEDMONTS OF NC/VA. QUESTION WILL BE IF SUNSHINE CAN BREAK OUT. AT THE MOMENT SEEMS BEST CHANCE OF THIS WILL BE IN WV/FAR SW VA AND ACROSS THE NW NC PIEDMONT...BUT THINK CLOUDS WILL BE AROUND MOST OF THE DAY. WITH FLOW TURNING SSW BY AFTERNOON WENT CLOSE TO MOS ON HIGHS...BUT COULD SEE IT COOLER IN LYH TO HSP. MOST WILL SEE HIGHS IN THE LOWER TO MID 70S.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... AS OF 230 PM EDT SATURDAY... A WEAK WAVE OF LOW PRESSURE WILL BE TRACKING NORTHEAST FROM THE OHIO VALLEY TOWARD NEW ENGLAND OVERNIGHT SUNDAY DRAGGING A COLD FRONT SLOWLY ACROSS THE REGION EARLY MONDAY. CHANCES FOR SHOWERS OVERNIGHT WILL BE DECREASING DURING THE DAY AND SHOULD SEE SOME PARTIAL CLEARING ESPECIALLY EAST OF THE MOUNTAINS LATER IN THE DAY. EXPECT MILD TEMPS BEHIND THE FRONT ON MONDAY RANGING FROM NEAR 70 NORTHWEST TO LOW 80S SOUTHEAST AS COOLING IS MODEST BEHIND IT..H85 TEMPS DROPPING ONLY A FEW DEGREES BY LATE IN THE DAY. THIS BOUNDARY MAKES ONLY SLIGHT PROGRESS TO THE SOUTHEAST BY LATE MONDAY LEAVING ENOUGH CLOUDS TO HOLD TEMPS UP SOMEWHAT HIGHER MONDAY NIGHT...GENERALLY UPPER 40S TO MID-50S. THE SAME FRONT WILL BECOME NEAR STATIONARY ALONG COAST AND BECOME THE FOCUS FOR SHOWERS AND POSSIBLY SOME THUNDERSTORMS ON TUESDAY AS SEVERAL WEAK WAVES TRAVERSE NORTHEAST ALONG IT. MODELS DIFFER IN THE PLACEMENT OF THIS BOUNDARY STRENGTH OF PERTURBATIONS ALONG IT WHICH WILL HAVE A SUBSTANTIAL IMPACT ON PRECIPITATION CHANCES ON TUESDAY. WPC AND GFS SOLUTIONS CURRENTLY FURTHER SOUTHEAST THAN EARLIER CMC OR ECMWF RUNS WHICH BOTH BRING CONSIDERABLY MORE CLOUDS AND SHOWERS INTO OUR CWA. WENT WITH A MODEL BLEND RETAINING CHANCE POPS ACROSS THE ENTIRE CWA BUT THE HIGHEST OVER THE SOUTHEAST. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 230 PM EST SATURDAY... LOW PRESSURE WILL CONTINUE TO LINGER ALONG THE SOUTHEAST COAST EARLY WEDNESDAY WITH ASSOCIATED CLOUDS AND SHOWERS MAINLY CONFINED TO THE COASTAL PLAIN AND EASTERN PIEDMONT DURING THE DAY BUT STILL LINGERING POPS ACROSS OUR CWA BUT MAINLY SOUTHEAST. TEMPS WILL REMAIN NEAR SEASONAL LEVELS WEDNESDAY WITH PARTIAL CLEARING DURING IN THE DAY ESPECIALLY NORTHWEST. MEANWHILE ANOTHER FRONT OVER THE UPPER PLAINS BEGINS TO DROP SOUTHEAST TOWARD THE AREA LATE WEDNESDAY INTO THURSDAY AS NORTHERN STREAM TROUGH BEGINS TO AMPLIFY SHARPLY.BOTH GFS AND EURO SHOW UPPER LOW CLOSING OVER THE EASTERN CONUS BY LATE THURSDAY WITH EXACT POSITION UNCERTAIN AND LIKELY TO HAVE CONSEQUENCES FOR SENSIBLE WEATHER BY THAT TIME. 00Z EURO IS THE MOST AGGRESSIVE WITH DEEP COMPLEX SURFACE LOW MORE OR LESS MERGING WITH THE EXISTING COASTAL SYSTEM AND ACTUALLY BACKING IN TOWARD THE MID-ATLANTIC COAST. GFS/CMC NOT QUITE AS FAR SOUTH AND DEEP WITH UPPER TROUGH AND SURFACE REFLECTION WHICH SEEMS MORE CLIMATOLOGICALLY PLAUSIBLE BUT WENT WITH BLEND TO ACCOUNT FOR SIGNIFICANT UNCERTAINTY. EITHER WAY A PERSISTENT DEEP NORTHWEST FLOW WILL EXIST FRIDAY INTO SATURDAY WITH COOL TEMPS AND PLENTY OF CLOUDS ESPECIALLY ACROSS THE MOUNTAINS. HIGHS FRIDAY WILL STRUGGLE TO REACH 60 OVER THE MOUNTAINS...CLOSE TO 10F BELOW NORMAL. SLOWLY RISING HEIGHTS SATURDAY WILL ALLOW FOR SLOWLY IMPROVING CONDITIONS. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... AS OF 740 PM EDT SATURDAY... SURFACE WEDGE WILL CONTINUE TO HOLD FAST IN THE EASTERN PART OF THE REGION OVERNIGHT. LOW LEVEL WINDS WILL CONTINUE TO INCREASE IN ADVANCE OF AN APPROACHING SYSTEM. MOISTURE ADVECTION WILL BE STRONG WITHIN THESE WINDS. EXPECT LIGHT PRECIPITATION TO INCREASE ACROSS THE REGION FROM WEST TO EAST DURING THE OVERNIGHT HOURS...WITH COVERAGE GREATEST IN THE WEST. CIGS WILL LOWER TO INTO THE LIFR/IFR RANGE WITH VSBYS MAINLY IFR/MVFR. THE STRONG LOW LEVEL WINDS ABOVE THE WEDGE WILL ALLOW FOR A FEW HOURS OF LOW LEVEL WIND SHEAR LATE TONIGHT INTO EARLY SUNDAY MORNING. RAIN WILL CONTINUE ACROSS THE REGION SUNDAY MORNING...WITH ONLY MINOR IMPROVEMENTS TO FLIGHT CATEGORIES. THE PRECIPITATION WILL START TO BECOME MORE SHOWERY IN THE WEST BY THE LATE MORNING. CIGS/VSBYS IMPROVING TO MVFR/VFR BY SUNDAY AFTERNOON AS THE WEDGE ERODES. SUNDAY AFTERNOON BRINGS THE POTENTIAL FOR SCATTERED CONVECTION...SOME POSSIBLY STRONG TO SEVERE AS SHORT WAVE ENERGY TRACKS NORTHEAST ACROSS THE REGION IN THE WARM/UNSTABLE AIR MASS. SITUATION APPEARS SOMEWHAT SIMILAR TO WHAT WAS OBSERVED THURSDAY ACROSS THE REGION...BUT PERHAPS MORE ACTIVITY NORTH-WEST OF THE BLUE RIDGE THIS TIME AROUND THAN WHAT WAS OBSERVED SUNDAY. EXTENDED AVIATION DISCUSSION... SFC LOW PRESSURE TRACKS NORTHEAST ACROSS GA/SC/NC SUN NIGHT- TUE...LIKELY PROLONGING SUB-VFR CIGS AND POTENTIALLY LEAVING SOME LIGHT PRECIPITATION ACROSS THE REGION...ESPECIALLY EAST OF THE BLUE RIDGE. FOR THE MID AND LATER PART OF NEXT WEEK...A DEEP UPPER LOW IS EXPECTED TO DROP DOWN ACROSS THE GREAT LAKES INTO THE APPALACHIANS AND MID-ATLANTIC REGION...WHICH WILL LEAVE THE REGION WITH VARIABLE CLOUDINESS...SHOWERS...AND PERIODS OF SUB-VFR CONDITIONS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/WP NEAR TERM...JH/WP SHORT TERM...PC LONG TERM...PC AVIATION...DS/WP

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