Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KRNK 040636 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 236 AM EDT MON MAY 4 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 TODAY/... AS OF 200 AM EDT MONDAY... LATE NIGHT CONDITIONS FEATURE MAINLY CLEAR SKIES ACROSS VA/WV WITH SOME SCT-BKN ALTO-CU...TRAPPED UNDERNEATH SUBSIDENCE INVERSION NEAR 8-10KFT AGL...ALONG AND SOUTH OF THE VA/NC BORDER. HIGH PRESSURE WILL REMAIN CENTERED VCNTY OF THE CAROLINA COASTLINE FOR THE REMAINDER OF THE OVERNIGHT...CLOCKWISE FLOW AROUND THE HIGH RESULTING IN A LIGHT SOUTHWEST WIND ACROSS OUR FCST AREA. THE AIRMASS OVER THE AREA IS STILL QUITE DRY...SO TEMPERATURES SHOULD SLIP INTO THE U40S/LOWER 50S MOST AREAS. READINGS MAY DIP INTO THE LOWER 40S IN THE COLDER MOUNTAIN VALLEYS OF THE VA/WV HIGHLANDS. A WARMER SOUTHWEST FLOW CONTINUES MONDAY AS THE UPPER LEVEL RIDGING OVER THE CENTER OF THE COUNTRY DRIFTS EASTWARD. SCATTERED HIGH BASED CU WILL DEVELOP LATE MORNING AND EXPECT A FEW SHOWERS AND ISOLATED THUNDERSTORM DURING THE AFTERNOON. THE BEST CHANCE OF CONVECTION WILL OCCUR SOUTHERN PORTIONS OF FORECAST AREA...WITH THE DEEPER MOISTURE AND BETTER INSTABILITY ASSOCIATED WITH A WEAK UPPER LEVEL DISTURBANCE. THE NAM...RAP...HIRESW-ARW SHOWED CONVECTION DEVELOPING AFTER 18Z ESPECIALLY ALONG THE SOUTHERN BLUE RIDGE. THE GFS IS THE MOST ROBUST WITH CONVECTION AND FURTHER NORTH COMPARED TO MOST OF THE REST OF SOLUTIONS. BELIEVE THE GFS IS OVERDONE BECAUSE OF THE DRY AIRMASS IN PLACE. HIGH TEMPERATURES MONDAY WILL RANGE FROM AROUND 70 DEGREES IN THE MOUNTAINS TO THE LOWER 80S IN THE PIEDMONT. 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 WIND FLOW 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 /TONIGHT 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 /06Z MONDAY THROUGH FRIDAY/... AS OF 200 AM EDT MONDAY VFR CIGS EXPECTED THROUGH THE TAF VALID PERIOD. THERE IS A PERSISTENT LAYER OF TRAPPED MID-LEVEL MOISTURE IN THE 5-10KFT RANGE UNDERNEATH AN PRONOUNCED INVERSION. THIS WILL PERSIST THROUGH THE VALID TAF PERIOD WITH HIGH PRESSURE ALOFT OVER THE REGION. THUS...EXPECT SCT-BKN CLOUD BASES...ALL CLOUD ELEMENTS REMAINING ABOVE 5KFT AGL. DURING THE PEAK HEATING PART OF THE AFTERNOON SOME ISOLATED DEEPER CONVECTION MAY DEVELOP VCNTY OF THE BLUE RIDGE SOUTHWEST OF ROANOKE...KROA...INTO THE MOUNTAINS OF NORTH CAROLINA. STEERING WINDS ARE LIGHT...LESS THAN 10 KTS...SO EXPECT LITTLE MOVEMENT FOR ANYTHING THAT DEVELOPS. WHILE THREAT FOR DEEP CONVECTION EXISTS ALONG BLUE RIDGE...THE PROBABILITY REMAINS TOO LOW TO INCLUDE IN ANY OF THE TAF SITES AT THIS TIME. MEDIUM TO HIGH CONFIDENCE IN CLOUD BASES THROUGH THE TAF VALID PERIOD. HIGH CONFIDENCE IN VISIBILITIES. MEDIUM CONFIDENCE IN WIND DIR AND SPEED 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...ASSOCIATED WITH MVFR CONDITIONS. SHOWERS AND THUNDERSTORMS WILL BE MORE NUMEROUS ON WEDNESDAY AND THURSDAY AS A BACK DOOR FRONT ENTERS THE REGION FROM THE NORTHEAST. 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. && .EQUIPMENT... AS OF 200 AM EDT MONDAY... THE VISIBILITY SENSOR AT THE BLUEFIELD...KBLF ASOS...IS EXPERIENCING INTERMITTENT OUTAGES. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/NF NEAR TERM...KK/NF/PM SHORT TERM...SK LONG TERM...SK AVIATION...PM EQUIPMENT...PM

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.