Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 311412 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1012 AM EDT SUN AUG 31 2014 .SYNOPSIS... THE REGION WILL STAY BETWEEN A LARGE HIGH PRESSURE SYSTEM OVER THE SOUTHEAST UNITED STATES AND WESTERN ATLANTIC AND A COMPLEX LOW PRESSURE SYSTEM CROSSING THE GREAT LAKES. A COLD FRONT FINALLY ARRIVES FROM THE NORTH BY THURSDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 950 AM EDT SUNDAY... INITIAL BAND OF EARLY MORNING SHOWERS HAS ALREADY FADED UPON CROSSING THE BLUE RIDGE SO UPDATED TO CUT BACK ON POPS THROUGH EARLY AFTERNOON. ALSO EXPECTING MORE SUNSHINE ACROSS MOST OF THE REGION THIS MORNING PER LATEST VISIBLE PICS WITH THE MAIN AXIS OF DEEP MOISTURE REMAINING WEST OF THE MOUNTAINS. THIS SHOULD ALLOW FOR A BIT MORE INSTABILITY THIS AFTERNOON GIVEN SW FLOW AND LOW LEVEL MOISTURE. HOWEVER MORNING SOUNDINGS SHOWING CAPPING JUST OFF THE SURFACE AND A MORE SIGNIFICANT MID LEVEL INVERSION ABOVE WHICH SHOULD ACT TO DETER ANY WIDESPREAD ADDED CONVECTIVE COVERAGE UNTIL PERHAPS EARLY THIS EVENING AT BEST. OTRW APPEARS BETTER AFTERNOON CHANCES WILL BE ALONG THE SOUTHERN BLUE RIDGE PER LOW LEVEL SW FLOW...HIGHER THETA-E AND FORECAST INSTABILITY...AS WELL AS OVER THE NW WHERE THE UPPER SHEAR AXIS LOOKS TO FOLD INTO LATE BEHIND THE PASSING WAVE FROM THIS MORNING. ALSO SOME ADDITION OF DIFFERENTIAL HEATING ON THE EDGE OF THE FAR WESTERN CLOUD SHIELD MAY ALONG WITH OROGRPAHICS AID INITIAL DEVELOPMENT AT LEAST ON A SCATTERED BASIS. THUS BASICALLY KEPT GOING LOW LIKELY POPS IN THESE SPOTS WHILE TRIMMING BACK OVER THE PIEDMONT WHERE MORE UNDER THE RESIDUAL RIDGE AND WITHOUT MUCH FOCUS FOR NOW SIMILAR TO THE LATEST HRRR. THICKNESS OFF 12Z RAOBS REMAINS QUITE WARM...AND GIVEN A MILD START INCLUDING MORE HEATING EARLY...WOULD EXPECT READINGS OUT EAST TO POSSIBLY REACH 90/LOW 90S WITH MID/UPPER 80S ELSW FROM THE BLUE RIDGE EAST. SHOULD BE A LITTLE COOLER FAR WEST PER CLOUDS BUT EVEN THERE APPEARS UPPER 70S/LOW 80S LIKELY. LARGER BAND OF SHOWERS WILL PIVOT ENOUGH TO REACH SOUTHEAST WEST VIRGINIA TONIGHT...SIMILAR TO ORIENTATION OF WPC QPF FORECAST AND THE 00Z GFS...SLIGHTLY FARTHER SOUTH THAN THE 00Z NAM. HUMID AIR MASS AND VERY MILD DEW POINTS WILL RESULT IN LITTLE COOLING TONIGHT. USED WARMER MET GUIDANCE FOR OVERNIGHT LOWS.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 AM EDT SUNDAY... PROGRESSIVE NORTHERN STREAM FLOW WILL PRODUCE TROUGHING ACROSS THE NORTHEAST BY MONDAY MORNING. SEVERAL SHORTWAVES TRAVERSE ACROSS THE MID ATLANTIC REGION. THESE UPPER DISTURBANCES WILL SHAPE THE TIMING OF CONVECTION. AN UPPER DISTURBANCE WILL SHIFT ACROSS THE GREAT LAKES FROM THE OHIO RIVER VALLEY MONDAY MORNING...ENHANCING THE CHANCES OF SHOWERS IN THE WEST-NORTHWEST. THE SUBTROPICAL BERMUDA HIGH PRESSURE WILL REMAIN IN PLACE. A VERY MOIST SOUTHWEST FLOW WILL CONTINUE LABOR DAY. HIGH TEMPERATURES MONDAY WILL RANGE FROM THE UPPER 70S IN THE MOUNTAINS TO THE LOWER 90S IN THE PIEDMONT. SCATTERED SHOWERS AND THUNDERSTORMS REDEVELOP MONDAY AFTERNOON WITH SOLAR HEATING. SOME OF THE THUNDERSTORMS MAY CONTAIN LOCALLY HEAVY RAINS. RAINFALL WILL DIMINISH QUICKLY AS THE SUN SETS AND SHOULD SEE DRY...ALBEIT WARM AND MUGGY...CONDITIONS PERSIST THROUGH MONDAY NIGHT. LOW TEMPERATURES MONDAY NIGHT WILL VARY FROM THE LOWER 60S IN THE WEST TO THE AROUND 70 IN THE EAST. DEEP LAYER MOISTURE INCREASES TUESDAY AS ANOTHER LOW PRESSURE SYSTEM MOVING ACROSS EASTERN CANADA WILL DRAG A COLD FRONT SOUTH OF THE GREAT LAKES. BETTER CHANCES FOR CONVECTION WILL BE FOUND ACROSS THE HIGHER TERRAIN...WHERE STRONGER UPPER LEVEL SUPPORT WILL BE LOCATED. HIGHS TUESDAY WILL CLIMB INTO THE LOWER 80S IN THE MOUNTAINS TO THE LOWER 90S IN THE PIEDMONT. MODEL TREND HAVE BEEN SLOWING THE TIMING OF THE FRONT AND EXPECT THE COLD FRONT WILL STALL FURTHER NORTH TUESDAY NIGHT DUE TO THE UPPER LEVEL RIDGING IN PLACE ACROSS THE SOUTHEAST STATES. LOWS WILL FALL INTO THE MID 60S TO THE LOW 70S TUESDAY NIGHT. KEPT THE HIGHEST POPS ACROSS THE SOUTH WEDNESDAY ALONG THE STALLED FRONTAL BOUNDARY. WHILE...HIGH PRESSURE PASSING ACROSS THE GREAT LAKES SHOULD KEEP THE NORTHERN HALF OF OUR AREA DRY. HIGHS WEDNESDAY WILL BE FROM THE LOWER 80S IN THE WEST TO AROUND 90 DEGREES IN THE EAST. SLOWLY DRY THINGS OUT WEDNESDAY NIGHT FROM NORTH TO SOUTH. LOW TEMPERATURES WILL DROP INTO THE UPPER 50S IN THE NORTHWEST MOUNTAINS TO NEAR 70 DEGREES IN THE PIEDMONT. && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 330 PM SATURDAY... UPPER LEVEL RIDGING WILL SHIFT NORTHWARD FROM THE SOUTHEAST STATES OVER THE MID ATLANTIC DURING THE SECOND HALF OF THE WEEK...RESULTING IN BOTH WARMER TEMPERATURES AND WEAKER WINDS ALOFT. THIS WILL MAKE FOR MORE STABLE CONDITIONS THAT WILL KEEP SHOWER AND THUNDERSTORM ACTIVITY DISORGANIZED THROUGH THE PERIOD. ANY RAINFALL WHICH DEVELOPS WILL BE DRIVEN MAINLY BY DAYTIME HEATING...WHICH WILL ALLOW THIS ACTIVITY TO FIZZLE AFTER SUNSET. HIGH PRESSURE WILL PASS OFF THE NEW ENGLAND COAST ON THURSDAY... RESULTING IN A WEAK WEDGING PATTERN WITH EASTERLY FLOW OFF THE ATLANTIC. THIS WILL LIKELY BE THE DRIEST DAY OF THE PERIOD. WINDS WILL SHIFT SOUTHWESTERLY AGAIN ON FRIDAY AS ANOTHER COLD FRONT SINKS SOUTH FROM THE GREAT LAKES. STRONGER FLOW OFF THE ATLANTIC WILL RESULT IN INCREASED MOISTURE...AND WILL EXPECT SPOTTY SHOWER AND THUNDERSTORM ACTIVITY DURING THE AFTERNOON AND EVENING. EXPECT TEMPERATURES TO REMAIN SLIGHTLY ABOVE NORMAL FOR THE PERIOD. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/... AS OF 735 AM EDT SUNDAY... SATELLITE PICTURES SHOWED AN AREA OF IFR CLOUDS SPREADING NORTH OUT OF NORTH CAROLINA. THESE CLOUDS MAY BRIEFLY REACH KLYH OR KDAN BEFORE 10AM. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WERE MOVING NORTH- NORTHEAST ACROSS THE CENTRAL APPALACHIANS THIS MORNING. EXPECT RAIN AT KROA/KBCB AND KLWB THROUGH 14Z/10AM THIS MORNING. CEILINGS AND VISIBILITIES WILL REMAIN VFR IN ALL BUT THE HEAVIEST SHOWERS. THE PRECIPITATION WILL GRADUALLY DIMINISH THIS MORNING AS IT MOVES EAST. THERE WILL BE A BREAK IN THE PRECIPITATION THROUGH ABOUT 1PM/17Z...THEN MORE SHOWERS AND THUNDERSTORMS WILL DEVELOP. HRRR GUIDANCE SHOWED THE MOST LIKELY LOCATION FOR REDEVELOPMENT WILL BE ALONG THE BLUE RIDGE. BUT THIS WILL DEPEND ON HOW MUCH HEATING AND RESULTING INSTABILITY HAS OCCURRED. MEDIUM CONFIDENCE ON THE LOCATION OF STORMS THIS AFTERNOON AND EVENING. ONCE THE PRECIPITATION MOVES OUT OF THE AREA LATE TONIGHT...HIGH AMOUNTS OF LOW LEVEL MOISTURE...ALONG WITH SOME BREAKS IN THE CLOUD COVER WILL RESULT IN FOG FORMATION. HIGH CONFIDENCE OF MVFR FOG ACROSS THE REGION LATE TONIGHT. EXTENDED DISCUSSION... IMPULSES EXIT BY MONDAY LEAVING THE REGION IN BETWEEN THIS EXITING SYSTEM AND THE NEXT UPSTREAM COLD FRONT. THIS SHOULD ALLOW FOR MORE IN THE WAY OF WIDESPREAD VFR ON MONDAY AFTER EARLY FOG FADES...WITH ONLY ISOLATED CONVECTION LIKELY DURING THE AFTERNOON INCLUDING SPOTTY MVFR CONDITIONS. ANOTHER COLD FRONT IS EXPECTED TO PRODUCE SIMILAR CONDITIONS AS IT APPROACHES FROM THE NW TUESDAY...THEN BETTER COVERAGE OF SHRA/TSRA WEDNESDAY WITH THE FRONT PASSING...AND ACROSS THE SOUTH THURSDAY WHERE THE BOUNDARY STALLS. HOWEVER LOW CONFIDENCE ON THE TIMING AND SOUTHWARD POSITION OF THE BOUNDARY AT THIS POINT. THUS APPEARS MAINLY VFR FOR NOW TUE-THU OUTSIDE OF AFTERNOON/EVENING CONVECTION AND TYPICAL EARLY MORNING FOG IN THE VALLEYS AND WHERE EARLIER HEAVY RAIN OCCURRED. && .EQUIPMENT... AS OF 730 AM EDT FRIDAY ... THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS/JH SHORT TERM...KK LONG TERM...NF AVIATION...AMS EQUIPMENT...AMS

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