Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 271743 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 143 PM EDT WED MAY 27 2015 .SYNOPSIS... HIGH PRESSURE OFF THE SOUTHEAST COAST WILL MAINTAIN A BROAD SOUTHERLY FLOW OF MOISTURE INTO THE REGION THROUGH THE REMAINDER OF THIS WEEK. AN UPPER LEVEL TROUGH OF LOW PRESSURE WILL REMAIN OVER THE CENTRAL PART OF THE COUNTRY...DISTURBANCES ALOFT OCCASIONALLY EJECTING NORTHEAST OUT OF THE TROUGH AND INTERACTING WITH THE MOISTURE OVER OUR REGION. THIS WEATHER PATTERN IN COMBINATION WITH DAYTIME HEATING AND INSTABILITY WILL RESULT IN PERIODIC ROUNDS OF SHOWERS AND STORMS OVER THE NEXT FEW DAYS. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1000 AM EDT WEDNESDAY... MUCH OF THE REMAINDER OF THE DAY WILL BE SPENT IN BETWEEN TWO UPPER LEVEL WAVES OF ENERGY...WITH ONE EXITING TO THE NORTHEAST AS OF MID MORNING...AND ANOTHER OVER MISSISSIPPI VALLEY AREA NOT ARRIVING UNTIL OVERNIGHT. MANY AREAS HAD CONSIDERABLE CLOUD COVER EARLY THIS MORNING BUT MUCH OF THE WEST HAS CLEARED OFF WITH EFFICIENT HEATING FOR MUCH OF THE DAY. STILL WITH WEAK FLOW AND WEAK CONVERGENCE...DONT SEE MUCH IN THE WAY OF ANY ORGANIZED CONVECTION. SOUNDING QUITE MOIST...BUT WITH HIGH FREEZING LEVEL AND NOT MANY LEVEL OF DRY AIR...AND MODIFIED SOUNDING ONLY SHOWING SBCAPE OF 1200 J/KG OR SO...ANY SCATTERED STORMS TODAY WILL BE FAIRLY WEAK AND SEE VERY LITTLE IF ANY THREAT FOR SEVERE. MEAN FLOW SHOULD KEEP ANY STORMS MOVING ALONG SO ALSO VERY LITTLE THREAT FOR FLOODING ISSUES...ESPECIALLY GIVEN DRYING TRENDS OVER LAST SEVERAL DAYS AND MINIMAL COVERAGE OF SHWRS/STORMS YESTERDAY. WITH SOME HEATING IN MTNS AND WEAK CONVERGENCE NEAR BLUE RIDGE...THINK THIS WILL BE MOST LIKELY AREA FOR INITIAL DEVELOPMENT BY MIDDAY...THEN DRIFTING INTO FOOTHILLS AND PIEDMONT LATER IN THE AFTERNOON THROUGH EARLY EVENING WHERE BEST INSTABILITY THIS AFTERNOON IS FORECAST. LEAST COVERAGE MAY BE BACK OVER WRN SLOPES WHERE SHOWERS EARLY THIS MORNING LIKELY STABLIZED ATMOSPHERE SOMEWHAT. HIGH RES MODELS SUPPORT THE IDEA OF MINIMAL COVERAGE...ESPECIALLY OVER FAR WEST...AND THUS HAVE LOWERED POPS A LITTLE MORE WITH SLIGHT CHANCE FAR WEST TO MID CHANCE FROM BLUE RIDGE EAST. PREV DISCUSSION AS OF 530 AM EDT WEDNESDAY... RIDGE OF HIGH PRESSURE IS ANCHORED JUST OFF THE SOUTHEAST ATLANTIC COAST WITH A TROUGH OF LOW PRESSURE OVER THE MID SECTION OF THE COUNTRY...ITS ASSOCIATED SURFACE COLD FRONT EXTENDING FROM THE WESTERN GREAT LAKES SOUTHWEST INTO KANSAS. SOUTHERLY FLOW AROUND THE PERIPHERY OF THE COASTAL ANTICYCLONE AND THE MIDWEST TROUGH WAS RESULTING IN AN ABUNDANCE OF MOISTURE FLOWING NORTH FROM THE GULF OF MEXICO INTO THE EASTERN ONE THIRD OF THE CONUS. SURFACE DEWPOINTS FROM ONTARIO CANADA SOUTHWARD...ALL THE WAY TO THE GULF COAST WERE IN THE 60S. THIS MOISTURE RICH AIRMASS WILL REMAIN IN PLACE THE NEXT SEVERAL DAYS HELPING TO FUEL SCATTERED SHOWERS AND THUNDERSTORMS OVER A BIG CHUNK OF REAL ESTATE. BEST CHANCE FOR ORGANIZED THUNDERSTORM ACTIVITY TODAY WILL BE FROM THE OHIO VALLEY NORTHEAST INTO NEW ENGLAND ASSOCIATED WITH SHORT WAVE IMPULSE EXITING THE UPPER LEVEL TROUGH AND PASSING NORTH OF OUR REGION. OTHER ORGANIZED DEEP CONVECTION WILL OCCUR FARTHER WEST ALONG THE TAIL END OF THE SURFACE FRONT OVER THE CENTRAL AND SOUTHERN PLAINS. FOR OUR FORECAST AREA...THE SHOWER ACTIVITY IS EXPECTED TO BE MORE DISORGANIZED AND MAINLY DIURNALLY DRIVEN. HEATING TODAY SHOULD RESULT IN BUILD-UPS ALONG THE BLUE RIDGE...THE DEVELOPMENT OF SCATTERED SHOWERS/STORMS THEN MOVING NORTHEAST INTO THE FOOTHILLS AND PIEDMONT DURING THE MID/LATE AFTERNOON. DEEP LAYER FLOW OF 20-30KTS OUT OF THE SOUTH-SOUTHWEST SHOULD KEEP THE SHOWERS MOVING ALONG FAIRLY QUICKLY. SINCE THE ACTIVITY IS EXPECTED TO BE DISORGANIZED...TRIMMED POPS INTO THE 40-60 PERCENT RANGE...EMPHASIZING SCATTERED AS OPPOSED TO NUMEROUS OR WIDESPREAD. TEMPERATURES WILL BE SUMMER-LIKE WITH HIGHS IN THE 80S AND LOWS IN THE 60S...COMPLIMENTED BY DEWPOINTS IN THE 60S. && .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... AS OF 500 AM EDT WEDNESDAY... UPPER LEVEL RIDGING WILL BECOME ESTABLISHED ON THURSDAY ACROSS THE SOUTHEAST AND MID ATLANTIC STATES...RESULTING IN LIGHT WINDS ALOFT HEADING INTO THE WEEKEND. DO NOT EXPECT MUCH CHANGE IN THE WEATHER PATTERN FOR THE LOW LEVELS OF THE ATMOSPHERE...WITH SOUTHERLY WINDS MAINTAINING THE FLOW OF MOIST SUBTROPICAL AIR ALONG THE APPALACHIAN CHAIN. FOR THE THURSDAY THROUGH SATURDAY PERIOD...EXPECT TO START EACH MORNING WITH PATCHY FOG BURNING OFF...GIVING WAY TO PARTLY CLOUDY SKIES BY LATE MORNING. SPOTTY SHOWERS AND THUNDERSTORMS WILL INCREASE IN COVERAGE ACROSS THE MOUNTAINS DURING EACH LATE MORNING/ EARLY AFTERNOON...WITH COVERAGE PEAKING DURING EARLY EVENING. CONVECTION WILL WEAKEN AND FADE AROUND SUNSET...BUT WILL LIKELY SEE A FEW SHOWERS LINGER THROUGH THE OVERNIGHT HOURS. PATCHY LOCALLY DENSE FOG CAN BE EXPECTED TO DEVELOP EACH NIGHT...ESPECIALLY IN RIVER VALLEYS AND IN AREAS WHICH RECEIVED SIGNIFICANT RAINFALL THE EVENING BEFORE. WEATHER FORECAST MODELS DO NOT INDICATE ANY DISTURBANCES PASSING ACROSS THE AREA WHICH WILL SUPPORT ORGANIZED SEVERE THUNDERSTORMS... BUT CANNOT RULE OUT A FEW STORMS PULSING UP TO STRONG/SEVERE INTENSITY AT TIMES. LIGHT UPPER LEVEL WINDS WILL MAKE FOR SLOW STORM MOVEMENT...INDICATING THE POSSIBILITY OF LOCALLY HEAVY RAIN WHERE CELLS STALL OR TRAIN...AND PERHAPS ISOLATED MINOR FLOODING ISSUES IF RAINFALL REMAINS PROLONGED. TEMPERATURES ACROSS THE AREA WILL BE SIMILAR EACH DAY...WITH HIGHS RANGING FROM THE UPPER 70S AND LOW 80S ACROSS THE MOUNTAINS...TO THE MID 80S ACROSS THE PIEDMONT. OVERNIGHT LOWS WILL RANGE FROM THE UPPER 50S IN SPOTS...TO THE LOW/MID 60S FOR MOST OF THE AREA. && .LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 500 AM EDT WEDNESDAY... LOOKING INTO SUNDAY...THE NEXT UPPER TROUGH MAKES HEADWAY INTO THE RIDGE...JUST LIKE ITS PREDECESSOR A FEW DAYS PRIOR. ANTICIPATE THIS FEATURE TO GENERATE A GREATER COVERAGE OF SHOWERS AND STORMS... ESPECIALLY ACROSS THE WESTERN HALF OF THE AREA. THE SURFACE COLD FRONT ASSOCIATED WITH THE TROUGH IS EXPECTED TO ENTER THE AREA SUNDAY NIGHT...AND STALL OVERHEAD OR JUST TO OUR SOUTH ON MONDAY. THE FRONT WILL BUCKLE BACK NORTH EARLY NEXT WEEK AS SOUTHERLY FLOW AROUND THE WEST SIDE OF THE HIGH RE-ESTABLISHES ITSELF. THIS WILL KEEP THE CHANCE OF SHOWERS AND STORMS IN THE FORECAST...AGAIN WITH THE FOCUS WITH THE GREATEST CONCENTRATION IN THE WEST. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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AS OF 143 PM EDT WEDNESDAY... MOIST ATMOSPHERE WITH VFR CUMULUS FIELD AND SCATTERED CIRRUS LAYERS FOR REMAINDER OF AFTERNOON. SCATTERED SHOWERS WITH SOME THUNDER POSSIBLE VCNTY OF BLUE RIDGE BY 18-20Z...DRIFTING WEST INTO FOOTHILLS THROUGH ABOUT 00Z. CONFIDENCE FAIRLY HIGH THESE WILL NOT IMPACT FAR WESTERN AIRPORTS OF KBLF AND KLWB...BUT CANNOT RULE OUT COMPLETELY. KEPT A VCSH MENTION AT KBCB AND KROA...WITH TEMPO GROUP FOR A LITTLE LATER AT KLYH...BUT LEFT OUT OF DANVILLE AS MUCH GUIDANCE STRUGGLES TO GET MUCH THAT FAR EAST BEFORE DYING. STILL...SOMETHING COULD BE IN VCNTY BY LATE THIS AFTERNOON...BUT CONFIDENCE TOO LOW AT THIS TIME TO MENTION IN TAF. OTHERWISE VFR CONDITIONS PREVAIL REST OF TODAY AND EVENING UNLESS A HEAVIER SHOWER OR STORM PASSES RIGHT OVER AN AIRPORT. OVERNIGHT ANY SHOWER ACTIVITY EXPECTED TO DIMINISH...WITH ONLY VERY SMALL CHANCE OF AN ISOLATED SHOWER IN FAR WEST OF FAR EAST. SOME MID LEVEL RESIDUAL CLOUDS SHOULD PREVENT FOG FROM FORMING...BUT GUIDANCE IS QUITE LOW NOW FOR PLACES LIKE LWB AND BCB...AND IF ANY SITE GETS RAINFALL FROM A PASSING SHOWER OR STORM...THEY WOULD SEE A MUCH HIGHER CHANCE BY MORNING. GENERALLY LEFT THIS OUT...EXCEPT FOR SOME LIGHT MVFR FOG AT KLWB...KBCB...AND KLYH. THURSDAY A WEAK UPPER LEVEL DISTURBANCE WILL HELP TO DRAG A WEAK SURFACE BOUNDARY ACROSS THE REGION...HARD TO CALL IT EVEN A FRONT...BUT THIS APPEARS LIKELY TO RESULT IN ENOUGH CONVERGENCE TO HELP DEVELOP MORE WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY BY MIDDAY IN MTNS. ADDED VCSH FOR WESTERN TAF SITES BY 16 OR 17Z...AND GOOD CHANCE THAT NEXT ISSUANCE OF TAFS WILL ADD TEMPO OR PREVAILING GROUPS FOR THUNDERSTORMS AT SEVERAL OF THESE LOCATIONS FOR THE AFTERNOON. EXTENDED AVIATION DISCUSSION... FOR THE REMAINDER OF THE PERIOD...A MOIST UNSTABLE AIR MASS REMAINS ACROSS THE REGION WITH WEAK TRIGGERING MECHANISMS AND DYNAMICS. A FRONTAL SYSTEM WILL APPROACH FROM THE NORTH BY THE WEEKEND...BUT WILL LIKELY REMAIN WELL NORTH OF THE CWA THROUGH SUNDAY. THUS...NO CHANGE IN AIR MASS OR THE OVERALL SYNOPTIC PATTERN IS EXPECTED THROUGH THE PERIOD. EARLY MORNING LOW CLOUDS/FOG AND ASSOCIATED IFR-LIFR CIGS/VSBYS BECOME INCREASINGLY MORE LIKELY THROUGH THE PERIOD...ESPECIALLY FOLLOWING ANY LATE DAY RAINFALL. OTHERWISE...EXPECT MOSTLY VFR-MVFR CIGS OUTSIDE HEAVIER SHOWERS/THUNDERSTORMS.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...PM/SK SHORT TERM...NF LONG TERM...DS/NF AVIATION...PM/SK

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