Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 041702 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 102 PM EDT MON MAY 4 2015 .SYNOPSIS... HIGH PRESSURE SURFACE AND ALOFT WILL REMAIN CENTERED NEAR THE CAROLINA COAST THROUGH TUESDAY. THIS FEATURE WILL RESULT IN MAINLY FAIR WEATHER WITH UNSEASONABLY WARM TEMPERATURES THROUGH MID WEEK. MOISTURE WILL GRADUALLY INCREASE PER MOIST SOUTHWEST WINDS...SO CANNOT RULE OUT A STRAY SHOWER OR ISOLATED THUNDERSTORM DURING THE PEAK HEATING HOURS EACH DAY. A BACKDOOR FRONT IS EXPECTED TO DROP SOUTHWARD FROM NEW ENGLAND ON WEDNESDAY...PROVIDING A BETTER OPPORTUNITY FOR SHOWERS. ANOTHER FEATURE TO WATCH FOR LATE IN THE WEEK IS AN AREA OF LOW PRESSURE WHICH IS FORECAST TO DEVELOP OVER THE BAHAMAS MID WEEK...THEN DRIFT NORTHWARD TO ALONG THE SOUTH CAROLINA COAST TOWARDS WEEKS END. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1255 PM EDT MONDAY... FORECAST ADJUSTMENTS FOR THIS AFTERNOON INCLUDE ON PRIMARY CHANGE AND A FEW MINOR ONES. TEMPERATURES ACROSS MUCH OF THE AREA ARE ALREADY WITHIN A COUPLE OF DEGREES WITHIN FORECAST HIGH TEMPERATURES. BECAUSE OF THIS...HAVE INCREASED FORECAST HIGHS BY TWO TO THREE DEGREES ACROSS MOST AREAS EAST OF THE CREST OF THE RIDGE...AND A LESSER DEGREE ACROSS THE MOUNTAINS WERE CLOUD COVER WILL BECOME MORE ABUNDANT. THE MINOR ADJUSTMENTS HAVE BEEN TO TWEAK THE EXPECTED AREA OF ISOLATED SHOWER DEVELOPMENT THIS AFTERNOON...INITIALLY PARALLELING THE BLUE RIDGE...THEN INTO MORE OF THE WESTERN PIEDMONT OF VA AND NC THIS AFTERNOON. HAVE ALSO ALLOWED FOR SOME ISOLATED CONVECTION OVER PARTS OF SOUTHEAST WEST VIRGINIA LATE THIS AFTERNOON INTO THE EARLY EVENING. AS OF 950 AM EDT MONDAY... NO MAJOR CHANGES TO THE ONGOING FORECAST. HAVE ONLY MADE MINOR ADJUSTMENTS TO HOURLY TEMPERATURES...DEW POINTS...WIND AND SKY COVER FOR THE REMAINDER OF THE MORNING INTO THE EARLY AFTERNOON BASED UPON THE LATEST OBSERVATIONS AND EXPECTED TRENDS. AS OF 445 AM EDT MONDAY... IN SPITE OF A WEATHER PATTERN THAT IS BECOMING INCREASINGLY ACTIVE ACROSS THE CONUS...OUR PART OF THE COUNTRY IS PRETTY QUIET AT THE MOMENT. HIGH PRESSURE SURFACE AND ALOFT CENTERED NEAR THE CAROLINA COAST WILL PROVIDE ANOTHER MAINLY FAIR/DRY DAY WITH TEMPERATURES CLIMBING 5 TO 10 DEGREES ABOVE NORMAL. THE AIRMASS OVER THE AREA IS STILL RELATIVELY DRY...SO THE COMBINATION OF DEWPOINTS IN THE 40S AND DEEP MIXING WILL RESULT IN THE RELATIVE HUMIDITY BOTTOMING OUT IN THE 25 TO 30 PERCENT RANGE THIS AFTERNOON. SINCE THE SURFACE HIGH IS CENTERED CLOSER TO THE COAST TODAY COMPARED TO YESTERDAY...CLOCKWISE WIND FLOW AROUND THE HIGH WILL BEGIN TO DRAW SOME MOISTURE UP ALONG THE SPINE OF THE BLUE RIDGE FROM THE SOUTHWEST. FORECAST CAPE OF 500-1000 J/KG SUGGEST ENOUGH MOISTURE MAY BE AVAILABLE FOR A FEW SHOWERS...ISOLATED THUNDERSTORM...LATE AFTERNOON...MAINLY SOUTHWEST OF ROANOKE...VCNTY OF THE BLUE RIDGE PARKWAY FROM FLOYD INTO THE MOUNTAINS OF NORTH CAROLINA. MEAN WINDS ARE PRETTY WEAK...LESS THAN 10 KTS...SO ANYTHING THAT DEVELOPS WILL MOVE VERY LITTLE. INHIBITING FACTOR FOR ANYTHING MORE THAN ISOLATED COVERAGE IS FACT THAT AIRMASS ABOVE ABOUT 15KFT IS STILL DRY...LIMITING DEEP CONVECTION. FOR TONIGHT...MILD CONDITIONS ANTICIPATED. SOUTHWEST WINDS WILL CONTINUE THE OVERALL WARMING AND MOISTENING PROCESS WITH DEWPOINTS INCHING UPWARD. LOW TEMPERATURES MOST AREAS ARE EXPECTED IN THE 50S...AND SIMILAR TO LAST NIGHT LOOK FOR SCT-BKN ALTO-CU. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 400 AM EDT MONDAY... AN UPPER LEVEL RIDGE WILL BRING WARM TEMPERATURES TO THE REGION INTO WEDNESDAY. TUESDAY`S TEMPERATURES LIKELY TO PEAK ABOVE NORMAL WITH MID TO UPPER 70S WEST TO LOWER 80S EAST. BEING AHEAD OF A COLD FRONT TO THE NORTH...WEDNESDAY WILL BE A FEW DEGREES WARMER THAN TUESDAY UNLESS MORE WIDESPREAD SHOWERS DRIFT ACROSS THE AREA. WITH AN UPPER LEVEL RIDGE OVER THE REGION...ANY SHOWERS THAT DEVELOP LATE IN THE AFTERNOON TUESDAY WILL MOVE SLOWLY AND NOT LAST LONG PAST SUNSET. WITH THE APPROACH OF A BACK DOOR COLD FRONT WEDNESDAY AFTERNOON...MORE AREAL COVERAGE OF SHOWERS ARE EXPECTED. MODELS MAY BE TO AGGRESSIVE WITH THE FRONTAL PASSAGE WEDNESDAY AFTERNOON...ESPECIALLY WITH NO STRONG CONVECTION DEVELOPING OVER THE AREA. WITH THE SLOWER TIMING OF THE FRONT ACROSS THE AREA...WILL INCREASE POPS WEDNESDAY EVENING...ESPECIALLY IN THE EAST AS THE FRONT WEDGES SOUTH ACROSS THE PIEDMONT. && .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 /18Z MONDAY THROUGH SATURDAY/... AS OF 800 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...PM NEAR TERM...DS/PM SHORT TERM...RCS LONG TERM...SK AVIATION...PM EQUIPMENT...PM

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