Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 032355 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 755 PM EDT SUN MAY 3 2015 .SYNOPSIS... WITH HIGH PRESSURE SHIFTING OFF THE COAST TONIGHT...EXPECT A SUMMER LIKE WEATHER PATTERN WITH SPOTTY SHOWERS AND A FEW THUNDERSTORMS DEVELOPING ACROSS THE MOUNTAINS ON MONDAY AND TUESDAY. A TROPICAL LOW PRESSURE SYSTEM WILL PUSH NORTH FROM THE CARIBBEAN TOWARD THE CAROLINA COAST ON WEDNESDAY...WHICH WILL HELP DRAW A BACKDOOR COLD FRONT ACROSS THE MID ATLANTIC WEDNESDAY NIGHT AND THURSDAY. && .NEAR TERM /THROUGH MONDAY/... AS OF 330 PM EDT SUNDAY... SATELLITE IMAGERY INDICATES SCATTERED CLOUDS ACROSS THE REGION THIS AFTERNOON...A MIXTURE OF HIGH AND LOW CLOUDS. RAPID UPDATE MODELS HAVE BEEN HINTING AT THE POSSIBILITY OF A FEW SHOWERS DEVELOP ACROSS THE NORTH CAROLINA HIGHLANDS INTO EXTREME SOUTHERN VIRGINIA THIS AFTERNOON THROUGH EARLY EVENING...HOWEVER RADAR REMAINS CLEAR AS OF THIS WRITING...AND HIGH CLOUDS PASSING OVER THE AREA SEEM TO BE KEEPING A LID ON INSTABILITY. WILL SIMPLY CONTINUE TO MONITOR AS THE EVENING PROGRESSES. EXPECT LOW CLOUDS TO DIMINISH TOWARD SUNSET...LEAVING ONLY OCCASIONAL PASSING HIGH CLOUDS IN OTHERWISE CLEAR SKIES OVERNIGHT. WITH HIGH PRESSURE NOW CENTERED NEAR THE CAROLINA COAST...MILDER SOUTHWESTERLY WINDFLOW HAS BECOME ESTABLISHED...AND EXPECT WARMER OVERNIGHT LOWS FOR MOST LOCATIONS...GENERALLY RANGING FROM THE MID 40S TO THE LOW 50S. MONDAY`S WEATHER PATTERN WILL BE SIMILAR TO THAT OF TODAY...ALBEIT SLIGHTLY WARMER AS UPPER LEVEL RIDGING OVER THE CENTER OF THE COUNTRY DRIFTS EASTWARD. WHILE STARTING THE DAY MOSTLY CLEAR...WE CAN EXPECT ANOTHER ROUND OF SCATTERED LOW CLOUDS TO DEVELOP DURING LATE MORNING...WITH A SPOTTY SHOWERS AND A FEW THUNDERSTORMS DEVELOPING DURING THE AFTERNOON. HIGHEST RAIN CHANCES WILL BE FOUND ACROSS THE MOUNTAINS SOUTH OF HIGHWAY 460...WHERE DEEPER MOISTURE AND BETTER INSTABILITY ASSOCIATED WITH A WEAK UPPER LEVEL DISTURBANCE WILL BE LOCATED. HOWEVER...WOULD NOT BE SURPRISED TO SEE A FEW SHOWERS DEVELOP FURTHER TO THE NORTH AS WELL. AFTERNOON HIGHS WILL BE SLIGHTLY WARMER COMPARED TO SUNDAY...RANGING FROM THE MID AND UPPER 70S ACROSS THE MOUNTAINS...TO THE LOW 80S FURTHER EAST. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... AS OF 315 PM EDT SUNDAY... GIVEN THE LIMITED ISOLATED CONVECTION MAY FORM OVER THE HIGHER TERRAIN DURING THE DAY MONDAY WILL QUICKLY WEAKEN BUT MAY SLIDE INTO THE FOOTHILLS BEFORE IT COMPLETELY DIES WITH THE MEAN FLOW EASTERLY BUT WEAK. DOES NOT APPEAR THAT WEAK UPPER WAVE OVER SOUTHEASTERN NC WILL HAVE ANY INFLUENCE ON KEEPING ANYTHING GOING OVERNIGHT AND THERE IS STILL PRETTY DRY AIR ALOFT. WHILE LOW LEVEL MOISTURE EVER SO SLOWLY INCREASES AGAIN FOR TUESDAY...INSTABILITY REMAINS VERY LIMITED. SOUTHERLY LOW LEVEL FLOW...WITH WEAK NORTHERLY FLOW AT MID LEVELS...WILL HELP WITH CONVERGENCE ALONG BLUE RIDGE AND ANY WEAK STORMS WILL HARDLY MOVE. THUS WHILE COVERAGE OF CONVECTIVE ACTIVITY WILL BE LIMITED...STORMS COULD PRODUCE SOME LOCALLY HEAVY RAINFALL AMOUNTS DUE TO LITTLE MOVEMENT...AND EVEN WITH PRECIP WATER VALUES GENERALLY BELOW ONE INCH...WILL HAVE TO WATCH FOR ISOLATED GULLY WASHERS ALONG BLUE RIDGE...ESPECIALLY NW NC AND FAR SW VA. ANY CONVECTION WILL BE STRONGLY TIED TO DIURNAL HEATING SO SHOULD DISSIPATE AGAIN FAIRLY QUICKLY BY EARLY EVENING. WITH SLIGHT INCREASING TREND IN LOW LEVEL MOISTURE THROUGH THIS PERIOD MIN TEMPS SHOULD BE A COUPLE DEGREES MILDER COMPARED TO MONDAY NIGHT. UPPER RIDGE REMAINS DOMINANT WEDNESDAY WITH MAX TEMPS PERHAPS THEIR WARMEST OF THE WEEK...MID 80S PIEDMONT TO MID AND UPPER 70S MANY MTN LOCATIONS. WITH WEAK EASTERLY FLOW AT LOW LEVELS AND STILL SOME CONVERGENCE OVER HIGHER TERRAIN...WILL ONCE AGAIN SEE SCATTERED WEAK CONVECTION OVER HIGHER TERRAIN MAINLY...AND AGAIN SLOW MOVING. BY LATE IN THE DAY A BACK DOOR COLD FRONT MAY APPROACH THE NORTHEAST PORTION OF THE FCST AREA AS RIDGE AMPLIFIES OVER OHIO VALLEY BUT SO DOES TROUGH OVER NEW ENGLAND AND DOWN INTO NEW JERSEY. THERE COULD BE A SLIGHT ENHANCEMENT TO COVERAGE OF ANY WEAK CONVECTION ACROSS THE NORTHERN EDGES BECAUSE OF THIS BOUNDARY...SO INCREASED POPS A BIT TO THE NORTH OF A ROA TO LYH LINE. STILL ONLY LOW CHC CATEGORY THOUGH. FARTHER SOUTH IN PIEDMONT OF SOUTHSIDE VA AND NORTH-CENTRAL VA MAY NOT SEE ANYTHING BUT WITH OVERALL MOISTURE STILL INCREASING A TAD FROM TUES AND POTENTIAL FOR THIS BACK DOOR COOL FRONT TO SNEAK FARTHER SOUTH BY LATE IN THE DAY...THREW IN A SLIGHT CHC POP. THEN ONCE AGAIN DAYTIME CONVECTION SHOULD DIE FAIRLY QUICKLY MOST LOCATIONS...WITH POSSIBLE EXCEPTION OF NEAR BLUE RIDGE WHERE BETTER UPSLOPE FLOW ALONG AND BEHIND BACK DOOR FRONT COULD KEEP ISOLATED SHOWERS GOING A LITTLE LATER INTO OVERNIGHT. DONT SEE ENOUGH MOISTURE AND COOL AIR ADVECTION FROM A STRONG ATLANTIC FETCH TO BE TOO CONCERNED ABOUT LOW STRATUS AND FOG. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 335 PM EDT SUNDAY... MAIN ISSUE THIS PERIOD WILL BE INTERPLAY BETWEEN SUB-TROPICAL LOW DEVELOPING OFF OF THE FLORIDA ATLANTIC COAST AND THEN INITIALLY DRIFTING NORTH...AND THE POSITION OF THE BACK DOOR FRONTAL BOUNDARY. BECOMING MORE CONFIDENT THAT ON THURSDAY THE FRONT WILL CONTINUE TO MOVE SOUTHWESTWARD...POSSIBLY AIDED BY THE STRENGTHENING LOW OFF THE SOUTHEAST U.S. COAST. THIS WILL PLACE A FOCUS ON ANY CONVECTIVE DEVELOPMENT MAINLY ACROSS THE WESTERN PORTION OF THE FCST AREA...MAINLY WEST OF I-77...AND POSSIBLY EVEN FARTHER SOUTHWEST IF TRENDS CONTINUE. A LITTLE TRICKIER IN SOUTHEAST WV AS FRONTAL BOUNDARY COULD GET HUNG UP THERE OR COULD AT LEAST STILL BE IN THAT AREA EARLIER IN THE DAY...SO KEPT A CHANCE POP FROM ALLEGHANY HIGHLANDS SOUTH TOWARD NW NC FOOTHILLS. THIS ALL MAY NEED TO BE PULLED FARTHER TOWARD SOUTHWEST AS WE GET CLOSER TO THURSDAY. BY FRIDAY MOST LONGER RANGE MODELS ARE THEN SHIFTING THE LOW BACK TOWARD THE WEST OR STALLING IT...WELL SOUTH OF US AND STILL PROBABLY OFF THE COAST...AS PATTERN BECOMES BLOCKED. IN THIS POSITION THERE COULD ACTUALLY BE INCREASING SUBSIDENCE OVER OUR REGION INTO THE WEEKEND...PERHAPS WITH STILL WEAK CONVERGENCE OVER MTNS AND AT LEAST ISOLATED SHOWER ACTIVITY. THINK THUNDER CHANCES WOULD BE LIMITED GIVEN THIS SUBSIDENCE ALOFT...SO KEPT THUNDER MENTION OUT BY SATURDAY AND SUNDAY. THIS OF COURSE IS ALL VERY DEPENDENT ON WHERE THIS SUB-TROPICAL LOW...POTENTIALLY WITH SOME TROPICAL CHARACTERISTICS...ENDS UP DRIFTING. SO OVERALL A FAIRLY LOW CONFIDENCE FORECAST. WHILE APPEARING LESS LIKELY WITH ALL 12Z MODEL CYCLES THAT THIS WILL DRIFT NORTHWESTWARD ALL THE WAY INTO THE SOUTHERN APPALACHIANS...THIS SYSTEM NEEDS TO BE WATCHED CLOSELY SINCE A TRACK THIS FAR NORTH COULD MEAN SIGNIFICANT RAINFALL IF IT DID. SUCH A PATH WOULD ALSO HAVE A MAJOR INFLUENCE ON HIGH TEMPS BY LATE WEEK INTO THE WEEKEND...BUT FOR NOW THE RATHER WARM CONDITIONS WITH RIDGE BEING THE DOMINANT FACTOR LOOK THE MOST LIKELY. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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AS OF 745 PM EDT SUNDAY VFR CIGS EXPECTED THROUGH THE TAF VALID PERIOD. HOWEVER...THERE IS A PERSISTENT LAYER OF TRAPPED MID-LEVEL MOISTURE IN THE 050-080 RANGE UNDERNEATH AN PRONOUNCED INVERSION. THIS WILL PERSIST INTO MONDAY WITH HIGH PRESSURE ALOFT OVER THE REGION. THUS...THERE WILL BE PERIOD OF SCT-BKN050-080 CIGS...MOST PRONOUNCED DURING THE MID-AFTERNOON/EARLY EVENING HOURS. A FRONTAL SYSTEM WILL ENCROACH ON THE FAR NORTHERN FRINGES OF THE CWA LATE MON/MON NIGHT...BUT WILL NOT ENTER THE CWA UNTIL TAKING ON A BACKDOOR CONFIGURATION TUE- WED. SOME CIRRUS WILL AGAIN SPILL INTO THE REGION FROM THE NORTHWEST IN ASSOCIATION WITH UPSTREAM CONVECTION ACROSS THE MID- WEST/OHIO VALLEY. ADDED A BRIEF PERIOD OF EARLY MORNING GROUND FOG FOR LYH/DAN...NOTING THAT MOISTURE LEVELS ARE SLOWLY INCREASING...EARLY MORNING WINDS CALM...AND SEEING THAT DANVILLE OBSERVED SUCH THIS MORNING. IF ANYTHING...MOISTURE LEVELS WILL CONTINUE TO INCREASE WITH SOUTH FLOW...SO SEEMS EVEN MORE LIKELY THAT A BRIEF PERIOD OF BR COULD OCCUR AT THESE LOCATIONS MON MORNING. DID NOT INCLUDE AT LWB YET AS THE SFC AIR MASS THERE IS MUCH DRIER. WILL NEED TO WATCH BCB...AS IT IS POSSIBLE THERE...BUT NOT LIKELY. NO NEED FOR ANY FOG AT BLF/ROA AT THIS POINT. WINDS PREVAILING SSE-SSW THROUGH MUCH OF THE TAF VALID PERIOD...VEERING A LITTLE MORE TOWARD SW BY MON AFTERNOON. SPEEDS 5KTS OR LESS OVERNIGHT...BECOMING 5-10KTS WITH SOME LOW END GUSTS AT ROA/DAN/BCB/BLF AFT 17Z MON. WHILE THE THREAT FOR SCT -SHRA INCREASES MON AFTERNOON NEAR THE BLUE RIDGE AND INTO SW VA...PROBABILITIES REMAIN TOO LOW TO INCLUDE AT SPECIFIC POINTS/TAF SITES AT THIS TIME. MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. HIGH CONFIDENCE IN VFR VSBYS THROUGH 08Z...THEN MEDIUM CONFIDENCE IN VSBYS...THEN HIGH CONFIDENCE AFT 14Z. MEDIUM CONFIDENCE IN WIND DIR THROUGH THE TAF VALID PERIOD...MEDIUM TO HIGH CONFIDENCE IN WIND SPD THROUGH THE TAF VALID PERIOD. NOTE...THE VISIBILITY SENSOR AT THE ASOS AT KBLF CONTINUES TO BE SPORADICALLY OUT OF SERVICE. REPAIRS MAY NOT BE POSSIBLE UNTIL THE END OF MAY. WILL CONTINUE WITH AMD NOT SKED APPENDED TO BLF TAF. EXTENDED AVIATION DISCUSSION... SCATTERED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS ARE EXPECTED ALONG THE SOUTHERN BLUE RIDGE ON TUESDAY...WHICH WOULD YIELD PERIODS OF MVFR CONDITIONS. SHOWERS AND THUNDERSTORMS WILL BE MORE WIDESPREAD ON WEDNESDAY AND THURSDAY AS A BACK DOOR FRONT ENTERS THE REGION. HIGH PRESSURE ALOFT WILL LIMIT MUCH IN THE WAY OF ANY SYNOPTIC-SCALE FORCING THROUGH THE PERIOD. EXTENDED PERIODS OF SUB-VFR CIGS/VSBYS APPEAR UNLIKELY THIS WEEK...BUT MORNING FOG WILL BECOME AN INCREASING ISSUE THROUGHOUT THE WEEK AT THE USUAL SPOTS...LYH/DAN/BCB/LWB. WINDS OVERALL WILL BE ON THE LIGHT SIDE THROUGH THE WEEK.
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&& .EQUIPMENT... AS OF 200 PM EDT SUNDAY... THE VISIBILITY SENSOR AT THE BLUEFIELD...KBLF...ASOS WILL ALTERNATE BETWEEN AVAILABLE AND UNAVAILABLE UNTIL FURTHER NOTICE. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/NF NEAR TERM...NF SHORT TERM...SK LONG TERM...SK AVIATION...JR/NF/RAB EQUIPMENT...AMS

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